海南省农产品重金属污染评价与特征分析

采用单项与综合污染指数法,以海南省农产品为研究对象,开展了农产品中重金属Cu、Zn、Pb、Cd、Ni、As、Cr和Hg含量的抽样调查分析与评价。结果表明,全省农产品中重金属的平均含量均低于食品中规定的限值,各重金属的单项与综合污染指数均≤1,综合污染指数为0.57;全省农产品未受重金属污染,属于安全水平,适宜发展无公害农产品。同时发现,个别监测点的农产品中重金属含量有超标现象,新鲜水果中个别样品Pb、Cd、Hg超标,超标率在2.17%～10.87%之间;豆类蔬菜中个别样品Ni超标,超标率为9.09%;瓜果类蔬菜中个别样品Pb、Cd超标,超标率为12.24%～24.49%;叶菜蔬菜中个别样品Pb超标,超标率为6.67%;谷物中个别样品Pb、Cd、As超标,超标率在2.11%～7.37%之间。农产品中重金属含量间多呈正相关,其中Zn与Ni、As与Hg之间差异达到极显著水平,Cu与Zn、Cu与As、Cu与Hg、Zn与As、Zn与Hg、Cd与As、Cd与Cr、Cd与Hg、Ni与As、Ni与Hg、As与Cr之间差异达到显著水平。结合主成分分析结果,推测Cu、Zn、Ni、As、Hg含量主要受农业生产和人类活动的影响,而Cr、Pb和Cd含量受土壤母质的影响比较大。     

酸雨地区蔬菜对重金属的吸收及重金属健康风险基准的估算

通过盆栽实验,以小白菜(上海青)、大白菜和萝卜为指示作物,研究了酸雨作用下Cu,Zn,Pb,Cd,Cr和Ni复合污染物在土壤-作物系统中的吸收与富集情况。结果表明,酸雨-重金属复合污染处理使Cu,Pb,Cr和Ni在蔬菜中积累量明显高于对照处理;Zn和Cd一般只有在复合污染处理中外源Zn或Cd含量较高时才明显高于对照处理。与对照相比,酸雨-重金属复合污染处理使Pb和Ni的富集系数增大,Cu的富集系数多数情况下增大,Cd的富集系数多数情况下减小,Zn和Cr富集系数的变化在不同蔬菜之间存在较明显的差异;重金属在不同蔬菜中的富集系数一般表现为萝卜>上海青>大白菜,蔬菜中不同重金属富集系数一般表现为Zn>Cd>Ni>Cu>Pb>Cr。酸雨-重金属复合污染条件下蔬菜中重金属积累量与其在土壤中总量之间的相关性均达到显著或极显著水平。以大宗蔬菜上海青、大白菜和萝卜为指示作物对酸雨地区蔬菜地中重金属的健康风险基准进行了估算,这对开展酸雨地区土壤重金属环境容量评价、重金属污染修复目标及地方性土壤环境质量标准的制订提供了参考依据。     

重庆市蔬菜基地土壤重金属含量情况

通过重庆市蔬菜基地土壤中Pb、Cd、Hg、As、Cr的分析得出 :重庆市蔬菜基地土壤中Pb、Cd、Hg、As、Cr的含量差异较大 ;重金属在不同地貌类型土壤中的含量也有较大差异 ;城市区划的不同 ,重金属在土壤中的含量也有较大差异。另一方面 ,土壤中Hg和Cd的平均含量远远大于土壤背景值 ,Pb、As、Cr的平均含量同土壤背景值相一致     

重庆市蔬菜地土壤重金属特征研究

研究结果表明重庆市蔬菜地0~20cm和20~40cm土层土壤重金属Cr、Ni、Cu、Zn、As、Pb含量无显著差异,Cd、Hg含量差异显著。不同土壤类型平均重金属含量和变异系数差异均较小。城郊区、工矿区和一般农区重金属Ni、Cu、Zn、As、Pb含量及阳离子代换量无显著差异。不同土壤类型和不同区域重金属间均具较强相关性,重金属Cu、Ni、Cr间具有较强伴生关系。重庆市蔬菜地土壤重金属Cd污染较重。     

