Qualitative and Quantitative Analysis of Source for Organic Carbon and Nitrogen in Sediments of Rivers and Lakes Based on Stable Isotopes T

Ecotoxicology and Environmental Safety 195 (2020) 110436

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Ecotoxicology and Environmental Safety

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Qualitative and quantitative analysis of source for organic carbon and nitrogen in sediments of rivers and lakes based on stable isotopes T

∗ ∗∗ Qingjun Guoa,b, , Chunyu Wangc, Rongfei Weia, , Guangxu Zhud, Meng Cuia, Chukwunonso Peter Okolice a Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China b College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100190, China c Naiman County Environmental Protection Bureau of Tongliao, Inner Mongolia, 028300, China d College of Biology and Environment Engineering, Guiyang University, Guiyang, 550005, China e Analytical/Environmental Chemistry Unit, Department of Chemistry/Biochemistry & Molecular Biology, Alex Ekwueme Federal University, Ndufu Alike, Nigeria

ARTICLE INFO ABSTRACT

Keywords: Sediment is the most dominant reservoir of organic pollutants in the aquatic environment. Understanding carbon Source and fate and nitrogen sources in sediments and factors that controls distribution enhances our understanding of bio- Carbon and nitrogen geochemical cycles of carbon and nitrogen. Different end-members and surface sediments of rivers and sedi- Isotopes ments profiles of lakes were collected. The concentrations of TOC and TON and their δ13C and δ15N were studied Qualitative and quantitative analysis for qualitative and quantitative analysis of natural and anthropogenic sources. The results show that TOC and Sediments TON concentrations of the sediments from rivers range from 0.63% to 10.83% and 0.06%–0.86%, respectively, indicating substantial great environmental risks in these rivers. The concentrations of TOC and TON for the four sediment profiles below the 5 cm, increase in the order of Miyun < Chuidiao < Qunming < Houhai, as influenced by their respective environment condition. Moreover, water quality was quite good and there was no 13 15 risk of eutrophication in Miyun reservoir. δ Corg and δ Norg in surface sediments of the studied 18 rivers range from −27.2‰ to −24.9‰ and −2.2‰ to +10.9‰, respectively. Based on a simple δ13C-based end-member mixing and a C/N ratio model, organic matter in the surface sediments of these rivers were mainly derived from sewage and C3 plant. In addition, the sources of organic matter differed in each layer of the four sediment profiles. This study provides a reliable method for qualitative and quantitative identification of the source of organic matter in sediments, and offers theoretical basis for better management of rivers and lakes.

1. Introduction and understanding of basic factors that control distribution, enhance our knowledge to biogeochemical carbon and nitrogen cycles. Although Eutrophication and environmental pollution pose a serious issue in numerous studies have been carried out about the organic matter the oceans, rivers, lakes and coastal water worldwide (Lotze et al., sources in sediments, most of them focused on the estuarine and marine 2006; Ke et al., 2017). Sediment is the most dominant sink of en- sediments (Lotze et al., 2006; Rooze and Meile, 2016; Gu et al., 2017; vironmentally released organic pollutants in the aquatic environment Kubo and Kanda, 2017). (Kubo and Kanda, 2017). The aquatic environmental impact and risk In order to elucidate the sources and fate of organic matter in se- could be assessed by monitoring the distribution of organic matter in diments, stable carbon and nitrogen isotopes and C/N elemental ratios sediments (Gu et al., 2017). Nitrogen isotopic signatures of sources and have been widely applied in an aquatic environment (Graham et al., sinks of ﬁxed nitrogen (N) in sediments can be used to elucidate marine 2001; Schubert and Calvert, 2001; Gao et al., 2012; Kanaya et al., 2013; nitrogen budgets (Rooze and Meile, 2016). Moreover, knowledge of the Rooze and Meile, 2016; Gu et al., 2017; Kubo and Kanda, 2017). sources of sedimentary organic carbon in coastal water is essential for Generally, the values of δ13C, δ15N and the C/N have certain range in better understanding of the global carbon cycle (Kubo and Kanda, diﬀerent sources (Gao et al., 2012). Moreover, terrestrial organic matter 2017). Therefore, source apportionment of organic matter in sediments usually exhibits negative δ13C and δ15N values compared to marine

∗ Corresponding author. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China. ∗∗ Corresponding author. E-mail addresses: [email protected] (Q. Guo), [email protected] (R. Wei). https://doi.org/10.1016/j.ecoenv.2020.110436 Received 3 November 2019; Received in revised form 1 March 2020; Accepted 3 March 2020 0147-6513/ © 2020 Elsevier Inc. All rights reserved. Q. Guo, et al. Ecotoxicology and Environmental Safety 195 (2020) 110436 organic matter (Gao et al., 2012; Ke et al., 2017). For example, δ13C and include Kunyu River, Chang River, North moat River, South moat River δ15N in the marine phytoplankton usually range from −19.1‰ to and so on. Urban drainage rivers include four main drainage systems: −22‰ and from 3.0‰ to 12.0‰ respectively, while they vary from Qing River, Ba River, Tonghui River and Liangshui River. Rainwater, −35.0‰ to −25.0‰ and from 5‰ to 8‰ in freshwater phyto- domestic sewage and industrial wastewater in the urban area pass plankton, respectively (Boutton, 1991; Wada and Hattori, 1991; through these four drainage systems and eventually flow into the Gearing et al., 1984). Meanwhile, the C/N ratios for organic matter Beiyun River. The suburban rivers include Wenyu River, Beiyun River, were 5–8 in marine while it is > 15 in the terrestrial organic matters Feng River, Ganggou River and so on. (Meyers, 1997). Moreover, δ13C signatures and C/N ratios of sediments There are more than 30 lakes in Beijing. The total surface area of the are usually used to assess the source of organic matter in an ecosystem, lakes is about 7.3 km2. The water depth of lakes is approximately whereas δ15N signatures are commonly used to evaluate anthropogenic 1.5–2 m. We selected 4 lakes with different degree of human dis- discharge and trophic structure of aquatic organisms (Ke et al., 2017). turbance and cleanliness of sediments for more detailed investigation in The sediments of urban lake and river always come from various this study: 1) Qunming Lake located near the old site of the Capital Iron sources. Beijing is one of the largest cities in East Asia with rapid and Steel Factory. Industrial activities and human disturbance are the economic growth and about 20 million residents track (BSY, 2017). strongest compared with other three lakes. Sediments are the darkest Considering the municipal and industrial activities to sustain the huge with fishy smell; 2）Houhai is in the city center with frequent human population, discharge of municipal and industrial wastewater into the activities. The sediments are dark and slightly odorous; 3）Chuidiao environment has led to a significant decline in quality of the local Garden is less disturbed by human activities. The properties of sediment surface water bodies. Consequently, the surface water bodies which are similar to soils; 4）Miyun reservoir is the largest and the only serve as the source of raw water of the municipal water supply are source of drinking water supply of Beijing. polluted, and influence the quality of tap water which is often below the drinking water quality benchmark requirements, in some sections of the 2.2. Sample collection city (He et al., 2011; Peters et al., 2015; Zhang et al., 2017). The pollution of certain river sections in Beijing has reached a critical level. River surface sediment samples were collected using stainless-steel Many previous studies have investigated the pollution of these rivers in grab sampler at a depth of 0–5 cm from the middle of 18 rivers in Beijing through isotope techniques and elements analysis (He et al. Beijing area between July 2012 and May 2013 (Fig. 1). Three sediment 2011, 2014; Zhou et al., 2012; Peters et al., 2019; Zhang et al., 2017). samples were collected at 5–10 cm upstream and downstream from However, there are few studies about the organic matter distribution in each site and the three replicate samples were mixed. Sediment profiles the sediments of rivers and lakes in Beijing area. were collected from the middle of four lakes in Beijing area (Miyun Here, different end-member species, surface sediments of 18 rivers reservoir, Chuidiao Garden, Houhai and Qunming lakes) using a and sediments profiles of 4 lakes in different areas of Beijing were Gravity sampler. The sediment columns were stratified as a sample for collected, and the concentrations of total organic carbon (TOC), total each 2 cm or 5 cm. Four soils, four algae, three atmospheric deposi- organic nitrogen (TON), and their isotope ratios (δ13C and δ15N) of the tions, three C3 plants, and three C4 plants were selected as the end- samples were analyzed accordingly. We combined carbon and nitrogen members in or around the rivers and lakes. isotopes with the C/N ratio to examine the sources and fate of organic Samples were stored at −20 °C in self-sealing polyethylene bags matter in the sediments of rivers and lakes. This study provides a until analysis. Each sample was then gently ground using an agate method to identity the source of organic matter in sediments and lays pestle and mortar, sieved through a 200 μm mesh sieve for homo- theoretical basis for management of rivers and lakes. genization, and then stored in glass bottles for subsequent TOC, TON, δ13C, and δ15N analysis. On-site measurements of temperature, pH, 2. Materials and methods redox potential (Eh) and electric conductivity (EC) were carried out during sampling using the electrode kit SX731 (Sanxin®). Table 1 lists 2.1. Study area

