Evaluation of Organic Contamination in Urban Groundwater Surrounding a Municipal Landfill, Zhoukou, China

Environ Monit Assess (2013) 185:3413–3444 DOI 10.1007/s10661-012-2801-z

Evaluation of organic contamination in urban groundwater surrounding a municipal landfill, Zhoukou, China

D. M. Han & X. X. Tong & M. G. Jin & Emily Hepburn & C. S. Tong & X. F. Song

Received: 9 February 2012 /Accepted: 23 July 2012 /Published online: 8 August 2012 # Springer Science+Business Media B.V. 2012

Abstract This paper investigates the organic pollution ranging from not detected to 2.19 μg/L. The results status of shallow aquifer sediments and groundwater show that sediments below the waste dump were low around Zhoukou landfill. Chlorinated aliphatic hydro- in pollution, and the shallow aquifer, at a depth of 18– carbons, monocylic aromatic hydrocarbons, halogenat- 30 m, was heavily contaminated, particularly during the ed aromatic hydrocarbons, organochlorine pesticides wet season. An oval-shaped pollution halo has formed, and other pesticides, and polycyclic aromatic hydrocar- spanning 3 km from west to east and 2 km from south to bons (PAHs) have been detected in some water samples. north, and mainly occurs in groundwater depths of 2– Among the detected eleven PAHs, phenanthrene, fluo- 4 m. For PAH source identification, both diagnostic rine, and fluoranthene are the three dominant in most of ratios of selected PAHs and principal component analy- the groundwater samples. Analysis of groundwater sam- sis were studied, suggesting mixed sources of pyro- and ples around the landfill revealed concentrations of PAHs petrogenic derived PAHs in the Zhoukou landfill. Groundwater table fluctuations play an important role : in the distribution of organic pollutants within the shal- D. M. Han X. F. Song low aquifer. A conceptual model of leachate migration Key Laboratory of Water Cycle & Related Land Surface in the Quaternary aquifers surrounding the Zhoukou Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, landfill has been developed to describe the contamina- Beijing 100101, China tion processes based on the major contaminant (PAHs). D. M. Han The groundwater zone contaminated by leachate has e-mail: [email protected] been identified surrounding the landfill.

* X. X. Tong ( ) Keywords Landfill . Organic contamination . School of Water Resources & Environment, China University of Geosciences, Hydrogeology. PAHs . Conceptual model Beijing 100083, China e-mail: [email protected] Introduction M. G. Jin : C. S. Tong School of Environmental Studies, China University of Geosciences, Groundwater, used mostly for irrigation, drinking water, 430074 Wuhan, China and municipal water supplies, is essential to the economic viability and livability of many cities in China. E. Hepburn School of Earth Sciences, The University of Melbourne, Groundwater contamination caused by human activities Parkville 3010, Australia is universal, with extensive pollutant sources such as 3414 Environ Monit Assess (2013) 185:3413–3444 wastewater, landfill leachate, storage and disclosure of environment owing to redox processes, biodegradation, petroleum products, and pesticide and herbicide use. dissolution/precipitation, complexation, ion exchange, Unsuitable disposal of organic products can result in and sorption processes (Christensen 1992). unreasonable emissions and harmful byproducts entering This research focuses on one municipal landfill in the geological environment, causing groundwater con- Zhoukou city, which is located at the Huaihe River tamination. The burial of municipal solid waste in land- Basin (Fig. 1). The results of an investigation into seven fills is the most common disposal alternative in most big rivers in China in 1993 showed that the main pollu- countries. According to the investigation in Henan part tion type in Huaihe River was organic contamination of Huaihe River Basin, the total amount of domestic (Cui and Fu 1998). Huaihe River has the highest popu- garbage from 17 primary cities is up to 3,640×103 m3, lation density of these rivers and, with rapid develop- with approximately 80 landfill sites in major towns ment of economic society, gradually increasing water (Tong 2012). Most of early established landfills do not demands will conflict with water shortages in many have an engineered liner, leachate collection system, or cities, including Zhoukou city. Groundwater is the main engineered cover system. Thus, landfill leachate could source of water supply for industrial, agricultural, and, have the potential to pollute soil and water system directly. locally, domestic water in Zhoukou city, and it is facing The current policies surrounding landfill management in groundwater quality problem. There is a major concern China are guided by the Standard for Pollution Control on that urban pollution can affect the production wells in the Landfill Site of Municipal Solid Waste (GB 16889- this and other similar settings in Northern China. It is 2008), which is released by Ministry of Environmental therefore both necessary and urgent to develop reason- Protection of the People’s Republic of China. able groundwater utilization practices and effective pro- Organic contamination issues resulting from landfill tection of the resource. If no successful measures are in many urban areas are of particular concern to local taken for reducing the leakage and transport of pollu- authorities and scientists, since agricultural activities are tants in urban soils and groundwater, the accumulation carried out close to near these cities and since ground- of contaminants can not only degrade soil quality but water is a major supply of both irrigation and domestic also pose a health risk to humans and the ecosystem. water. Most volatile halogenated compounds, even at This study investigated the hydrogeological conditions low concentrations, are probably carcinogens or muta- and the status of organic pollution in groundwater and gens (Baudoin et al. 2002). These have been paid inter- soil in a typical landfill around Zhoukou city. The national attention and are strictly controlled by water objectives of this study were therefore (1) to investigate and air quality standards. Substantial research on the the extent of chlorinated aliphatic hydrocarbons environment, such as polycyclic aromatic hydrocarbons (CAHs), monocylic aromatic hydrocarbons (MAHs), (PAHs), organochlorine pesticides (OCPs), and tetra- halogenated aromatic hydrocarbons (HAHs), OCPs chloroethylene (Nielsen et al. 1995; Persson et al. and other pesticides, and polycyclic aromatic hydrocar- 2006; Eggen et al. 2010), has theoretical significance bons (PAHs) in aquifer sediments and surface and and applicability to field based studies of landfills such groundwater around Zhoukou landfill, and (2) to deter- as those located throughout the numerous small urban mine the potential sources and pathways of PAHs as the centers in China (Zhou and Maskaoui 2003). Due to main contaminant in polluted groundwater. Finally, PAHs ubiquitous occurrence, recalcitrance, bioaccumu- some suggestions are put forward for the reasonable lation potential, and carcinogenic activity, the PAHs development of water resources and better protection have gathered significant environmental concern. of the eco-geological environment. These can provide a PAHs have a detrimental effect on the flora and fauna basic framework and scientific foundation for protecting of affected habitats, resulting in the uptake and accumu- and managing groundwater resources. lation of toxic chemicals in food chains, which cause serious health problems and/or genetic defects in Study area description humans. The major potential environmental impacts related to landfill leachate are pollution of groundwater Landfill background and surface water. The leaking of strongly reduced landfill leachate, high in organic matter, into a shallow, The landfill is located in the north of Zhoukou city in presumably aerobic aquifer creates a very complicated Henan province, China. The study area lies between Environ Monit Assess (2013) 185:3413–3444 3415

Fig. 1 Map of the sampling sites around the Zhoukou landfill, groundwater table contours (m.a.s.l), 9 major groundwater-flow China. 1 residential area, 2 landfill, 3 farmland, 4 orchard, 5 direction, 10 flow direction of surface water, 11 sewage ditch, 12 waters, 6 groundwater monitoring wells (sampling wells with local factory. The dashed line delineates the pollution range. labels in Table 1), 7 surface water sampling sites, 8 shallow Groundwater contours from December 2009 longitudes 114°36.7′ and 114°40.8′ E and latitudes 33° characterized by small bed slope and big changes of 37.1′ and 33°39.8′ N, and has an area of 18 km2.Itis water table and flux. During flood season, surface an alluvial depositional plain, bordered by LuDong water recharges local groundwater. After the conflu- Trunk Canal to the north, Ying River to the south, ence of Ying River and Jialu River, the stream flows Jialu River to the west and the Low-lying Gully to the towards the southeast and into Huaihe River. Ying east (Fig. 1). Elevation ranges between 45 and 51 m River and Jialu River converge at the south of a.s.l. with land surface gradient ranging from 1/3,000 Zhoukou city and flow towards the southeast. Only to 1/6,000. The area has a continental monsoonal during the devastating floods, the river water climate, with an annual mean air temperature of recharges groundwater, and river receives groundwa- 14.6 °C, a mean rainfall of 790.8 mm (averaged be- ter discharge in most cases. tween 1951 and 2004) and a mean potential evapora- Landfilling operations at the Zhoukou site spanned tion of 1,736 mm. As much as 54 % of yearly a period of 13 years, from 1998 to 2010. The landfill precipitation is concentrated in July, August, and site was the borrow pits of the Beijiao brickworks September. The main rivers flowing through the study before 1998. The activities for excavating soil at the area include Ying River and Jialu River, which are former brickworks have resulted in the formation of both perennial rivers and belong to the Huaihe River pits and trenches with different sizes and depths. In network. The Ying River and Jialu River are 1998, the brickworks were closed and began piling up 3416 Environ Monit Assess (2013) 185:3413–3444 household and construction waste, ceasing in 2010. Hydrogeological setting The length of the landfill site measures 200 m from southtonorthand90mfromeasttowestandis The hydrogeological conditions play an important role currently surrounded by the city planning area. The in controlling the distribution of groundwater organic depth of the solid waste disposal ranges from 6 to 9 m. contamination. Zhoukou city is located in the southern The waste generated by city life has been stacked in part of the Yellow River alluvial–diluvial fan. The the landfill since 1998, and the landfill was closed in vadose zone is characterized by coarse grains. 2010. The accumulative amount of municipal solid Generally, there are two aquifers within 55 m depth waste, mainly composed of household waste, is now around the Zhoukou landfill. Figure 2 shows the char- up to approximately 140×103 m3, including garbage, acterization of the hydrogeology based on drilling trash, and septic tank waste, derived from houses, around the landfill. The shallow aquifer at the depth apartments, hotels, campgrounds, and picnic grounds of 11–25 m, mainly consists of fine sand and silty (Tong 2012). The construction of this landfill has no sand, is the major aquifer exploited for local irrigation. design features intended to prevent movement of The thickness of the aquitard on top of the first aquifer leachate into the ground water. The landfill does not is approximately 11 m. The deep aquifer consists of have an engineered liner, leachate collection system, interbedded fine sand and silty sand is distributed at or engineered cover system. There is a wastewater the depth of 45–52 m, with a hydraulic conductivity of discharge canal to the east of the landfill. The landfill 12–16 m/day (Qu 2010). One weak permeable layer leachate and wastewater discharge have resulted in composed of silt and silty clay with 20 m thickness is serious contamination to the ambient groundwater distributed between the two aquifers. Aquifer sand and surface water. This landfill with a life of over thickness becomes slightly thinner towards the Ying 10 years was managed by the Zhoukou City River. From pumping testing at the field site (Tong Environmental Sanitation Management Office. 2012), the hydraulic conductivity was determined to