南宁市蔬菜基地土壤重金属含量及评价

通过调查和采样分析结果表明,南宁市蔬菜基地土壤重金属平均含量分别为Cd 0.33 mg/kg、Hg 0.15 mg/kg、As 27.7 mg/kg、Pb 46.7 mg/kg、Cr 133 mg/kg。部分蔬菜基地土壤受到不同程度重金属污染,主要污染物为Cd,其平均单项污染指数为1.10。全市平均综合污染指数为0.91。     

广东省典型区域蔬菜重金属含量特征与污染评价

以广东省典型区域湛江市、中山市、珠海市、东莞市、惠州市和佛山市顺德区为研究对象,通过对其大型蔬菜基地生产中5类22种蔬菜171个样品中8种重金属元素进行检测,用国家蔬菜卫生标准计算污染指数并进行评价。结果表明:蔬菜中Cu、Zn、Ni、Cr、Pb、Cd、As和Hg的平均含量分别为0.6718、3.7431、0.1928、0.1451、0.0776、0.0205、0.0825和0.0022mgkg-1,其中有13.45%的蔬菜样品受到不同程度的重金属污染,Cd和Pb是蔬菜中主要污染元素;叶菜类蔬菜中重金属含量和综合污染指数都高于豆类、块根类、瓜类和茄果类等类型蔬菜;蔬菜中的重金属含量存在着复合污染关系。     

丽水市蔬菜与茶叶基地土壤肥力及土壤环境质量综合评价

为全面了解丽水市农业生产基地土壤质量情况,本研究以土壤肥力和土壤环境质量为评价指标,采用单因子指数与内梅罗指数相结合的方法对该市蔬菜和茶叶基地土壤质量进行综合评价。结果表明,蔬菜与茶叶基地耕层土壤全氮、速效钾含量充足,但速效磷平均含量和p H值的平均值分别为162mg·kg~(-1)、4.39和106 mg·kg~(-1)、3.77,土壤磷素均过量,且酸化严重。蔬菜基地全氮、速效钾以及土壤磷酸酶与脲酶活性均高于茶叶基地,土壤微生物数量低于茶叶基地。2个基地土壤中Cd、Pb、Cr、Cu、Zn、Ni、As、Hg、六六六及滴滴涕平均含量均低于国家土壤环境质量二级标准,其中Cd和Pb为潜在污染因子,蔬菜和茶叶基地综合污染指数分别为0.57和0.42。2个基地灌溉水与肥料重金属含量均低于国家相关标准,蔬菜及茶叶样品重金属和农残超标率均为0。综上,丽水市蔬菜与茶叶基地环境整体处于清洁水平。本研究为土壤质量综合管理提供了科学依据。     

蔬菜重金属污染状况及风险评估研究——以新疆乌昌库地区为例

以新疆乌鲁木齐市、昌吉市和库尔勒市蔬菜及其对应的土壤为研究对象,测定菜地土壤和蔬菜中Pb、Cd、Ni的含量,评价蔬菜摄入对人体可能产生的健康风险。结果表明,乌鲁木齐市和昌吉市蔬菜产地土壤中Pb、Cd、Ni含量均低于HJ 332-2006《食用农产品产地环境质量评价标准》和GB 15618-1995《土壤环境质量标准》的限量值,运用内梅罗指数进行土壤重金属污染程度评价,乌鲁木齐市、昌吉市和库尔勒市菜地土壤的综合污染指数分别为1.07、0.33、1.25;在所采集的样本范围内,昌吉市菜地土壤未受到污染,乌鲁木齐市和库尔勒市部分菜地土壤受到轻度污染。乌鲁木齐市和库尔勒市蔬菜中Pb、Cd、Ni含量均未超过限量值,乌昌库地区蔬菜中Pb、Cd、Ni单一重金属暴露健康风险较低,Pb、Cd、Ni单一重金属对成人和儿童都无暴露健康风险,豆类、叶菜类、鳞茎类蔬菜中多种重金属也无暴露健康风险。     

