Thallium Concentrations, Sources and Ecological Risk in the Surface

Marine Pollution Bulletin 138 (2019) 206–212

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Marine Pollution Bulletin

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Baseline Thallium concentrations, sources and ecological risk in the surface T sediments of the Yangtze Estuary and its adjacent east China marginal sea: A baseline study ⁎ Wen Zhuanga,b, , Yongxia Liua, Lebin Tanga, Wen Yuea, Jinhu Liua, Yuxuan Rena, Xiping Wanga, ⁎⁎ Shanshan Xua, Shaohua Taia, Jing Zhanga, Yu Zhenga, Feng Guoa, Qian Wanga, Jinming Songb, , Liqin Duanb, Qing Chenc a College of City and Architecture Engineering, Zaozhuang University, Zaozhuang, Shandong 277160, China b Key Laboratory of Marine Ecology and Environmental Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, China c College of Life Sciences, Zaozhuang University, Zaozhuang, Shandong 277160, China

ARTICLE INFO ABSTRACT

Keywords: The distribution characteristics, sources and ecological risk of thallium (Tl) in the surface sediments of Yangtze Thallium Estuary and its adjacent sea were studied. Tl concentrations ranged from 0.369 to 1.197 μg g−1 with an average Variation characteristics of 0.674 μg g−1, which was slightly higher than the corresponding background values. Tl concentrations were Sources relatively high in sediments of the south bank of Chongming Island and the Hangzhou Bay mouth, and gradually Ecological risk decreased from inner shelf to outer seas. The variation trend of Tl concentrations was controlled by sediment Surface sediment characteristics, hydrodynamic conditions and sources together. The sediment flux of Tl in the study area was The Yangtze Estuary and its adjacent seas 428.6 t/yr. The Yangtze River, the Yellow River and atmospheric inputs of Tl accounted for 52.7%, 10.5%, and 0.15% of the total sediment flux, respectively. The result of potential ecological index indicated that Tl insurface sediments of the study area had no threat to the ecological environment.

As a natural component of the earth's crust, thallium (Tl) exists in Viraraghavan, 2005; Zhang et al., 2014; Campanella et al., 2016). almost all kinds of environmental media. Tl has higher toxicity to The average concentrations of Tl in the continental crust and the human bodies than other heavy metals such as mercury, cadmium, marine crust are 0.013 ppm and 0.49 ppm, respectively (Delvalls et al., lead, copper or zinc. The chemical properties of Tl are very similar to 1999). Tl concentrations in uncontaminated sediments are generally heavy metals such as lead, gold and silver, and alkali metals such as K, between 0.01 and 5.7 ppm, while the concentrations of Tl can reach Rb and Cs (Peter and Viraraghavan, 2005). Moreover, since the ionic tens of ppm or more in industrial contaminated sediments (Wang et al., radius of Tl (I) (1.49 Å) is similar to that of the hard cation, K (I) 2010). Previous studies suggest that Tl concentrations are higher in the (1.33 Å), the nondiscriminatory uptake of Tl (I) over K (I) has been Pacific Ocean sediments compared to other oceans of the world(Belzile suggested as a mechanism for its toxicity to biota (Duan et al., 2012). and Chen, 2017). Ferrous manganese ore containing hydrogen and Because of the very low concentrations of Tl in natural environment, oceanic clay usually contains relatively high Tl content. Tl also can be pollution and poisoning caused by Tl in natural environment are rare. crystallized in interlayers of illitic or vermiculitic clays; therefore, the Since Tl is usually associated with various metallic sulfide ores and coal distribution of Tl in sediments is often controlled by clay (Duan et al., mines, the wastes from smelting and mining activities are the main 2012). FeeMn oxides also play important roles in the distribution of Tl. sources of Tl pollution (Liu et al., 2017). Tl enrichment has been ob- A large percentage (45–70%) of Tl extracted in the reducible fraction served in the southwest of Guizhou province (China) due to weathering made of iron and manganese oxyhydroxides was reported on estuarine of Tl-Hg-As sulfides (Xiao et al., 2004). In recent years, many un- sediments (Anagboso et al., 2013). Previous studies show that MnO2 expected, occupational or deliberate Tl poisoning incidents have been has strong affinity for Tl, and this closely integrated mechanism isthat caused by mining, metal smelting, industrial production and geo- Tl (I) is oxidized to Tl (III) and thus tightly adsorbed on or precipitated thermal development and utilization (Enviro Tools, 2002; Petera and on the surface of manganese oxide to form Tl2O3 (Dahal and Lawrance,

