Contamination assessment,source apportionment and associated health risks of PTEs in agricultural soil under five land-use patterns in Sanya,China

To understand the levels of potentially toxic elements(PTEs)contamination in soils and their effects on human health from different agricultural land use in Sanya,China.128 soil samples(64 topsoil samples and corresponding subsoil samples)were collected from the five representative land-use patterns.Inductively coupled plasma mass spectrometry(ICP-MS),Atomic fluorescence spectrometry(AFS),and Inductively coupled plasma optical emission spectrometry(ICP-OES)were used to determine the content of PTEs(As,Cd,Hg,Cu,Cr,Ni,Pb,Zn,Co,Mo,Sb,and V).Correlation analysis and factor analysis were used to determine the source of PTEs.Geo-accumulation index(I_(geo)),hazard quotient(HQ),and total carcinogenic risk index(TR)were used to measure the PTEs contamination and its relative health impacts.Results showed that the average values of 12 PTEs in topsoil were higher than the Hainan soil geochemical baseline,showing different degrees of PTEs accumulation effect.The concentration of PTEs in the topsoil was lower than those in the subsoil except for Cd and Hg.The I_(geo)revealed that the major accumulated element in soils was As followed by Mo.Source apportionment suggested that parent materials and agricultural practices were the dominant factors for PTEs accumulation in the topsoil.Noncarcinogenic risks of soil samples from five land-use patterns presented a trend of paddy field>dry field>woodland>orchard>garden plot.However,the HQ values of 12 PTEs were less than the recommended limit of HQ=1,representing that there are no non-carcinogenic risks of PTEs for children and adults in the study area.The TR values are within 6.95×10^(-6)-1.38×10^(-5),which corresponds to the low level.Therefore the PTEs in the agricultural soil of the study area show little influence on the health status of the local population.

MUTAGENICITY AND CARCINOGENICITY OF FISH SAUCE FROM A COUNTY WITH THE HIGH RISK FOR GASTRIC CANCER IN CHINA

The mutagenicity and carcinogenicity of fish sauce (FS) sample from Changle County, a high gastric cancer mortality (113.20/105) area, were investigated with the biologic short-term tests and laboratory animal experiment. The results showed that the extract of FS was markedly direct mutagenic toward S. typhimurium TA100, induced high sister chromatid exchanges (SCE) and micronucleus (MN) in V79 cells after nitrosation with sodium nitrite. But the non-nitrosated FS did not. The nitrosated fish sauce (NFS) also induced SOS in E. coli PQ37 and alkylation of calfthymus DNA. The potency of NFS to induce unscheduled DNA synthesis (UDS) in human normal gastric mucosal cells was increased about fivefold compared with FS. When the NFS extract was given to newborn rats by gavage, dys-plasia and adenocaroinoma were induced in the glandular stomach in the 4th and 16th experimental week, respectively. N-nitrosamides were also found in NFS, which may account for the mutagenicity and carcinogenicity of NFS. It is indicated that FS, a traditional daily eaten seasoning, may contribute to the causes of the high gastric cancer mortality for the local residents.

Pitfalls in Assessing Risks from Carcinogens

The decision to classify a chemical as a human carcinogen must depend upon agreed conclusions from epidemiology, bioassays, and some short-term corroborating tests; information from only one of these disciplines is inadequate. Most pitfalls appear in interpreting the results from animal bioassays; this report will concentrate on them. Often the conclusion is accepted that a chemical is an animal carcinogen without a critical appraisal of the experimental design. By manipulating the experiment, 90 + % of all chemicals can induce some tumor in a rodent. Pitfalls encountered in bioassays result from not specifying the exact agent under test and how it relates to human exposure, using inappropriate routes of administration unrelated to humans, administering illogically high doses, or concluding that a cancer was induced without adequate histopathological description of the lesion. Importance of animal husbandry is often overlooked. Pitfalls are also related to short-term tests. Finally, a major pitfall in assessing carcinogenic risk from chemicals is drawing global conclusions about the carcinogenicity of an agent after the detection of only one or two tumors in the treated group.