Fig. 2 Simplified hydrogeological sections of the Zhoukou located at some 150 m south of the landfill. The hydraulic landfill. ZKE, ZKW, ZKN, and ZKS are the groundwater mon- parameters of the aquifers are obtained from the results of the itoring wells. ZKC is located at the center of the landfill. ZKS′ is pumping test (Tong 2012) Environ Monit Assess (2013) 185:3413–3444 3417 be in the range 1.2–63.4 m/day. The main recharge Some criss-crossing ditches and scattered ponds were sources of the shallow aquifer include vertical precip- constructed due to the irrigation and drainage needs of the itation infiltration, lateral recharge by rivers and region. These ditches, channels, pits, and ponds can store canals, and irrigation return flows. The groundwater precipitation and surface water during the rainy season discharge also includes human exploitation and drain- and become receivers of wastewater emission in the dry age to rivers. Local groundwater flow under natural season; this is one of the sources of potential pollution of conditions is towards the southeast with a gradient of shallow groundwater. The N–S drainage ditch passes 1/3,000 to 1/5,000. through the eastern landfill and probably provides local One control bore (17 m depth) has been drilled in recharge to groundwater. Artificial exploitation makes the the center of the landfill. The garbage layer, composed surrounding water level slightly lower than that in the of domestic waste material, is located between 0 and position of nonexploitation areas. A water-table mound 9.3 m. The strata intersected by the drilled bore can be exists beneath the landfill in response to the rainfall seen in Fig. 2. According to drilling data, the depth of infiltration, and this has diffused into the surroundings. waste dump at the center of the landfill reached 9.3 m. Different types of pollution, such as waste from the There is a silty clay layer of 2–3 m thickness below the local winery, food factory, pesticide factory, gas station, depth of 9.4–13.8 m, which has a certain protective municipal landfill, and garbage pollution treatment plant function for the shallow aquifer. However, the silt and (locations in Fig. 1), may be potential pollution sources fine sand below the silty clay layer is less protective to the shallow aquifer. Pollution sources may also in- (more permeable). In the east, west, south, and north clude sewage, municipal wastewater, and agricultural of the landfill, four bores, namely, ZKE, ZKW, ZKS, fertilizers. Previous investigation (Tong 2012) shows and ZKN, respectively, have been drilled at a depth of that groundwater pollution away from urban areas and 27 m in order to monitor the groundwater table and villages are relatively mild in this area; hence, the major sample for organic pollutants. The mean groundwater source of groundwater pollution is likely to be the table depth around the landfill was 3.6 m in May 2009 municipal landfill and possibly sewage ditches, which and 3.9 m in December 2009. receive wastewater discharge.

Fig. 3 Sediment distribution in the core profile located at the center of the landfill, and the main organic pollutants’ concentrations in the sediment samples. The water depth is about 3.5 m 3418 Environ Monit Assess (2013) 185:3413–3444

Material and methods began as soon as possible after returning to the laboratory. The measured results are shown in Table 1. Sample collection Water sampling Field investigations were carried out around the landfill site in the north of Zhoukou city. During three main sampling campaigns in December 2008, May 2009, and December 2009, 40 wells and 10 Sediment sampling in the shallow aquifer surface water sites were investigated for organic matter analysis (Table 2).The locations of the sampling Seven sediment samples from different depths were stations are shown in Fig. 1. The wells, including collected by drilling the control bore in May 2009. production and observation wells, were purged before The bore was located at the center of the landfill, sampling, and groundwater was sampled by pumping where depth to water was 3.5 m. Sediment sample after constant values of conductivity and redox poten- depths were 9.3, 9.3–9.5, 9.7–9.9, 10.1–10.3, 10.5– tial had been established. Most selected sampling 10.7, 10.9–11.1, and 11.3–11.5 m (Fig. 3). Within points for groundwater were situated near the landfill. 3 min, 5 g of sediment was collected in an amber Seven sampling sites were selected for surface water bottle (40 mL), with 5 mL NaHSO4 (20 %) and sub- (sampling depth 0.5 m below surface) (Fig. 1). A fresh jected to one magnetic stirring, which was ultrasoni- sample tube was used for each piezometer to prevent cally cleaned by methanol in advance. The collected cross contamination. All samples were filtered through samples were sealed tightly, placed upside down slow- GF/Fs (Whatman, Brentford, UK) to separate the par- ly and stored at 0–4 °C in the freezer. Sample analysis ticulate from the dissolved fraction. The samples were

Table 1 Concentrations of organic compounds in the sediment samples in the Zhoukou landfill

Compound name Sampling depth (m)

9.3 9.3–9.5 9.7–9.9 10.1–10.3 10.5–10.7 10.9–11.1 11.3–11.5

Phenol-D5 1.54 1.59 1.30 1.83 1.80 0.71 1.37 Phenol,2-fluoro 1.53 1.62 1.34 1.74 1.73 0.66 1.42 Phenol 0.06 ––– 0.05 –– Phenol,3-methyl 0.00 –––––– Nitrobenzene-D5 1.36 1.48 1.11 1.78 1.93 0.69 1.26 Naphthalenea 0.06 ––0.03 0.04 – 0.04 Naphthalene,1-methyla 0.06 –––––– 1,1-Biphenyl ss 1.41 1.42 1.16 1.51 1.69 0.69 1.27 Dibenzofurana 0.04 0.03 –– 0.03 –– Fluorenea 0.04 –––––– Phenanthrenea 0.11 –––––– Anthacenea 0.14 –––––– Dibutyl phthalate 0.00 ––– 0.16 –– p-Terphenyl-d14 2.05 1.82 1.57 1.85 2.44 0.87 1.23 1,2-Benzenedi acid ,disooctyl ester 1.42 –––––– Benzo(b)fluoranthenea 0.54 –––––– ∑All compounds 10.35 7.97 6.48 8.75 9.87 3.77 6.58 ∑PAHs 0.99 0.03 0.00 0.03 0.07 0.11 0.04

Units are in nanograms per milligram (–) “not detected” a PAHs Environ Monit Assess (2013) 185:3413–3444 3419

Table 2 Physico-chemical values of water samples around the landfill

Location Sampling Well depth Water depth Utilization T (°C) pH Turbidity EC Eh (mV) DO site time (m) (m) (μS/cm) (mg/L)

ZA December 2008 30 3.4 Agricultural irrigation 16.6 7.7 0.4 964 256 6.38 ZB December 2008 50 3.5 Domestic water 14.6 7.7 0.9 1,086 195 5.46 ZC December 2008 SU Sewage water 19.6 7.7 90.1 1,602 −208 4.03 ZD December 2008 SU water from pond 13.9 8.1 82.5 638 138 3.06 ZE December 2008 SU Waste leachate 11.1 7.9 79.2 3,255 −184 5.76 ZF December 2008 18 3.3 Agricultural irrigation 16.8 7.3 0.5 3,365 328 1.54 ZG December 2008 20 3.3 Domestic water 17.3 7.3 0.7 2,235 283 4.97 Z6A December 2008 16 3.0 Domestic water 17 7.1 0.3 1,734 149 5.59 Z6 December 2008 20 2.6 Domestic water 17 7.3 0.2 1,770 160 8.67 SW29 December 2008 9 4.0 Domestic water 16.3 7.5 0.1 1,255 60 6.1 SW49 December 2008 14 5.0 Domestic water 18.3 7.0 1.9 1,231 137 0.48 SW59 December 2008 6 3.0 Domestic water 17.5 7.5 1.6 1,325 −5 0.54 ZK1 December 2008 300 Urban water supply 22 8.5 0.1 893 72 2.41 ZKE May 2009 27 3.4 Observation well ZKW May 2009 27 3.6 Observation well 18.3 8.9 3.5 396 98 1.07 ZKS May 2009 27 3.5 Observation well 18.4 7.5 10.3 961 3 1.98 ZKN May 2009 27 4.0 Observation well 19.3 6.9 17.2 3,644 115 1.92 ZF May 2009 18 4.1 Agricultural irrigation 17.6 7.6 0.9 1,316 151 2.55 ZG7 May 2009 9 Observation well ZG9 May 2009 9 Observation well ZG10 May 2009 9 2.0 Observation well 18.9 7.5 9.6 1,076 73 2.29 ZG11 May 2009 9 3.7 Observation well 18.7 6.8 4.6 3,430 25 2.29 ZG12 May 2009 9 Observation well Z16 May 2009 30 4.3 Agricultural irrigation Z34 May 2009 28 3.9 Agricultural irrigation 17.6 7.6 4.3 1,809 194 2.35 Z40 May 2009 30 4.1 Agricultural irrigation 17.2 7.6 4.1 1,162 189 1.98 DW09 May 2009 16 3.9 Domestic water 18.9 7.4 4.8 1369 153 1.85 DW18 May 2009 30 4.1 Domestic water 21.5 8.0 1.8 2,930 106 2.05 DW23 May 2009 18 4.1 Domestic water 18.4 7.5 3.2 1,671 198 2.06 DW25 May 2009 30 3.9 Domestic water 20.5 7.5 6.2 1,332 171 2.13 ZC May 2009 SU Sewage water ZD May 2009 SU Water from pond SUJL May 2009 SU River water 22.7 7.8 SULG May 2009 SU Sewage water 22.4 7.9 SUY May 2009 SU River water 18.9 7.9 SULD May 2009 SU Agricultural irrigation 20.5 7.8 ZKE December 2009 27 4.0 Observation well 17.8 7.3 1,676 −91.3 ZKW December 2009 27 3.6 Observation well 16.6 7.2 1,652 ZKS December 2009 27 4.1 Observation well 17.5 7.4 1,353 −87.2 ZKN December 2009 18 3.9 Observation well 18.4 6.6 3,999 ZF December 2009 18 4.2 Agricultural irrigation 16.1 7.4 1,502 ZG9 December 2009 9 3.7 Observation well 18.5 7.4 1,219 Z06 December 2009 15 2.8 Agricultural irrigation 16.8 7.3 1,378 Z16 December 2009 30 3.2 Agricultural irrigation 17.4 7.7 787 3420 Environ Monit Assess (2013) 185:3413–3444

