Assessment of the degree of mercury contamination of marine fish around Bonaire

Many reports indicate that the levels of mercury (Hg) contamination of marine fish in other regions are above the United States Food and Drug Administration safe limit (0.5μg/g). No such studies were conducted on fish in the Dutch Caribbean region. Local fish are significant in the diet of the people of Bonaire. Mercury accumulates through the food web and would be expected to be greatest in the top predators. Four species of fish (wahoo, mahi mahi, black fin tuna and barracuda) that are caught for human consumption and occupy top predator positions within the food web were sampled and analyzed for their degree of contamination with Hg. Mercury concentrations were analyzed using semi-quantitative kits and the results verified by a private analytical lab in South Africa. There were no significant differences between the species. Black fin tuna showed the highest Hg concentrations, wahoo and mahi mahi showed lower levels and barracuda the lowest. These levels compare favorably with data published elsewhere. Uncontrolled illegal gold mining in Brazil and Venezuela contaminates ground and river water with Hg. This ultimately reaches the Atlantic where prevailing currents bring it past the Bonaire region. Bonairean fish's Hg levels are not a concern at present, but this may change with time.     

Total mercury in marine species from the French coast of the Eastern English Channel

Mercury (Hg) in fish can present a potential risk to wildlife and human consumers. Mercury levels were determined in 12 fish species and 2 invertebrate species from the French coast of the Eastern English Channel collected in June and November 2012. Total mercury concentrations in the muscle tissues ranged between 0.04 and 1.63 µg g^-1 (d.w.). Dab and sandeel displayed a significant positive correlation between Hg concentrations and fish length. Seasonal differences in Hg concentrations were observed for dab and shrimp. The lesser weever showed significantly higher concentrations of Hg (0.97 ± 0.34 µg g^-1 d. w.) than all other species. Gobies and sprat, which had the smallest size, showed significantly lower concentrations than herring, whiting, pout and sardine. Among the considered species, flatfish such as dab, flounder, plaice and sole displayed intermediate levels of Hg. In the present study, the fish age expressed as specimen length seems to be one of the major factors governing Hg contents in muscle tissues. Finally, mercury concentrations in commercial fish from the Eastern English Channel were below the levels fixed by the European Union for total mercury in edible parts of fish products.     

Determination of mercury and arsenic levels in fish caught in the Beheshtabad River,Chaharmahal and Bakhtiari Province,Iran

Mercury and arsenic pollution has been recognized as a potential environmental and public health problem for over 40 years. The major source of exposure to mercury for humans is the ingestion of fish. This study was conducted with the aim of determining the levels of mercury and arsenic in the muscles of four fish species caught in the Beheshtabad River and comparing the results with the maximum tolerance levels for mercury and arsenic. The samples of 90 fish were used for the determination of both the metals by graphite furnace atomic absorption spectrometry. The results showed that the concentrations ranged from 1.5 to 3.8 µg kg^?1 for mercury and from 35 to 70 µg kg^?1 for arsenic, with means of 2.7 ± 0.5 and 57 ± 12 µg kg^?1, respectively. Both mean levels were lower than the threshold limits acceptable by WHO standards.     

Methylmercury, total mercury and total selenium in four common freshwater fish species from Ya-Er Lake, China

Snakehead fish (Ophiocephalus argus cantor), silver carp (Hypophthalmichthys molitrtix), crucian carp (Carassius carassius), and common carp (Cyprinus carpio) are four common freshwater fish species in China. In this study, the level of methylmercury (MeHg), total mercury (T-Hg), and total selenium (T-Se) in muscle samples of these four fish species from Ya-Er Lake, China, were analyzed using atomic fluorescence spectrometry coupled with high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. The concentrations of MeHg in all the fish species were significantly correlated with those of T-Hg. Higher T-Hg and MeHg concentrations had accumulated in the snakehead fish, which is a strongly predatory fish, than in the other three species. The concentration ratios of MeHg and T-Hg in the muscles of these four fish species were almost equal. Conversely, there was negative correlation between the concentrations of T-Hg and T-Se, which implies that there is a competition between these two elements with respect to bioaccumulation. It is noteworthy that of all the muscle samples tested, the level of T-Hg exceeded the maximum allowable limit in fish [0.4 mg kg⁻¹ (w/w) recommended by the World Health Organization] in 38.46% of those of the silver carp, 18.18% of those of the crucian carp, and 100% of those of snakehead fish. These results show that the consumption of contaminated fish is a potential threat to human health and that necessary preventive measures to safeguard public health should be emphasized.     