Non-Genotoxic Carcinogens.Approaches to Their Risk Assessment

Epidemiological studies support the idea that most human cancers are related to chemicals present in the human environment. In turn, chemicals are believed to cause cancer via either genotoxic or non-genotoxic mechanisms. There were described in literature several simple, rapid and inexpensive short term tests to reasonably predict the genotoxic nature of chemicals but in contrast, there is no reliable test or battery of tests available to predict the carcinogenicity of non-genotoxic compounds and this poses a major problem to their risk assessment. In addition, there are conflictive opinions about risk assessment needs for both classes of carcinogens. Some workers believe that for non-genotoxic carcinogens, thresholds for exposure can be drawn while others do not. In this review, the reasons behind both of these opinions and the present hypotheses about the mechanism of action of non-genotoxic carcinogens are described and analyzed in relation to future needs.

New development in risk assessment of genotoxic carcinogens in foods

The no-observed-effect level (NOEL) in a study of carcinogenicity for compounds that are both genotoxic and carcinogenic represents the limit of detection in that bioassay, rather than an estimate of a possible threshold. Therefore, for those genotoxic and carcinogenic contaminants (e.g. acrylamides, PAHs, etc.) in foods it is not possible to develop health-based guidance values (e.g. ADI or PTWI) using the traditional NOEL and safety/uncertainty factors.

Dietary Intake, Carcinogenic and Non-Carcinogenic Risk Potentials of Lead, Cadmium, Mercury and Arsenic Exposure via Consumption of Dried Crayfish in Calabar, Nigeria

Intense pressure from both onshore and offshore oil exploration and exploitation activities, together with the accompanying urbanization and industrialization has resulted in massive contamination of land and water resources in Niger Delta, Nigeria. Whereas crayfish is very sensitive to contaminant in the aquatic environment and constitute an important part of human diet, its quality and safety from environmental pollutant is of serious health concern. Evaluation of dietary intake, potential carcinogenic and non-carcinogenic risk of lead, cadmium, mercury and arsenic exposure via consumption of dried crayfish purchased from major markets in Calabar, Nigeria was carried out between June and August 2021. Thirty-six composite samples of dried crayfish purchased from 180 vendors were used for the study. Heavy metals concentrations were determined using Atomic Absorption Spectrophotometer (Model AA-6800, Japan) after wet digestion. Metals concentrations (Mg/kg) were of the ranges 0.02 - 0.24, 0.14 - 0.86, 0.32 - 0.72, 0.04 - 0.19 for Pb, Cd, Hg and As respectively. The mean content of cadmium and mercury exceeded FAO/ WHO and Commission of European Communities maximum levels for crustaceans. Average Estimated Daily Intake for each of the metals was found to be above the recommended daily intake level except for arsenic. The average estimated daily intake values for Cd and Hg were also above the tolerable upper intake level. Average Target Hazard Quotient of all the metals and Hazard Index of all the markets were below 1.00. The Incremental Lifetime Cancer Risk of the metals was greater than the standard tolerable regulatory risk (10-4) for carcinogens. Consumption of crayfish purchased from major markets in Calabar could pose a range of carcinogenic and non-carcinogenic human health risks.

Human Health Risks from Exposure to Heavy Metals of Suspended Particulate Matter around the Tongon Gold Mine, Côte d’Ivoire

The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM10 and PM2.5) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM10;PM2.5 by heavy metals and their impact on the health of populations exposed to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM10 and PM2.5) were done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM2.5 and PM10) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM10 particles reveals that their inhalation over a long period could cause a carcinogenic risk.

