兰州城关区地表灰尘中Pb、Cr含量及其赋存形态分布研究

利用原子吸收光谱仪测定了兰州城关区地表灰尘中Pb、Cr含量,并采用Tessier连续提取法分析了其赋存形态分布.结果表明:(1)地表灰尘中Pb质量浓度以居民小区最高,Cr质量浓度以商业中心最高,分别达到120.36、108.10mg/kg.(2)兰州城关区地表灰尘中Pb、Cr平均值分别是甘肃省土壤背景值(17.9、69.3mg/kg)的5.34、1.35倍.总体来说,兰州城关区地表灰尘Pb、Cr含量处于国内中等偏下水平.(3)Pb、Cr在地表灰尘中主要以残渣态和铁锰氧化物结合态存在,各采样点平均值中Pb、Cr残渣态分别占75.33％、79.01％.(4)地表灰尘中Cr赋存形态分布规律与土壤中一致,因受工业污染影响较小,推测Cr主要来自土壤源,各采样点含量相近且略高于背景值的分布特点是由于甘肃省土壤Cr背景值本身较高造成的.(5)地表灰尘中Pb除公园绿地为轻度污染外,其他采样点均已达到中度污染水平;Cr总体处于无实际污染水平.结合Pb、Cr主要以残渣态为主的特点,总体来说,兰州城关区地表灰尘中Pb累积污染程度严重,Cr无污染.     

六氯苯在中国典型持久性有机污染物污染场地中空间分布研究

在多年六氯苯生产车间及周围布设采样点,采取不同深度的土壤进行分析,研究持久性有机污染物(POPs)污染场地中六氯苯的空间分布规律.结果表明,生产车间附近污染严重,六氯苯的最高质量浓度为25 911.95 mg/kg,平均为4 944.07 mg/kg,在风力作用下六氯苯浓度向东南方向扩散;-3 m土层(以表土层为基准,表土层以下的土层深度为负值)中六氯苯最高质量浓度为369.63 mg/kg.平均为54.77 mg/kg,六氯苯浓度较表土层迅速下降,六氯苯污染中心位置与表土层对应;-5 m土层由于土壤类型为黏土或淤泥质黏土,六氯苯浓度相对于- m土层反而升高.平均质量浓度为92.13 mg/kg.纵观整个污染场地六氯苯的污染分布情况,污染中心位置向南移动,且六氯苯在垂直方向的迁移和浓度与土壤有机质含量相关.     

土壤重金属铅镉形态和有效态的提取方法研究

选择一步提取法(CaCl2法、NaNO3法、NH4NO3法、HCl法)提取土壤铅镉有效态含量,顺序提取法(BCR提取法、Tessier提取法)提取土壤中铅镉各形态含量。结果表明,4种一步提取法对供试土样有效态铅镉的提取效率为HCl法NH4NO3法CaCl2法NaNO3法。当镉质量浓度为0~20、40~90 mg/kg时,BCR法对土壤中镉的总提取率分别为104.9%、105.3%,Tessier法对土壤中镉的总提取率分别为101.7%、98.9%;当镉质量浓度为20~40mg/kg时,两种顺序提取法的提取效果均不佳。BCR法适合铅质量浓度为20 000~45 000 mg/kg时应用,此时BCR法对铅的总提取率为99.8%;Tessier法适合铅质量浓度为0~1 500、9 000~15 000mg/kg时应用,此时Tessier法对土壤铅的总提取率分别为100.7%、90.9%。土壤重金属铅镉各形态的含量受土壤自身pH影响不明显,但在遇到外界酸性环境影响时容易发生重金属铅镉迁移。     