Total mercury and methylmercury concentrations in fish from the Mojana region of Colombia

Total mercury (T-Hg) and methylmercury (MeHg) concentrations have been measured in the muscle tissue of 16 fish species consumed in the Mojana region of Colombia. T-Hg analysis was performed by cold-vapor atomic-absorption spectroscopy (CV-ASS) and MeHg analysis by gas chromatography with electron-capture detection. Higher T-Hg and MeHg concentrations were detected in carnivorous species (T-Hg = 0.371 ± 0.172 (μg g⁻¹ fresh wt, MeHg = 0.346 ± 0.171 μg g⁻¹ fresh wt) than in non-carnivorous fish (T-Hg = 0.155 ± 0.108 μg g⁻¹ fresh wt, MeHg = 0.146 ± 0.102 μg g⁻¹ fresh wt). In the different species mercury was present almost completely as the methylated form, with percentages between 80.5 and 98.1% (mean 92.0 ± 3.4%). In 13.5% of fish-tissue samples T-Hg concentrations exceeded the maximum level recommended by the World Health Organization for human consumption (Hg = 0.5 μg g⁻¹ fresh wt). Although mean T-Hg concentrations in all fish samples (0.269 ± 0.181 μg g⁻¹ fresh wt) did not exceed this limit, risk assessment suggested that the consumption of 0.12 kg fish day⁻¹ could increase the risk of mercury poisoning of the inhabitants of this region.     

A review of mercury contamination in marine fauna in Thailand

Mercury (Hg) is a ubiquitous environmental toxin that produces a wide range of adverse health effects in humans. Bioaccumulation of mercury in the aquatic food chain is a public concern for many countries. The aim of this study was to review the prevalence of Hg contamination in marine fauna in Thailand.     

典型汞污染地区食物汞含量及人体汞暴露健康风险

系统采集典型汞污染地区(铅锌冶炼、金矿冶炼和燃煤电厂)食物样品(大米、蔬菜和鱼肉) 409个,测定其总汞含量以评估当地居民食物摄入汞暴露的健康风险。结果显示:铅锌冶炼地区大米总汞含量的几何均值为5.99μg·kg~(-1)(3.02～30.7μg·kg~(-1)),仅有1个样品总汞含量超过我国大米汞限量标准(20μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为0.646～5.44μg·kg~(-1)和1.80～26.4μg·kg~(-1),均未超过我国食品汞限量标准;金矿冶炼地区大米总汞含量的几何均值为4.46μg·kg~(-1)(3.13～8.67μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为0.760～7.83μg·kg~(-1)和1.59～21.9μg·kg~(-1),所有食物均未超过我国食品汞限量标准;燃煤电厂地区大米总汞含量的几何均值为3.63μg·kg~(-1)(1.05～11.4μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为1.12～3.78μg·kg~(-1)和2.24～12.3μg·kg~(-1),所有食物均未超过我国食品汞限量标准。铅锌冶炼、金矿冶炼和燃煤电厂3个地区居民通过食用食物(大米、鱼肉和蔬菜途径)总汞摄入量的均值分别为0.068、0.038和0.031μg·d~(-1)·kg~(-1),均未超出联合国粮农组织和世界卫生组织食品添加剂联合专家委员会(JECFA)推荐的人体安全总汞摄入量0.71μg·d~(-1)·kg~(-1);表明3个研究地区居民汞暴露的风险较低。大米汞摄入量占3个地区居民食物总汞摄入量的比例分别为77.2%、70.8%和71.4%,食用大米是当地居民汞暴露的主要途径。     