渭河陕西段干支流多环芳烃分布特征及潜在生态风险研究

【目的】为研究渭河陕西段干支流多环芳烃的时空分布特征,分析其来源与潜在的生态风险,【方法】采用气相色谱-质谱法(GC-MS)连续2 a对研究区内30个采样点水体的15种多环芳烃进行了定量检测分析,使用异构体比值法解析其来源种类及贡献程度,并运用苯并(a)芘毒性当量生态风险评价(TEQBap)和终生致癌风险评价(ILCR)分析其潜在风险。【结果】结果显示:渭河陕西段水体中ΣPAHs范围为0~93.00 ng·L^(-1),检出平均值为9.67 ng·L^(-1);单体浓度范围为0~30.50 ng·L^(-1),其中苯并蒽和芴的检出浓度最高,检出平均值分别为3.25 ng·L^(-1)、2.83 ng·L^(-1);在环数占比上,多环芳烃主要以三环、四环和五环的中高环形态存在。【结论】结论表明:渭河陕西段平水期各多环芳烃浓度相比丰水期有所增加,丰水期各多环芳烃种类分布相比平水期较为单一;各采样点处多环芳烃小于轻污染水平,与国内外其他河流相比处于较低水平;多环芳烃主要来源为煤等化石燃料及生物质的燃烧,并具有一定的生态风险,致癌风险不容忽视。

华南地区典型食用鱼中4类卤代芳香化合物的污染特征和摄入风险

卤代芳香类化合物(HACs)具有环境普遍存在性、持久性、生物富集性和各种毒性,其污染和风险因此受到广泛关注。本研究对华南地区5种常见鱼肉中4类典型HACs进行了分析,结果表明,鱼肉中多氯代二苯并二噁英/呋喃(PCDD/Fs)、类二噁英多氯联苯(DL-PCBs)、多溴代二苯并二噁英/呋喃(PBDD/Fs)和总二噁英类(dioxins)毒性当量(TEQ)的平均值±标准偏差(范围)分别为(0.0680±0.3230)pg·g^(-1)(0~2.21 pg·g^(-1))、(0.118±0.124)pg·g^(-1)(0.000451~0.528 pg·g^(-1))、(0.139±0.164)pg·g^(-1)(0.00882~0.917 pg·g^(-1))和(0.325±0.366)pg·g^(-1)(0.0409~2.30 pg·g^(-1))(以单位湿质量计),均低于欧盟规定的鱼肉中dioxins的TEQ限值;5种鱼中桂花鱼的总TEQ和摄入风险最高,其次是鳗鱼和鲶鱼,鲈鱼最低,但种类间并无显著差异。鱼肉中多溴联苯醚(PBDEs)的浓度(0.347±0.297)ng·g^(-1)(0.0191~1.40 ng·g^(-1))(以单位湿质量计)与国内外相比中等偏低,种类变化顺序为三文鱼>鳗鱼>鲈鱼>桂花鱼>鲶鱼。鱼肉中的PCDD/Fs以高氯代PCDDs为主,可能源于污染饲料和五氯酚/五氯酚钠的使用;DL-PCBs以PCB-118和PCB-105为主,主要源于其商业品和金属冶炼过程;PBDEs的来源包括其商业品和高溴PBDEs脱溴降解;PBDD/Fs以高溴PBDFs为主,其污染与PBDEs密切相关。华南地区居民通过膳食鱼肉摄入4类HACs的致癌和非致癌风险值分别为6.56×10-6~2.87×10-5和0.0314~0.114,其中儿童风险值高于青少年和成人。PBDD/Fs对总TEQ和摄入风险的贡献(平均45.6%)远高于其他HACs,其生物体污染和风险值得持续关注。