铅同位素解析技术在工业园污染溯源中的应用

针对土壤中重金属污染溯源及解析不同污染源对土壤中铅的相对贡献率问题,以陕西西部某工业园区为例,采集土壤样品、铅锌冶炼厂矿石混合样、热电厂煤样及焦化厂混合煤样共40个,用ICP-MS测定样品的铅浓度及铅同位素比值(208Pb/204Pb、207Pb/204Pb、206Pb/204Pb).借助于铅同位素比值散点图来对比分析采样点土壤、背景点土壤和可能的污染源样品的铅同位素特征分布,判定其主要污染来源.用混合多元模型计算不同污染区域各污染源的贡献率,结果表明,土壤中的铅同位素比值落在铅锌矿石、炼焦用煤及热电燃煤及背景点的铅同位素比值之间,说明各端元介质均有可能对工业园区土壤中的铅污染有贡献.在铅同位素比值散点图中土壤铅浓度大于60 mg/kg的采样点的铅同位素比值集中落在热电燃煤与炼焦用煤附近.统计定量解析结果可知,对工业园区土壤铅污染的贡献大小依次为热电厂、焦化厂和铅锌冶炼厂.研究表明,铅同位素指纹解析技术用于定性与定量解析工业园区土壤铅污染效果较为理想.     

功能微生物对污染农田土壤中铅锌的溶出实验

用微生物修复重金属污染的土壤是当今的研究热点之一。试图寻找一类可以增加土壤中重金属铅、锌的可溶态的功能微生物,并研究该微生物在不同土壤含水率和不同投菌比条件下对铅、锌溶出作用的影响。最终筛选出符合条件的菌JK3,并发现当土壤含水率为35%,投菌比为0.15 mL/g土(菌液OD=1)时,土壤中铅和锌的可溶态增加量最多。其中,可溶态铅的含量由原来的0.49 mg/kg增加到了5.04 mg/kg,可溶态锌的含量由原来的2.23 mg/kg增加到了22.44mg/kg。该方法为后续用植物提取或化学淋洗等方法将土壤中的重金属彻底去除提供了可能。     

北京高校校园道路灰尘重金属污染特征及健康风险评价

为了解高校校园道路灰尘重金属污染特征及其可能带来的健康风险,在北京10所高校共采集了50个道路灰尘样品,测定了灰尘中Cr、Ni、Cu、Zn、Cd和Pb的浓度,采用美国环境保护署(USEPA)推荐的健康风险评价模型对高校道路灰尘重金属做了初步的健康风险评价。结果表明,北京10所高校校园道路灰尘中Cr、Ni、Cu、Zn、Cd和Pb的平均质量浓度分别为0.77、85.07、82.41、34.03、54.30、308.31mg/kg,均高于北京土壤重金属背景值。10所高校的重金属平均地累积指数(Igeo)排序为ZnCdCuCrPbNi,其中Zn、Cd和Cu处于中度污染水平,Cr和Pb处于轻度污染水平,Ni处于无污染水平。对于非致癌风险,呈现摄食皮肤接触呼吸吸入的特征,摄食是主要的暴露途径,Cr和Pb是主要的风险元素。对于致癌风险,Cr、Ni、Cd的致癌风险均低于风险阈值。高校校园道路灰尘重金属引起的健康风险处于较低水平。     

外源铅污染对紫色土中微生物酶活性的影响研究

以森林和耕地紫色土为研究对象,研究了外源铅在6种不同浓度水平下对土壤微生物酶活性的影响。结果表明:(1)森林土壤中微生物酶活性总体较耕地土壤高。(2)在连续培养56d后,森林土壤中除亮氨酸氨基肽酶(LAP)外其余4种酶活性与铅外源添加量和有效态铅呈显著或极显著正相关,外源铅污染促进了林地中C和P的矿化循环过程;耕地土中酸性磷酸酶(ACP)、β-葡萄糖苷酶、LAP活性与铅外源添加量和有效态铅呈显著或极显著负相关,在铅质量浓度≥250mg/kg时ACP基本失活,铅质量浓度达1 000mg/kg时,LAP抑制率为95.8%,外源铅污染抑制了耕地中养分元素的矿化循环过程。     