Table 2 (continued)

Location Sampling Well depth Water depth Utilization T (°C) pH Turbidity EC Eh (mV) DO site time (m) (m) (μS/cm) (mg/L)

Z34 December 2009 28 4.0 Agricultural irrigation 15.6 7.2 1,985 Z40 December 2009 30 4.4 Agricultural irrigation 16.5 7.3 1,494 ZB December 2009 50 4.0 Domestic water 10.1 7.6 1,164 50.7 DW09 December 2009 16 3.2 Domestic water 15.8 7.0 1,726 DW25 December 2009 30 4.0 Domestic water 7.6 7.6 1,412 SUJL December 2009 SU River water 6.9 7.9 1,085

SU surface water, EC specific electrical conductivity, Eh redox potential, DO dissolved oxygen taken using precleaned, brown glass bottles, trans- purge and trap extraction systems followed by gas ported under anaerobic conditions in refrigerated box- chromatography/mass spectrometry (P&T-GC-MS). es to the laboratory, and stored in the dark under water Only SVOCs could be detected in the sediment sam- at 4 °C until the time of analysis. Water chemistry ples and were quantified by HPLC equipped with a characteristics of the samples are given in Table 2, variable wavelength fluorescence detector and a including temperature (°C), pH, turbidity, specific Supelcosil LC-PAH (250×4.6 mm i.d., 5 μm particle electrical conductivity (EC), redox potential (Eh), size, Supelco) column. The injection volume was and dissolved oxygen (DO). These parameters and 5.0 μL, and the column temperature was 30 °C. The water table depth were measured in the field. gradient elution program consisted of 65 % water and In each instance, duplicate water samples for volatile 35 % acetonitrile for 2 min, then 100 % acetonitrile for organic compound (VOC) measurement were collected 12 min at a flow rate of 2.0 mL/min. and placed in precleaned 40 mL amber glass bottles with All organic pollutants in the water samples, includ- Teflon-lined rubber septa. Samples for semivolatile or- ing VOCs, SVOCs, and OCPs, were analyzed in the ganic compound (SVOC) and OCP measurement were Ministry of Land and Resources P.R.C. Huadong collected in 1-L amber glass bottles. The bottles were Mineral Resources Supervision and Testing Center carefully filled to overflowing, without passing air bub- (Research Center of Nanjing Institute of Geology bles through the sample or trapping air in the sealed and Mineral Resources). bottles. Preparation of bottles included washing with VOCs in water samples were analyzed by P&T-GC/ detergent, rinsing with tap water, ultrapure water MS, derived from US EPA method 524.2 (Eichelberg (Millipore: Milli-Ro 5 plus and Milli Q plus 185), and and Bundle 1989). The Tekmar 3000 Purge and Trap acetone (Mallinckrodt Chemical Works St. Louis), and autosampler device, operated with Helium as a carrier placing in an oven at 150 °C for 2 h. At each site, HCL (4 (gas flux, 50 mL/min; purge time, 11 min), was drops 6 N/40 mL) was added to the water sample in order connected to a GC-MS system (HP 6980). A to bring the solution’s pH down to 2 and prevent bio- Carbopack C and B (Supelco) trap was used at a degradation and dehydrohalogenation (APHA 1992). desorption temperature of 225 °C and a desorption time of 4 min. An HP 5.5 % phenyl methyl siloxan Analytical procedure GC column was used for the separation of the target compounds (film thickness, 0.25 μm; interior diame- The analysis of organic pollutants in the sediment ter, 0.25 mm; length, 60 m). The mass spectrometer samples was performed at the National Research was operated at 315 °C in the selected ion mode. A Center for Geoanalysis. PAHs (US EPA Method stock solution of 2,000 μg/mL (EPA 524, Supelco) of 8310) were tested by high performance liquid chro- both fluorobenzene and 1,2-dichlorobenzene-d4 in matography–mass spectrometry (HPLC-MS), OCPs methanol was diluted to 200 μg/mL and used as an (US EPA Method 8081A) were measured by gas chro- internal standard for calibration. matography with electron capture detector (ECD), and SVOCs (mainly PAHs) in water samples were de- VOCs (US EPA Method 8260B) were analyzed by termined by HPLC-MS, derived from US EPA method Environ Monit Assess (2013) 185:3413–3444 3421

610. PAHs in the water samples were analyzed using acid, disooctyl ester), and benzo(b)fluoranthene. The an HPLC (Waters 5890) with UV detector and a concentrations of SVOCs in the sediments varied to a Waters 3.9×300 mm μBondapak C18 reverse phase great extent at different sampling depths. The total column. The HPLC was operated under the following concentration of ∑SVOCs in sediments sampled in conditions: a flow rate of 1.8 mL/min, an injection May 2009 ranged between 3.8 and 10.4 ng/mg. As volume of 15 μL, a wavelength of 254 nm, and a the bottom of the waste disposal site is at 9.3 m depth, mobile phase of acetonitrile to water of 80:20, and the detected types of SVOCs and their total concen- with isocratic flow conditions. The concentrations of trations are greater at this depth than at others. The 11 PAHs were quantified in this study. According to core was taken from the base of the landfill (starting at their elution orders, they were acenaphthene (Acp), 9.3 m depth) for 2.2 m into silty clay (Fig. 3). fluorene (Flu), phenanthrene (Phe), anthracene (Ant), Therefore, as a whole, the concentrations of different fluoranthene (FLT), pyrene (Pyr), benzo(a)anthracene SVOCs are characterized by a decrease with depth. It (BaA), chrysene (CHR), benzo(b)fluoranthene (BbF), can be seen from Table 1 that phenol-d5, phenol,2- and benzo(k)fluoranthene (BkF).The detection limits fluoro, nitrobenzene-d5, 1,1-biphenyl ss, and p-ter- for these congeners are 0.2, 0.01, 0.005, 0.01, 0.01, phenyl-d14 were continually detected at all seven 0.005, 0.002, 0.001, 0.001, 0.002, and 0.001 μg/L, depths. Figure 2 shows the vertical variation of these respectively. five compounds in the core profile. The total concen- OCPs and other pesticides in water samples were trations of the five compounds are highest (≥9.6 μg/kg) detected by GC using a Hewlett Packard Gas at 10.5–10.7 m depth, and lowest (≥ 3.6 μg/kg) at Chromatograph 5890 Series II, supported by a 63Ni 10.9–11.1 m depth. The silty clay, 3.2 m thick, exists ECD, derived from US EPA Method 8081A. A 30 m× from 9.4 to 12.6 m depth and can be regarded as a 0.53 mm i.d.×0.5 μm film thickness fused silica cap- natural barrier for preventing direct pollution from the illary column HP-608 was used for the chromato- landfill into underlying material. graphic separation of pesticides. Helium was used as There are seven PAHs in the detected 16 SVOCs, the carrier gas and nitrogen as the makeup gas, and the namely, naphthalene, (naphthalene, 1-methyl), diben- injection technique was split/splitless. The detection zofuran, fluorene, phenanthrene, anthacene, and benzo limit for OCPs is 0.01 μg/L. (b)fluoranthene. The total PAH concentrations Detailed procedures for sample collection, transpor- (Table 1) at the different depths range from 0 to tation, extraction, and cleanup were referenced from 990 μg/kg. According to the classification standards the Geological Survey Standard of Groundwater of Maliszewska-Kordybach (1996), sediments with Pollution (China Geological Survey 2008). Quality PAH concentrations close to 1,000 μg/kg at 9.3 m control samples were prepared and analyzed for each depth, namely, at the bottom of the landfill, are heavily batch of samples. The QC results showed that the contaminated. Conversely, the detected PAH concen- deviation between duplicates was within 20 % and trations below 100 μg/kg (∑PAHs) at the remaining the recovery of laboratory control standards was six depths could be indicative of low pollution in between 80 and 120 %. sediment.