赣南废弃离子型稀土矿区稻米重金属污染评价

江西赣州的离子型稀土资源丰富,已开发利用数十载,遗留下了300多处废弃离子型稀土矿区,其中以池浸堆浸工艺开采者居多。一些废弃矿区已有居民迁入,有必要对该区域的重金属污染问题及存在的健康风险进行评价。以废弃青山子矿区为例,测定矿区稻米样品中的重金属含量,并采用单因子污染指数法和内梅罗综合污染指数法对矿区稻米的重金属污染状况进行评价,然后采用美国环保局(USEPA)推荐的风险暴露模型评价食用矿区稻米对成人及儿童造成的健康风险,结果表明,废弃矿区稻米中主要重金属Cd、Pb、As、Zn、Cu的平均质量分数分别为0.048、1.18、2.45、60.9、5.99 mg/kg,其中Cd和Cu的平均质量分数均低于相应的标准限值,Pb、As和Zn的平均质量分数均高于相应的标准限值;废弃矿区稻米基本未受重金属Hg、Cd和Cu污染,但受Pb重度污染,受As和Zn轻微污染,综合污染程度为重度污染;以废弃矿区产出的稻米为主食可能会对成人构成轻微致癌综合健康风险,对儿童构成轻微非致癌综合健康风险。

基于5种风险评估方法评估汽车制造业喷漆和焊接岗位中化学有害因素的职业健康风险

目的:采用5种风险评估方法对汽车制造业重点岗位的化学有害因素进行职业健康风险评估,优化汽车制造业职业健康风险评估方案。方法:选取2022年河南省某3家汽车制造企业喷漆岗位(产生苯、甲苯、乙苯、二甲苯)和焊接岗位(产生锰及其无机化合物)为研究对象,运用接触比值法、半定量综合指数法、国际采矿与金属委员会(ICMM)赋值定量法、定量非致癌风险评估法和风险指数评估法进行喷漆和焊接等岗位的健康风险评估,并比较风险评估的结果。结果:企业2喷漆岗位二甲苯时间加权平均浓度最大值超过职业接触限值(OEL)时间加权平均容许浓度,企业3喷漆岗位乙苯和二甲苯的短时间接触浓度(C STEL)最大值超过OEL短时间接触容许浓度。3家企业的苯和甲苯浓度均低于OEL。接触比值法评估的有害因素风险等级为1~5级,半定量综合指数法评估的为2~3级,ICMM赋值定量法评估的为1~3级,定量非致癌风险评估法评估的为1~5级,风险指数评估法评估的为1~5级。半定量综合指数法、定量非致癌风险评估法和风险指数法评估的风险等级高于或等于接触比值法和ICMM赋值定量法。对于二甲苯超标的岗位,5种方法进行风险评估的风险等级均高于或等于不超标的岗位,且接触比值法和定量非致癌风险评估法评估的风险等级高于其他方法。定量非致癌风险评估法评估3家企业的锰及其无机化合物的风险等级均为5级,高于其他4种方法。结论:接触比值法、半定量综合指数法、ICMM赋值定量法、定量非致癌风险评估法和风险指数评估法各有优缺点,必要时多种方法联合应用更能客观评估汽车制造业化学有害因素的职业健康风险。

重庆城口地区黑色页岩风化土壤重金属元素的富集特征和健康风险评价

通过对重庆城口地区黑色页岩风化土壤进行系统采样,分析风化土壤重金属元素的含量组成和化学形态,探讨风化土壤重金属元素的富集特征,基于元素含量和化学形态开展人类健康风险评价.结果表明,研究区黑色页岩风化土壤中多种重金属元素的平均含量都超过中国土壤背景值,甚至超过农用地的风险管控值,表现出不同程度的重金属元素富集特征,尤其是Mo、Cd、As和Tl.致癌风险评价模型结果表明,As对于儿童和成人的大部分TCR值都超过风险安全限,Cr对于儿童和成人的绝大部分TCR值介于风险筛选值和风险安全限之间,少部分TCR值超过风险安全限,Pb对于儿童和成人的TCR值都小于风险筛选值.致癌元素地球化学形态萃取结果显示,土壤中As(92.53%—99.51%)、Cr(89.22%—97.87%)和Pb(62.59%—89.74%)主要以残余态的形式存在,具有很低的生物利用度和可给性,表明土壤中As、Cr和Pb对人类产生的致癌风险可以忽略不计.但是,土壤中Cd主要以可交换态(13.04%—36.82%)、碳酸盐结合态(18.69%—30.11%)和铁锰氧化物结合态(17.79%—31.07%)的形式存在,表现出较高的生物可获得性.由于Cd的TCR值均超过风险筛选值,且部分TCR值接近甚至超过风险安全限值.因此,研究区黑色页岩风化土壤中Cd可能对人类产生潜在的致癌风险,需要引起关注和重视.