生活垃圾焚烧厂周边铅的分布规律研究与影响评估

生活垃圾焚烧厂排放烟气中含有铅等污染物,经过大气扩散后通过沉降作用在土壤累积。以上海某生活垃圾焚烧厂作为研究对象,采用AERMOD模型探讨烟气中的铅在大气中的扩散分布规律,采用沉积模型研究铅的土壤沉积规律,并通过IEUBK模型评估了垃圾焚烧厂对周围儿童最大可产生的血铅浓度几何均数值。结果表明,生活垃圾焚烧厂排放烟气中铅的落地质量浓度最大值位于排放源的东南方向,距离排放源1 338m处,为0.017μg/m~3,远低于《环境空气质量标准》(GB 3095—2012)中的限值0.5μg/m~3。使用IEUBK模拟得到此暴露场景对周边儿童产生的血铅质量浓度几何均数值为6.63μg/L,低于开始产生不良影响的风险阈值100μg/L。进一步结合土壤污染累积模型计算得到,当生活垃圾焚烧厂运行30a时,对周边土壤的最大铅累积量为7.6μg/kg,远小于《土壤环境质量建设用地土壤污染风险管控标准(试行)》(GB 36600—2018)筛选值800mg/kg。将土壤铅暴露纳入评价范围后,儿童体内的血铅质量浓度几何均数值仍为6.63μg/L。     

桂林市表层土壤总汞分布特征研究

为了研究桂林市表层土壤汞污染情况,采集了不同功能区(包括校园区、风景旅游区、交通运输区、居民区、商业区、农业用地区和其他区域)的表层(0~10cm)土壤样品36个,采用硫酸-硝酸混合液浸提、原子荧光方法测定土壤中的总汞。结果表明,桂林市表层土壤的总汞质量浓度在0.136~1.873mg/kg,平均值为0.557mg/kg,中值为0.440mg/kg。各功能区土壤中汞的平均值均超过《土壤环境质量标准》(GB 15618—1995)的一级标准(0.15 mg/kg),以风景旅游区最高,为0.900 mg/kg,其次为商业区,为0.595 mg/kg。进一步对桂林市表层土壤总汞浓度与环境参数的关系进行了研究,结果表明,各采样点土壤的总汞浓度与有机质显著相关,与土壤pH无相关关系。     

雷州半岛土壤重金属分布特征及其污染评价

在雷州半岛采集了106个土壤表层样品,分析了其中8种重金属元素(Cu、Pb、Zn、Cr、Ni、Cd、Hg和As)的全量.结果表明,雷州半岛土壤重金属污染由高到低排序为Ni＞Cr＞Hg＞Cu＞Zn＞Cd＞As＞Pb,Zn、Cd、As和Pb质量浓度均没有超标,Hg和Cu质量浓度超标率亦不高,但Ni和Cr平均质量浓度达49.81、87.13 mg/kg,高于国内外其他对照区域,超标率分别为25.47%和24.53%;重金属元素在雷州半岛各土壤利用类型中分布规律不明显,按4种主要土壤利用类型受重金属污染程度大小排序为甘蔗地＞果园土＞水田＞菜地;雷州半岛土壤综合污染指数总平均为0.970,土壤总体上尚清洁,重金属污染处于警戒水平;雷州半岛各区域中,徐闻、雷州两地土壤重金属质量浓度明显高于其他地区,其主要原因是徐闻、雷州两地成土母质主要为玄武岩,造成土壤Cr、Ni及其他重金属背景值较高.     

Uptake and accumulation of lead by plants from the Bo Ngam lead mine area in Thailand

A field survey of terrestrial plants growing on Bo Ngam lead mine area, Thailand, was conducted to identify species accumulating exceptionally high concentrations of lead. Plant and soil samples were collected from five areas. Lead concentrations in surface soil ranged from 325 to 142,400 mg/kg. The highest lead concentration in soil was found at the ore dressing plant area and lowest at a natural pond area. In different areas, the concentrations of lead in plants were different when comparing various study sites. A total of 48 plant species belonging to 14 families were collected from five sampling sites. Twenty-six plant species had lead concentrations more than 1000 mg/kg in their shoots. Three species (Microstegium ciliatum, Polygala umbonata, Spermacoce mauritiana) showed extremely high lead concentrations in their shoots (12,200-28,370 mg/kg) and roots (14,580-128,830 mg/kg).     