Surface and groundwater Results and Discussion General characteristics Concentration variation of organic pollutants in the core profile The physicochemical characteristics of the water samples can be seen in Table 2. EC values range from 0.4 Sixteen SVOCs (Table 1) have been detected in the to 4 mS/cm in groundwater samples, with total dis- sediment samples, including phenol-d5, (phenol, 2- solved solid (TDS) between 0.4 and 3.9 g/L, pH 6.6 fluoro), phenol, (phenol, 3-methyl), nitrobenzene-d5, and 8.9, DO 0.5 and8.7 mg/L, and turbidity 0.1 and naphthalene, (naphthalene, 1-methyl), (1,1-biphenyl 17.2. EC values range from 0.6 to 3.3 mS/cm in ss), dibenzofuran, fluorene, phenanthrene, anthacene, surface water samples, with TDS between 0.6 and dibutyl phthalate, p-terphenyl-d14, (1,2-benzenedi 1.1 g/L, pH 7.7 and 8.1, DO 3.1 and 5.8 mg/L, and 3422 Environ Monit Assess (2013) 185:3413–3444 turbidity up to 90. The groundwater sample (ZKN) rate of the CAHs, MAHs, HAHs, OCPs and other in the north of the landfill shows a high mineral pesticides, and PAHs in water samples. The detected content (EC ≥4mS/cm),whichisduetoalarge results of these organic compounds in the water sam- number of anthropogenic sources. The pHs of the ples are shown in Tables 4 and 5. The relative percent- groundwaters at the Zhoukou landfills were slightly age of the total concentration of the detected pollutants alkaline (Table 2). The mean pHs of groundwaters can be seen from the pie map in Fig. 4, showing PAHs were 7.57 and 7.40 in May 2009 and December are the main organic contaminants in shallow aquifers 2009, respectively. around the Zhoukou landfill. The pulse of oxygen introduced by lowering the water table likely causes a partial and temporal oxidation of CAH, MAH, and HAH in water samples previously reduced species. The dissolved oxygen (DO) values of the wells with 9 m depth are >1 mg/L, indicat- Seven CAHs (out of 29 analyzed) were detected in ing the condition is aerobic. The phenolic compounds the water samples, namely, dichloromethane, chlo- generally degrade readily under aerobic conditions, roform, 1,2-dichloroethane, 1,2-dichloropropane, while nitrification of ammonium can also occur if oxy- cis-1,2-dichloroethylene, tetrachloroethylene, and gen is present. However, as nitrifying bacteria grow 1,1,2,2-tetrachloroethane. Besides groundwater slowly relative to heterotrophic bacteria responsible for samplesZKN,ZG7,andZG11(all≤0.2 μg/L) from degradation of organic compounds, available oxygen May 2009, CAHs were mainly detected in surface may be utilized in the degradation of organic substances water samples with concentrations ranging between thereby preventing nitrification (Keener and Arp 1994). 0.2 and 2.8 μg/L. Comparing these concentrations Nitrification has also been observed to be inhibited in the with the drinking water quality standards (GB5749- presence of phenols due to their toxicity (Stafford 1974; 2006) (e.g., chloroform, 60 μg/L; 1,2-dichloropro- Dyreborg and Arvin 1995). pane, 5 μg/L; tetrachloroethylene, 5 μg/L), the In the interior of the Zhoukou landfill, levels of CAH concentrations in these water samples are alkalinity were very high (average 1,025 mg/L as not above the standards, indicating low levels of

CaCO3), and they decreased along flow path to about contamination, probably by industrial discharge in 155 mg/L at ZKW. Excess of the alkalinity relative to sewage water. calcium (Ca) is likely to be derived from the biodeg- Nine MAHs (out of 14 analyzed) were detected, radation of organic matter (Borden et al. 1995; including benzene, toluene, ethylbenzen, ortho- Basberg et al. 1998; Lee et al. 2001). The alkalinity xylene, m+p-xylenes, 1,2,4-trimethylbenzene, isobu- values of groundwater samples in the Zhoukou landfill tylbenzene, styrene, and isopropylbenzene. ranged between 155 and 2,045 mg/L in May 2009. As Concentrations of the total MAHs ranged from 0.57 expected, the nearest well (ZG11) to the landfill showed to 8.96 μg/L in surface water (highest in sewage water the highest values of alkalinity (2,045 mg/L), which ZC), and 0.12 μg/L (Z34, depth 28 m) to 1.14 μg/L indicates that groundwater near landfill site is being (ZG7, depth 9 m) in groundwater samples (mainly significantly affected by leachate percolation. from May 2009). Only one HAH (out of 9 analyzed), Thirty-one organic compounds (out of 92 analyzed) namely 2-chlorotoluene, was detected in the water exceeded detection limits. Table 3 shows the detection sample ZG12.

Table 3 Frequency of detection (%) in water samples Sampling time Number of CAHs MAHs HAHs OCPs+other PAHs samples pesticides

December 2008 10 (GW) 0 20.0 0 0 40.0 3 (SU) 66.7 66.7 0 66.7 66.7 May 2009 17 (GW) 23.5 58.8 5.9 5.9 76.5 6 (SU) 83.3 50.0 0 0 16.7 December 2009 13 (GW) 0 0 0 0 76.9 GW groundwater samples, SU 1 (SU) 0 0 0 100 surface water samples nio oi ses(03 185:3413 (2013) Assess Monit Environ Table 4 CAH, MAH, and HAH concentrations in water samples

Location Sampling CAHs (μg/L) MAHs (μg/L) HAHs (μg/L) site time DCM TCM 1,2-DCA 1,2- cis-1,2- PCE 1,1,2,2- ∑CAHs B (0.2)a T (0.1)a E (0.1)a o-X m+p-X 1,2,4- IBB Styrene IPB ∑MAHs 2-Chlorotoluene (0.2)a (0.1)a (0.2)a DCP DCE (0.1)a PCA (0.1)a (0.2)a TMB (0.1)a (0.1)a (0.1)a (0.1)a (0.2)a (0.1)a (0.1)a (0.1)a

ZA December ------2008 ZB December ------2008 ZC December 0.41 0.63 0.66 0.47 - 0.63 - 2.8 - 8.15 0.17 0.22 0.42 - - - - 8.96 - 2008 –

ZD December ------3444 2008 ZE December - - 1.3 - - 0.25 - 1.55 - 1.33 0.16 ------1.49 - 2008 ZF December ------2008 ZG December ------2008 Z6A December ------2008 Z6 December ------2008 SW29 December ------0.51 ------0.51 - 2008 SW49 December ------2008 SW59 December ------2008 ZK1 December ------0.44 ------0.44 - 2008 ZKE May 2009 ------ZKW May 2009 ------0.13 ------0.13 - ZKS May 2009 ------ZKN May 2009 - - - - 0.15 - - 0.15 0.44 ------0.13 0.57 - ZF May 2009 ------ZG7 May 2009 - - - - 0.19 - - 0.19 0.97 - - 0.17 - - - - - 1.14 - ZG9 May 2009 ------0.19 ------0.19 - ZG10 May 2009 ------ZG11 May 2009 ------0.16 0.16 0.55 ------0.55 - ZG12 May 2009 ------0.37 ------0.37 0.26

Z16 May 2009 ------0.24 ------0.24 - 3423 Z34 May 2009 ------0.12 ------0.12 - 3424 Table 4 (continued)

Z40 May 2009 ------0.2 ------0.2 - DW09 May 2009 ------DW18 May 2009 - - 0.97 1.25 - - - 2.22 0.5 ------0.5 - DW23 May 2009 ------DW25 May 2009 ------ZC May 2009 - 0.26 0.38 0.38 - 0.61 - 1.63 - 5.43 1.14 - 1.45 0.13 0.13 0.59 - 8.87 - ZD May 2009 - - - - - 0.22 - 0.22 ------SUJL May 2009 - 1.33 - - - - - 1.33 ------SULG May 2009 ------1.07 ------1.07 - SUY May 2009 - 1.81 - - - - - 1.81 ------SULD May 2009 - - 1.11 - - - - 1.11 - 0.57 ------0.57 -

No CAH, MAH and HAH has been detected in water samples collected in December 2009 CAHs chlorinated aliphatic hydrocarbons (including DCM dichloromethane, TCM chloroform, 1,2-DCA 1,2-dichloroethane, 1,2-DCP 1,2-dichloropropane, cis-1,2-DCE cis-1,2- dichloroethylene, PCE tetrachloroethylene, 1,1,2,2-PCA 1,1,2,2-tetrachloroethane), MAHs monocylic aromatic hydrocarbons (including B benzene, T toluene, E ethylbenzen, o-X ortho-xylene; m+p-X m+p-xylenes; 1,2,4-TMB 1,2,4-trimethylbenzene, IBB isobutylbenzene, IPB isopropylbenzene), HAHs halogenated aromatics hydrocarbons a Detection limit nio oi ses(03 185:3413 (2013) Assess Monit Environ – 3444 nio oi ses(03 185:3413 (2013) Assess Monit Environ Table 5 OCP and PAH concentrations in water samples

Location Sampling OCPs (μg/L) PAHs (μg/L) site time BHC γ-chlordane Endosulfan-I Endosulfan Nap Acp Flu Phe Ant FLT Pyr BaA CHR BbF BkF ∑PAHs (0.01)a (0.01)a (0.01)a sulfate (0.2)a (0.01)a (0.005)a (0.01)a (0.01)a (0.005)a (0.002)a (0.001)a (0.001)a (0.002)a (0.001)a (0.01)a

ZA December - - - - - 0.38 0.682 0.519 0.168 0.261 0.158 0.0181 - - - 2.19 2008 ZB December ------2008 ZC December - 0.058 - - - - 0.0477 0.125 - 0.0323 0.0306 - - - - 0.24 2008 –

ZD December ------3444 2008 ZE December - 0.014 - - - - 0.0184 0.043 - 0.0097 0.007 - - - - 0.08 2008 ZF December - - - - - 0.215 0.362 0.452 0.079 0.153 0.0815 0.0086 - - - 1.35 2008 ZG December ------0.0241 0.033 ------0.06 2008 Z6A December ------2008 Z6 December ------2008 SW29 December ------2008 SW49 December - - - - 0.6 ------0.60 2008 SW59 December ------2008 ZK1 December ------2008 ZKE May 2009 0.18 - - - - 0.147 0.3642 0.8299 0.174 0.2984 0.1763 0.0334 0.0396 0.0131 0.0042 2.08 ZKW May 2009 ------0.2793 0.645 0.122 0.3549 0.1691 0.029 0.0363 - - 1.64 ZKS May 2009 - - - - - 0.144 0.2971 0.5953 0.117 0.2096 0.1224 0.0139 - - - 1.50 ZKN May 2009 - - - - - 0.06 0.177 0.2833 0.038 0.0531 0.0295 - - - - 0.64 ZF May 2009 - - - - - 0.212 0.4391 0.7569 0.168 0.2753 0.1578 0.0214 0.0207 - - 2.05 ZG7 May 2009 ------0.0259 0.028 ------0.05 ZG9 May 2009 ------0.02 0.024 ------0.04 ZG10 May 2009 ------0.0338 0.028 ------0.06 ZG11 May 2009 - - - - - 0.02 0.0395 0.0312 ------0.09 ZG12 May 2009 ------0.0215 0.0189 ------0.04

Z16 May 2009 - - - - - 0.115 0.2596 0.3552 0.075 0.1474 0.097 0.0093 0.0099 - - 1.07 3425 Z34 May 2009 - - - - - 0.129 0.2818 0.452 0.104 - 0.0943 0.0118 0.0098 - - 1.08 3426 Table 5 (continued)

