Environmental Science: Processes & Impacts
Spatial distribution of heavy metals in the West Dongting Lake floodplain, China
Journal: Environmental Science: Processes & Impacts
Manuscript ID EM-ART-11-2019-000536.R1
Article Type: Paper
Page 1 of 28 Environmental Science: Processes & Impacts
1 2 3 Environmental Significance Statement 4 5 The study aims to understand heavy metal pollution in the West Dongting Lake (Ramsar Site) 6 and to assess ecological hazards to humans, wildlife and even ecosystems. Comparing to the 7 soil quality criteria in China, the concentration of total Hg and Cd were over the China’s risk 8 screening values for soil contamination of agricultural land of these metals by 103.9 and 2.1 9 times, respectively. According to this study, we found that West Dongting Lake is at high 10 11 ecological risk of heavy metal pollution, and the major contaminant, mercury, may come from 12 continuous pollutant anthropogenic activities such as regional industrial activities within Yuan 13 River and Li River watershed. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Environmental Science: Processes & Impacts Page 2 of 28
1 2 3 1 Spatial distribution of heavy metals in the West Dongting Lake floodplain, 4 5 6 2 China 7 8 1,2 1 1 1,3 1 9 3 Dong Peng (1), Ziyu Liu (2), Xinyue Su (2), Yaqian Xiao (3), Yuechen Wang (4), 10 11 4 Beth A Middleton4, Ting Lei1,* 12 13 5 *Corresponding author email: [email protected]. 14 15 6 1 Address: Beijing Forestry, School of Nature Conservation, 35 Tsinghua East Road Haidian 16 17 18 7 Distinct, Beijing 100083, P.R. China; 19 2 20 8 [email protected] 21 22 9 3 Beijing Normal University, No. 19, XinJieKouWai St., HaiDian District, Beijing 100875, P. R. 23 24 10 China 25 26 11 4 U.S. Geological Survey, Wetland and Aquatic Research Center, 700 Cajundome Boulevard, 27 28 12 Lafayette, LA 70506 USA; [email protected] 29 30 13 *Corresponding author. 31 14 32 33 15 34 16 35 17 36 18 37 19 38 20 [Predecisional information for manuscript submission only] This draft manuscript is 39 21 distributed solely for purposes of scientific peer review. Its content is deliberative and 40 22 predecisional, so it must not be disclosed or released by reviewers. Because the manuscript 41 23 has not yet been approved for publication by the U.S. Geological Survey (USGS), it does 42 24 not represent any official USGS finding or policy. [This is removed from the final version 43 44 25 after it is accepted by the journal]. 45 26 46 47 48 49 50 51 52 53 54 55 56 57 1 58 59 60 Page 3 of 28 Environmental Science: Processes & Impacts
1 2 3 27 Abstract 4 5 6 28 The protection of Dongting Lake is important because it is an overwintering and 7 8 29 migration route for many rare and endangered birds of East Asia and Australasia, but an 9 10 11 30 assessment of heavy metal contamination in West Dongting Lake is lacking. A total of 75 12 13 31 sediment samples (five sites x three sediment depths x five repeats) were collected in West 14 15 32 Dongting Lake in January 2017 to assess the spatial distribution and ecological risk of 16 17 33 heavy metal in West Dongting Lake. Heavy metal values varied by sediment depth 18 19 20 34 including As, Cd, Zn, and Cu, with depth giving an indication of recent vs. historical 21 22 35 deposition. The major input of Hg, Cu, Ni may come from continued anthropogenic 23 24 36 activities related to regional industrial activities within Yuan River and Li River whereas, 25 26 27 37 the major sources of spread Cd pollution may be from agricultural fertilizers. 28 29 38 30 31 39 Key words 32 33 34 40 West Dongting Lake, Floodplain, Heavy metals, Spatial distribution 35 36 41 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 2 58 59 60 Environmental Science: Processes & Impacts Page 4 of 28