Metal content in street dust as a reflection of atmospheric dust emissions from coal power plants, metal smelters, and traffic

Resuspended street dust is a source of inhalable particles in urban environments. Despite contaminated street dust being a possible health risk factor for local population, little is known about the contribution of atmospheric dust emissions and other factors to the content of toxic metals in street dust. The impact of smelting, traffic, and power plants on metal contaminates in street dust is the focus of street dust sampling at 46 locations in the Witbank area (Republic of South Africa). This area is characterized by numerous open-pit coal mines in the Karoo coal basin, which provides a cheap source of energy to numerous metallurgical smelters and ironworks and supplies coal to the coal-fired power plants located nearby. Street dust was collected on asphalt or concrete surfaces with hard plastic brushes, avoiding collecting of possible sand, soil, or plant particles. Chemical analysis was done on the <0.125 mm fraction using inductively coupled plasma mass spectrometry subsequent to total digestion. Exceptionally high concentrations of metals were detected with concentrations of Fe reaching 17.7 %, Cr 4.3 %, Mn 2 %, Ni 366 mg/kg, and V 4,410 mg/kg. Factor analysis indicates three sources for the pollution. Road traffic which contributes to the high concentrations of Cu, Pb, Sb, and Sn, with the highest impacts detected in the town of Witbank. The second source is associated with the metal smelting industry, contributing to Fe, Co, Mn, and V emissions. The highest factor scores were observed around four metallurgical smelter operations, located in the Ferrobank, Highveld, and Clewer industrial areas. Impact of vanadium smelter to street dust composition could still be detected some 20 km away from the sources. Exceptionally high concentrations of Cr were observed in four samples collected next to the Ferrobank industrial area, despite Cr not being loaded in factor 2. The last source of the pollution is most probably fly ash associated with the coal-fired power plants and fly ash dumps. Elements which are associated with this source are Al, Sr, and Li. This factor is abundant in the coal mining part of the study area.     

Lead contamination in tea garden soils and factors affecting its bioavailability

The consumption of heavy metals is detrimental to human health and most countries restrict the concentration of metals such as lead (Pb) in food and beverages. Recent tests have detected high Pb concentrations in certain commercial brands of tea leaves and this finding has raised concerns for both producers and consumers. To investigate what factors may be contributing to the increase in Pb accumulation in the tea leaves we collected tea leaves and soils from tea producing areas and analyzed them for Pb concentration, pH and organic matter content. The result showed the Pb concentration of 47% investigated tea leaves samples was beyond 2 mg kg(-1), the permissible levels given by China. The total Pb concentration in the surface and subsurface soil layers averaged 36.4 and 32.2 mg kg(-1), respectively which fall below of the 60 mg kg(-1) limit provided for organic tea gardens in China. The pH of the tea garden soils was severely acidic with the lowest pH of 3.37. Soils under older tea gardens tended to have a lower pH and a higher Pb bioavailability which was defined as the amount of lead extracted by CaCl2 solution than those under younger tea gardens. We found that the concentration of bioavailable Pb and the percentage of bioavailable Pb (bioavailable Pb relative to total Pb concentration) were positively correlated with soil H+ activity and soil organic matter content, and the organic matter accumulation contribute more effects on Pb bioavailability in these two factors. We conclude that soil acidification and organic matter accumulation could contribute to increasing Pb bioavailability in soil and that these could increase Pb uptake and accumulation in the tea leaves.     

Copper contamination in paddy soils irrigated with wastewater

Copper (Cu) contamination was investigated in paddy soils where Cu-rich wastewater (12 mg Cu/l) was used for irrigation. The results showed that Cu contamination increased the soil Cu content from 17.0 mg Cu/kg in the non-wastewater irrigated soils (NWIS) to 101.2 mg Cu/kg in the wastewater irrigated soils (WIS), and Cu accumulated mostly in the surface layer (0-10 cm) of the paddy soil. The average Cu contents in brown rice, rice hull and rice straw from NWIS were 1.4, 7.3 and 14.5 mg Cu/kg, while those from WIS were 15.5, 133.2, and 101.4 mg Cu/kg, respectively. Correlation analysis revealed that the relationship between the Cu content in the rice straw and the rice hull with the total Cu content of the soil could be described by an exponential function (R2 = 0.921 and 0.831, respectively; P <0.01). Rice plants grown in the WIS showed symptoms of black roots, less effective tiller, etc. Subsequently, the rice yield decreased by 18-25%, compared with that grown in NWIS.     