太原市污灌区土壤重金属污染现状评价

对太原市污灌区土壤重金属分布特征进行了分析评价,结果表明重金属Pb、Zn、Cu、Ni、Mn、Cr、As、Hg、Cd含量均值均未超过土壤环境质量标准（GB15618—1995）,但其平均值均显著高于太原市土壤背景值。各重金属间的相关分析表明,Pb、Zn、Cu、Ni、Mn、Cr、As、Cd之间呈极显著相关,说明这8种元素污染源可能相同。Hg是本区表层土壤重金属污染的主要因子,重金属元素的污染程度依次为Hg〉Cd〉Pb〉As〉Cu〉Zn〉Cr〉Mn〉Ni。土壤重金属单项污染指数均值均大于1,综合污染指数为2.81,总体上,污染水平为中度及其以上。各种重金属单因子污染指数和综合指数在研究区有相似的空间分布格局,总体分布趋势为东南部小店地区和中南部晋源区相对较高,南部清徐县相对较小;通过因子分析并结合污灌区污染源调查,表明Hg除受污水灌溉的影响外,燃煤释放的Hg可能是重要来源之一,Cd、Zn、Pb和Cu可能来自污水灌溉和大气沉降,以污水灌溉的贡献为主,Ni、Mn、As、Cr来自污水灌溉。Hg、Cd是太原市污灌区土壤中需要优先控制的重金属。     

贵州万山汞矿区某农田土壤重金属污染特征及来源解析

研究采集万山汞矿区典型农田土壤样品,分析测试其Hg、As、Cd、Cr、Pb、Cu、Zn、Ni含量,利用综合污染指数法、地累积指数法和潜在生态危害指数法评估农田土壤的污染状况及生态风险,结合相关分析和主成分分析解析农田土壤中重金属的来源。结果表明,该农田土壤Hg、As、Cd、Cr、Pb、Cu、Zn、Ni的平均含量分别为4.29、117.6、0.43、59.06、48.99、43.77、29.13、18.80 mg kg~(-1)。土壤重金属综合污染指数为7.16,表明该农田土壤重金属重度污染,其中100%的位点Hg、As重度污染,66.7%的位点Pb轻度污染,25%的位点Cd轻度污染。土壤重金属的综合潜在生态危害指数为469.0,生态风险强,Hg对综合潜在生态危害指数的贡献率为78.30%,是该农田土壤生态风险的主要来源。该农田中重金属的来源包括:交通运输源、矿业污染源、农业污染源和自然活动源,主要污染物Hg来源于矿业活动,As来源于交通运输和矿业活动,Cd来源于农业活动,Pb来源于交通运输。     

贵州草海耕地土壤与农作物中DDTs和HCHs残留及污染特征

采集草海流域周边成熟期整株农作物及土壤样品,分析测试其中DDTs和HCHs的含量,对比研究了土壤和作物中DDTs和HCHs污染水平及其在作物中富集能力。结果表明：研究区域土壤中HCHs和DDTs残留检出率均为100％,残留范围分别为0．06～16．66μg·kg^-1和0．08-39．77μg·kg^-1,土壤中HCHs和DDTs的残留量均小于国家土壤环境质量一级标准;三种农作物中DDTs、HCHs及∑（DDTs,HCHs）残留量差异显著,HCHs含量最高的是玉米,DDTs和（DDTs,HCHs）最高的是马铃薯;三种农作物中HCHs和DDTs残留的风险系数均为1．1,属于低度风险,农作物中DDTs、HCHs及∑（DDTs,HCHs）的安全指数IFSc均小于1,DDTs和HCHs残留量对三种农作物安全影响的风险是可以接受的。     

我国亚热带山地丘陵区特征及开发中的有关问题

我国亚热带山地丘陵区，山多地少、人口众多、经济基础薄弱，生态环境严重恶化，障碍着区内经济的发展，区内开发应按照以下几个方面搞好：１、协调山－林－地－人的关系；２．调整粮食－林牧－融渔关系；３．改善生产－生活－生态环境。４．提高生态－经济－社会效益。     

红薯对Pb、Cd的吸收累积特征及根际土壤Pb、Cd形态分布研究

为了解土壤在Pb、Cd单一以及复合污染条件下红薯对Pb、Cd的吸收和积累规律,通过盆栽试验对红薯地上部和地下部的生物量和重金属含量进行测定,分析了单一及复合污染土壤中重金属Pb、Cd形态分布特点。结果表明,相对于对照,较低浓度的Pb、Cd能显著促进红薯的生长（P〈0.05）,Pb超过50mg.kg-1、Cd超过3mg.kg-1时,红薯生长受到显著抑制（P〈0.05）,Cd是影响红薯生长的主要因素;随着试验处理浓度的升高,红薯体内重金属含量也随之升高,二者之间存在极显著的相关性（P〈0.01）,Pb、Cd共存对红薯吸收累积Pb、Cd具有明显的交互作用,Pb促进Cd向地上部转移,Cd促进Pb在地下部积累。根际土壤中Pb、Cd以可交换态与碳酸盐结合态为主,二者均占总量的55以上,在复合污染条件下,Pb浓度为50mg.kg-1时其活性系数显著高于其他Pb处理（P〈0.05）,并在很大程度上促进有效态Cd含量的增加。     