Exposure of the urban population to mercury in Changchun city, Northeast China

An assessment of exposure to mercury in Changchun city has been undertaken. We estimated Hg exposure to members of the general population based on currently available information and our research. We also studied the Hg concentrations in scalp hair of adults. Adults have an estimated intake of all Hg species via all routes of 6.780 μg day⁻¹ (excluding dental amalgam), which equates to an absorbed dose of 1.718 μg day⁻¹. Fish consumption was the most important exposure route (12% of intake, 43% of absorbed dose). Furthermore, air, cereals and vegetables were important exposure routes, and these exposure were estimated for absorbed dosed at 0.296, 0.209 and 0.318 μg day⁻¹, respectively. The mean Hg concentration in hair was 0.448 μg g⁻¹ (range 0.092–10.463 μg g⁻¹). Hg concentration in the hair of males was 0.422 μg g⁻¹ (0.105–2.665 μg g⁻¹), and was 0.474 μg g⁻¹(0.092–10.463 μg g⁻1) in the hair of females. Neither place of residence nor age had any significant effect on hair Hg concentrations.     

桂林市菜地土壤-蔬菜汞污染研究和评价

对桂林市近郊8个不同片区蔬菜产地的118个土壤样品和71个蔬菜样品中汞的含量水平进行了调查和分析。运用单因子污染指数法评价了菜地土壤一蔬菜中汞的污染现状。研究表明，桂林市及近郊菜地土壤和蔬菜已受到不同程度的汞污染，全市各片区菜地土壤汞含量平均值为0．098-0．523mg／kg，以国家土壤环境质量标准二级标准评价，土壤平均污染指数在0．33-1．74范围内，属非污染或轻污染状态，除穿山南片和纸马铺外，其余采样点均有样本超过国家二级标准，其中七星公园东北片的土壤汞超标率较高，达71．4％，污染情况比较均一；虞山桥东南岸土壤汞超标率较低，为33．3％，但土壤汞含量变异较大，说明污染情况变化大。全市各片区老菜的汞含量平均值为0．0625-0．128mg／kg，为国家标准GB2762—1994规定蔬菜汞含量(0．01mg／kg)的6．25—12．8倍，超标率已达100％。实验还发现，蔬菜中的汞含量与土壤中的汞含量具有显著的相关性，且蔬菜汞的大部分分布于地上部可食部分。分析了菜地土壤汞污染的主要原因，可能与使用含汞农药和生活垃圾肥有关。     

沿海和内陆地区居民汞暴露量对比

通过对沿海和内陆居民食用水产品消费情况调查以及居民头发汞含量的分析,对不同地区普通居民的汞暴露水平进行了对比研究.居民水产品的消费情况采用调查问卷的形式,对沿海地区大连和内陆地区河南两地普通居民进行了随机调查,并同时采集被调查者的头发作为汞暴露情况的生物样本.本次研究共收集到有效调查问卷及头发样本213份(大连112份;河南101份),两地居民水产品消费量分别为:大连104 g.d-1,河南74 g.d-1;收集到的头发样本采用DMA-80测汞仪(按美国EPA-7473的方法)进行总汞含量的测定.头发总汞含量分析结果显示,大连为(0.363±0.256)μg.g-1,河南地区为(0.192±0.167)μg.g-1.两地区对同一年龄段居民发汞水平比较发现,大连地区居民发汞水平明显高于河南地区.以美国环境保护署(EPA)参考剂量1μg.g-1作为发汞基准,大连地区的超出比例为3%,河南地区的超出比例为1%.该研究结果为了解我国普通居民的汞暴露情况以及后续的汞暴露风险的定量计算提供了基础数据.     