Beijing is located on the Beijing Plain, northwest of the larger North China Plain (NCP). Beijing exhibits a continental semiarid climate with an annual mean temperature of around 13 °C (Aji et al., 2008). The annual average precipitation is ~600 mm/year with 80% occurring during the summer monsoon between June and September. There are 5 big rivers and around 200 small rivers crossing Beijing municipality. These 5 major river catchments are Yongding River and Juma River in the west, Chaobai River and Beiyun River in the east as well as Jiyun River in the northeast of the city. Beiyun river is the main drainage channel in the urban and plain areas of the city. It accounts for more than 80% of the sewage discharge and 90% of the rain and ﬂood discharge. However, with the development of the city and population rise, domestic sewage discharge has also increased dramatically. There are direct or indirect discharge into the Qing River, Ba River, Tonghui and Liangshui rivers which are tributaries of Beiyun Rivers. As a result, many water quality indicators of the Beiyun River system exceed the class IV water quality of national water quality standard (Zhang et al., 2015). Therefore, the water quality was very poor according to the national guideline on surface water quality (GB3838-2002) (class I: very good, class II: good, class III: moderate, class IV: poor, class V: very poor). Therefore, the Beiyun River is the most polluted water system in Beijing. Beiyun river systems can also be divided into urban central rivers, Fig. 1. Geographic setting and location of sediment samples in rivers and lakes, urban drainage rivers and suburban rivers. The central rivers mainly Beijing, China.