2018—2022年苏州市生活饮用水中三氯甲烷浓度分析及健康风险评估

目的分析苏州市生活饮用水中三氯甲烷浓度水平,评估其健康风险。方法于2018—2022年对苏州市集中式供水出厂水、末梢水和二次供水采样,收集三氯甲烷监测数据,采用《化学物质环境健康风险评估技术指南》(WS/T 777-2021)推荐的模型评估人群饮用水中三氯甲烷暴露的健康风险。结果共收集2610份水样,三氯甲烷浓度范围为ND~57.00μg/L,浓度中位数为8.00μg/L,达标率为100%。研究期间丰水期三氯甲烷浓度高于枯水期(P<0.01),末梢水中三氯甲烷浓度高于出厂水和二次供水(P<0.01),使用一氯胺消毒的饮用水中三氯甲烷浓度低于使用液氯和次氯酸钠消毒的浓度(P<0.01),以江河为水源的饮用水中三氯甲烷浓度高于以湖泊为水源的浓度(P<0.01)。人群饮水三氯甲烷暴露的致癌风险男性为0.45×10^(-5)~3.02×10^(-5),女性为0.46×10^(-5)~3.03×10^(-5)。结论苏州市集中式供水生活饮用水中三氯甲烷浓度均合格,人群经饮水途径暴露三氯甲烷的健康风险水平低。

苏州市饮用水中全氟辛酸与全氟辛烷磺酸浓度分析及健康风险评估

本研究采集了具有较高代表性的苏州市8家水务公司18个水厂的出厂水、15个点位二次供水以及11个点位末梢水水样,分析其全氟辛酸(Perfluorooctanoic Acid,PFOA)和全氟辛烷磺酸(Perfluorooctane Sulfonate,PFOS)浓度水平,并根据《化学物质环境健康风险评估技术指南》(WS/T 777—2021)推荐的模型评估苏州市生活饮用水中PFOA和PFOS经口摄入的健康风险。结果显示,PFOA和PFOS浓度均低于《生活饮用水卫生标准》(GB 5749—2022)规定的限值,PFOA与PFOS经饮水暴露的非致癌风险值均小于1,非致癌风险较低。

南方某市公租房室内挥发性有机化合物的污染特征及健康风险研究

为了解新装修公租房室内空气中的污染特征及评估其环境健康风险,本研究对南方某市公租房室内挥发性有机化合物(VOCs)的多组分化学物质(33项指标)进行了分析,在此基础上筛选出检出频繁、毒性较高、含量较高的典型VOCs,并讨论了其在不同功能区域、不同楼层、不同装修时间的污染特征,最后,对典型VOCs的致癌和非致癌风险进行评估。结果表明,筛选得到5种典型有毒有害化学物质,分别是苯、乙苯、间,对-二甲苯、1,1,2,2-四氯乙烷、甲醛;公租房装修程度越低、楼层升高、装修时间延长,污染物浓度越来越低;不同年龄人群的致癌风险评估可知,1,1,2,2-四氯乙烷、甲醛的致癌风险均超过1×10^(-6),该风险值不可忽略,且年龄越小、致癌风险越大;非致癌风险评估可知,苯、乙苯、间,对-二甲苯、甲醛的非致癌风险分别为3.3×10^(-3)、9.8×10^(-4)、4.7×10^(-4)、1.99,即甲醛存在非致癌健康风险。