⁎ Correspondence to: W. Zhuang, College of City and Architecture Engineering, Zaozhuang University, Zaozhuang, Shandong 277160, China. ⁎⁎ Corresponding author. E-mail addresses: [email protected] (W. Zhuang), [email protected] (J. Song). https://doi.org/10.1016/j.marpolbul.2018.11.049 Received 12 October 2018; Received in revised form 12 November 2018; Accepted 20 November 2018 Available online 24 November 2018 0025-326X/ © 2018 Elsevier Ltd. All rights reserved. W. Zhuang et al. Marine Pollution Bulletin 138 (2019) 206–212

1996). A spectacular Tl enrichment in ferromanganese nodules of the digestion tank and digested using HNO3, HF, and HClO4. The details of Pacific and Indian Oceans was also recorded (Dutta et al., 1998). Sur- analytical method were presented in our previous study (Zhuang et al., face sediments of Bohai Bay and Laizhou Bay in China showed Tl 2016a). Tl concentration was determined using ICP-MS (PerkinElmer, strongly associated to iron, aluminum and/or manganese oxide (Duan NexION 350D). Al, Fe, and Mn concentrations were determined using et al., 2010; Zhuang and Gao, 2015). ICP-OES (PerkinElmer, Optima 8000DV). Fe and Mn concentrations