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Table 1 code:449278/1 41803102) is used as reference materials, and Physical and chemical properties of surface waters in the sample sites. δ13C=−43.74‰, δ15N=−1.489‰. The deviation of δ13C and δ15N ‰ ‰ Numbers Sample sites T(°C) pH Eh (mV) EC (μS/ Location is 0.07 and 0.13 , respectively. Reproducibility as determined cm) through replicate measurements was better than 0.1‰. 1 TCR 22.7 7.00 84 207 Tucheng River 2 LMR 22.8 7.02 −248 556 Liangma River 2.4. Bayesian mixing model 3 BR 23.1 7.81 106 946 Ba River 4 XZRT 24.4 7.99 88 1214 Xiaozhong River (Tongshun road) The Bayesian isotope mixing model (MixSIAR, version 3.1.7) was 13 5 TH 34.8 7.78 74 950 Tonghui Irrigation applied in this research. The δ C and C/N ratios for the sediments and Canal the end members were used as input parameters. The Markov Chain − 6 FTQ 24.2 8.16 138 1368 Fatouqiao River Monte Carlo (MCMC) was set to “very long”, and the Gelman-Rubin and 7 XTR 27.6 8.07 −50 1290 Xiaotai River 8 LSRE 26.9 7.87 100 1325 East of Liangshui Geweke diagnostic tests were used to determine whether the output River was reasonable (Stock and Semmens, 2013). The error structure and 9 LSR 26.0 8.06 −136 1302 Liangshui River specify prior were set to “residual error” and “uninformative”, respec- 10 XFR 25.7 8.11 83 1571 Xinfeng River tively. The median values (50% quartiles) were analyzed for contribu- 11 HR 30.3 7.77 96 794 Han River tions from different sources. 12 YDRJ ––– – Yongding River (Jinding west street) 13 YDRD 28.8 8.76 83 319 Yongding River 2.5. Data analysis (Dongcui road) − 14 WYR 28.8 7.59 46 789 Wenyu River Descriptive statistics were computed with SPSS for Windows, ver- 15 YDRT 23.8 8.05 −206 1063 Yongding River (Trunk Canal) sion 19.0 and Origin for Windows, version 8.0. 16 WYQ 23.6 7.92 55 955 Wenyu Qiao 17 XZR 24.7 8.07 42 1450 Xiaozhong River 3. Results and discussion 18 BQ 21.6 8.02 90 721 Channel of Beiqing road 3.1. TOC and TON, C/N ratios in sediments 19 QML – 9.83 188 355 Qunming Lake 20 HH – 7.85 63 516 Houhai 21 CDG – 8.44 60 1345 Chuidiao Garden 3.1.1. Concentration of TOC and TON, and C/N ratios in surface sediments 22 MYR ––– – Miyun Reservoir of Beijing rivers The concentrations of TOC, TON and C/N ratios of sediments in 18 rivers of Beijing are as shown in Fig. 2A. on-site measurement of physical and chemical properties (temperature, Obtained concentrations of TOC markedly differ within the rivers. pH, Eh, EC) of surface waters in the sample sites. The concentrations of TOC in the surface sediments of Beijing rivers range from 0.63% to 10.83% with an average of 3.53 ± 2.31% 2.3. Analytical methods (n = 18). The lowest concentration of TOC observed at the sampling site of XTR (XiaoTai River) while the highest value was at FTQ (FaTou − Organic carbon in the samples were extracted using 0.5 mol L 1 Qiao). Except these two sites, the concentration of TOC in other sites ff HCl for 24 h, centrifuged and washed with deionized water repeatedly, ranged from 3% to 5%. There are some di erences between the results ～ until supernatant liquid was neutral (Midwood and Boutton, 1998). of this study and those of Chaobai areas (0.11% 1.76%) in North of Then, samples were frozen dry and used for analysis of TOC con- Beijing as reported by Lu et al. (2012). Higher range values in this study centration. Meanwhile, TON analyses were conducted by using indicated that initial productivity in the 18 rivers were higher than that − − 2 mol L 1 KCl and 0.5 mol L 1 HCl sequentially to remove inorganic of Chaobai areas. Furthermore, the TOC concentrations of sediments in nitrogen. Then, the samples were rinsed subsequently with deionized Beijing rivers were also higher than those from other Chinese and – water to neutralize and were frozen dry. The concentrations of TOC and worldwide coastal sea areas, such as Zhelin Bay (0.46 1.23%) (Gu – TON were measured by elemental analyzer (Vario micro cube, Ele- et al., 2017), Zhifu Bay (0.35 0.91%) (Wang et al., 2016), Bohai Bay – – mentar) at the Institute of Geographic Sciences and Natural Resources (0.85 7.24%) (Gao et al., 2012), Jiaozhou Bay (0.07 0.45%) (Dai et al., – Research, Chinese Academy of Sciences. Acetanilide (C:71.09%, N: 2007), Pearl river Estuary (0.88 1.15%) (Qi et al., 2010), Chesapeake – 10.36%) were used as the certified standards. The precision of this Bay, USA (0.75 3.46%) (Zimmerman and Canuel, 2000), Gulf of – method based on replicate measurements of the reference standards is Trieste, Adriatic Sea (0.5 1.3%) (Ogrinc et al., 2005), Beppu Bay, Japan – 0.1% for carbon and 0.01% for nitrogen. (1.8 2.9%) (Kuwae et al., 2007). The isotopic composition of carbon (δ13C) and nitrogen (δ15N) was The concentrations of TON in surface sediments of Beijing rivers measured via sealed-tube combustion (e.g., Strauss et al., 1992) and range from 0.06% to 0.86% with an average of 0.30 ± 0.21% subsequent mass-spectrometric analysis using the combination of ele- (n = 18). The lowest concentration of TON was observed at sampling mental analyzer (FLASH EA1112, Thermo) with mass spectrometry site WYQ (Wen Yu Qiao) while the highest value was at FTQ (Fa Tou ff (Thermo Finnigan MAT 253) at the Institute of Geographic Sciences and Qiao). The distribution of TON also di ered from the rivers. The highest Natural Resources Research, Chinese Academy of Sciences. The stable concentrations of TOC and TON in FTQ indicated a risk of eu- carbon and nitrogen isotope is expressed in “delta” (δ) notation to in- trophication. The results of TON in this study are higher than those of dicate differences between the isotopic ratio of the sample and accepted Chaobai areas in Lu et al. (2012) report. It indicated that there might be standard materials expressed as: big eutrophication risks in these rivers. The possible sources con- tributing to the TOC and TON will be discussed in section 3.2. δ13 ‰ ＝， 13 12 C( ) [(R sample -Rstandard)/ R standard] × 1000 R= C/ C The values of C/N ratios in the surface sediments of Beijing rivers range from 7.53 to 25.97 with an average of 12.99 ± 4.59 (n = 18) higher than Chaobai areas (8.50～13.68) (Lu et al., 2012). The lowest δ15N(‰)＝[(R – R )/ R ] × 1000, R = 15N/14N sample standard standard values of C/N ratios observed at the samples from the site XZRT where δ13C and δ15N are reported in permil (‰)difference to the (Xiaozhong River) while the highest value was at YDRD (Yongding

Vienna PDB standard (VPDB) and atmospheric nitrogen N2, respec- River). The ratios of C/N are usually applied to ascertain the source of tively. Carbamide (Thermo Electron (Bremen), Lot &Filling organic matter. In general, the ratios of C/N were typically between 10

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13 15 Fig. 2. The concentrations of TOC and TON, C/N ratios, δ Corg and δ Norg of Beijing river sediments. and 13 in soil samples (Kendall et al., 2001; Guo et al., 2013), higher from Miyun reservoir are consistent with those by Lu et al. (2012). than 15 in terrestrial plants (Deines, 1980; Kendall et al., 2001) while it With regard to the four sediment profiles below the 10 cm, the was between 6.6 and 13 in sewage (Thornton and McManus, 1994; concentrations of TOC and TON in Houhai lake were the highest, while Andrew et al., 1998; Liu et al., 2007; Machiwa, 2010). Based on this, it was the lowest in Miyun reservoir. This is likely associated with the the organic matters of sediments of investigated rivers mainly came environmental conditions in these lakes. Miyun reservoir is protected from soil and sewage. The sites of YDRD and YDRJ had the high ratios well as it is the main source of drinking water to Beijing. The Chuidiao of C/N, which indicate the organic matters of these two sites may come garden was a private club with a cleaner water. Apart from those two from the terrestrial plants, such as C3 and C4 plants. sites, Qunming lake is polluted with various mixed wastes, owing to its location near the Capital Iron and Steel plant, and this factor affected the sediment deposition. The Houhai is not protected properly and 3.1.2. Concentration of TOC, TON and C/N ratios in sediments profiles of consequently, its sediments quality is very low. Beijing lakes In Qunming lake, the variation of C/N ratios shows an obvious in- The concentrations of TOC, TON and C/N ratios in sediments pro- crease along the depth for the four sediment profiles. This suggests that files of the four Beijing lakes are as shown in Fig. 3. the degree of degradation of sediments in Qunming lake varies greatly The concentrations of TOC and TON varies for all the four sediment at different periods. Moreover, the C/N ratios differ within different profiles. The concentrations of TOC and TON increased from the bottom sediment profiles, and this revealed that the degree of degradation of to the surface in the Qunming lake, which could be suggested that the organic matter is different, and the difference in sources of organic productivity of the lake has increased over time. Moreover, the con- matter between the four lake sediments formed during their respective centrations of TOC and TON in the surface sediments (0–10 cm) of sedimentary ages. Qunming lake are increasingly obvious, while the range of change is not obvious in the rest sediment profiles. The concentration of TON increased to 0.29% in the surface (2–4 cm) from 0.12% in the subsurface 3.2. δ13C and δ15N in sediments (6–8 cm), which indicated more nutrient input into the Qunming lake recently. The concentrations of TOC and TON in sediment profiles of 3.2.1. δ13C and δ15N in surface sediments of rivers 13 Chuidiao garden remained constant from 70 cm to 30 cm, and increased δ Corg in surface sediments of these 18 rivers range from −27.2‰ from 30 cm to 20 cm, then decreased from 20 to 10 cm. The con- to −24.9‰ with an average of −25.9 ± 0.6‰ (n = 18) (Fig. 2B). centrations of TOC and TON in sediment profiles of Houhai decreased The values are comparable to the values of Chaobai river (−27.8‰～- 13 slowly from the bottom to the surface. All concentrations of TOC and 21.6‰ for δ Corg and the average value was −25.3 ± 1.7‰ TON in sediment profiles of Miyun reservoirs are low in which TOC (n = 20))(Lu et al., 2012) while it is lighter compared with that of 13 varied between 0.18%～0.85%. Relatively high values in the surface Bohai Bay (−25.7～-18.2‰ for δ Corg and the average value was 13 showed that the initial productivity was more vigorous recently. −22.9 ± 1.43‰). The lowest value of δ Corg was observed at sam- Meanwhile, the concentrations of TON in sediment profiles of Miyun pling site LMR (Liangma River) while the highest value was at XZRT 13 reservoirs varied between 0.008%～0.085%, which is lower than that (Xiaozhong River). In the previous studies, the δ Corg of sediments was 15 of sediment profiles in other lakes. This suggests that Miyun reservoirs usually lighter than −20‰ (Meyers and Teranes, 2002) while δ Norg water quality is quite good and no risk of eutrophication. These results of sediments varied between −1‰～18‰ (Kendall and Galdwell,