1 2 3 42 1. Introduction 4 5 6 43 West Dongting Lake it is a key biodiversity hotspot in China and designated as a 7 8 44 Ramsar Key Wetland because of its unique aquatic ecosystem and rich biodiversity. It 9 10 11 45 also is the main resource of industrial and agriculture water for millions of residents in the 12 13 46 region (e.g., Changde City). Thus, poor water quality and potential effects on biota have 14 15 47 received increased attention in this region during recent years (1-4). Heavy metal 16 17 48 contamination exists in Dongting Lake, but studies did not explore the connection of the 18 19 20 49 delta of the lake to the tributaries feeding it (Li and Yuan River). For example, Jiang et al. 21 22 50 sampled the entire lake (Jiang et al. 2008), but not the tributaries flowing into the lake. 23 24 51 Other studies have found higher levels of contamination coming from the Yuan vs. the Li 25 26 27 52 River entering West Dongting Lake but do not sample in various places along these rivers, 28 29 53 using the same methodology (5-7). One of the objectives of our research was to sample 30 31 54 these river gradients from up to downstream into the delta area where these tributaries meet, 32 33 34 55 to better track potential sources of heavy metals on the Dongting Lake floodplains (Figure 35 36 56 1). 37 38 57 Heavy metal pollution has toxic effects on the human body causing headaches, muscle 39 40 58 and joint aches, confusion and other symptoms (8, 9). Arsenic can promote cancers and 41 42 43 59 cadmium can attack kidney, liver, bone and the female reproduction system, also lead and 44 45 60 mercury are neurotoxins, which can be consumed via seafood, vegetables and rice (8-10). 46 47 61 Especially in countries with developing industries, industrial effluent, atmospheric 48 49 50 62 deposition and sewage, polluted rivers are more likely to discharge heavy metals into the 51 52 63 aquatic ecosystems (5, 11-16). Besides, heavy metals are persistent and have complex 53 54 64 ecological effects on livestock, birds, and human beings (17-21). Various forms of heavy 55 56 57 3 58 59 60 Page 5 of 28 Environmental Science: Processes & Impacts
1 2 3 65 metals and their interactions can have complex ecological effects on organisms (22). These 4 5 6 66 toxins are also carried by streams and influenced by the sedimentation condition, for 7 8 67 example, in the middle-reach of the Yangtze River (4, 23, 24). Moreover, the remediation 9 10 68 methods of soil heavy metal various might be accomplished using plant species that 11 12 69 hyperaccumulate these toxins (25), burial by sediment,or remediation via the application 13 14 15 70 of biochar (26, 27). 16 17 71 Our objective was to determine the contamination level of heavy metals in the soils of 18 19 72 tributaries feeding the deltaic floodplains of Dongting Lake at various depths. This study 20 21 22 73 is helpful for wildlife conservation, especially for migratory waterfowl, and environmental 23 24 74 policies regarding fisheries in the lake. 25 26 75 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 4 58 59 60 Environmental Science: Processes & Impacts Page 6 of 28
1 2 3 76 2. Materials and methods 4 5 6 77 2.1 Study area 7 8 78 Dongting Lake is the largest freshwater lake of Hunan Province and the second largest 9 10 11 79 in China. The western portion of Dongting Lake (West Dongting Lake, 30044 ha) connects 12 13 80 the Yangtze River with South Dongting Lake and collects water from both the Yuan and 14 15 81 Li Rivers. West Dongting Lake was designated as a Ramsar Wetland of International 16 17 82 Importance in 2002 (https://rsis.ramsar.org/ris/1154). Therefore, this complex river system 18 19 20 83 is crucial to the storage of flood water and the irrigation of farmland in the region (28). 