Estuaries often have unique geographical locations, monsoons and were showed as FeOOH and MnO2. circulation conditions, therefore, they are characterized by complex The concentrations and distribution of Tl in the surface sediments of ecosystems, changeable conditions, and diverse functions. Hazardous Yangtze Estuary were shown in Table 1 and Fig. 2. The Tl concentra- metal elements enter the estuary through various pathways such as tions ranged from 0.369 to 1.197 μg g−1 with an average of atmospheric sedimentation and surface runoff, and are absorbed into 0.674 μg g−1, most of which were slightly higher than the background particulate matters, and enter the sediment with the sedimentation of values of Tl in sediments of the Yangtze Estuary (0.53 μg g−1; He, 2018) these particulate matters. In addition, hazardous metal elements in and in Chinese Soil (0.580 μg g−1; Qi et al., 1992), and much higher sediments could enter water body and organisms through flocculation, than the background value of shallow sea sediments in China precipitation and desorption due to the complex hydrodynamic condi- (0.30 μg g−1; Zhao and Yan, 1992). tions in estuaries, and further affect human health through biological The average Tl concentration in surface sediments of the Yangtze enrichment and food chain enlargement (Zhuang and Gao, 2015). Estuary was close to that of the Bohai Bay, but the highest Tl con- Therefore, estuarine sediments are “sinks” and “sources” of metals and centration in the Yangtze Estuary was higher than that in the Bohai Bay. play important roles in the migration and transformation of metals Tl concentrations in surface sediments of the Yangtze Estuary were (Song, 2010). obviously higher than those of the Laizhou Bay. Both the Bohai Bay and The Yangtze River is the third largest river in the world, and its the Laizhou Bay belong to the Bohai Sea, but the Bohai Bay Rim is estuary is located in the Yangtze River Delta with highly developed dominated by industry and the Laizhou Bay Rim is dominated by industry and agriculture. With the rapid growth of population and de- aquaculture. The Yangtze River Delta is also dominated by industrial velopment of economy in the Yangtze River basin, the discharge of activities, which might be an important factor resulting in the high Tl industrial wastewater and domestic sewage in the coastal cities has content in sediments. increased dramatically, and the water quality has been deteriorating The Tl concentrations exhibited a large fluctuation among the sites (Song, 2010; Song et al., 2018). The Yangtze River carries huge (CV% = 27.510). The high Tl concentrations mainly occurred in two amounts of heavy metals into the sea every year. Up to now, there are regions. One region (referred to as H region) was in the south of many studies on traditional heavy metals such as As, Cd, Cr, Cu, Hg, Ni, Chongming Island, including site H1, H2 and H3; the other region Pb and Zn in sediments of Yangtze Estuary (Duan et al., 2013; Cao et al., (referred to as F-G region) was located in the northeast of Zhoushan 2015; Yao et al., 2016; Sun et al., 2018). Despite the rising global at- Islands and Hangzhou Bay mouth, including site F3, F4, G1and G2. The tention on Tl, geochemical characteristics and pollution status of Tl in low Tl concentrations mainly occurred in the region around site C5 to the Yangtze Estuary and its adjacent seas are poorly known. Conse- C7 and D6 to D8, referred to as C-D region. quently, the main objectives of this study are: (1) investigate the con- H region was adjacent to Shanghai City, so this region was sig- tents and dispersal characteristics of Tl in surface sediments of the nificantly affected by industrial activities and shipping. In addition, H Yangtze Estuary; (2) discuss the factors controlling Tl concentration region was close to one of the main sewage outlets in Shanghai, and the variation; (3) identify the origins of Tl in the surface sediments of discharge of sewage might have increased the content of Tl in sedi- Yangtze Estuary; and (4) finally evaluate the potential ecological risk of ments. Located at the easternmost end of the Yangtze Estuary, H region Tl. belonged to the mixed zone of seawater and fresh water. Increasing The present study was based on the 61 surface sediments sampled salinity in the water accelerated the flocculation and sedimentation of from Yangtze Estuary and its adjacent sea during July 2016 (Fig. 1). suspended particulate matters (Zhao et al., 2012). The sampling area covered an area with longitude from 121°06′18″E to The ocean currents in the Yangtze Estuary and its adjacent sea are 123°59′57″E and latitude from 29°58′00″N to 32°15′00″N. Surface se- very complex, and this area is affected by many water masses, such as diments were collected using a grab sampler. Immediately after col- the Yangtze River Diluted Water, the Taiwan Warm Current, the North lection, samples were placed in polyethylene bags, sealed, refrigerated, Jiangsu Near-shore Current, the Zhejiang and Fujian Near-shore and transported to the laboratory. The samples were frozen and dried Current, and continental mixed waters (Duan et al., 2013; Qiao et al., by a freeze drier, ground, and selected through a 200 mesh sieve; 2017). The Yangtze River Diluted Water is divided into two branches 0.1000 ± 0.0010 g of each sample was accurately weighed to PTFE under the influence of geomorphological characteristics. One branch

Fig. 1. Location of the sites in Yangtze Estuary and its adjacent sea, East China.

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Table 1 Comparison of Tl concentrations in the surface sediments of Yangtze Estuary and the related values reported in other part of China (unit: μg g−1).

Sampling Range Mean Median CV% References

Yangtze Estuary Jul. 2016 0.369–1.197 0.674 0.631 27.510 This study Laizhou Bay May - Jun. and Sep. - Oct. 2012 0.30–0.56 0.43 Zhuang and Gao, 2015 Bohai Bay Apr. 2008 0.506–0.770 0.688 Duan et al., 2012 Shallow sea sediments in China 0.30 Zhao and Yan, 1992 Chinese soil 0.58 Qi et al., 1992 Sediments in the Yangtze Estuary and offshore marine areas Jun. 2007 0.53 He, 2018

CV: coefficient of variation.