百菌清和毒死蜱在大棚番茄中的分布与降解特征

大棚和露地环境下,分别对番茄植株一次性喷洒推荐剂量的百菌清（CHT）和毒死蜱（CHP）,研究喷药后两周内农药在番茄根、茎、叶和果实中分布的持久性及其动态降解规律。实验结果表明,百菌清在大棚番茄中的残留浓度分布呈现为叶片垌果实〉茎〉根;毒死蜱呈现为叶片〉果实垌茎〉根。大棚番茄各部位的最高残留浓度出现时间滞后于喷药时间8~60h;空间浓度分布上表现为大棚中间区域浓度高于两侧,这与棚内的空气对流有关。大棚番茄果实中百菌清和毒死蜱的残留半衰期分别为5.8d和7.2d,明显高于文献报道。     

Sources of sulphate and acidity in wetlands and lakes in Nova Scotia

There is a declining gradient of wet SO₄ deposition from south to north in Nova Scotia with the highest values being in the south, along with a localized increase around the Halifax metropolitan area, due to local SO₄ emission. Edaphic conditions such as drainage from soils containing gypsum or drainage on disturbed rocks containing pyrite, provide additional SO₄ to surface waters.Acidity is usually absent in the former (pH > 7.0) and very high in the latter (as low as pH 3.6). By contrast peaty, organic drainages release water low in SO₄ during the growing season but they release high amounts of organic anions (A?), consequently, these waters maintain decreased pH values, usually < 4.5. A study of over 80 wetlands and lakes during the ice free period in Nova Scotia showed that sea salt corrected SO₄ concentrations range from 45 ueq L^?1 in the south end of the province, ～30 ueq L^?1 in the Kejimkujik area and < 17 ueq L^?1 in the northern areas with values > 85 ueq L^?1 in the Halifax area, reflecting the atmospheric deposition pattern of SO₄ The SO₄ concentrations may be > 2000 ueq L^?1 in drainages containing gypsum, > 700 ueq L^?1 in drainages over pyrite bearing socks but < 20 ueq/L^?1 in streams draining bogs. The SO₄ concentrations change considerably during the non-growing season when the ground is saturated with water or frozen, and the runoff is high (snow and rain often alternate in winter). Under such conditions SO₄ concentration drops in the two former cases and increases in bog drainages, accompanied with a considerable drop in (A?) concentrations. Care should be taken when interpreting SO₄ concentrations in surface waters in Nova Scotia with respect to atmospheric SO₄ deposition.     

Degradation and development of peatlands in Peninsular Malaysia and in the islands of Sumatra and Borneo since 1990

In this study, we investigated the extent of peatland degradation and development in Peninsular Malaysia and in the islands of Sumatra and Borneo, in the western part of insular Southeast Asia, since 1990. Furthermore, carbon emissions caused by these land cover changes were estimated in order to evaluate their contribution to global climate change. High resolution Landsat (30 m spatial resolution) and Satellite Pour l'Observation de la Terre (SPOT; 10–20 m) satellite images were used to derive information on land cover in 1990 and 2008. Analysis of land cover changes since 1990 revealed remarkable reduction and degradation of peatswamp forest ecosystems. In less than 20 years, 5·1 Mha of the total 15·5 Mha of peatland had been deforested (11·6 Mha → 6·5 Mha; 75 per cent → 42 per cent) and the great majority of the remaining forests had been selectively logged. Simultaneously, area covered by unmanaged secondary growth ecosystems had doubled to nearly a quarter of all peatlands and industrial plantations had expanded dramatically (0·3 Mha → 2·3 Mha; 2 per cent → 15 per cent). It was conservatively estimated that these changes have caused minimum of 1·5 Gt carbon emissions into the atmosphere since 1990. Currently, peatlands of the study area emit at least 81 Mt of carbon (equivalent to 300 Mt of carbon dioxide) on annual basis due to mere peat decomposition. Thereby, it was concluded that peatland degradation and development in insular Southeast Asia during the past two decades have not only put the existence of Southeast Asian peatswamp forest ecosystems in danger but it has also caused globally significant carbon emissions and created a constant source of carbon dioxide. Copyright © 2010 John Wiley & Sons, Ltd.     