Health Risks due to Consumption of <i>Malus domestica</i>Golden Delicious Containing Heavy Metals

The intake of heavy metals through food consumption is a food safety problem that severely impacts the health of consumers, so information about food intake and heavy metal concentrations in food products is required to estimate the potential risk to the health of the population. The main purpose of this study was to estimate the potential risks to human health from exposure to Cd, Cu, Ni, Pb and Zn through the intake of Malus domestica Golden Delicious consumed in the Mexican southeast, considering the age group and gender. The concentration of each of the metals was quantified by spectrometry of atomic absorption (AAE) and the daily intake of metals (DIM) and health risk indices through the consumption of apple: health risk index (HRI), total health risk index (THRI), target hazard coefficient (THQ) and the probability of carcinogenic risk (CR) were estimated. The concentrations of the metals analyzed in the apple samples showed the following decreasing order: Zn ≥ Ni ≥ Cu ≥ Pb ≥ Cd. The DIM values showed the following decreasing order: child > young adult > adoescent > elders. The health risk assessments (HRI, THRI, THQ and CR) obtained from the samples of Golden Delicious apples are located within the acceptable and/or tolerable limits, however, the increase in the intake of heavy metals through consumption of apples from establishments in the study area or the consumption of various foods contaminated with heavy metals may increase the health risk potential of consumers. For this reason, it is recommended to carry out studies on the concentration of heavy metals in food products, mainly those of greater popular consumption, to guarantee food security of the population.

Ecological and Human Health Risk Assessment of Pesticide Residues in Fish and Sediments from Vea Irrigation Reservoir

The low yield of food production ascribed to harm caused by pests has led to the application of pesticides to food crops. Pesticide residues from the application on crops are mostly found in foods that can cause diseases for consumers of such products. A total of 37 pesticide residues consisting of 15 organochlorines (OC), 13 organophosphorus (OP) and 9 synthetic pyrethroids (SP) were determined. The QuEChERS method was exploited for extraction and clean-up. Gas Chromatograph was used for detection and quantification which was equipped with an electron capture detector and pulse flame photometric detector. The results showed that the mean concentrations of pesticides in fish ranged from 0.007 mg·kg-1 to 1.026 mg·kg-1 for OCs, 0.002 mg·kg-1 to 0.190 mg·kg-1 for OPs and 0.004 mg·kg-1 to 0.032 mg·kg-1 for SP. Sediments have mean concentrations ranged from 0.005 mg·kg-1 to 1.207 mg·kg-1 for OCs. OP ranges from 0.002 mg·kg-1 to 0.399 mg·kg-1 and 0.003 mg·kg-1 to 0.202 mg·kg-1 for synthetic pyrethroids. Maximum Residue Limits were exceeded in both fish and sediment samples except for malathion, fenitrothion, profenofos, gamma-chlordane, and deltamethrin. Exposure in children ranged from 4.60 × 10-6 mg·kg-1·d-1 to 2.36 × 10-3 mg·kg-1·d-1 and in adults it is from 1.97 × 10-6 mg·kg-1·d-1 to 1.01 × 10-3 mg·kg-1·d-1. Health risk estimation revealed a non-cancer risk potential of β-HCH in sediment and aldrin and p,p'-DDE in fish. Carcinogenic risk assessed for organochlorine pesticide residues indicates cancer benchmark concentrations greater than 10-4 to 10-6 threshold for acceptance.