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13 15 Fig. 3. Vertical distribution of TOC, TON, C/N ratios, δ Corg and δ Norg with depths in Beijing Lakes.

1998; Meyers and Teranes, 2002; Kreitler, 1979; Mariotti et al., 1984). of multiple sources. The sources of organic matters of these rivers will Generally, terrestrial C3 plants have δ13C values ranging from −30‰ be discussed in detail using mixed model of end-members. to −23‰ while it ranges from −17‰ to −9‰ for C4 plants (Lamb et al., 2006; Yu et al., 2010). 15 13 15 δ Norg in surface sediments of all 18 rivers ranged from −2.2‰ to 3.2.2. δ C and δ N in sediment profiles of lakes 13 +10.9‰ with an average of +3.0 ± 2.8‰ (n = 18). The range is The δ Corg in the four sediment profiles are shown as Fig. 3. The 13 13 larger than the values in Chaobai river (+1.3‰～+6.7‰ and average δ Corg differed within different places. The δ Corg compositions in the 15 value of +3.6 ± 1.5‰ (n = 20)) (Lu et al., 2012). The lowest δ Norg sediment profiles of Miyun reservoir were more negative when com- values was observed at sampling site BQ (Channel of Beiqing road) pared to the other three profiles. This could be due to the little accu- 13 while the highest value was at LSR (Liangshui River). Marine organic mulation of Corg in the Miyun reservoir during the degradation pro- 15 13 matter usually has δ Norg value of +3‰～+12% derived from phy- cess of the organic matter. The δ Corg is quite similar in Chuidiao toplankton that normally use dissolved nitrate (Brandes and Devol, garden, Houhai and Qunming lake at 20–50 cm, depicting similarity in 2002; Lamb et al., 2006; Gao et al., 2012). In consistent with the results their sediment-deposited organic matter sources, formed during the of the previous studies (Maksymowska et al., 2000; Gaye-Haake et al., same sedimentary stage. 15 15 2005; Gao et al., 2012), the δ Norg values of river sediments are lower The variations of δ Norg values for the four sediment profiles are 13 15 than oceanic values. This maybe attribute to the contributions from the similar to those of δ Corg. The δ Norg in the sediment profiles of Miyun 15 forest and soil nitrogen. Generally, terrestrial plants have low δ Norg reservoir are different from the other three profiles. The variation of 15 values while anthropogenic origins (such as waste, livestock) δ Norg values in sediment profiles of Qunming lake was obvious with (+10‰～+22‰) are enriched with heavy nitrogen isotopes the increment in depth, but it was not evident in Chuidiao garden and 13 15 (McClelland et al., 1997; Cole et al., 2006; Banaru et al., 2007). Houhai. In a similar pattern with δ Corg, the variation trend of δ Norg 13 15 In this study, the values of δ Corg and δ Norg for different sample are consistent with increment in depth in the sediment of Chuidiao 15 sites differ between the rivers, which indicates that the organic matter garden and Houhai. The δ Norg values are similar between 20 and 13 15 of different rivers are distinct. The variation of δ Corg and δ Norg re- 50 cm depth in the sediment of the Chuidiao garden and Houhai lakes. vealed that organic matter in Beijing rivers sediments consists a mixture