Z40 May 2009 ------0.0137 - - 0.0818 0.1471 0.0095 - - - 0.25 DW09 May 2009 ------DW18 May 2009 ------DW23 May 2009 ------DW25 May 2009 ------ZC May 2009 ------0.0465 0.1189 - 0.0581 0.0348 0.0077 0.0134 - - 0.28 ZD May 2009 ------SUJL May 2009 ------SULG May 2009 - - - 0.088 ------SUY May 2009 ------SULD May 2009 - - 0.021 ------ZKE December 2009 ------0.0322 0.017 - 0.016 0.0097 - - - - 0.07 ZKW December 2009 ------0.0311 0.066 0.015 0.0327 0.0213 - - - - 0.17 ZKS December 2009 - - - - - 0.025 0.0869 0.103 0.041 0.1135 0.057 0.0077 0.0076 - - 0.44 ZKN December 2009 - - - - - 0.014 0.0491 0.108 0.023 0.0339 0.026 - - - - 0.25 ZF December 2009 - - - - - 0.013 0.0506 0.142 0.027 0.0272 0.0491 0.0344 0.0053 - - 0.35 ZG9 December 2009 ------0.0916 0.196 0.028 0.0301 0.0195 - - - - 0.37 Z06 December 2009 ------

Z16 December 2009 ------0.0625 0.156 0.026 0.0457 0.0361 0.0033 0.0033 - - 0.33 185:3413 (2013) Assess Monit Environ Z34 December 2009 ------0.0323 0.0466 - - - - 0.08 Z40 December 2009 ------0.0732 0.171 0.033 0.0661 0.0525 0.005 0.0058 - - 0.41 ZB December 2009 ------0.006 - - - - 0.01 DW09 December 2009 ------DW25 December 2009 ------SUJL December 2009 ------0.008 - - - - 0.01 a Detection limit OCPs organochlorine pestcides (BHC benzene hexachloride), PAHs polycyclic aromatic hydrocarbons (Nap naphthalene, Acp acenaphthene, Flu fluorine, Phe phenanthrene, Ant anthracene, FLT fluoranthene, Pyr pyrene, BaA benzo(a)anthracene, CHR chrysene, BbF benzo(b)fluoranthene, BkF benzo(k)fluoranthene) – 3444 Environ Monit Assess (2013) 185:3413–3444 3427

Fig. 4 Total frequency of the detected organic compounds in the groundwater samples, like CAHs, OCPs, MAHs, and PAHs

BTEX compounds (benzene, ethylbenzene, tolu- The detection rate of BTEX in May 2009 is higher ene, and three isomers of xylene) of MAHs are clas- than that in December 2009. BTEX concentrations at sified as environmental priority pollutants, which may individual boreholes were highly variable over time. not exceed 10, 700, 300, and 500 μg/L in drinking These temporal variations appeared to result from not water, respectively, according to the National Chinese only hydraulic variations and seasonal groundwater (NC) standards (GB-5749-2006). They are commonly flow variations but also preferential dissolution and found together in crude petroleum and petroleum biodegradation. In particular, systematic decreases in 2− − products such as gasoline and diesel fuel. The pres- SO4 concentrations, increases in HCO3 concentra- ence of these hydrocarbons in the environment is a tions, and the presence of degradation products in hazard to public health and an ecological concern, due regions of the plume where BTEX concentrations are to their toxicity and ability to bioaccumulate through relatively high are indicative of degradation processes the food chain (Brigmon et al. 2002). BETX are (Grbic-Galic and Vogel 1987; Wiedemeier et al. prominent components of gasoline, and their presence 1995). Ranking the hydrocarbon compounds by the in water is usually an indication of gasoline contami- plume-scale degradation rate estimate, from highest to nation. The contaminants in this study do not exceed lowest rate gave the order: toluene, o-xylene, naphtha- the defined limits for Chinese drinking water stand- lene, m-andp-xylene, trimethylbenzene, ethylben- ards, which is the same with the World Health zene, and benzene (Davis et al. 1999). For an Organization (WHO) guidelines for drinking water aerobic, nitrate-rich BTEX contaminated aquifer, quality (WHO 2006).Toluene is mainly detected in Daniel and Borden (1997) found highest degradation the water samples from the Low-Lying Gully and rates near the source of their plume, with decreasing sewage ditch (ZC), xylene detected in the sewage degradation rates with distance down the plume. ditch (ZC), and benzene mainly detected in ground- During biodegradation, microorganisms transform water samples (such as ZG7, ZKN, ZG11, and ZG12 available carbon into forms useful for energy and cell at 9 m depth) close to the landfill. production. This results in oxidation of the electron 3428 Environ Monit Assess (2013) 185:3413–3444 donor (such as organic matter) and reduction of elec- for local point polluted by OCPs in the eastern part of tron acceptor [such as DO, nitrate, iron (III) or Mn the landfill, there is less pesticide contribution to the (III), sulfate, and carbon oxide] (Essaid et al. 1995;Lu shallow aquifer. Three kinds of common pesticides et al. 1999). The aquifer near the landfill is character- (out of 13 analyzed), including γ-chlordane (detected ized by elevated BTEX concentrations in May 2009, in ZC and ZE), endosulfan-I and endosulfan sulfate, relatively low concentrations of nitrate, and sulfate. In were detected in water sample from the sewage ditch contrast, the distribution area of low BTEX concen- with concentrations varying from 0.021 to 0.088 μg/L, trations (Fig. 5e) under aerobic condition (DO indicating that local agricultural activities contribute detected over 1 mg/L) and nitrate (Fig. 5b), sulfate irrigation return flows to the sewage water. This is also (Fig. 5c), and manganese (Fig. 5d) concentrations is a potential source for some shallow groundwater pol- high. The in situ microbes seem to be using fuel lution due to the untreated bed of the sewage ditch. hydrocarbons as their carbon and energy sources, The sources of pesticide residues in the waters studied thereby contributing to the natural removal process. are agricultural practices within the study area, in combination with rainfall. Maximum concentrations OCPs and other pesticides in water samples of this compound were detected in May, possibly due to surface run-off. The spatial and temporal dis- From Table 5, it can be seen that only one OCP (out of tribution of pesticides obtained from the monitoring 11 analyzed), namely, benzene hexachloride was network shows no clear trends for prediction of future detected in the groundwater sample ZKE (27 m depth) concentrations. Nitrate–N concentrations and pesticide with a concentration of 0.18 μg/L, which is far below detections show no clear relationship, suggesting dif- the Chinese drinking water standard of 5 μg/L. With ferent source, transport, or degradation pathways. the exception of well ZKE, groundwater samples are not contaminated by OCPs and other pesticides, which PAHs distribution in water samples have been detected in drainage canals in the east of the landfill and in water from the LuDong Trunk Canal PAHs are the main contaminants of concern detected and the Low-Lying Gully. This indicates that, except in the water samples. Unlike CAHs, MAHs, HAHs,

Fig. 5 Concentration contours for the chloride (a), nitrate (b), sulfate (c), manganese (d), BTEX (e), and PAHs (f) of groundwater samples in May 2009. Units are micrograms per liter for BTEX and PAHs and milligrams per liter for the rests Environ Monit Assess (2013) 185:3413–3444 3429

is 0.6 μg/L for two-ring PAHs (Nap), ranged 0.01– 1.75 μg/L for three-ring PAHs (Acp, Flu, Phe, and Ant), 0.01–0.59 μg/L for four-ring PAHs (FLT, Pyr, BaA, and CHR), and 0.02 μg/L for five-ring PAHs (BbF and BkF). The total concentrations of these 11 PAHs in water ranged from 0.01 μg/L at well ZB to 2.19 μg/L at well ZA, with a mean concentration of 0.62 μg/L (Table 5). The three dominant PAHs found in most groundwater samples are Phe, Flu, and FLT in the study area (Fig. 8). They formed 0–52 (mean, 35)%, 0–46 (mean, 19)%, and 0–40 (mean, 17)% of the total PAHs, respectively. The lower molecular weight (LMW, two to three rings) PAHs Fig. 6 Non-outlier range, interquartile range (IQR), and median dominate in all samples with the exception of Z40. concentrations (box-and-whisker plots)of∑11PAHs in shallow groundwater samples (ZKE, ZKS, ZKW, ZKN, Z16, Z34, Z40, Generally, PAHs from a petrogenic source show a ZF and ZG9) during the two sampling campaigns depletion of higher molecular weight (HMW, four to six rings) PAHs relative to LMW PAHs, while pyrogenic sources are abundant in HMW PAHs and OCPs, most groundwater samples contained (Zakaria et al. 2002). Most groundwater around PAHs in the summer and winter 2009 samples, with the Zhoukou landfill not only contains a consider- a high detection rate of more than 75 % (Table 3). able amount of LMW PAHs but is also abundant in PAH concentrations in nine representative wells HMW PAHs, indicating the input of both petrogenic and (Fig. 6) varied from 0.04 to 2.08 μg/L in May 2009 pyrogenic origins. and from 0.07 to 0.44 μg/L in December 2009, indicating that rainfall can enhance contaminant leakage Source and degradation of PAHs from the waste disposal site into groundwater during the summer. It is clear that PAH concentrations in Source diagnosis by diagnostic ratios of PAHs summer are higher than those in winter. Many of the PAH compounds in water samples were present at Inferring the sources of PAHs is widely considered to concentrations in excess of 1 μg/L, suggesting that be very important to study the transport and fate of water in this area was heavily contaminated (Zhou PAHs in environment (Wan et al. 2006). Generally, and Maskaoui 2003), especially in May 2009. In this ratios of various PAH concentrations have usually study, the heavily contaminated water samples, such been undertaken to diagnose the possible sources of as ZA and ZF sampled in December 2008, and ZKE, PAHs (Fernandes et al. 1997; Yunker et al. 2002). ZKS, ZKW, ZF, Z16, and Z34 sampled in May 2009, When the concentrations of different PAHs in water mainly occur at water depths of 18–30 m, in some cases with concentrations of total PAHs (in ZKE and ZF) beyond 2 μg/L (Fig. 7). The detectable propor- tions of three- and four-ring PAHs were the highest, with two- and five-ring PAHs the lowest (Fig. 6). Univariate Pearson correlation matrix (Table 6) shows a good correlation among all PAHs except BaA. Higher Pearson coefficients of different PAHs under the 0.01 significant level can reflect the similar pollution sources, e.g., Acp, Ant, FLT, and Pyr. Eleven PAHs (out of 16 analyzed) were detected, including Nap, Acp, Flu, Phe, Ant, FLT, Pyr, BaA, CHR, BbF, and BkF. No six-ring PAHs were detected Fig. 7 Plots (a) of PAHs concentrations corresponding to in water samples. The detected concentrations in water groundwater sampling depth 3430 Environ Monit Assess (2013) 185:3413–3444