Plant uptake of trace elements on a Swiss military shooting range: uptake pathways and land management implications

Over 400tons of Pb enters Swiss soils annually at some 2000 military shooting ranges (MSRs). We measured elements in the leaves of 10 plant species and associated rhizospheric soil on the stop butt of a disused MSR. The geometric mean concentrations of Pb, Sb, Cu, Ni in rhizospheric soils were 10,171mg/kg, 5067mg/kg, 4125mg/kg and 917mg/kg. Some species contained Pb, Cu and Ni, above concentrations (30mg/kg, 25mg/kg and 50mg/kg) shown to be toxic to livestock. Most contaminants in leaves resulted from surface deposition. However, at soil Pb concentrations >60,000mg/kg, Equisetum arvense and Tussilago farfara took up >1000mg/kg Pb into the leaves. These plants are not hyperaccumulators, having <100mg/kg Pb in leaves at lower soil concentrations. Removal of soil with more than 30,000 Pb, from which one could smelt this metal to offset remediation costs, followed by revegetation, would minimise dust and hence leaf-borne contaminants.     

Status of trace elements in paddy soil and sediment in Taihu Lake region

Thirteen paddy soil profiles and river sediments which are sources of irrigation water were collected around the Taihu Lake, and the trace elements were estimated. The content of La and Ce in paddy soil and sediment were 39.3 and 68.6 mg/kg soil and 36.9 and 65.1 mg/kg soil, being within the range of background values. The values for Pb, Cu, Ni, Cr, Co, Mn, Zn, Se in paddy soil were 23.3, 27.8, 25.5, 63.5, 10.2, 386, 68.7 and 0.25 mg/kg soil respectively, all below the national permission level. There was a decline of Zn in paddy soil. Some of the river sediments were seriously polluted. The river in Yangjin site was most contaminated with 5.47 g Cu/kg and 7.4 g Zn/kg. The high concentration of Pb and Ni also was observed in this sediment. River in Weitang, Huashi, Xinzhuang and Meiyan were contaminated with Pb, Cu and Ni to some extent. Zn, Cu and Pb were the main pollutants in present experiment sites. The fast development of village/township industries have caused severe environmental pollution in the Taihu Lake region, especially irrigation river sediments. Se content in plant and seed was 0.04 and 0.03 mg/kg respectively, showed Se-deficiency in paddy soil in the Taihu Lake region.     

Microbial cellulose decomposition in soils from a rifle range contaminated with heavy metals

The objective of this study was to assess the effects of heavy metals on microbial decomposition of cellulose in heavy metal-contaminated soils using a cotton strip assay. The assay is a measure of the potential of soil microorganisms to decompose the plant polymer, cellulose. Cellulolytic activity in soil was assessed by determining the reduction in tensile strength of the buried cotton strips over a 25- and 45-day period. Soils were obtained from a rifle range that contain high levels of lead, copper and zinc. The site has been used for approximately 50 years, resulting in metal levels of up to 30,000 mg/kg of lead, 4000 mg/kg of copper and 600 mg/kg of zinc in the most contaminated soils. All the metal-contaminated soils had lower degradation rates than the uncontaminated soils tested. Among the contaminated soils, however, the heavy metal concentration was not the major factor in determining the loss in tensile strength of the cotton strips, where cellulose decomposition was governed by other soil physicochemical properties. Soil with a higher cation exchange capacity, readily oxidisable material and volatile solids content had the greatest loss in tensile strength of cotton strips. Microbial adaptation to the presence of high concentrations of soil heavy metals and reduced bioavailability of metals is the likely explanation for this phenomenon.     