Fig. 2. The spatial distribution of Tl in the surface sediments of Yangtze Estuary (the inner areas of the black dotted lines are H region, C-D region and F-G region, respectively; Concentration unit: μg g−1). stretches south-east, across the Hangzhou Bay to the sea around The land-derived weathering products carried by the Yangtze River Zhoushan Islands; another branch stretches north-east to the southwest have much high contents of Fe and Mn, which can precipitate in the of the South Yellow Sea. The Taiwan Warm Current is a branch of the water and lead to more FeOOH-MnO2 in the sediments. FeOOH-MnO2 Kuroshio, characterized by high salinity, high nutrients and low dis- has large specific surface area and many surface charges, thus ithas solved oxygen. The Taiwan Warm Current which is originated to the strong adsorption capacity (Yang et al., 2018). The results showed that southeast of Taiwan and in the east of the Bass Strait flows northeast there was a significant correlation between Tl concentration and and on the way through Fujian and Zhejiang coasts. The confluence of FeOOH-MnO2 concentration (r = 0.559, p < 0.001; Fig. 3). Therefore, the south branch of Yangtze River Diluted Water and the Taiwan Warm FeOOH-MnO2 was also a main controlling factor for the distribution of Current could result in the deposition of suspended particulate matter and the formation of fine-grained areas. Previous studies showed that about 50% sediment load of Yangtze River was deposited at its mouth and delta, and most of the rest was carried southward along the coast by coastal currents (Chen et al., 1985; Fang et al., 2009). F-G region was located at the confluence of the Yangtze River Diluted Water andthe Taiwan Warm Current. Previous studies showed that the contents of clay and total organic carbon (TOC) in sediments were relatively high in this region (Song, 2010). The distribution of Tl in sediments is often controlled by the content of clay and TOC (Duan et al., 2012). In addition, the Qiantangjiang River could carry 4.4 × 106 t of sediment to the Hangzhou Bay annually (Duan et al., 2013). So the high Tl concentrations in surface sediments of F-G region could be brought by the Yangtze River and the Qiantangjiang River, and the distribution characteristics were controlled by grain size and TOC. The C-D region was located on the middle and outer continental shelves, thus it was weakly affected by terrigenous input and anthropogenic activities. In addition, the surface sediment in this area was characterized by coarse grain size and low organic carbon content (Qiao et al., 2017; Song et al., 2018). Therefore, the adsorption of Tl on sediment was weakened, resulting in lower Tl concentration in the sediments in this area. Fig. 3. Correlation between concentrations of Tl and FeOOH-MnO2.

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Tl in the surface sediments of the Yangtze Estuary. heavy metal contents (Zhang and Liu, 2002). Therefore, Tl enrichments Enrichment factor (EF) has been used widely to track normalized were more obvious in H region and in east and west of F-G region. H changes in composition that are driven by anthropogenic or geologic region received plenty of pollutants from the Yangtze River and forces. Generally, low volatile elements with few artificial pollution Shanghai City. As mentioned above, F-G region received pollutants sources, good chemical stability and high analysis accuracy existing from both the Yangtze River and the Qiantangjiang River (Duan et al., widely were selected as normalization elements. Al is relatively im- 2013; Song et al., 2018). i mobile in sediments and has been shown to be conserved upon emission Single-factor potential ecological index (Er ) was used to assess i (Frie et al., 2017). Therefore, Al was used as the normalization element ecological risks of Tl in surface sediments of the Yangtze Estuary. Er is in this study. EF values were calculated via: calculated as shown below (Hakanson, 1980):