珠江三角洲养殖鱼塘水体中重金属污染特征和评估

为了解珠江三角洲主要养殖环境中重金属含量及潜在生态危害程度,用电感藕合等离子质谱法和原子荧光法测定了肇庆、广州、惠州和茂名4市14个样点沉积物中7种元素的水体及底泥总量,并对底泥中主要重金属污染状况及潜在生态风险进行了评价。结果表明：养殖鱼塘水体中Cr质量浓度范围是nd-0.1011 mg·L-1,超标率为7.1%,Cu质量浓度范围为nd-0.1438 mg·L-1,超标率为64.3%,As质量浓度范围是0.0112-0.0812 mg·L-1,超标率为24.1%,Hg质量浓度范围是0.00004-0.00458 mg·L^-1,超标率为35.7%,Pb质量浓度范围为nd-0.0973 mg·L^-1,超标率为6.8%,其余Ni、Zn和Cd质量浓度范围分别为nd-0.0218、nd-0.0232和nd-0.00319 mg·L^-1,均未超渔业水质标准;底泥中重金属元素Cr、Cu、Zn、As、Hg、Cd和Pb的平均值分别为83.86、46.19、242.16、32.38、0.64、1.00和60.06 mg·kg^-1,地积累指数评价结果显示,表层沉积物重金属污染程度顺序为Cd＞Hg＞Zn＞Pb＞As＞Cu＞Cr,其中,Cd污染程度为中-强,是底泥污染最严重的元素。潜在生态风险指数分析,单项潜在生态风险指数生态风险均值排列顺序为 Hg＞As＞Cd＞Pb＞Cu＞Zn＞Cr。对区域综合潜在生态风险指数RI的贡献率最大的元素为Hg、As和Cd。4个市底泥潜在生态风险综合指数（RI）比较,惠州（290.13）＞广州（240.54）＞茂名（193.23）＞肇庆（116.40）。Hg和Cd是该水域污染和潜在生态风险最大的元素。     

Total and methyl mercury in small marine biota caught off the Coast of Chennai,India

Abstract

This study reports the concentrations of total mercury and methyl mercury in sixteen families of marine biota caught off the coast of Kasimedu in Chennai, India, an important but understudied fish landing region. These included the commonly caught croakers, carangids, rays, goat fish, anchovies, crabs, and prawns. There was no correlation between total mercury or methyl mercury with fish length or mass. All concentrations were lower than the Food Safety and Standards Authority of India limits (total mercury = 500?μg/kg; methyl mercury = 250?μg/kg). Some values were above screening levels (total mercury >40?μg/kg wet weight) when considering possible adverse effects in predatory fish that consume the analyzed biota.

Abbreviations: dw: dry weight; MeHg: methyl mercury; THg: total mercury; ww: wet weight     

大连市区普通居民的汞暴露风险研究

为了解沿海地区居民的汞暴露情况及其膳食汞的主要来源,对大连市区普通居民的膳食消费情况及其发汞浓度进行了调查与分析。普通居民的膳食消费情况采用调查问卷的形式进行,调查问卷的内容包括水产品消费情况、年龄、性别、身高、体重等,填写调查问卷的志愿者们同时自愿提供头发样品。膳食样品,如水产品、谷物、蔬菜等常见品种在大连市区的市场采用随机采购的方式获得。头发和膳食样品中的汞含量采用原子荧光光谱法测定,测定结果为:水产品中总汞含量为15.32(1.89~86.40)μg·kg-1,其中甲基汞含量为8.05(1.79~40.33)μg·kg-1;谷物和蔬菜总汞含量分别为2.04(0.05~11.95)μg·kg-1和0.96(0.05~2.74)μg·kg-1;头发样品中总汞浓度为(0.46±0.55)μg·g-1,其中甲基汞浓度为(0.28±0.19)μg·g-1。通过估算得知,大连市普通居民日平均的汞摄入量为0.043μg·(kg·d)-1,其中来自水产品的摄入量占膳食摄入的63.6%。居民发汞浓度与年龄、水产品食用量呈正相关,与身高、体重没有显著的相关性;与美国国家环境保护局规定的人体发汞风险参考剂量1μg·g-1相对照,此次调查人群中约有4.6%的居民发汞浓度超出该标准限值,这表明大连市区普通居民可能面临汞暴露的潜在风险。该研究结果将为我国普通居民的汞暴露评估和风险控制提供重要参考数据。     