21 22 84 Yuan and Li River, which have mining industries and vast farmland along the river, are in 23 24 85 the upper reaches of West Dongting Lake. Thus, many pollutants enter into the lake by the 25 26 27 86 river. The sedimentation in the western part of the lake is the highest in Dongting Lake 28 29 87 (24). The research sites including Taiyangcha (YnUp, upper reaches of Yuan River), 30 31 88 Guanceta (YnMd, middle reaches of Yuan River), Liuzu (YnLiDelta, downstream reaches 32 33 34 89 of Yuan and Li River) were placed in the flow direction of the Yuan River. Dabatai (LiUp, 35 36 90 upper reaches of Yuan River), Dalianzhang (LiMd, middle reaches of Yuan River; in the 37 38 91 delta) and Liuzu (YnLiDelta, downstream reaches of Yuan and Li River) were along the 39 40 92 Li River; YnLiDelta near the intersection of the two rivers (Figure1). 41 42 43 93 2.2 Sample Collection 44 45 94 A total of 75 sediment samples were collected in West Dongting Lake to evaluate the 46 47 95 spatial distributions of heavy metals in January 2017. Each at 3 depths (0-10, 10-20, 20-30 48 49 50 96 cm were collected and marked as surface sediment, medium sediment and deep sediment, 51 52 97 respectively, in all five sites with five samples within plots of 10 ×10 m (see in Table 1). 53 54 55 98 Each of the 75 samples were collected with a spade (20×20×10 cm), and were packed in 56 57 5 58 59 60 Page 7 of 28 Environmental Science: Processes & Impacts
1 2 3 99 re-closable bags and transported to the laboratory at room temperature (0 ℃ to 8 ℃) 4 5 6 100 within 24 hours. 7 8 101 2.3 Laboratory Analysis 9 10 ℃ ℃ 11 102 The samples were air dried at room temperature (0 to 8 ) for five days in the 12 13 103 laboratory. Air dried sediment samples were ground using a ceramic mortar and pestle, 14 15 104 sieved through a 100-mesh nylon sieve (29), and placed into plastic bags at room 16 17 18 105 temperature. Following this, every powdered samples (0.5 g) was digested by various acids 19 20 106 (HNO3, HClO4, HF; analytical reagent grade, produced from Beijing Chemicals Factory, 21 22 107 Beijing, China) and heated in a 100 ml polyfluoroethylene-crucible with lid at 220 ℃ 23 24 25 108 *1h+280℃ until dry. All dry digestion products were dissolved by 5 ml 50% HNO3 in a 26 27 109 50 ml volumetric flask. The digested solutions were stored in 25 ml centrifuge tubes (30, 28 29 30 110 31). 31 32 111 All elemental analysis work was done by Beijing Forestry University Public Analysis 33 34 112 Center. Concentrations of total Hg, Pb, Cd, Ni, Zn and As were analyzed with Inductively 35 36 37 113 Coupled Plasma Mass Spectrometry (ICP-MS, optima 8X00, USA). Cu was analyzed 38 39 114 using an Atomic Absorption Spectrometer (AAS, SPECTRAA-220, Australia). Initial 40 41 115 calibration verification and reagent blanks were used for quality control. 42 43 44 116 2.4 Statistical method 45 46 117 To assess the differences of heavy metals concentration at various sediment depths 47 48 118 and sample sites, two-way ANOVA analysis was performed and data were appropriately 49 50 119 log transformed to meet statistical assumptions. Two-way ANOVA were used to test 51 52 53 120 treatment differences, using SNK to test differences in specific means (SPSS 19.0, 2018). 54 55 121 Principal Components Analysis was applied used to explore the relationships of heavy 56 57 6 58 59 60 Environmental Science: Processes & Impacts Page 8 of 28
1 2 3 122 metals in floodplain sediments of the West Dongting Lake. Normally, a source of pollution 4 5 6 123 contains various kinds of heavy metal contamination. For example, the waste water 7 8 124 discharged by industry would have many different heavy metal pollutants. Principle 9 10 125 Components Analysis (PCA) was used to assess if certain metals occurred together at the 11 12 126 same sites to suggest if these may have come from a similar source using R (R 3.5.0, 2018). 13 14 15 127 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 7 58 59 60 Page 9 of 28 Environmental Science: Processes & Impacts