i i i (CSample /Al Sample ) ETC= × EF = r r f (CBackground /Al Background ) i i i CC/Cf = o n where CSample and CBackground are the measured mass concentration of i i an element within a sample and its corresponding back ground value, where Er is the potential ecological risk factor for a given element i; Tr i i i respectively; AlSample and AlBackground are the measured mass con- is the toxic response factor of the element i; Cf , Co , and Cn are the centration of Al within a sample and its corresponding back ground pollution coefficient of element i, element i concentration in thesedi- value, respectively. According to EF, the sediments can be divided into ments, and its environmental background value, respectively. Ac- i seven classes: (1) EF < 1, no enrichment; (2) 1 < EF < 3, slight en- cording to Er , risks of metals in sediments were categorized into five i i richment; (3) 3 < EF < 5, moderate enrichment; (4) 5 < EF < 10, levels: (1) Er < 40, low risk; (2) 40 < Er < 80, moderate risk; (3) i i moderately severe enrichment; (5) 10 < EF < 25, severe enrichment; 80 < Er < 160, moderate to high risk; (4) 160 < Er < 320, high i (6) 25 < EF < 50, highly severe enrichment; and (7) EF > 50, ex- risk; and (5) 320 < Er , very high risk. tremely severe enrichment (Zhuang et al., 2016b). The background The toxicity coefficients of As, Cd, Cr, Cu, Hg, Pb and Zn have been value of Al in sediment of Yangtze Estuary is 61.80 mg g−1 (He, 2018). determined (Hakanson, 1980), but the toxicity coefficient of Tl had not i The results showed that EF values of Tl ranged from 0.563 to 2.281 been determined, so Er method could not be used for assessment of its with the mean value of 1.069 (Fig. 4). The highest EF value was re- pollution before. Thus, in our previous study, the toxicity coefficient of corded at site H2 which was located in the south Chongming Island. EF Tl was calculated according to the calculation principle proposed by values higher than 1 were recorded mainly in region to the west coastal Håkanson, and its toxicity coefficient was determined as 10(Liu et al., i area of site H5 and to the south of E section, indicating slight enrich- 2018). The spatial distributions of calculated Er s for Tl were shown in ment of Tl in these regions. The relatively higher EF values were dis- Fig. 5. Similar to distribution characteristics of Tl concentrations, the i tributed in H region near the south of Chongming Island and on both regions with the highest Er value were located in H region and F-G i sides of F-G region near Zhoushan Islands and the Hangzhou Bay region. The lowest Er values were recorded in sediments of the C-D mouth. In addition, the EF values of Tl in site A4, A5, B4 and D4 were region which was located on middle and outer continental shelves. In i also a little higher than 1. However, no EF value was higher than 3, general, the Er values of Tl varied from 6.95 to 22.58 with an average showing only slight enrichment. of 12.72, which could hardly cause any ecological risk. The EF values in C-D region were obviously lower, showing no In the environment, Tl is usually accumulated naturally accom- enrichment. Distribution characteristics of EF values and Tl con- panied by anthropogenic activities. Lithogenic Tl (TlL) and non-litho- centrations were relatively consistent. genic Tl (TlNL) represent the natural input and the non-natural input of Although it was believed that EF value above 1 showed slight en- Tl, respectively (Duan et al., 2012). The lithogenic and non-lithogenic richment of heavy metals, considering that different regions had dif- parts of Tl were calculated in sediments of Yangtze Estuary by the ferent background values and sediment composition, some researchers following formula (Turekian and Wedepohl, 1961): thought that only EF above 1.5 represented significant enrichment of TlNL= Tl total Tl L= Tl total [Al total (Tl/Al) UCC ] heavy metals, i.e. anthropogenic activities significantly contributed to

Fig. 4. The spatial variations of calculated EF values for Tl in the surface sediments of Yangtze Estuary and its adjacent sea.

209 W. Zhuang et al. Marine Pollution Bulletin 138 (2019) 206–212

i Fig. 5. The spatial variations of calculated Er values for Tl in the surface sediments of Yangtze Estuary.

−1 Fig. 6. The spatial variations of calculated TlNL concentrations in the surface sediments of Yangtze Estuary (concentration unit: μg g ).

The TlL of each sample is the result of the measured total con- directly into the study area mainly include the Yangtze River and the centration of Al (Altotal) times the Tl/Al ratio for global average shale or Qiantangjiang River. In addition, the Jiangsu Near-shore Current also crust; the TlNL was calculated as the difference between the total and delivers a large amount of sediment from the eroded Yellow River delta TlL. This calculation assumed that all Al was of lithogenic origin rather to the study area (Duan et al., 2013). Sediment loads of the Yangtze than the result of scavenging or biogenic production (Duan et al., River, the Qiantangjiang River and the Yellow River in the study area 2012). In this study, the upper continental crust (UCC) was used as the were 461 × 106 t/yr, 4.4 × 106 t/yr and 100 × 106 t/yr, respectively lithogenic reference (Taylor and McLennan, 1995). The Al and Tl (Hu and Yang, 2001; Zhang and Liu, 2002; Fang et al., 2009). Sedi- concentrations in UCC are 80.4 mg g−1 and 0.750 μg g−1, respectively. mentary Tl concentrations in the Yangtze River and the Yellow River Results indicated that there was a small amount of non-lithogenic Tl were 0.49 μg g−1 and 0.45 μg g−1, respectively (Zhao and Yan, 1992). ranging from ~0 to 0.626 μg g−1 with a mean value of 0.066 μg g−1 in Therefore, about 226 t and 45 t of sedimentary Tl from the Yangtze the surface sediments of Yangtze Estuary (Fig. 6), which on average Estuary and the Yellow River entered the study area annually. Tl input accounted for 9.76% of the total Tl concentration. The concentrations by the Qiantangjiang River was not monitored due to logistic problem, of non-lithogenic Tl were relatively high in southern Chongming Island but due to the much lower sediment load of the Qiantangjiang River and in the Hangzhou Bay mouth. The particle size of surface sediments comparing with the Yangtze River and the Yellow River, the Tl input by in the east and north of the E section were coarser and dominated by this river could be Negligible. sand, and the surface sediments in these areas contained almost no non- Atmospheric deposition was also an important way to carry terres- lithogenic Tl but mainly lithogenic Tl. trial Tl to the oceans. According to Hsu et al. (2010), the atmospheric Rivers are the main carriers of natural and anthropogenic Tl en- dry influx for Tl was estimated as 0.034 ± 0.078 mg/m2/d. The sea tering into Yangtze Estuary and the adjacent sea. Rivers discharging area in present study was about 5.3 × 105 km. The calculated annual