珠江三角洲4种淡水养殖鱼类重金属的残留及食用风险评价

为全面了解珠江三角洲淡水水产品中重金属污染现状,评估其生态风险与食用安全,于2014年8月至2015年8月采集罗非鱼、草鱼、乌鳢及鳜鱼主要养殖鱼类样品共计57份,采用原子荧光光谱仪(AFS),电感耦合等离子体质谱(ICP-MS)仪进行分析测定,并采用单因子污染指数(Pi)、重金属污染指数(MPI)、每周可耐受摄入量(PTWI)以及食入健康风险指标(Ri总)分别评估其污染程度、食用安全性与健康风险。结果表明,样品中Cr、Ni、Cu、Zn、As、Cd、Hg、Pb的含量范围分别为0.020~3.240,0.020~0.800,0.110~1.100,0.190~19.970,0.030~1.480,nd~0.606,0.003~0.118,0.040~0.803 mg·kg-1(湿重),Cr、As、Cd、Pb在水产品中超标率大小依次为As(7.0%),Pb(7.0%),Cd(5.3%),Cr(1.8%)。Pi结果表明,目前珠江三角洲养殖水域水产品中Cu与Zn残留处于正常范围内,Cr和Hg有少量样品为轻度污染,Pb、Cd与As存在重度污染样品,所占比例为2.86%、6.02%和5.74%。MPI结果显示不同水产品污染程度为乌鳢>鳜鱼>罗非鱼>草鱼,总体上各种水产品MPI依然处于较低的水平;食用安全性结果显示,目前成人每周摄入水产品是安全的,但乌鳢Cr,罗非鱼As含量较高分别达到PTWI的37.76%和19.51%,表明水产品中Cr、As残留可能存在一定的食用安全隐患。健康风险模型结果显示,所有样品均未超过国际辐射防护委员会(ICRP)的推荐的最大可接受水平(5×10-6a-1)。综合分析珠江三角洲淡水养殖主要水产品可知,其尚未出现明显的污染安全问题,但As与Cr等元素的潜在风险值得进一步关注。     

Sulfonated cross-linked polyethylenimine for selective removal of mercury from aqueous solutions

Polymeric materials are among the most promising, effective, and increasingly important adsorbents for the removal of toxic metals from wastewater. This study was dedicated to the development of an insoluble, modified chelating polymer for use as an adsorbent for abstraction of Hg from aqueous solutions. Cross-linked polyethylenimine (CPEI) was sulfonated by 3-chloropropanesulfonyl chloride for selective removal of Hg. The binding affinity of the sulfonated CPEI (SCPEI) to Hg was assessed as well as its ability to be regenerated for reuse. It exhibited high removal percentage for Hg up to 87% in synthetic solutions, with high selectivity even in the presence of competing ions: “Mn, Ni, Fe, Pb, Zn, and Cr.” The removal mechanism followed was observed to be adsorption and precipitation at pH 3 and 8, respectively. High adsorption capacities were also observed for wastewater to which the polymer was applied. The Freundlich isotherm was found to be the best fit describing the adsorption process of Hg onto the SCPEI. The pseudo second-order equation was found to better explain the adsorption kinetics, implying chemisorption. The thermodynamic study of the adsorption revealed high activation energies which confirmed the chemisorption as the mechanism of adsorption. The polymer exhibited up to 72% removal efficiency after regeneration, thus showing potential for re-use.     

Bioaccumulation of organochlorine contaminants in fish species from Lake Qarun,a protected area of Egypt

The purpose of this study was to determine concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in Nile tilapia (Oreochromis niloticus) and Bouri fish (Mugil cephalus) from Lake Qarun, a protected area of Egypt, and evaluate the relative ecological risk of these compounds. Different tissues of the fish species were analyzed for 26 chlorinated pesticides and 29 PCB congeners. Total concentrations (µg/kg wet weight, ww) of OCPs ranged between 1487 and 6217 (mean: 3260) and of PCBs between 9.0 and 61 (mean: 34). The trend of detected organochlorine pollutants was: endrin aldehyde > dieldrin > hexachlorobenzene > PCBs > endrin > 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethanes (DDTs). Heptachlor epoxide; oxy-, cis-, and trans-chlordane; trans-nonachlor; β-hexachlorocyclohexane; δ-hexachlorocyclohexane; and endosulfan I and endosulfan sulfate levels were below the detection limit. The ratios of (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylenes [DDEs] + 1,1-dichloro-2,2-bis(p-chlorophenyl)ethanes [DDDs])/ΣDDTs in fish tissues indicated no recent DDT exposure. Concentrations of DDTs and PCBs were generally comparable or higher than those found in studies of similar species worldwide. The concentrations of hexachlorobenzene, dieldrin, and endrin aldehyde in fish muscles exceeded the maximum residue level recommended by various organizations.     