1 2 3 128 3 Results 4 5 6 129 3.1 Metal concentrations in sediments 7 8 130 In West Dongting Lake, the concentrations of Ni, As, Cd, Hg, Pb, Zn, Cu varied from 9 10 11 131 13.23 to 71.55 mg/kg, not detected (ND) to 14.59 mg/kg, ND to 2.65 mg/kg, 149.00 mg/kg 12 13 132 to 323.19 mg/kg, ND to 5.50 mg/kg, 28.85 to 118.40 mg/kg, 12.80 to 54.00 mg/kg, 14 15 133 respectively, with mean concentrations of 26.95, 0.97, 0.64, 249.25, 0.14, 78.09, 41.55 16 17 134 mg/kg, respectively (Table 2). 18 19 20 135 3.2 Differences between sites and depths 21 22 136 Except Pb, the other heavy metals showed significant differences between sample sites 23 24 137 (Table 3). Only As, Cd and Zn showed significant difference at different sediment depths. 25 26 27 138 The concentration of As in difference depths from highest to lowest included: surface 28 29 139 sediment > medium sediment > deep sediment; the concentration of Cd was ranked as: 30 31 140 medium sediment > deep sediment > surface sediment. The concentration of Zn was ranked 32 33 34 141 as: deep sediment > medium sediment > surface sediment. Sample sites locator and 35 36 142 sediment depths did not interact (p > 0.05). The concentration of As in LiUp was higher 37 38 143 than other sample sites. In addition, the concentration of Cd in YnMd and LiUp were higher 39 40 144 than YnUp, LiMd and YnLiDelta. 41 42 43 145 3.3 Principal Component Analysis, PCA 44 45 146 Using three axes in the Principal Component Analysis, 70% of the data variance could be 46 47 147 explained (Table 4, Figure 2). Hg, Cu, Ni, Zn and Pb were all related to the first principal 48 49 50 148 component (RC1) (proportion variance = 0.28). Cd, Cn and As were related to the the 51 52 149 second axis (RC2) (proportion variance = 0.25). Pb and As were related to the third axis 53 54 150 (RC3) (proportion variance =0.16). 55 56 57 8 58 59 60 Environmental Science: Processes & Impacts Page 10 of 28
1 2 3 151 3.4 Spatial distribution analyze and sources identify of heavy metals 4 5 6 152 In general, Yuan River may carry more pollutants into the lake than the Li River (Figure 7 8 153 3). LiMd shows a lower concentration of Ni, Cd, Hg, Zn and Cu than LiUp, suggesting 9 10 154 that deposition may be occurring upstream. In contrast, YnMd shows a higher 11 12 155 concentration of Ni, Hg and Cu than YnUp. There was obvious pattern of soil heavy metal 13 14 15 156 pollution along the two rivers. In YnMd, the flow and relative position of the river show 16 17 157 a balance and then relatively high concentrations of Hg are found in the middle reaches 18 19 158 of this river. The reason why LiMd shows a lower concentration of pollutant may be 20 21 22 159 because is the site is not quite close to theoff the main channel of the river. And tThe 23 24 160 concentration of As, Ni, Cd and Zn show highest value inare highest in the YnLiDelta. 25 26 161 This may indicate that the pollutants carried by the two rivers have an additive effect on 27 28 29 162 each other at the junction and the main pollutants were cameoriginated from upstream 30 31 163 sources on the Yuan River (Figure 3). 32 33 164 Usually, the surface sediment contains more heavy metals of Cd and Zn, but, the 34 35 165 highest level of As is the middle sediment (Figure 4). The significant differences of As, 36 37 38 166 Cd and Zn along sediment depths suggested that As, Cd and Zn pollution may come from 39 40 167 annual human activities or seasonal human activities such as fisheries aquaculture. Other 41 42 168 heavy metal such as Hg pollution had no significant difference between sediment depth. 43 44 45 169 So, its input came from continuous human activities and it may be more related to regional 46 47 170 industrial activities, and could enter the wetlands via air or water (32, 33). 48 49 171 According to the PCA analysis, Hg, Cu, Ni contamination sources are related, and may 50 51 52 172 enter the wetland from the same way. From 2008 to 2017, previous research suggested that 53 54 173 the mercury concentration in Dongting Lake was stable and continuous (3, 34, 35) and 55 56 57 9 58 59 60 Page 11 of 28 Environmental Science: Processes & Impacts