Immobilization and species of heavy metals in soils in the absence and presence of rhizobia

Abstract

The effect of bacterial inoculation of Rhizobium fredii HN01 on the immobilization and speciation of Cu, Zn, and Cd was studied in Red and Cinnamon soil which are typical Chinese soils. The soil was mixed with bacterial suspension for one week followed by an immobilization of each heavy metal for another week. The total binding and fractionation of heavy metals in soils were analyzed. As compared with the control, the retention of total Cu, Zn, and Cd in Red soil increased by 28, 16, and 28%, respectively, in the presence of rhizobia. The amount of exchangeable, NH₄OAc-extractable, Mn oxides-bound and organic matter-bound Cu increased by 23–123%. There were significant decrease of exchangeable Cu and marked increases of NH₄OAc-extractable and Mn oxide-bound Cu in Cinnamon soil with the presence of rhizobial cells, although no changes for the total retention of Cu were observed. The amount of exchangeable Zn in Red soil-rhizobia composite was 20% greater than that of the no-rhizobia soil. Addition of rhizobia also increased exchangeable Cd and specifically-adsorbed Cd by 25 and 93%, respectively, in Red soil. No considerable differences were found for the total immobilization of Zn and Cd as well as their distribution in various solid fractions of Cinnamon soil in the absence and presence of rhizobial cells. In terms of soil components, it is assumed that bacterial biomass had a relatively less impact on the species of heavy metals bound with Fe oxides. Results suggested that the retention and speciation of heavy metals in soil are governed largely by the interactions of bacteria with various inorganic and organic soil constituents. The data are useful in understanding the impact of microorganisms on the behavior, mobility and transformation of heavy metals in soil environments.     

Distribution and fractionation of heavy metals in pairs of arable and afforested soils in Denmark

Afforestation of sandy arable soils in northern Europe is likely to lead to an increase in the soil's acidity and changes in the behaviour of the organic matter, and this might affect the ability of the soil to retain heavy metals. It is important to assess the impact of such a change in the land use on the solubility of the heavy metals and to assess the risk of leaching to surface‐ and groundwater and the possible entrapment of heavy metals in the tree canopy. The impact of afforestation was assessed by excavating soil profiles in adjacent 34‐year‐old Norway spruce stands and arable plots at four different sites. We found that after 34 years the pH had decreased and cations were depleted in the topsoil under forest. The aqua regia‐extractable heavy metals were determined, and the heavy metal binding within the soil was assessed using a modified version of the BCR (Community Bureau of Reference) sequential extraction procedure. Higher contents of heavy metal were found in the arable plots in the loamy sand soils. Cadmium was found only in the most mobile fractions. The content of Pb in the subsoil was strongly correlated with the clay content, but not in the topsoil, which suggested that Pb had been added to the topsoil. We found strong correlations between the clay content and the Cu, Ni and Zn in the residual fraction, leading us to conclude that much of the Cu, Ni and Zn is of geological origin. No significant differences in the heavy metal fractionation between forest and arable soil were found, presumably because 34 years of different land use is not long enough to produce such differences.     

Concentrations and amounts of methylmercury in water and fish in the limed and acid basins of a small lake

Three months after neutralization concentrations of methylmercury (MeHg) were higher in the water of the limed than in the control basin of a small lake. After two years, the concentrations in the limed basin were somewhat lower than in the control (0.056–2.19 ng L^?1 and 0.129–2.65 ng L^?1, respectively). The highest concentrations were found in the anoxic hypolimnia. The total amount of MeHg in the water mass of the lake varied from 19 to 68 mg, showing a drop after spring and autumn overturns and a maximum during stratification periods. The total Hg concentrations of fish in L. Iso Valkjärvi varied from 0.06 to 0.14 μg g^?1 (ww) in whitefish to 0.1 to 0.7 μg g^?1 in perch and to 0.2 to 1.4 μg g^?1 in pike. The total amount of MeHg bound in the fish of the lake was quite similar to that in the water column, 43 to 59 mg in 1990–1993, 33 to 47 mg of which was in the perch population.