贵州省务川地区土法炼汞工人汞蒸汽暴露调查及健康影响评价

为探讨土法炼汞过程中汞蒸汽暴露对炼汞工人健康的影响,测定了贵州省务川土法炼汞区和对照区(贵州省长顺县)人群的尿汞、尿常规参数(pH、葡萄糖、尿胆红素原、潜血、尿蛋白)、尿肌酐和尿β2微球蛋白含量,并对两地区人群进行了详细的健康检查．测定结果显示,土法炼汞区人群尿汞和尿β2微球蛋白的平均含量分别高达779μg·g-1 Cr 和208．5μg·g-1 Cr,远远高于对照区人群的尿汞1．24μg·g-1 Cr和尿β2微球蛋白75．4μg·g-1 Cr．分析表明,务川地区土法炼汞人群遭受了较严重的汞蒸汽暴露,部分暴露人群已经表现出轻度慢性汞中毒的症状,其肾脏已经遭受到一定程度的损伤．     

Distribution,enrichment, accumulation and potential ecological risks of mercury in the sediments of Kaohsiung Harbor,Taiwan

The distribution, enrichment, accumulation and potential ecological risks of mercury (Hg) in the surface sediments of Kaohsiung Harbor, Taiwan, were investigated. Sediment samples from 20 locations throughout Kaohsiung Harbor were collected quarterly from 2006 to 2011, and characterised for mercury, aluminium, water content, organic matter, total nitrogen, total phosphorous, total grease and grain size. The results showed that Hg concentrations varied from 0.06–6.73 mg kg^?1 with an average of 0.54±0.71 mg kg^?1. The spatial distribution of Hg reveals that the Hg concentration is relatively higher in the river mouth regions, especially at the Love River and Canon River mouths from where it gradually diminishes toward the harbour entrance region. The results from the enrichment factor and geo-accumulation index analyses reveal that the sediments near the Love River and Canon River mouths experience severe enrichment and strong accumulation of Hg that originates from upstream sources of pollution. The assessment of biological effects indicates that concentrations of 92.5% Hg found in the sediment are higher than effects range low, implying that the harbour sediments may cause an adverse impact on aquatic lives. The results of a potential ecological risk index indicate that the sediment has higher to serious levels of ecological potential risks.     

北京市场常见水产品中总汞、甲基汞分布特征及食用风险

以甲苯二次萃取-直接测汞的方法对北京市场常见水产品中的甲基汞进行分析测定,并评价了食用人群的暴露风险。分析样品包括大黄鱼（Pseudosciaena crocea）、虾（Penaeus chinensis）等9种常见海产品以及武昌鱼（Megalobrama amblycephala Yih）、鳙鱼（Aristichthys nobilis）2种淡水海产品。测定结果表明：海产品中总汞和甲基汞质量分数要远高于淡水鱼中的总汞和甲基汞质量分数,总汞绝大多数是以甲基汞的形式存在,所占比例从74.7%到96.0%不等;对其中3种鱼类的鱼体甲基汞分布研究表明：肌肉中的甲基汞质量分数最高,肝脏中次之,鱼鳃中质量分数最低。根据我国水产品甲基汞标准,本研究中水产品甲基汞质量分数均低于国家标准,但根据世界卫生组织（WHO）和美国环保署EPA颁布的甲基汞摄入量参考值,食用银鳕鱼等甲基汞质量分数相对较高的水产品仍然存在一定的风险,应注意限量。     

珠江三角洲淡水养殖沉积物及鱼体中DDTs和PAHs的残留与风险分析

采用GC-ECD和GC-MS分析了珠江三角洲淡水养殖鱼塘沉积物及鱼体中DDTs、PAHs的质量分数。结果表明,珠江三角洲地区鱼塘积物中DDTs质量分数范围为2.87～8.25ng·g-1,PAHs质量分数分布在61.76～196.05ng·g-1(干物质量)之间;鳙鱼、草鱼等5种鱼肌肉样品中DDTs质量分数为5.47～125.27ng·g-(1湿质量),PAHs质量分数为30.94～410.06ng·g-1(湿质量),5个品种鱼体内DDTs质量分数均未超过国家食用卫生标准。部分鱼塘中含有o,p’-DDT和p,p'-DDT,表明近期曾受到DDT污染。生态风险分析表明,珠江三角洲部分地区DDTs污染生态风险较高。