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Table 2 The riverine and atmospheric influxes and sediment burial fluxes of the adjacent sea of Yangtze Estuary.

Influx Suspended load (×106 t/yr) Atmospheric dry flux (mg/m2/d) Tl (μg g−1) Tl flux (t/yr)

Yangtze River 461a 0.49c 226 Qiantangjiang River 4.4a – Yellow River 100b 0.45c 45 Atmosphere 0.034d 0.66

Burial fluxe Areae Average MAR (g/cm2/yr)e Tl (μg g−1) Sediment Tl flux (t/yr)

km2 %

I 11,988 11.73 0.27 0.627 20.3 II 23,976 23.45 1.66 0.675 268.7 III 14,652 14.33 0.86 0.809 101.9 IV 29,970 29.32 0.16 0.519 24.9 V 21,645 21.17 0.072 0.825 12.9 Total 102,231 100.00 428.6

a Fang et al. (2009) and Zhang and Liu (2002). b Hu and Yang (2001). c Zhao and Yan (1992). d Hsu et al. (2010). e Duan et al. (2013). aerosol dry deposition flux of Tl was 0.66 t/yr. Comparing with the References riverine load, the atmospheric deposition to the Tl contribution was very small in the adjacent sea of Yangtze Estuary. Anagboso, M.U., Turner, A., Braungardt, C., 2013. Fractionation of thallium in the Tamar In order to understand the Tl contributions of the above mentioned estuary, south west England. J. Geochem. Explor. 125, 1–7. Belzile, N., Chen, Y.W., 2017. Thallium in the environment: a critical review focused on inputs to sediments of the study area, the sediment flux of Tl was cal- natural waters, soils, sediments and airborne particles. Appl. Geochem. 84, 218–243. culated. Because of the different geographical position, sediment rates Campanella, B., Onor, M., D'Ulivo, A., Giannecchini, R., D'Orazio, M., Petrini, R., and currents in different part of the study area, their sediment fluxes of Bramanti, E., 2016. Human exposure to thallium through tap water: a study from Valdicastello Carducci and Pietrasanta (northern Tuscany, Italy). Sci. Total Environ. Tl were different. According to mass accumulation rates (MARs), Duan 548–549, 33–42. et al. (2013) divided the adjacent sea area of Yangtze Estuary into five Cao, L., Hong, G.H., Liu, S.M., 2015. Metal elements in the bottom sediments of the zones (Fig. 1). Data of MARs was shown in Table 2. Because the sea area Changjiang Estuary and its adjacent continental shelf of the East China Sea. Mar. of the present study was entirely in the sea area studied by Duan et al. Pollut. Bull. 95 (1), 458–468. Chen, J.Y., Zhu, H.F., Dong, Y.F., Sun, J.M., 1985. Development of the Changjiang estuary (2013), the area data of the five zones in their study were used directly. and its submerged delta. Cont. Shelf Res. 4 (1), 47–56. The calculated sediment fluxes of Tl in zone I to zone V were 20.3 t/yr, Dahal, M.P., Lawrance, G.A., 1996. Adsorption of thallium (I), lead (II), copper (II), 268.7 t/yr, 101.9 t/yr, 24.9 t/yr, 12.9 t/yr, 428.6 t/yr, respectively bismuth (III) and chromium (III) by electrolytic manganese dioxide. Adsorpt. Sci. Technol. 