1 2 3 174 usually the major input of these metals are related to human activities(36, 37). Thus, the 4 5 6 175 major input of Hg, Cu, Ni may come from continued anthropogenic activities related to 7 8 176 regional industrial activities within Yuan and Li River Watershed. The concentration of Cd 9 10 177 is affected by sample location and sediment depths (Figure 3, 4). The natural occurred Cd 11 12 178 levels are extremely low (9, 38) with the major source of spread Cd pollution are often 13 14 15 179 from agricultural fertilizers (29, 39), therefore the PCA group related to Cd, Zn may come 16 17 180 from agriculture activities. The irrigation and parent sediments or rock erosion are main 18 19 181 sources of the contaminations of lead and arsenic (10, 40-42). In contrast, there was no 20 21 22 182 groundwater irrigation going on in the region and there is little difference between the 23 24 183 concentration of Pb and the early geochemical concentration of Pb, so Pb and As may come 25 26 184 from sediment parental materials. 27 28 29 185 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 10 58 59 60 Environmental Science: Processes & Impacts Page 12 of 28
1 2 3 186 4 Discussion 4 5 6 187 Compared to the heavy metal pollution status in the other regional wetlands in China 7 8 188 or elsewhere (Table 5), such high levels of contamination of Hg in West Dongting Lake is 9 10 11 189 rare in other parts of the world. The concentration of Ni, As and Pb were significantly lower 12 13 190 than other those of other lakes. The concentrations of several other metals (i.e., Cd, Zn and 14 15 191 Cu) in West Dongting Lake areis similar to that of other wetlands exclude the high Cu 16 17 192 pollution in Hindon River .The mercury pollution in West Dongting Lake is much higher 18 19 20 193 than other wetlands including Poyang Lake, Dongping Lake, Yellow River, Yangtze River, 21 22 194 Huludao Fresh River in China and Hindon River, Awash River Basin, Nemrut Bay, 23 24 195 Candarli Gulf, Shur River, Tigris River in developing country and Esaro in developed 25 26 27 196 country. Other heavy metals pollution is not as serious as Hindon River, Esaro river, Awash 28 29 197 River Basin, Nemrut Bay and Tigris River. 30 31 198 Heavy metals contamination is a critical problem in the Yangtze River basin (6) and 32 33 34 199 Dongting Lake (34). Dongting Lake is one of the most polluted lakes in China, possibly 35 36 200 due to the nonferrous mining, metallurgy, and manufacturing industries in Hunan Province 37 38 201 (43). In Dongting Lake, the background values(44) of Ni, As, Cd, Hg, Pb, Zn, Cu are 21.2 39 40 202 mg/kg, 12mg/kg, 0.33mg/kg, 0.047mg/kg, 23.3mg/kg, 83.3mg/kg, 33.3mg/kg, 41 42 43 203 respectively. Other values were reported by Jiang et al. (34) for Ni, As, Cd, Hg, Pb, Zn, Cu 44 45 204 and varied from 18.8-60.5mg/kg, 6.03-34.78mg/kg, 0.06-3.65mg/kg, 0.053-1.08mg/kg, 46 47 205 22.4-118.6mg/kg, 63-189mg/kg, 12.9-83.1mg/kg, respectively. China’s Sediment 48 49 50 206 Environmental Quality Risk Control Standard for sediment contamination of agricultural 51 52 207 land (45) was updated by the Chinese government in 2018 to adopt the new regulation. The 53 54 208 detail of the risk screening values and risk intervention values of the standard are given in 55 56 57 11 58 59 60 Page 13 of 28 Environmental Science: Processes & Impacts
1 2 3 209 Table 6. The pH of the sediments in West Dongtin Lake are between 6.5 and 7.5. The 4 5 6 210 floodplain sediments of Dongting Lake show the following results: At first, levels of Ni, 7 8 211 As, Pb, Zn, Cu in sediments were lower than the risk screening values for sediment 9 10 212 contamination of agricultural land, and the minimum concentration of Cd, As, Pb were too 11 12 213 low to detect. The mean concentrations of Cd were higher than its risk screening values for 13 14 15 214 sediment contamination of agricultural land and the concentration of Hg was much higher 16 17 215 than its risk intervention values for sediment contamination of agricultural land. Also, the 18 19 216 mean concentrations of Cd and Hg exceeded 2.1 and 103.9 times their risk screening values 20 21 22 217 for sediment contamination of agricultural; the mean concentration of Hg was as high as 23 24 218 62.3 times its risk intervention values for sediment contamination of agricultural land. 25 26 219 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 12 58 59 60 Environmental Science: Processes & Impacts Page 14 of 28