Table 6 Pearson coefficient of different PAHs in the groundwater samples (n026) around the Zhoukou landfill

Acp Flu Phe Ant FLT Pyr BaA CHR PAHs

Acp 1 Flu 0.99a 1 Phe 0.69b 0.86a 1 Ant 0.80a 0.90a 0.95a 1 FLT 0.76b 0.80a 0.92a 0.93a 1 Pyr 0.75a 0.71a 0.94a 0.96a 0.91a 1 BaA -0.10 0.28 0.51 0.47 0.51 0.51 1 CHR 0.60 0.71b 0.88a 0.84a 0.94a 0.94a 0.67b 1 PAHs 0.88a 0.95a 0.97a 0.98a 0.93a 0.84a 0.47 0.86a 1 a Correlation is significant at the 0.01 level (two-tailed) b Correlation is significant at the 0.05 level (two-tailed) samples reaches the quantitation limit, some selected pyrogenic and petrogenic values, compared with the diagnostic ratios have been calculated and shown in reported values for particular processes (Table 8). Table 7. Most of the water samples detected PAHs in Petroleum often contains more thermodynamically this study show these ratios intermediate between stable compounds such as Nap, Flu, Phe, and CHR,

Fig. 8 Distribution of organic compound groups identified in GC-MS full scan analysis. ∑PAHs denotes total PAH concen- water samples around the landfill a in May 2009 and b in tration, i.e., the sum of the individual mass concentrations of the December 2009. Results are based on GC peak areas of the 11 PAH congeners Environ Monit Assess (2013) 185:3413–3444 3431

Table 7 Diagnostic ratios used with their typically reported values for particular processes

PAH ratio Value range Source Reference This study

∑LMW/∑HMW <1 Pyrogenic Zhang et al. 2008; Budziński 0.06–8.34 et al. 1997 >1 Petrogenic Flu/(Flu+Pyr) <0.5 Petrol emissions Ravindra et al. 2008b 0.09–0.86 >0.5 Diesel emissions Ant/(Ant+Phe) <0.1 Petrogenic Pies et al. 2008 0.12–0.29 >0.1 Pyrogenic FLT/(FLT+Pyr) <0.4 Petrogenic Gogou et al. 1998;DeLa 0.36–0.68 Torre-Roche et al. 2009 0.4–0.5 Fossil fuel combustion >0.5 Grass, wood, coal combustion FLT/Pyr <1 Petrogenic Sicre et al. 1987; Baumard 0.55–2.1 et al. 1998a; b >1 Pyrogenic BaA/(BaA+CHR) <0.2 Petrogenic Akyüz and Çabuk 2010; 0.37–0.87 Yunker et al. 2002; Wang et al. 2010 0.2–0.35 Coal combustion >0.35 Combustion CHR/BaA <1 Pyrogenic Soclo et al. 2000 0.15–1.74 >1 Petrogenic Phe/Ant <10 Pyrogenic Baumard et al. 1998 a; 2.51–7.46 b; Cao et al. 2005 >15 Petrogenic while FLT and Pyr are usually the most abundant been suggested as diagnostic indicator for distin- compounds for pyrolytic PAHs (Doong and Lin guishing between pyrogenic and petrogenic sources 2004). The FLT/Pyr and FLT/(FLT + Pyr) ratios can be with values >0.1 indicating pyrolytic souces, where- useful tools to check PAHs pollution origin (Gschwend as <0.1 suggest petrogenic (Budzińskietal.1997). and Hites 1981; Gogou et al. 1998;Magietal.2002). In this study, this ratio is >0.1 for the water samples Values of FLT/Pyr <1, FLT/(FLT + Pyr) <0.5, Phe/ (e.g., ZA, ZF, ZKE, and ZKS in Table 6)whereAnt Ant >15, and CHR/BaA >1 indicate a petrogenic and Phe are detectable, indicating dominance of fuel origin of contamination (De Luca et al. 2004). In combustion and coal burning processes in these this context, Z40 (May), Z34 (December), ZF sample sites. Most samples with Phe/Ant <10 and (December) show a strong petrogenic character FLT/Pyr <1 were characterized as a mixture of py- and that FLT/Pyr and FLT/(FLT + Pyr) ratios are rolytic and petrogenic contamination, which is in much below 1 and 0.5, respectively, where the good agreement. rests show ratios compatible with pyrogenic sour- The distribution of LMW and HMW PAHs is also a ces of contamination, probably originate mainly tool for identifying the petrogenic/pyrolytic origin of from grass, wood, and coal combustion. PAHs (Sicre et al. 1987; Budziński et al. 1997). The Similar results were observed for the CHR/BaA higher the LMW/HMW ratio is, the higher the preva- ratios. CHR and BaA are both derived from the com- lence of petrogenesis on pyrolytic origin of PAHs is bustion processes with CHR/Pyr ratio lower than 1. (De Luca et al. 2004). The LMW/HMW ratios of the This ratio in this study ranges between 0.15 and 1.74, collected water samples range from 0.06 to 8.34 with indicating combustion processes and petroleum hydro- mean value of 3.24. Except for Z34 (May) and Z40 carbons are the possible main source of PAHs in water (December), Table 3 also shows that LMW are clearly samples in this study. The ratio Ant/(Ant + Phe) has predominant over HMW, suggesting a definite 3432 Environ Monit Assess (2013) 185:3413–3444

Table 8 PAH characteristics and diagnostic ratios from water samples around the Zhoukou landfill

ID ∑PAHs LMW/ LMW% HMW% Phe/ Flu/ FLT/ FLT/ CHR/ Ant/ BaA/ HMW Ant (Flu+Pyr) Pyr (FLT+Pyr) BaA (Ant+Phe) (BaA+CHR)

Water samples in May 2009 ZKE 2.08 2.68 72.8 27.2 4.77 0.67 1.69 0.63 1.19 0.17 0.46 ZKS 1.50 3.33 76.9 23.1 5.09 0.71 1.71 0.63 0.16 ZKW 1.64 1.89 64.0 33.8 5.29 0.62 2.10 0.68 1.25 0.16 0.44 ZKN 0.64 6.76 87.1 12.9 7.46 0.86 1.80 0.64 0.12 ZC 0.28 1.45 59.2 40.8 0.57 1.67 0.63 1.74 0.36 ZF 2.05 3.32 76.8 23.2 4.51 0.74 1.74 0.64 0.97 0.18 0.51 Z16 1.07 3.17 75.3 23.7 4.74 0.73 1.52 0.60 1.06 0.17 0.48 Z34 1.08 8.34 89.3 10.7 4.35 0.75 0.83 0.19 0.55 Z40 0.25 0.06 5.4 94.6 0.09 0.56 0.36 Water samples in December 2009 ZG9 0.37 6.36 86.4 13.6 7.00 0.82 1.54 0.61 0.13 Z34 0.08 0.00 0.0 100.0 0.69 0.41 ZF 0.35 2.01 66.7 33.3 5.26 0.51 0.55 0.36 0.15 0.16 0.87 ZKN 0.25 3.24 76.4 23.6 4.70 0.65 1.30 0.57 0.18 ZKE 0.07 1.91 65.7 34.3 0.77 1.65 0.62 ZKS 0.44 1.38 57.9 42.1 2.51 0.60 1.99 0.67 0.99 0.28 0.50 ZKW 0.17 2.08 67.5 32.5 4.40 0.59 1.54 0.61 0.19 Z40 0.41 2.24 68.2 30.4 5.18 0.58 1.26 0.56 1.16 0.16 0.46 Z16 0.33 2.87 73.4 25.6 6.00 0.63 1.27 0.56 1.00 0.14 0.50

petrogenic origin of PAHs. The low solubilities of (Fig. 9) obtained by PCA can show the similarities LMW PAHs compared to the HMW compounds or dissimilarities between ambient PAH profiles. (Lee and Lee 2004; Sahu et al. 2004) may also be After autoscaling, two significant components were responsible for the high ratios in water, as opposed to identified, giving account for 62.5 and 16.3 % of the source material alone (Tobiszewski and Namieśnik total variance, respectively. The third component takes 2012). These results showed that the PAHs contami- into account only 8.9 % of the total variance and was nation in this study was probably from mixture sour- not considered in the present analysis. Figure 9a ces of petroleum and combustion products. shows the loading plot and substantiates that the first component is mainly related to Phe, FLT, Ant, Pyr, Source apportion by principal component analysis Acp, Flu, and BaA, whereas the second component is mainly related to BkF, BbF, and CHR. High To provide insight into the accuracy and quantification loads of Pyr, Phe, and FLT might be an indication of source apportion, principal component analysis of diesel combustion (Ravindra et al. 2008a). There (PCA) was applied to analyze the data set. PCA are also three groups identified on the factor score reduces the number of variables in the original data plot (Fig. 9b). Group 1 clusters samples (such as set into principal components without significant loss ZG7, ZG9, and ZG10) mostly collected around the in the total variance of the data. The loading that each landfill in Decemeber; group 2, samples collected variable in the original data contributes to the principal from ZKN, ZKW, Z16, and Z34 in May and ZF in components enables grouping of data with similar December; and group 3 only contains one sample, behaviors. Values below the detection limit were which collected from the ZA. The discrimination in replaced by half of the method detection limits for three groups was confirmed by hierarchical cluster- the statistical analysis. The score and loading plots ing analysis (Fig. 10). Environ Monit Assess (2013) 185:3413–3444 3433

Fig. 9 Principal component analysis (PCA) loadings for PAHs component 1 and 2 (PC1 and PC2) account for 62.5 and 16.3 % in groundwater samples in the Zhoukou landfill site: a Principal of the variance in the data set, respectively (ZKE not reported components loading plot and b component score plot. Principal here because located outside the graph b)