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4. Discussions might also be due to the number of selected end-members were not enough. Even though, this method was not complete as desired, it is 4.1. Source of organic matter in sediments very useful and significant. As depicted in Fig. 4B, the organic matter in two sites lying channel of Yongding river came from the algae and C3 The carbon isotopes of organic matter in sediment are influenced by plants, except the contribution of atmospheric deposition, which was 13 various factors, such as the chemical properties of water, initial pro- included by the method of combination of δ Corg and C/N. Therefore, ductivity, hydrological characteristics of basin, regional natural en- this method reduced the scope of end-members and played a very im- vironment, sedimentary environment, and the preservation status of portant auxiliary role. Beside this, from Fig. 4B, the organic matter of buried deposits (Talbot, 1990; Aravena et al., 1992; Meyers, 1994). parts of river sediments came from the soil organic matters or algae 15 Meanwhile, these factors will also affect each other. Therefore, en- while the δ Norg and C/N of soil organic matter were just between that vironmental conditions should be taken into consideration when in- of sewage organic matter and algae. Combined with the information of 13 vestigating the source of organic matter. C/N ratios of sediments are δ Corg and C/N, it can be inferred that the organic matters of these related not only directly to the number and variety of organic matter river sediments came from the sewage organic matter and algae. sources, but also to the change with the degradation of organic matter. Therefore, the organic matter of the river sediments mainly came During early diagenesis, nitrogen is more easily mineralized than from the sewage organic matter, algae and C3 plants. This is consistent carbon, enhancing an increase in the C/N ratio with diagenesis. with the results by Li et al. (2016), which stated that the pollution of Nevertheless, degradation of sedimentary organic matter is not enough Beijing rivers were mainly due to the untreated sewage discharge. to obliterate the initial C/N ratio of terrestrial plants and aquatic plants. Moreover, it was reported that residential areas produced 3.3 million Therefore, C/N ratios are still believed to preserve information of or- tons’ domestic sewage per day and about 17% wastewater is directly ganic sources (Meyers and Ishiwatari, 1993; Kaushal and Binford, discharged into the environment (Dai et al., 2015; Li et al., 2016). In 13 1999). In addition, the organic nitrogen isotopes in sediments can summary, the method of combination of δ Corg, C/N and qualitative provide environmental information of organic matter in sewage, so analysis of end-members in order to identify sources of organic matter organic nitrogen isotopes can be applied for analyzing the source of in surface sediments of Beijing rivers was useful, effective and sig- organic matter in the sediments. Furthermore, this study combines two nificant. 13 15 stable isotopic compositions (δ Corg and δ Norg) with the C/N ratio to investigate the possible sources of organic matter. It is very important to analyze end-members in order to identify the 4.1.2. Qualitative analysis of sources of organic matter in sediment profiles source and contribution of each source. Combined with previous re- of lakes searches in this field and the current situation of Beijing environmental From Fig. 4C and D, the organic matter in sediment profiles of pollution, end-members were selected. They include soil organic Miyun reservoir originated from soil organic matter, algae and C3 matter, C3 plants, C4 plants, atmospheric deposition, sewage organic plants. matter, and phytoplankton (algae). The distribution of each end- Besides the three end-members, the organic matter in sediment member was shown in Table 2. profiles of Chuidiao garden also evolved from the sewage. The organic matter in sediment profiles of Houhai originated from the soil organic matter, algae and sewage. Besides the three end-members, the organic 4.1.1. Qualitative analysis of sources of organic matter in surface sediments matter in sediment profiles of Qunming lake also came from the ter- of rivers restrial C3 plants. Furthermore, the contribution of the terrestrial C3 Based on both stable isotopes and C/N ratio (Fig. 4A), we believe plants was dominant among the various sources of organic matter at the that there are three different major sources of the organic matters in layers of 5–10 cm of Chuidiao garden, 28–30 cm of Miyun reservoir, surface sediments of the 18 rivers. The sewage is the major source of 6–8 cm and 20–25 cm of Qunming lake. organic matter in the sediments of most rivers. However, the major Qualitative analysis indicates that there are four major sources of source of organic matter in the sediments of TCR (Tucheng river), LMR organic matter in studied sediment profiles: sewage, C3 plant, algae and (Liangma river), TH (Tonghui irrigation canal), HR (Han river) is algae. soil organic materials. However, the organic matter of The YDRJ (Yongding River, Jinding The soil organic matter and algae were the main sources in the four west street) and YDRD (Yongding River, Jinding west street) sediments sediment profiles. Sewage and C3 plants were the sources in three of were sourced from the composition of atmospheric deposition, algae those sediment profiles. However, C3 plants were the only source of the and C3 plants. Based on this, organic matter source identification in the several layers as mentioned earlier. Hence, soil organic matter, algae ff di erent sampling points of the same river is more reliable via the fi 13 and sewage were selected as main end-members of sediment pro les for combination analysis of δ Corg and C/N. 15 further quantitative analysis of the sources. From Fig. 4B, the δ Norg and C/N of 6–7 sample sites are beyond the scope of the selected end-members. This concerns that sources 15 identification by the combination of δ Norg and C/N have defects. It

Table 2 13 15 Distribution of δ Corg, δ Norg and C/N ratios of diﬀerent end-members.

13 15 End-members δ Corg (V-PDB, ‰） δ Norg（air, ‰） C/N Numbers

Soil −22～-24(-23.5 ± 1.1) 3～9(5.9 ± 2.5) 10～16(13.7 ± 2.5) 4 Algae −14～-27(-19.3 ± 6.3) 3～8(6.2 ± 2.5) 13～26(17.7 ± 5.6) 4 Atmospheric −23～-26(-24.5 ± 1.7) −7～2(-2.1 ± 4.5) 23～46(38.7 ± 13.1) 3 C3 plants a −23～-30(-28.9 ± 0.5) −5～18(4.5 ± 0.7) ＞18(18.0 ± 7.3) 5 C4 plants b −9～-17(-15.3 ± 4.2) 3～6(5.8 ± 2.4) ＞15(15 ± 4.6) 2 Sewage c −23～-28.5(-25.3 ± 2.75) 7～25 6.6～13(12.5 ± 0.8) 4

a Kendall et al., (2001), Goni et al., (2003), Pancost and Boot (2004), Lamb et al., (2006), Yu et al., (2010), Gao et al., (2012), Lu et al., (2012), Gu et al., (2017), Rao et al., (2017). b Deines (1980), Kendall et al., (2001), Goni et al., (2003), Rao et al., (2017). c Thornton and McManus (1994), Andrew et al., (1998), Liu et al., (2007), Machiwa (2010).

6 Q. Guo, et al. Ecotoxicology and Environmental Safety 195 (2020) 110436

13 15 Fig. 4. Scatter plot of δ Corg vs C/N ratios, δ Norg vs C/N ratios of sediments from diﬀerent sources, Beijing rivers (A and B) and lakes (C and D).

4.2. Quantitative analysis of sources of the organic matter in sediments contribution to the sediment profiles of Houhai except the bottom, followed by sewage (10.4–20.3%) and algae (1.9–8.7%). In the surface The relative contribution from different sources to the organic (5.7%) and subsurface (8.7%) sediments of Houhai, contribution of matters in sediments of Beijing rivers and lakes have been evaluated algae is obvious. However, in the bottom of Houhai, sewage (75.9%) is 13 using Bayesian mixing model according to the δ Corg and C/N ratios in the main source of organic matter. The Qunming lake have complicated sediment samples and different sources (Fig. 5). The δ13C of sewage, sources when compared with other three lakes. Algae, atmospheric algae, C3, C4, soil and atmospheric are −26‰, −19.3‰, −28.9‰, deposition, C3, C4, sewage and soil have some contributions on each −15.3‰, −23.5‰ and −24.5‰, respectively. The C/N ratios of sediment layer in Qunming lake. sewage, algae, C3, C4, soil and atmospheric are 10, 17.7, 18, 15, 13.7 The variation trends with the increase of depth for the profiles of and 38.7, respectively. Chuidiao garden, Houhai and Qunming lakes are similar to those of soil The results (as shown in Fig. 5) indicated that 40.6–83.0% of or- profiles. In the soil profiles, decomposition of organic matter could ganic matter in all of the 18 river sediments originated from sewage. result in carbon isotopic fractionation (Balesdent et al., 1993; Schweizer Overall, the contribution of sewage is evident in all of the 18 river se- et al., 1999). This leads to a decrease in organic carbon content and an 13 diments, except in LMR (32.4%), followed by C3 plants (7.1–54.2%). increase in δ Corg value from the surface to the bottom of soil profiles. 13 This inference is based on the results of 4.1.1. However, the contribu- Most of organic matter in the soil have been degraded when the δ Corg tion of C3 plants (54.2%) is primary in LMR, followed by sewage value reached the maximum (Zhu and Liu, 2006). Thus, the content of (32.4%). Besides sewage and C3 plants, soil organic matter (2.1–8.9%) the refractory organic matter increased and accumulated at the bottom, also have some contribution on the sources of organic matter in sedi- which reduced the decomposition rate of organic matter. Therefore, 13 ments. Notably, the contribution from atmospheric deposition is ob- content of organic carbon and δ Corg composition were observed to be 13 vious in the YDRD (8.4%) and YDRJ (7.6%). This indicates that an- reducing slowly with increment in depth of the soil. The δ Corg in the thropogenic activities have an important infulence on compsotion of bottom of three sediment profiles (as shown in Fig. 3) is more positive organic matter in sediments of Beijing rivers besides the natural pro- than those of the surface layers. It illustrates that the organic matter 13 cesses. was degraded gradually and the Corg enriched material is accumu- 13 Sewage (34.7–68%) was the main source of the organic matter in lated with deposition time. Interestingly, the δ Corg in the sediments of sediment of Miyun reservoir, followed by C3 (12.1–22.9%). Though Chuidiao garden are heavier than the other two profiles. This could be