1 2 3 220 5 Conclusion 4 5 6 221 Surface sediment of the West Dongting Lake floodplain accumulates by sediment 7 8 222 deposition during flooding. A change in heavy metal concentration at different sediment 9 10 11 223 depths can reflect a change in heavy metal pollution over time. Also, the Yuan River and 12 13 224 Li River show different pattern on heavy metal input which is Yuan River brings more 14 15 225 pollutant to the main lake rather than Li River. Based on the sediment accumulation rate 16 17 226 (in press) in the region, five sample sites were collected at three sediment depths to access 18 19 20 227 the heavy metals (Ni, As, Cd, Hg, Pb, Zn, Cu), and In particular, the concentration of total 21 22 228 Hg in West Dongting Lake is much higher than its risk intervention values for sediment 23 24 229 contamination of agricultural land in the China’s sediment quality criteria. These heavy 25 26 27 230 metals enter the wetland ecosystem via industry, mines and domestic sewage discharged 28 29 231 directly or by surface runoff into Yuan and Li River, which feed into West Dongting Lake. 30 31 232 Additionally, the lower water levels in West Dongting Lake after the construction of the 32 33 34 233 Three Gorges Dam may cause polluted sediments to become exposed to air and 35 36 234 subsequently enter the food chain via plant absorption and the high concentration of heavy 37 38 235 metals indicated that the high contamination exceed acceptable standards and show huge 39 40 236 potential ecological risk. Therefore, the high heavy metals contamination in particular may 41 42 43 237 seriously impact the health of humans and wildlife in this region, especially threats to the 44 45 238 health of migratory birds in the area. The specific toxicity of high contamination mercury 46 47 239 in sediment is unknown because mercury absorbed by the organism in the form of methyl 48 49 50 240 mercury (33), which is we are going to do. Nevertheless, the control of the industrial 51 52 241 emission discharged into aquatic ecosystem and use fertilizer properly may be helpful to 53 54 242 reduce heavy metal contaminations input into West Dongting Lake. 55 56 57 13 58 59 60 Page 15 of 28 Environmental Science: Processes & Impacts
1 2 3 243 Acknowledgments 4 5 6 244 We thank Peng Lingli, Chen Mingzhu, Staff of West Dongting Lake National Nature 7 8 245 Reserve and my classmates in Beijing Forestry University for assistance with field and lab 9 10 11 246 work. We thank anonymous reviewers for comments on earlier versions of the manuscript. 12 13 247 Also thanks to the USGS Ecosystems Program. 14 15 248 16 17 249 Funding: This work was supported by the National Key R&D Program of China (No. 18 19 20 250 2018YFC0507200) and the National Training Program of Innovation and Entrepreneurship 21 22 251 for Undergraduates (No. 201710022069), under the US-China EcoPartnership program and 23 24 252 Beijing Forestry/U.S. Geological Survey Technical Agreement (TAA-15-3921). 25 26 27 253 28 29 254 Data Availability Statement (DAS) 30 31 32 255 The data used to support the findings of this study are available from the corresponding 33 34 256 author upon request. 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 14 58 59 60 Environmental Science: Processes & Impacts Page 16 of 28