13, 231–240. (Table 2). The total Tl sediment flux in the study area was 428.6 t/yr. Delvalls, T.A., Saenz, V., Arias, A.M., Blasco, J., 1999. Thallium in the marine environ- Therefore, the Yangtze River, the Yellow River and atmospheric inputs ment: first ecotoxicological assessments in the Guadalquivir estuary and its potential of Tl accounted for 52.7%, 10.5%, and 0.15% of the total sediment flux, adverse effect on the Doñana European natural reserve after the Aznalcóllar mining spill (SW Spain). Cienc. Mar. 25 (2), 161–175. respectively. The result indicated that the Yangtze River was the main Duan, L.Q., Song, J.M., Xu, Y.Y., Li, X.G., Zhang, Y., 2010. The distribution, enrichment contributor of sediment Tl in the study area. Besides, the rest of the Tl in and source of potential harmful elements in surface sediments of Bohai Bay, North sediment could be mainly originated from marine crust. China. J. Hazard. Mater. 183, 155–164. Duan, L.Q., Song, J.M., Li, X.G., Yuan, H.M., Li, N., Xu, Y.Y., 2012. Thallium con- The content of Tl in the surface sediments of the study area was centrations and sources in the surface sediments of Bohai Bay. Mar. Environ. Res. 73, relatively low, and there was no obvious enrichment. Contribution of Tl 25–31. by human activities was mainly occurred in the southern part of Duan, L.Q., Song, J.M., Yuan, H.M., Li, X.G., Li, N., 2013. Spatio-temporal distribution and environmental risk of arsenic in sediments of the East China Sea. Chem. Geol. Chongming Island and the mouth of Hangzhou Bay. But on the whole, 340, 21–31. Tl in the study area was mainly originated from lithogenic materials Dutta, R.K., Sudarshan, M., Bhattacharyya, S.N., Chakravortty, V., Chintalapudi, S.N., with non-lithogenic materials as assistant sources. The main sources of 1998. Quantitative PIXE analyses of ferromanganese oxide deposits from different Tl in the surface sediments of Yangtze Estuary and its adjacent sea were locations of the Indian Ocean and a deposit from the Pacific Ocean. Nucl. Instrum. Methods B 143, 403–413. riverine input, atmospheric transport and marine crust. Ocean current, Enviro Tools Factsheets, 2002. Factsheets on Thallium. available at. http://www. particle size and organic matter were the main factors controlling the envirotools.org/factsheets/contaminants/thallium.shtml. distribution characteristics of Tl in surface sediments. Overall, Tl con- Fang, T.H., Li, J.Y., Feng, H.M., Chen, H.Y., 2009. Distribution and contamination of trace metals in surface sediments of the East China Sea. Mar. Environ. Res. 68, 178–187. centrations in surface sediments of the study area were very low, and Frie, A.L., Dingle, J.H., Ying, S.C., Bahreini, R., 2017. The effect of a receding saline lake ecological hazards probably would not occur. (the Salton Sea) on airborne particulate matter composition. Environ. Sci. Technol. 51 (15), 8283–8292. Hakanson, L., 1980. An ecological risk index for aquatic pollution control. A sedi- mentological approach. Water Res. 14, 975–1001. Acknowledgements He, Z.F., 2018. Geochemical background values of sediments in the Yangtze Estuary and offshore marine areas. Shanghai Land Res. 1, 75–79 (In Chinese). Hsu, S.C., Wong, G.T.F., Gong, G.C., Shiah, F.K., Huang, Y.T., Kao, S.J., Tsai, F.J., Candice This study was co-supported by the Natural Science Foundation of Lung, S.C., Lin, F.J., Lin, I.I., Hung, C.C., Tseng, C.M., 2010. 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