Miyun reservoir water quality was quite good and no risk of eu- due to carbon isotope fractionation between CO2 and phytoplankton in trophication, contamination monitoring is recommended, in order to water decreasing with the increase of productivity. Meanwhile, the 13 13 preserve its quality integrity as source of raw water. Sediment sources increase in δ Corg in phytoplankton will directly lead to higher δ Corg of Chuidiao garden in the layer 0–20 cm differed from the other layers. in the sediments, which were higher than those of the general lake Atmospheric deposition (69.3%) is the main source of organic matters sediments, but less than- 25‰ (Lücke et al., 2003). 15 13 in the surface layer of Chuidiao garden, algae (26.9%) in the subsurface According to the trends of δ Norg and δ Corg in the four sediment layer and soil organic matter (91.1%) in the subsequent layers of profiles, we could find that 10 cm and 20 cm are the turning points of Chuidiao garden. The soil organic matter (39.5–70.4%) have major organic carbon and nitrogen isotopes in the Miyun reservoir. And we

7 Q. Guo, et al. Ecotoxicology and Environmental Safety 195 (2020) 110436

Fig. 5. The proportions of contribution from different end-members for surface sediments of rivers and sediment profiles of lakes in Beijing. can infer that the organic matter sources of the sediments have changed Beijing rivers range from 0.63% to 10.83% and 0.06%–0.86%, respec- 15 13 at these two layers. However, the δ Norg and δ Corg compositions tively. It indicated that there are great environmental risks in these shifted at 20 cm and 60 cm layers in the other three profiles. If the rivers. The concentrations of TOC and TON in the four sediment profiles deposition rates of lake sediments are same, this observation implies below the 5 cm increase in the order of that the organic matter sources of the sediments changed at the de- Miyun < Chuidiao < Qunming < Houhai, which is relative to their position time of the 20 cm layer. This may also be caused by environ- respective environment around the lakes. Moreover, the water quality mental events that occurred at the same year. was quite good and there was no risk of eutrophication in Miyun reservoir. The concentrations of TOC and TON increase from the bottom to the surface of sediments in the four lakes, indicating that the pro- 5. Conclusions ductivity of lakes have been improved over time. 13 15 δ Corg and δ Norg in surface sediments of 18 rivers range from This study assessed the distributions of total organic carbon, total −27.2‰ to −24.9‰ and −2.2‰ to +10.9‰, respectively. Using organic nitrogen, and their isotopes in sediments of rivers and lakes in δ13C-based end-member mixing and C/N ratio model, the organic Beijing. The TOC and TON concentrations in surface sediments from