Arsenic in Drinking Water Toxicological Risk Assessment in the North Region of Burkina Faso

Human health risks assessment were estimated by determining the nature and probability of adverse health effects in the North region’s populations who are now exposed to arsenic from drinking water or will be exposed in the future. Several questions were addressed in this study: what types of health problems may be caused by arsenic from drinking water? What is the chance that people will experience health problems when exposed to different levels of arsenic? What arsenic level are people exposed to and for how long? To answers these questions we have first identified the hazard by evaluating arsenic concentration in thirty-four (34) bore-hole water points among the region based on the assumption of clinical cases related to drinking water. Arsenic concentration ranged from 0 up to 87.8 micrograms per liter. Next we assessed the dose-response of exposure to arsenic. Dose-response relationship describes how the likelihood and severity of adverse health effects are related to the amount and condition of exposure to arsenic. This required us to choose toxicity reference values (TRVs) above which adverse effects may occur for noncarcinogenic and for carcinogenic effects. Exposure factors have been calculated in two scenarios: people from 0 to 14 years old and people from 15 to 70 years. Exposure has been estimated indirectly through consideration of measured concentrations of arsenic in drinking water. This study show that people in the Yatenga, Zondoma and Passore provinces are at very high risk for developing several pathologies such as hyper pigmentation, keratosis, cancer, etc. due by chronic exposure to arsenic in drinking water.

Geochemical signatures and human health risk evaluation of rare earth elements in soils and plants of the northeastern Qinghai-Tibet Plateau,China

Information on rare earth elements(REEs)in soils and plants of the Qinghai-Tibet Plateau is very limited.Therefore,in this study,we performed field sampling to explore the geochemical signatures and human health risk of REEs in soils and plants of the northeastern Qinghai-Tibet Plateau,China.A total of 127 soil samples and 127 plant samples were collected from the northeastern Qinghai-Tibet Plateau to acquire the geochemical signatures and related human health risks of REEs.The mean total concentrations of REEs in soils and plants of the study area reached 178.55 and 10.06 mg/kg,respectively.The light REEs in soils and plants accounted for 76%and 77%of the total REEs,respectively.REEs showed significantly homogenous distribution in soils but inhomogeneous distribution in plants of the study area.Characteristic parameters indicated that light REEs were enriched and fractionated significantly,while heavy REEs were moderately fractionated in soils and plants.REEs in soils and plants showed significantly negative Europium anomaly.Cerium showed slightly positive anomaly in plants and slight anomaly in soils.The normalized distribution patterns of REEs were generally similar in the analyzed soils and the corresponding plants of the study area.The average bio-concentration factor of REEs ranged from 0.0478(Scandium)to 0.0604(Europium),confirming a small accumulation of REEs by plants.Health risks caused by REEs in soils and plants were negligible,while risks for adults were lower than those for children.This study provides important information on REEs in soils and plants of the northeastern Qinghai-Tibet Plateau.

Degradation and Exposure Risk Assessment of Six Sulfonylurea Herbicides in Soil

[Objective] The paper was to understand the degradation tendency and carcinogenic risks of six sulfonylurea herbicides in soil, and guide the safe use. [Method] The herbicide residues were determined by UPLC-MS/MS and the degradation rates were calculated. In addition, the changing tendencies of directly exposed carcinogenic risk along with the herbicide residues were analyzed through the risk evaluation model. [Result] Significant differences were found among the degradation tendencies of the six sulfonylurea herbicides in soil, the longest theoretical half-life was 28.9 d and the shortest was 18.7 d. After application, the maximum carcinogenic risk value of the six herbicide residues in soil was 2.5×10^-8, lower than the reference value （×10^-6）. Oral intake and dermal contact were the major exposure routes, with the total contribution rate of 99.78% to the carcinogenic risk by direct exposure. When the P-value was less than 0.01, both original residue level and carcinogenic risk were significantly correlated with the dosage of herbicide, and the correlation coefficient was 0.983 1. [Conclusion] Under the condition of test, it does not have any unacceptable carcinogenic risk to human body. Moreover, selection of readily degradable herbicide with low residue level, and control of application rate are the effective approaches of reducing the carcinogenic risk of direct exposure.