Fig. 10 Hierarchical clus- tering of the PAHs concentrations from water samples around the Zhoukou landfill 3434 Environ Monit Assess (2013) 185:3413–3444

The samples circled in the group 1 contain similar table on organic contaminant degradation under field contaminants, particularly Nap, with a high contribu- situations. From laboratory experiments, it was demon- tion relative to the other PAHs. The samples in the strated that fluctuating the water table enhanced the group 1are mostly those collected around the landfill. degradation of diesel oil (Rainwater et al. 1993). It can Samplesingroup2weremostlycollectedinMay be expected that the dynamics regime imposed by a 2009 and show similar characteristics, which may be fluctuating water table and the resulting differences in related to the origins of contamination and timing of unsaturated zone (e.g., soil aeration), not only affect the the sampling. These samples are characterized by pos- microbial and chemical reactions that organic pollutants itive loading in the PC2 and negative loading in PC1, undergo but also the transport of gases and solutes so have more contribution from Phe, Ant, FLT, Pyr, through the aquifer (Sinke et al. 1998). Flu, and Acp the than other samples. Although the Some studies showed that some LWM PAHs are sample of ZA of the group 3 was collected from the biosusceptible and can be biodegraded more rapidly shallow aquifer west of the landfill with the highest than the HMW PAHs (Hinga 2003;Rothermichet total PAHs concentration (up to 2.19 μg/L); CHR, al. 2002). PAHs are known to dissipate under BaA, and Flu make up a relatively high contribution nitrate- and sulfate-reducing conditions; sometimes, to ZA. HMW PAHs after LMW PAHs have been utilized/ degraded (Meuller et al. 1989), while the presence Degradation of PAHs of phenanthrene is reported to inhibit degradation of pyrene (McNally et al. 1999). Because HMW Although PAH may undergo adsorption, volatiliza- PAHs (such as Pyr, BaA, and BbF) are more resis- tion, photolysis, and chemical degradation, microbial tant to microbial degradation processes, they tend degradation is the major degradation process (Zaidi to persist longer in contaminated environments (van and Imam 1999; Christensen et al. 2001; Haritash and Brummelen et al. 1998; Neilson and Allard 1998; Kaushik 2009). Sorption of leachate organic matter on Bosma et al. 2001), and their degradation pathways to aquifer material seems to be of only minor signifi- are less well understood. cance according to column experiments reported in the The Gibbs free energy for oxidation of organic literature (Christensen 1992; Rügge et al. 1995). The carbon decreases at neutral pH in the order: O2, − 2− biodegradation of PAHs has been observed under both NO3 ,MnO2, Fe(OH)3,SO4 ,andCO2 (van aerobic and anaerobic conditions (Haritash and Breukelen 2003; Wilson et al. 2004). Therefore, aero- Kaushik 2009), which depends on the environmental bic degradation followed by nitrate reduction oxidizes conditions, number and type of the microorganisms, organic carbon at the fringes of plumes. Figure 11 and nature and chemical structure of the chemical shows the chloride levels and the concentrations of compound being degraded. In this study, the DO con- redox-sensitive parameters with BTEX and PAHs concentrations of most groundwater samples in excess of centrations along the NS and WE cross-sections in the 1.0 mg/L are identified that the aquifer is aerobic. The Zhoukou landfill. A combination of geochemical data, value of 1.0 mg/L is defined in order to minimize the in terms of changes in solute concentrations along the presence of nitrate-reducing microenvironments in the flowpath, and the PAHs concentrations in each well aerobic aquifer (Lyngkilde and Christensen 1992). can be used to describe contaminated extent in the The pH values are lower in winter season than that shallow aquifer system. As groundwater moves away in summer season. Although altering the pH of water from the landfill the following changes occur: from neutral to pH 6.0 and 8.0 had very little or no effect on Phe (Zaidi and Imam 1999), the increasing 1. Chloride is not considered to undergo any chem- pH values of water in summer season may have effect ical or physico-chemical reactions in the aquifers on reducing the other PAHs degradation. and as such is considered inert or conservative The monitoring results show the water table is higher (Christensen 1992). For this reason, chloride can in December than that in May, due to the reduction in be used to study dispersion and dilution of a groundwater exploitation over the winter season. Little contaminant plume. Measured chloride concentra- is known about the effects of fluctuations of the water tion in groundwater samples was 239 mg/L Environ Monit Assess (2013) 185:3413–3444 3435

Fig. 11 Chloride and redox sensitive species with main organic (clayey silt), 5 landfill, 6 groundwater table, 7 groundwater flow contaminants along the NS and WE cross-sections in the Zhou- direction, 8 monitoring well with well screen kou landfill. 1 Middle and fine sand, 2 silt, 3 silty clay, 4 fill soil

ranging between 51 and 976 mg/L in May 2009. 2. Sulfate concentrations increase as groundwater There was a definite attenuation pattern observed moves outside the sulfate reduction zone. A de- in wells down gradient of the landfill site (Fig. 4a). cline of sulfate near the landfill is noted due to 3436 Environ Monit Assess (2013) 185:3413–3444

sulfate reduction. Sulfate concentration in landfill inorganic nitrogen under aerobic conditions and result leachate (<200 mg/L at the monitoring wells of in lower PAHs concentrations in winter season. In − 27 m depth) is generally too low to maintain a addition, the higher HCO3 concentrations (mean val- degradation potential equal to iron reduction. ue, 926 mg/L at 27 m depth) in December than in May 3. Groundwater near the landfill contains elevated (mean value, 487 mg/L) support this conclusion, as − concentrations of dissolved Fe and Mn, mainly HCO3 is probably a by-product of PAHs degradation. mobilized under reducing conditions from landfill leachate. Characteristics of organic pollution in water bodies + 4. The presence of ammonium (NH4 ) in groundwater has biochemical significance as a useful indi- Horizontal distribution of organic pollution cator of organic pollution (Chapman 1992). Ammonium appears to give way downstream to No organic compounds were detected in samples from a narrow zone in which elevated concentrations of wells ZB, Z6A, Z6, SW59, DW23, DW09, DW25, nitrite are detected (e.g., at Z40, ZKW, and Z16). and Z06. The contamination plume is identifiable by This may be interpreted as partial nitrification of the dashed oval-shaped line in Fig. 1 and is distributed the ammonium plume due to infiltrating oxic wa- across the area where groundwater depth is 2–4m.In ter. Downstream of the nitrite well, nitrate the horizontal direction, the extent of pollution around becomes the dominant species, suggesting further the landfill is 2 km from south to north and 3 km from nitrification. Nitrate reduction causes disappear- east to west. In the contaminated area, relatively fewer ance of nitrate with depth upstream from the land- organic compounds are detectable in December as fill (e.g., Postma et al. 1991), such as the opposed to May. Theoretically, VOCs are not often monitoring wells at 9 m depth (ZG10, ZG11, and found in surface waters (especially lakes, e.g., ZG12). Nitrate reduction is a likely process at the Nikolaou et al. 2002) because of their high volatility; mixing zone of landfill leachate and shallow ni- however, they are the most common groundwater trate containing groundwater. contaminants (Golfinopoulos et al. 2001). In the north- east of the landfill, surface water samples from ZC, Nitrate >1 mg/l (with a maximum of 487 mg/L at located in a sewage ditch, yielded similar results over DW18) was encountered downstream of the landfill, two sampling periods. MAHs accounted for 78 % of and nitrate <0.1 mg/L water samples were found near the total organic compounds, CAHs for 19 %, and the landfill at wells ZG10, ZG11, ZG12, ZKE, ZKN, PAHs for <2 %. In the pond surface water sample and ZF, especially ~9 m depth, indicating that denitri- ZD, near the southeast of the landfill, fewer CAHs fication is likely a dominant redox process at the were detected (only tetrachloroethylene, 0.22 μg/L) in downstream fringes of the plume. The contribution the summer period, with no organic pollutants of aerobic and nitrate-reducing zones to natural atten- detected in the winter. In the southwest of the landfill, − uation of a plume increases with the O2 and NO3 the leachate sample ZE showed CAHs to account for concentrations in pristine groundwater and the extent 50 % of the total organic compounds, MAHs for 48 %, of mixing with the leachate plume (van Breukelen PAHs for <3 %, and OCPs for only 0.4 %. Figure 12 − 2003). Figure 4c shows lower NO3 concentrations shows that PAH concentrations of groundwater char- near the landfill, and there are higher Phe concentra- acterized by a declining trend with increasing distance tions detected in ZKE, ZKW, ZKN, etc (Table 4), from the landfill center. According to the exceedance which are the monitoring wells near the landfill. This of 1 μg/L, the contaminated distance can be estimated is consistent with that the idea that a lack of N may to be 1,200 m from this map. Pollutant concentrations slow down the biodegradation of phenanthrene (Zaidi vary greatly in different directions (Fig. 13). Towards and Imam 1999) and cause it to accumulate in the the east and south direction, the concentration decreases groundwater. very significantly away from the landfill. By contrast, Most groundwater samples (such as ZKN, ZKE, there is no obvious decreasing trend of the pollutant − ZF, and Z16) in December have higher NO3 concen- concentrations in the north direction. Combined with trations and lower pH values than in May. These the variation of the different chemical composition and will enhance degradation of PAHs due to the added pollutants in shallow aquifers (Fig. 5a–f), it indicates Environ Monit Assess (2013) 185:3413–3444 3437