Comparative tolerance of Pinus radiata and microbial activity to copper and zinc in a soil treated with metal-amended biosolids

A study was conducted to evaluate the effects of elevated concentrations of copper (Cu) and zinc (Zn) in a soil treated with biosolids previously spiked with these metals on Pinus radiata during a 312-day glasshouse pot trial. The total soil metal concentrations in the treatments were 16, 48, 146 and 232 mg Cu/kg or 36, 141, 430 and 668 mg Zn/kg. Increased total soil Cu concentration increased the soil solution Cu concentration (0.03–0.54 mg/L) but had no effect on leaf and root dry matter production. Increased total soil Zn concentration also increased the soil solution Zn concentration (0.9–362 mg/L). Decreased leaf and root dry matter were recorded above the total soil Zn concentration of 141 mg/kg (soil solution Zn concentration, >4.4 mg/L). A lower percentage of Cu in the soil soluble?+?exchangeable fraction (5–12 %) and lower Cu²⁺ concentration in soil solution (0.001–0.06 μM) relative to Zn (soil soluble?+?exchangeable fraction, 12–66 %; soil solution Zn²⁺ concentration, 4.5–4,419 μM) indicated lower bioavailability of Cu. Soil dehydrogenase activity decreased with every successive level of Cu and Zn applied, but the reduction was higher for Zn than for Cu addition. Dehydrogenase activity was reduced by 40 % (EC₄₀) at the total solution-phase and solid-phase soluble?+?exchangeable Cu concentrations of 0.5 mg/L and 14.5 mg/kg, respectively. For Zn the corresponding EC₅₀ were 9 mg/L and 55 mg/kg, respectively. Based on our findings, we propose that current New Zealand soil guidelines values for Cu and Zn (100 mg/kg for Cu; 300 mg/kg for Zn) should be revised downwards based on apparent toxicity to soil biological activity (Cu and Zn) and radiata pine (Zn only) at the threshold concentration.     

Distribution of Pb, Cd and Ba in soils and plants of two contaminated sites

Evaluation of metal accumulation in soils and plants is of environmental importance due to their health effects on humans and other biota. Soil material and plant tissue were collected along transects in two heavily contaminated facilities, a Superfund site and a lead-acid battery dump, and analyzed for metal content. Soil lead (Pb), cadmium (Cd) and barium (Ba) concentrations for the Superfund site averaged 55,480, 8.5 and 132.3 mg/kg, respectively. Soil Pb occurred primarily in the carbonate, sulfide/residual and organic chemical fractions (41.6, 28.6 and 16.7%, respectively). Soil Pb, Cd and Ba concentrations for the dump site averaged 29,400, 3.9 and 1130 mg/kg, respectively. Soil Pb occurred mostly in the organic and carbonate fractions as 48.5 and 42.5%, respectively. Pb uptake in the two sites ranged from non-detectable (Agrostemma githago, Plantago rugelii, Alliaria officinalis shoots), to 1800 mg/kg (Agrostemma githago root). Cd uptake was maximal in Taraxacum officinale at 15.4 mg/kg (Superfund site). In the majority > or =65%) of the plants studied, root Pb and Cd content was higher than that for the shoots. Tissue Pb correlated slightly with exchangeable and soluble soil Pb; however, tissue Cd was poorly correlated with soil Cd species. None of the sampled plants accumulated measurable amounts of Ba. Those plants that removed most Pb and Cd were predominantly herbaceous species, some of which produce sufficient biomass to be practical for phytoremediation technologies. Growth chamber studies demonstrated the ability of T. officinale and Ambrosia artemisiifolia to successfully remove soil Pb and Cd during repeated croppings. Tissue Pb was correlated with exchangeable soil Pb at r(2)=0.68 in Ambrosia artemisiifolia.     

Pteris multifida Poir., a new arsenic hyperaccumulator: characteristics and potential

This paper reports a new arsenic hyperaccumulator, Pteris multifida Poir, a fern that grows widely in the southeast of China. The results show that the average arsenic content in the fronds was 1144.78 mg/kg, with a highest value of 2061 mg/kg. The average arsenic content in the roots was 692.7 mg/kg, and the average bioconcentration factor was 1.2, with a highest value of 1.78. The average translocation factor was 1.77, with a highest value of 3.13. The arsenic content in fronds was significantly correlated with the pH and the phosphorus available in the soil, but less correlated with the arsenic concentration in the soil. P.multifida Poir might accumulate the maximum arsenic in fronds when the soil-available phosphorus was 55 mg/kg and the soil pH was 8.34.