8 Q. Guo, et al. Ecotoxicology and Environmental Safety 195 (2020) 110436 matter in surface sediments of these 18 rivers were mainly derived from Goni, M.A., Teixeira, M.J., Perkey, D.W., 2003. Sources and distribution of organic matter sewage and C3 plant. The sources of organic matter for four sediment in a river-dominated estuary (Winyah Bay, SC, USA). Estuar. Coast Shelf Sci. 57, – fi ff 1023 1048. pro les di ered within each layer. The main sources from the surface to Graham, M.C., Eaves, M.A., Farmer, J.G., Dobson, J., Fallick, A.E., 2001. A study of bottom in the Chuidiao garden are atmospheric deposition, algae and carbon and nitrogen stable isotope and elemental ratios as potential indicators of soil organic matter, respectively. In the surface and subsurface sedi- source and fate of organic matter in sediments of the forth estuary, Scotland. Estuarine. Coastal and Shelf Science 52, 375–380. ments of Houhai, substantial contribution from algae is observed, Gu, Y.G., Ouyang, J., Ning, J.J., Wang, Z.H., 2017. Distribution and sources of organic however, the sewage is the main source of organic matter at the bottom carbon, nitrogen and their isotopes in surface sediments from the largest mariculture of the lake. The Qunming lake have complicated sources compared with zone of the eastern Guangdong coast, South China. Mar. Pollut. Bull. 120, 286–291. other three lakes. Guo, Q., Strauss, H., Chen, T.B., Zhu, G., Yang, J., Yang, J., Lei, M., Zhou, X., Peters, M., Xie, Y., Zhang, H., Wei, R., Wang, C., 2013. Tracing the source of Beijing soil organic carbon: a carbon isotope approach. Environ. Pollut. 176, 208–214. CRediT authorship contribution statement He, G., Fang, H., Bai, S., Liu, X., Chen, M., Bai, J., 2011. Application of a three-dimen- sional eutrophication model for the Beijing Guanting reservoir, China. Ecol. Model. 222, 1491–1501. Qingjun Guo: Conceptualization, Methodology, Supervision. He, W., Qin, N., Kong, X.Z., Liu, W.X., Wu, W.J., He, Q.S., Yang, C., Jiang, Y.J., Wang, Chunyu Wang: Data curation, Writing - original draft. Rongfei Wei: Q.M., Yang, B., Xu, F.L., 2014. Ecological risk assessment and priority setting for Writing - original draft, Software, Supervision. Guangxu Zhu: typical toxic pollutants in the water from Beijing-Tianjin-Bohai area using Bayesian matbugs calculator (BMC). Ecol. Indicat. 45, 209–218. Visualization, Investigation. Meng Cui: Software, Validation. Kanaya, G., Nakamura, Y., Koizumi, T., Yamada, K., Koshikawa, H., Kohzu, A., Maki, H., Chukwunonso Peter Okolic: Writing - review & editing. 2013. Temporal changes in carbon and nitrogen stable isotope ratios of macro- zoobenthos on an artificial tidal flat facing a hypertrophic canal, inner Tokyo Bay. Mar. Pollut. Bull. 71, 179–189. Declaration of competing interest Kaushal, S., Binford, M.W., 1999. Relationship between C: N ratios of lake sediments, organic matter sources, and historical deforestation in Lake Pleasant, Massachusetts, The authors declare that they have no known competing financial USA. J. Paleolimnol. 22, 439–442. fl Ke, Z., Tan, Y., Huang, L., Zhao, C., Jiang, X., 2017. Spatial distributions of delta(13)C, interests or personal relationships that could have appeared to in u- delta(15)N and C/N ratios in suspended particulate organic matter of a bay under ence the work reported in this paper. serious anthropogenic influences: Daya Bay, China. Mar. Pollut. Bull. 114, 183–191. Kendall, C., Galdwell, E.A., 1998. Fundamentals of isotope geochemistry. In: Kendall, C., Acknowledgments McDonnell, J.J. (Eds.), Isotope Tracers in Catchment Hydrology. Elsevier Science B.V., Amsterdam, pp. 51–89. Kendall, C., Silva, S.R., Kelly, V.J., 2001. Carbon and nitrogen isotopic compositions of This work was financially supported by National Natural Science particulate organic matter in four large river systems across the United States. – Foundation of China (No. 41625006, 41761144066, 41890822, Hydrol. Process. 15, 1301 1346. Kreitler, C.W., 1979. Nitrogen-isotope ratio studies of soils and groundwater nitrate from 41561144005, 41603012) and the Development Services of Featured alluvial fan aquifers in Texas. J. Hydrol. 42, 147–170. Institute of Chinese Academy of Sciences (No. TSYJS01). Kubo, A., Kanda, J., 2017. Seasonal variations and sources of sedimentary organic carbon in Tokyo Bay. Mar. Pollut. Bull. 114, 637–643. Kuwae, M., Yamaguchi, H., Tsugeki, N.K., Miyasaka, H., Fukumori, K., Ikehara, M., References Genkai-Kato, M., Omori, K., Sugimoto, T., Ishida, S., Takeoka, H., 2007. Spatial distribution of organic and sulfur geochemical parameters of oxic to anoxic surface – Andrews, J.E., Greenaway, A.M., Dennis, P.F., 1998. Combined carbon-isotope and C/N sediments in Beppu Bay in southwest Japan. Estuar. Coast Shelf Sci. 72, 348 358. ratios as indicators of source and fate of organic-matter in a poorly flushed, tropical Lücke, A., Schleser, G.H., Zolitschka, B., Negendank, J.F.W., 2003. A lateglacial and estuary - hunts Bay, Kingston Harbor, Jamaica. Estuar. Coast Shelf Sci. 46, 743–756. holocene organic carbon isotope record of lacustrine palaeoproductivity and climatic Aji, K., Tang, C., Song, X., Kondoh, A., Sakura, Y., Yu, J., Kaneko, S., 2008. Characteristics change derived from varved lake sediments of Lake Holzmaar, Germany. Quat. Sci. – of chemistry and stable isotopes in groundwater of Chaobai and Yongding river basin, Rev. 22, 569 580. North China plain. Hydrol. Process. 22, 63–72. Lamb, A.L., Wilson, G.P., Leng, M.J., 2006. A review of coastal palaeoclimate and relative δ13 Aravena, R., Warner, B., MacDonald, G., Hanf, K., 1992. Carbon isotope composition of sea-level reconstructions using C and C/N ratios in organic material. Earth Sci. – lake sediments in relation to lake productivity and radiocarbon dating. Quat. Res. 37, Rev. 75, 29 57. 333–345. Li, W., Gao, L., Shi, Y., Wang, Y., Liu, J., Cai, Y., 2016. Spatial distribution, temporal Balesdent, J., Girardin, C., Mariotti, A., 1993. Site-Related 13C of tree leaves and soil variation and risks of parabens and their chlorinated derivatives in urban surface – organic matter in a temperate forest. Ecology 74, 1713–1721. water in Beijing, China. Sci. Total Environ. 539, 262 270. Banaru, D., Harmelin-Vivien, M., Gomoiu, M.T., Onciu, T.M., 2007. Influence of the da- Liu, K.K., Kao, S.J., Wen, L.S., Chen, K.L., 2007. Carbon and nitrogen isotopic composi- nube river inputs on C and N stable isotope ratios of the Romanian coastal waters and tions of particulate organic matter and biogeochemical processes in the eutrophic – sediment (Black Sea). Mar. Pollut. Bull. 54, 1385–1394. Danshuei Estuary in northern Taiwan. Sci. Total Environ. 382, 103 120. Boutton, T.W., 1991. Stable carbon isotope ratios of natural materials: II. Atmospheric, Lotze, H.K., Lenihan, H.S., Bourque, B.J., Bradbury, R.H., Cooke, R.G., Kay, M.C., Kidwell, terrestrial, marine, and freshwater environments. In: Coleman, D.C., Fry, B. (Eds.), S.M., Kirby, M.X., Peterson, C.H., Jackson, J.B., 2006. Depletion, degradation, and – Carbon Isotopes Techniques. Academic Press, San Diego, pp. 173–185. recovery potential of estuaries and coastal seas. Science 312, 1806 1809. Brandes, J.A., Devol, A.H., 2002. A global marine-fixed nitrogen isotopic budget: im- Lu, F., Liu, Z., Ji, H., 2012. Carbon and nitrogen isotopes analysis and sources of organic plications for Holocene nitrogen cycling. Global Biogeochem. Cycles 16. matter in the upper reaches of the Chaobai River near Beijing, China. Sci. China Earth – BSY, 2017. Beijing Statistical Yearbook-Population and Employment. Beijing, China. Sci. 56, 217 227. Cole, M.L., Kroeger, K.D., McClelland, J.W., Valiela, I., 2006. Effects of watershed land Machiwa, J.F., 2010. Stable carbon and nitrogen isotopic signatures of organic matter – use on nitrogen concentrations and δ15 Nitrogen in groundwater. Biogeochemistry sources in near-shore areas of Lake Victoria, East Africa. J. Great Lake. Res. 36, 1 8. 77, 199–215. Maksymowska, D., Richard, P., Piekarek-Jankowska, H., Riera, P., 2000. Chemical and Dai, G., Wang, B., Huang, J., Dong, R., Deng, S., Yu, G., 2015. Occurrence and source isotopic composition of the organic matter sources in the Gulf of Gdansk (southern – apportionment of pharmaceuticals and personal care products in the Beiyun River of Baltic sea). Estuar. Coast Shelf Sci. 51, 585 598. Beijing, China. Chemosphere 119, 1033–1039. Mariotti, A., Lancelot, C., Billen, G., 1984. Natural isotopic composition of nitrogen as a Dai, J., Song, J., Li, X., Yuan, H., Li, N., Zheng, G., 2007. Environmental changes reflected tracer of origin for suspended organic matter in the Scheldt estuary. Geochem. – by sedimentary geochemistry in recent hundred years of Jiaozhou Bay, North China. Cosmochim. Acta 48, 549 555. Environ. Pollut. 145, 656–667. McClelland, J.W., Valiela, I., Michener, R.H., 1997. Nitrogen-stable isotope signatures in Deines, P., 1980. The isotopic composition of reduced carbon. In: Fritz, P., Fontes, J.C. estuarine food webs: a record of increasing urbanization in coastal watersheds. – (Eds.), Handbook of Environmental Isotope Geochemistry. vol. 1. The Terrestrial Limnol. Oceanogr. 42, 930 937. Environment, A, pp. 329–406. Meyers, P.A., 1997. Organic geochemical proxies of paleoceanographic, paleolimnologic, – Gao, X., Yang, Y., Wang, C., 2012. Geochemistry of organic carbon and nitrogen in surface and paleoclimatic processes. Org. Geochem. 27, 213 250. sediments of coastal Bohai Bay inferred from their ratios and stable isotopic sig- Meyers, P.A., Ishiwatari, R., 1993. Lacustrine organic geochemistry - an overview of in- natures. Mar. Pollut. Bull. 64, 1148–1155. dicators of organic matter sources and diagenesis in lake sediments. Org. Geochem. – Gaye-Haake, B., Lahajnar, N., Emeis, K.C., Unger, D., Rixen, T., Suthhof, A., Ramaswamy, 20, 867 900. fi V., Schulz, H., Paropkari, A.L., Guptha, M.V.S., Ittekkot, V., 2005. Stable nitrogen Meyers, P.A., 1994. Preservation of elemental and isotopic source identi cation of sedi- – isotopic ratios of sinking particles and sediments from the northern Indian Ocean. mentary organic matter. Chem. Geol. 114, 289 302. Mar. Chem. 96, 243–255. Meyers, P.A., Teranes, J.L., 2002. Sediment organic matter. Tracking Environmental – Gearing, J.N., Gearing, P.J., Rudnick, D.T., Requejo, A.G., Hutchins, M.J., 1984. Isotopic change using lake sediments. Physical and Geochemical Methods 239 269. ff variability of organic carbon in a phytoplankton-based, temperate estuary. Geochem. Midwood, A.J., Boutton, T.W., 1998. Soil carbonate decomposition by acid has little e ect δ13 – Cosmochim. Acta 48, 1089–1098. on C of organic matter. Soil Biol. Biochem. 30, 1301 1307. Ogrinc, N., Fontolan, G., Faganeli, J., Covelli, S., 2005. Carbon and nitrogen isotope