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1 2 3 395 Tables 4 5 6 396 Table 1 Locations and abbreviation names of sample sites and sampled at three depths (0- 7 8 397 10, 10-20 and 20-30 cm) using three replications at each site. 9 10 Site abbreviation Latitude Longitude 11 12 Taiyangcha YnUp 28°54′8″N 112°8′54.64″E 13 14 Guanceta YnMd 28°53′35.96"N 112°9′22.68″E 15 16 Dabatai LiUp 28°55′10.63″N 112°12′56.45″E 17 18 Dalianzhang LiMd 28°53′9.36″N 112°12′53.04″E 19 20 Liuzu YnLiDelta 28°51′59.68″N 112°13′18.43″E 21 22 398 23 24 25 399 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 18 58 59 60 Environmental Science: Processes & Impacts Page 20 of 28
1 2 3 4 5 400 Table 2 General characteristics by depth of the heavy metal concentration in sediments of the West Dongting Lake floodplain. 6 7 8 Mean of all depths Mean of all depths 9 Depth (cm) Maximum (mg/kg) Minimum (mg/kg) S.D. (depth) S.D. Background value (mg/kg) 10 (mg/kg) (mg/kg) 11 0-10 33.58 16.77 27.22a 4.09 12 Ni 10-20 34.23 14.75 26.46a 5.03 26.95 7.41 21.2 13 a 14 20-30 71.55 13.23 27.18 11.06 15 0-10 7.64 ND 0.47a 1.59 16 b 17 As 10-20 14.59 ND 2.02 3.67 0.97 2.48 12 18 20-30 2.71 ND 0.43a 0.86 19 0-10 2.49 ND 1.16a 0.79 20 21 Cd 10-20 2.65 ND 0.60b 0.74 0.64 0.77 0.33 22 20-30 1.05 ND 0.16b 0.32 23 a 24 0-10 295.71 180.17 252.37 31.34 249.25 25 Hg 10-20 323.19 149.10 250.38a 51.23 46.26 0.047 26 20-30 316.95 149.00 244.99a 52.76 27 28 0-10 1.20 ND 0.05a 0.23 29 Pb 10-20 2.25 ND 0.16a 0.51 0.14 0.71 23.3 30 31 20-30 5.50 ND 0.22a 1.08 32 0-10 112.50 48.15 94.68a 17.00 33 b 34 Zn 10-20 111.00 44.50 76.33 20.70 78.09 23.81 83.3 35 20-30 118.40 28.85 63.27c 22.01 36 a 37 0-10 54.00 12.80 44.28 10.00 38 Cu 10-20 52.00 22.40 40.39a 8.94 41.55 9.88 33.3 39 20-30 51.20 21.80 39.97a 10.08 40 41 42 401 The a, b, c in the table means different group by ANOVA. 43 44 45 402 ND means concentrations below the detection limit. 46 47 48 49 50 51 52 19 53 54 55 56 57 58 59 60 Page 21 of 28 Environmental Science: Processes & Impacts
1 2 3 4 5 403 Table 3 Two-way ANOVA comparison of sample sites, soil depths, and the interaction of site × soil depth. 6 7 Sample Soil 8 Variable YnUp LiUp YnLiDelta YnMd LiMd 0-10cm 10-20cm 20-30cm Sites × Depths 9 sites Depths 10 df 4 2 8 11 F 7.92 0.403 0.491 Ni 12 Sig. <0.001** 0.67 0.858 13 Mean±S.E. 1.454±0.026b 1.376±0.026ab 1.477±0.026b 1.471±0.026b 1.310±0.026a 1.431±0.020a 1.416±0.020a 1.406±0.020a 14 df 4 2 8 15 16 F 7.83 4.826 1.707 17 As Sig. <0.001** 0.011* 0.115 18 -4.163E- Mean±S.E. 0.163±0.056ab 0.380±0.056b 0.015±0.056a 0.072±0.056a 0.067±0.043a 0.235±0.043b 0.076±0.043a 19 17±0.056a 20 df 4 2 8 21 F 6.029 15.344 1.356 22 Cd 23 Sig. <0.001** <0.001** 0.235 24 Mean±S.E. 0.073±0.025ab 0.179±0.025c 0.160±0.025bc 0.039±0.025a 0.076±0.025ab 0.189±0.019a 0.081±0.019b 0.045±0.019b 25 df 4 2 8 26 F 29.481 0.709 1.805 Hg 27 Sig. <0.001** 0.579 0.32 28 Mean±S.E. 2.407±0.014bc 2.369±0.014b 2.437±0.014cd 2.468±0.014d 2.266±0.014a 2.399±0.011a 2.390±0.011a 2.380±0.011a 29 30 df 4 2 8 31 F 0.684 0.551 1.191 32 Pb Sig. 0.606 0.579 0.32 33 -2.082E- 2.776E- Mean±S.E. 0.023±0.025a 0.025±0.025a 0.049±0.025a 0.003±0.015a 0.026±0.015a 0.030±0.015a 34 17±0.025a 17±0.025a 35 df 4 2 8 36 F 6.425 19.012 0.924 37 Zn 38 Sig. <0.001** <0.001** 0.503 39 Mean±S.E. 1.865±0.03a 1.893±0.03ab 1.987±0.03b 1.860±0.03a 1.777±0.03a 1.979±0.023a 1.871±0.023b 1.779±0.023c 40 df 4 2 8 41 F 30.302 2.16 0.897 Cu 42 Sig. <0.001** 0.124 0.525 43 Mean±S.E. 1.655±0.02a 1.618±0.02a 1.646±0.02a 1.690±0.02a 1.409±0.02b 1.630±0.016a 1.594±0.016a 1.586±0.016a 44 45 ** means significant differences. 46 404 47 48 49 50 51 52 20 53 54 55 56 57 58 59 60 Environmental Science: Processes & Impacts Page 22 of 28