uncontaminated groundwater. The natural attenuation and/or mixing with fresh water can be shown from the chloride variation. In contrast, the sediments in the south of the landfill belong to the bank of Huaihe River and are characterized by fine grains, including silty clay and clay, which can prevent contamination from spreading due to lower permeability. The farmers in the south of the landfill must plant wheat because there is less groundwater available for irrigation. As a result, there is little groundwater abstraction. Local anthropogenic pollution input may have caused the − 2− Fig. 12 Variations of PAHs concentrations with distances from high NO3 and SO4 in east–south of the study area the landfill center (such as DW18). In the western part of the study area, groundwater discharges into the Jialu River. The dis- that leakages from the landfill into the aquifer have tribution characteristics of PAHs and BTEX are dif- developed in different directions and to different extents. ferent from other inorganic chemical composition. The Generally, as the groundwater table rises in the winter highest concentration of PAHs is distributed some season, pH lowers and the concentration of organic 300 m SE of the landfill, while BTEX is highest at compounds (especially PAHs) increases, compared to the NW corner of the landfill. those in the summer season. Large fluctuations in PAHs Only CAHs were detected in the river water sam- and BTEX concentrations in individual boreholes were ples (SUJL and SUY) in May 2009. This indicates that shown to be largely attributable to seasonal groundwater river water can become contaminated during the sum- flow variations, which can affect microbial and chemi- mer period. CAHs, MAHs, and OCPs, with the excep- cal reaction that organic pollutants undergo and the tion of PAHs, were detected in the sewage water transport of gases and solutes through aquifer. samples (SULG and SULD) to different extents during The sediments towards the north of the landfill, the multiple sampling campaigns. Lower detection belonging to the southern margin of the Yellow frequencies of CAHs, MAHs, and OCPs and higher River paleo-alluvial fan, are composed of coarse PAHs concentrations in groundwater than that in river grains, including medium-fine grained sand and are and sewage ditch suggest that there is no inflow of known to bear better quality water. This groundwater polluted groundwater into the stream, and the contam- has been utilized for vegetable planting by local farm- inated river and waste water from sewage ditch are ers, and as a result of groundwater exploitation, the generally not recharging the groundwater body. That natural flow field has changed, causing wastewater is, the interaction between groundwater and the sur- from the landfill to flow towards the north. The lower face water is likely weak. The municipal waste water chloride concentrations (Fig. 5a) of groundwater in emission and the agricultural irrigation return flow south portions of the aquifer relative to the leachate into the river and the sewage ditch could be sources plume are consistent with mixing of leachate with of surface water pollution upstream; however, the

Fig. 13 Variation of different contaminants in different directions 3438 Environ Monit Assess (2013) 185:3413–3444 landfill body is the main pollution source for ground- deepest well, ZK1 at 300 m depth, was not contami- water contamination in the study area. nated by organic pollutants, with the exception of 0.44 μg/L toluene, which may have resulted from Vertical distribution of organic pollution regional groundwater flow. Additionally, water samples from the monitoring wells (such as ZKW and In the contaminated area (dashed line, Fig. 1), the Z16) near the gas station (Fig. 11b) were not detected waste dump is immersed in groundwater. A ground- to have higher Phe and Nap, which are plentiful in water mound has formed at the landfill site and dif- fresh fuels (Colombo et al. 2005a, b;Iturbeetal. fused into the surroundings. Local water table 2005). Therefore, their nonprevalence in groundwater gradients just below and around the landfill may differ seems to show no recent leaks of petroleum products from the general gradients because the landfill may from tanks and pipelines. have a different hydrogeology than the surrounding The main conclusion can be drawn that based on strata (Christensen 1992). The unlined Zhoukou land- the organic contaminants distribution of different wa- fill without any top cover may result in a larger infil- ter bodies, the interaction between groundwater and tration than in the surrounding soil, and if leachate is the surface water (including water from the river, not removed quickly, this may result in a local water gully, and sewage ditch) is probably weak in this area. table mound potentially affecting the local gradients. The landfill body is hence the main pollution source Local mounding effects are enhanced lateral spreading for groundwater contamination. However, Municipal of the leachate plume and to downward directed hy- waste water emissions and agricultural irrigation re- draulic gradients in the groundwater zone beneath the turn flow into the river and the sewage ditch could be landfill. The enhanced lateral spreading of the plume the source of surface water pollution upstream. may increase the volume of contaminated groundwater and its spatial extent, but provides increased dilu- Quality assessment and conceptual model tion of contaminants. Controlled by aquifer heterogeneity, contaminated River water and groundwater monitoring together with groundwater has reached the shallow aquifer to depths the analysis of the organic pollutants demonstrated of 13–25 m, which is composed of fine and middle that the landfill leachate is significantly impacting on sand with hydraulic conductivity of 11–12 m/day (Qu the surrounding aquatic environments. PAHs are the 2010). The results show that, near the landfill, the major pollutants in groundwater surrounding the shallow aquifer within 25 m depth has been contami- Zhoukou landfill and can be used to evaluate ground- nated, but not the deeper aquifer at 50 m depth. The water quality. Compared with PAHs concentrations

Table 9 PAHs concentrations in surface water reported in the world

Year N Range(ng/L) Mean±SD(ng/L) References

River water: Jialu and Ying River December 2009 6 nd–10 60±107.3 This study Hai River, Tianjin, China 16 115±58.2 Shi et al. 2005 Tonghui River, Beijing, China 2002.Apr 16 193–2,651 762±777 Zhang et al. 2004 Middle and lower Yellow River, China 2004.Jun 15 179–369 248±78 Li et al. 2006 Xihe River, China 2006,Aug. 11 26–384 151±22 Song et al.2007 Gaoping River, Taiwan, China 1999/2000 16 10–9,400 430 Doong and Lin 2004 Lower Mississippi River, USA 1999 13 5.6–68.9 40.8±32.9 Mitra and Bianchi 2003 Elbe River, Hamburg, Germany 1992/1993 16 107–124 116±12 Götz et al.1998 Lower Seine River, France 1993.Oct 11 4–36 20±13 Fernandes et al. 1997 Lower Brisbane River, Australia 2001/2002 15 5–12 8.2±3.0 Shaw et al. 2004 Malaysian River, Malaysia 2009 3,925–5,126 4,682±238 Geik et al. 2009

N number of PAH compounds analysed in each study Environ Monit Assess (2013) 185:3413–3444 3439

Fig. 14 Conceptual diagram of leachate migration in the Qua- the distribution of the total PAHs concentrations in groundwater ternary aquifers surrounding the Zhoukou landfill. The data of samples. The boundary line of the contaminated zone is the geological background is referenced from Qu (2010). The contour of total PAHs concentration 0.1 μg/L, which is the groundwater zone contaminated by leachate is determined by maximum permissible value of the WHO standard reported for other contaminated rivers in China, USA, Jialu and Ying river water in this study area are char- Germany, Australia, and other countries (Table 9), acterized by relatively lower PAHs concentrations 3440 Environ Monit Assess (2013) 185:3413–3444

(<0.01 μg/L), indicating light organic contamination designing lining systems both beneath and down- in river water. The groundwater close to the river bed stream of landfills. With the gradual expansion of the should be diluted with lower PAHs concentrations if Zhoukou city area, the landfill has been surrounded by this was a major recharge source in the wet season. urban planning area. If the local government does not However, Z16 is featured by higher PAHs concentra- take preventive measures, the existing waste will con- tion (1.07 μg/L) in May 2009 than that (0.33 μg/L) in tinue long-term groundwater contamination. Long- December 2009, suggesting that the groundwater re- term detailed monitoring programs are essential to charge from river water is horizontally very limited develop conceptual models of natural attenuation, within short distances and that the dominant driver of and studies need to allow the recognition that our groundwater flow and contaminant migration is the understanding of microbial transformation pathways groundwater mound surrounding the landfill. is constantly changing. Figure 14 shows the conceptual model of leachate migration in the Quaternary aquifers surrounding the Zhoukou landfill. There is a groundwater mound dif- Conclusions and environmental implications fused into the surroundings at the landfill site. The levels of PAHs were generally higher in the vicinity of the The investigation of organic contamination around landfill. Based on the distribution of PAHs concentra- Zhoukou landfill shows the present status of pollution tions in groundwater along the NS and WE hydrogeo- in sediments and surface and groundwater. This paper logical cross-sections (Fig. 14a-b), the groundwater has provided important data on parent PAH levels and zone contaminated by leachate can be circled by the other organic contaminants in the water and sediments contour of total PAHs concentration 0.1 μg/L, which is of the Zhoukou landfill in Henan Province, China. the maximum permissible value of the WHO standard. Some conclusions can be drawn as follows: The results suggest that groundwater beneath the Zhoukou landfill and within 50 m depth is not suitable 1. The main source and pathway for organic contam- as a drinking water source, and pollution control should ination is infiltration of rainfall in the vicinity of be improved and enhanced in this area (for example, the landfill, which has created a local groundwater with the construction of artificial liner or providing mound. impermeable clay cover to reduce water infiltration into 2. Detected organic contaminants include MAHs, the waste site). The groundwater contaminated zone CAHs, OCPs, and PAHs. The concentrations of varies from May to December. From Fig. 14,itcanbe these compounds are affected by seasonal ground- seen that the zone becomes smaller in the W–E direction water table fluctuations. PAHs are the main organ- but has little change in the N–S direction between these ic contaminant in this study area. Among the times, suggesting anisotropy in the local permeability detected eleven PAHs, Phe, Flu, and FLT identi- distribution. fied by PCA are the three dominant in most of the Due to the complexity of leachate migration groundwater samples. PAH diagonostic ratios, in- through landfills, fundamental aspects of subsurface cluding FLT/Pyr, FLT/(FLT + Pyr), Phe/Ant, and contaminant transport include the thickness of the CHR/BaA, suggest the mixture of petrogenic and unsaturated zone, the permeability and moisture con- pyrolytic contaminations of groundwater near the tent of the earth materials within the unsaturated zone, Zhoukou landfill. − and the hydraulic conductivity and local hydraulic 3. Higher NO3 concentrations and lower pH values gradient of geological units in the saturated zone under aerobic conditions enhance degradation of (Taylor and Allen 2006). Poorly conductive units un- PAHs in December, resulting in lower PAHs and - derlying the landfill, e.g., clay-rich material or the HCO3 concentrations. presence of an installed artificial liner can reduce 4. The organic contaminants detected from different leachate migration. On the other hand, discontinuities water bodies show that the interaction between of the landfill bottom such as fissures and joints in the groundwater and the surface water (including wa- subsurface or faults or holes in a liner, dramatically ter from the river, gully, and sewage ditch) is weak increase leachate flow. Access to hydrogeological in- in this area. The landfill body is the main pollution formation is thus vital for situation assessments and source for groundwater contamination in this Environ Monit Assess (2013) 185:3413–3444 3441

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