9 Q. Guo, et al. Ecotoxicology and Environmental Safety 195 (2020) 110436

compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N conserver.iugocafe.org/user/brice.semmens/MixSIAR. Adriatic Sea): indicators of sources and preservation. Mar. Chem. 95, 163–181. Talbot, M., 1990. A review of the palaeohydrological interpretation of carbon and oxygen Pancost, R.D., Boot, C.S., 2004. The palaeoclimatic utility of terrestrial biomarkers in isotopic ratios in primary lacustrine carbonates. Chem. Geol. Isot. Geosci. 80, marine sediments. Mar. Chem. 92, 239–261. 261–279. Peters, M., Guo, Q., Strauss, H., Wei, R., Li, S., Yue, F., 2019. Contamination patterns in Thornton, S.F., McManus, J., 1994. Application of organic carbon and nitrogen stable river water from rural Beijing: a hydrochemical and multiple stable isotope study. Sci. isotope and C/N ratios as source indicators of organic matter provenance in estuarine Total Environ. 654, 226–236. systems: evidence from the Tay Estuary, Scotland. Estuarine. Coastal and Shelf Peters, M., Guo, Q., Strauss, H., Zhu, G., 2015. Geochemical and multiple stable isotope Science 38, 219–233. (N, O, S) investigation on tap and bottled water from Beijing, China. J. Geochem. Wada, E., Hattori, A., 1991. Nitrogen in the Sea: Forms, Abundances and Rate Processes. Explor. 157, 36–51. Boca Raton CRC Press, Florida 208. Qi, S., Leipe, T., Rueckert, P., Di, Z., Harff, J., 2010. Geochemical sources, deposition and Wang, Z., Lu, X., Zhang, K., 2016. Distribution and contamination of metals and biogenic enrichment of heavy metals in short sediment cores from the Pearl River Estuary, elements in sediments from Zhifu Bay of the Yellow Sea, China. J. Environ. Sci. Southern China. J. Mar. Syst. 82, S28–S42. (China) 41, 6–15. Rao, Z., Guo, W., Cao, J., Shi, F., Jiang, H., Li, C., 2017. Relationship between the stable Yu, F., Zong, Y., Lloyd, J.M., Huang, G., Leng, M.J., Kendrick, C., Lamb, A.L., Yim, carbon isotopic composition of modern plants and surface soils and climate: a global W.W.S., 2010. Bulk organic δ13C and C/N as indicators for sediment sources in the review. Earth Sci. Rev. 165, 110–119. Pearl River delta and estuary, southern China. Estuarine. Coastal and Shelf Science Rooze, J., Meile, C., 2016. The effect of redox conditions and bioirrigation on nitrogen 87, 618–630. isotope fractionation in marine sediments. Geochem. Cosmochim. Acta 184, Zhang, S., Li, Y., Zhang, T., Peng, Y., 2015. An integrated environmental decision support 227–239. system for water pollution control based on TMDL - a case study in the Beiyun River Schubert, C.J., Calvert, S.E., 2001. Nitrogen and carbon isotopic composition of marine watershed. J. Environ. Manag. 156, 31–40. and terrestrial organic matter in Arctic Ocean sediments: implications for nutrient Zhang, Y., Zhang, T., Guo, C., Lv, J., Hua, Z., Hou, S., Zhang, Y., Meng, W., Xu, J., 2017. utilization and organic matter composition. Deep-Sea Res. Part I Oceanogr. Res. Pap. Drugs of abuse and their metabolites in the urban rivers of Beijing, China: occurrence, 48, 789–810. distribution, and potential environmental risk. Sci. Total Environ. 579, 305–313. Schweizer, M., Fear, J., Cadisch, G., 1999. Isotopic (13C) fractionation during plant re- Zhou, Y.X., Wang, L.Y., Liu, J.R., Li, W.P., Zheng, Y.J., 2012. Options of sustainable sidue decomposition and its implications for soil organic matter studies. Rapid groundwater development in Beijing Plain, China. Phys. Chem. Earth 47–48, 99–113. Commun. Mass Spectrom. 13, 1284–1290. Zhu, S.F., Liu, C.Q., 2006. Vertical patterns of stable carbon isotope in soils and particle- Strauss, H., Des Marais, D.J., Hayes, J.M., Summons, R.E., 1992. Abundances and isotopic size fractions of karst areas, southwest China. Environ. Geol. 50, 1119–1127. compositions of carbon and sulfur species in whole rock and kerogen samples. In: Zimmerman, A.R., Canuel, E.A., 2000. A geochemical record of eutrophication and anoxia Schopf, J.W., Klein, C. (Eds.), In the Proterozoic Biospere-A Multidisciplinary Study. in Chesapeake Bay sediments: anthropogenic influence on organic matter composi- Cambridge University Press, Cambridge, pp. 711–798. tion. Mar. Chem. 69, 117–137. Stock, B.C., Semmens, B.X., 2013. MixSIAR GUI user Manual. Version 3.1. http://