1 2 3 405 Table 4 Rotated component matrix for PCA loadings of heavy metals in West Dongting Lake. 4 5 6 406 7 8 Component loadings 9 Elements 10 RC1 RC2 RC3 11 12 Ni 0.54 0.00 0.17 13 14 As -0.18 0.41 0.60 15 16 Cd 0.06 0.92 -0.10 17 18 Hg 0.83 0.21 0.10 19 20 Pb 0.21 -0.13 0.80 21 22 Zn 0.39 0.83 0.19 23 24 Cu 0.88 0.15 -0.22 25 26 SS loading 1.99 1.78 1.13 27 28 Proportion Var 0.28 0.25 0.16 29 30 Cumulative Var 0.28 0.54 0.70 31 32 407 33 34 35 36 408 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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1 2 3 4 5 409 Table 5 Summaries of heavy metal concentration in sediments from lakes in China. 6 7 Metal concentration （mg/kg） 8 Name of the Wetlands Explain Data from 9 10 Ni As Cd Hg Pb Zn Cu 11 12 West Dongting Lake, China Lake 26.95 0.97 0.64 249.25 0.14 78.09 41.55 This study 13 14 15 Dongting Lake, China Lake NA 29.71 4.65 0.157 60.99 185.25 47.48 (35) 16 17 East Dongting Lake, China Lake NA 4.5 0.82 NA 34.11 121.6 30.21 (3) 18 19 Poyang Lake, China Lake NA NA 0.7 NA 50.4 132.9 62 (46) 20 21 22 Dongping Lake, China Lake NA 25.3 0.285 0.055 35.5 100.5 52 (29) 23 24 Yellow River Riverbed, China River 28.5 NA NA NA NA 50.19 22.95 (19) 25 26 Mainstream 40.91 15.85 1.53 0.15 45.18 140.27 51.64 27 Yangtze River catchment of Wuhan, 28 Tributaries 43.31 14.82 115.56 0.3 47.13 255 57.06 (47) 29 China 30 31 Lakes 40.44 16.03 0.57 0.32 57.78 296.78 75.56 32 33 Yangtze River intertidal zone, China Coastal Wetland 31.8 NA 0.261 NA 27.3 94.3 30.7 (7) 34 28.50 ± 22.95 ± 35 Huludao Freshwater Rivers River NA NA NA NA 50.19 ± 19.26 (11) 36 8.01 7.67 37 13.90– 27.56– 22.22.50– 21.70– Hindon River, India River NA 0.29–6.29 NA (48) 38 57.66 313.57 288.29 280.33 39 40 Awash River Basin, Ethiopia River 89.46 15.87 2.6 0.17 13.53 382.73 79.43 (49) 41 42 Esaro, Italy River NA 20.9 0.22 0.044 13.1 NA NA (50) 43 44 45 Nemrut Bay, Turkey Coastal Wetland 18.1–63.4 14.4–20.2 0.005–0.25 1.70–9.60 22.3–89.4 75–271 9.6–43.7 (51) 46 47 Candarli Gulf, Turkey Coastal Wetland 7.6–100.3 11–35 NA 0.23–1.4 14.5–137.8 55–358 2.7–34.8 (52) 48 49 Shur River, Iran River NA NA 0.55 NA 32 187 26.2 (53) 50 51 52 Maden of Tigris River Turkey River 216.8 8.9 2.4 NA 393.9 530.5 1941.9 (54) 53 54 410 NA: not available 55 56 57 58 59 60 22 Environmental Science: Processes & Impacts Page 24 of 28
1 2 3 411 Table 6 The risk screening values and risk intervention values of China’s Sediment 4 5 6 412 Environmental Quality Risk Control Standard for sediment contamination of 7 8 413 agricultural land, mg/kg 9 10 Type pH≤5.5 5.5
1 2 3 416 Figure caption 4 5 6 417 Figure 1 Locations of sample sites in West Dongting Lake in China (A) Dongting Lake 7 8 418 in China, (B) West Dongting Lake with Dongting Lake and Yangtze River, (C) Yuan 9 10 419 River and Li River flow into Dongting Lake including Taiyangcha (YnUp), Guanceta 11 12 420 (YnMd), and Liuzu (YnLiDelta) along the Yuan River and Dabatai (LiUp), 13 14 15 421 Dalianzhang (LiMd) and Liuzu (YnLiDelta) along the Li River. The arrows indicate 16 17 422 the flow direction of the rivers. Surrounding cities have many industries including auto 18 19 423 parts and manufacturing. Areas directly adjacent to the river include farming and 20 21 22 424 forestry activities. 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 425 60 Environmental Science: Processes & Impacts Page 26 of 28
1 2 3 426 4 5 6 427 Figure 2 Principal Component Analysis loading plot showing heavy metal relationships 7 8 428 in West Dongting Lake. 9 10 429 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 430 31 431 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page 27 of 28 Environmental Science: Processes & Impacts
1 2 3 432 Figure 3 Two-way ANOVA comparison of sample sites 4 5 6 433 7 8 9 2.6 10 2.5 11 12 2.4 13 14 2.3 15 16 2.2 17 18 2.1 19 20 2.0 21 Ni 22 23 As 24 1.8 25 Hg 26 Cd 27 1.6 28 Zn 29 Cu 30 31 Log10(Element) 1.4 32 33 34 35 36 0.5 37 38 0.4 39 40 41 0.3 42 43 0.2 44 45 0.1 46 47 48 0.0 49 YnUp YnMd YnLiDelta LiMd LiUp 50 Sites 51 434 52 53 435 54 55 56 57 58 59 60 Environmental Science: Processes & Impacts Page 28 of 28
1 2 3 436 Figure 4 Two-way ANOVA comparison of sample depths 4 5 6 437 7 8 9 2.5 10 11 12 2.0 13 14 1.5 15 As 16 17 0.4 Cd 18 Zn 19 0.3
20 Log10(Element) 21 22 0.2 23 24 0.1 25 26 0.0 27 0-10 cm 10-20 cm 20-30 cm 28 29 Depth 30 438 31 32 439 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60