Derivation of Critical Soil Cadmium Concentrations for the State of São Paulo,Brazil, Based on Human Health Risks

The main cadmium exposure pathway for humans is through diet. A database on Cd concentration in soils and accumulation in edible vegetables from tropical and temperate regions was organized, soil–plant relationships were derived, and then critical soil Cd concentrations were calculated based on human exposure parameters for the State of São Paulo, Brazil. Cadmium accumulation in leafy and root vegetables could be predicted by multiple regression analysis and most of the variance was explained when total Cd concentration and pH in soil were included as predictors. The calculated Cd bioconcentration factors (BCFs) for the tropical dataset were higher as compared to the temperate dataset. Consequently, critical soil Cd concentrations were from 1.7- to 3.2-fold lower for tropical conditions. Higher humidity and temperature at the tropics, as well as more weathered soils with lower retention capacity of Cd, may explain the higher Cd uptake and accumulation in tropical than in temperate regions. To protect human health, exclusive data regarding Cd in soils and edible vegetables from tropical regions should be used for the State of São Paulo to derive critical soil Cd concentrations, instead of (additional) data from temperate regions.     

环境重金属污染物的生物有效性

利用生态系统研究了白银有色金属冶炼矿区周围环境中重金属的分布及生物有效性。结果表明 ,工厂在冶炼过程中已造成 Pb、Cd、Cu、Zn对周围环境不同程度的污染 ,其含量与距工厂的距离呈负相关 ;重金属在各种生物体内均有不同程度的吸收和累积 ,其吸收累积量随重金属和生物种类的不同而有差异 ;土壤的污染 ,使农作物和牧草中 Pb、Cd含量超过动物的最大耐受量和中毒的临界值 ;动物研究发现 ,肾脏、骨骼和肝脏是机体内重金属蓄积的主要器官。因此 ,放牧动物可作为环境重金属污染状况的标识 ,对评价重金属环境污染对当地人群的危害也有重要意义     

重金属污染区土壤酶活性变化

从福建龙岩新罗区特钢厂污灌区农田采集土壤,测定土壤基本理化性质及脲酶、纤维素酶、碱性磷酸酶、多酚氧化酶、过氧化氢酶活性和Cu、Cd、Pb、Zn含量,探讨重金属污染和土壤性质对土壤酶活性的影响.结果表明： 4种全量或有效态重金属与土壤脲酶、纤维素酶、碱性磷酸酶和多酚氧化酶活性呈显著正相关,与过氧化氢酶活性呈显著或极显著负相关;土壤pH与碱性磷酸酶活性呈极显著正相关,粉粒含量与过氧化氢酶活性呈显著负相关.经通径分析,重金属污染刺激了脲酶、多酚氧化酶和纤维素酶活性,但对碱性磷酸酶活性的影响较小.有效态Cu、Cd、Pb、Zn对过氧化氢酶活性的直接影响并不大,但通过间接途径抑制了过氧化氢酶活性.土壤理化性质对5种土壤酶活性的影响较大,碱解氮直接抑制了脲酶活性;全磷直接刺激了碱性磷酸酶和过氧化氢酶活性,并通过有效磷刺激了纤维素酶活性;有效磷直接刺激了纤维素酶活性,直接抑制了碱性磷酸酶和过氧化氢酶活性;全钾直接抑制了碱性磷酸酶和多酚氧化酶活性;速效钾通过有效磷刺激了纤维素酶活性;土壤颗粒组成明显影响多酚氧化酶和过氧化氢酶活性.5种酶活性与土壤Cu、Cd、Pb、Zn含量之间的关系不明确,因此其活性不是指示土壤Cu、Cd、Pb、Zn污染的良好指标.     

Water regime of metal-contaminated soil under juvenile forest vegetation

In a three-year factorial lysimeter study in Open Top Chambers (OTCs), we investigated the effect of topsoil pollution by the heavy metals Zn, Cu, and Cd on the water regime of newly established forest ecosystems. Furthermore, we studied the influence of two types of uncontaminated subsoils (acidic vs. calcareous) and two types of irrigation water acidity (ambient rainfall chemistry vs. acidified chemistry) on the response of the vegetation. Each of the eight treatment combinations was replicated four times. The contamination (2700 mg kg^–1 Zn, 385 mg kg^–1 Cu and 10 mg kg^–1 Cd) was applied by mixing filter dust from a non-ferrous metal smelter into the upper 15 cm of the soil profile, consisting of silty loam (pH 6.5). The same vegetation was established in all 32 lysimeters. The model forest ecosystem consisted of seedlings of Norway spruce (Picea abies), willow (Salix viminalis), poplar (Populus tremula) and birch (Betula pendula) trees and a variety of herbaceous understorey plants. Systematic and significant effects showed up in the second and third growing season after canopies had closed. Evapotranspiration was reduced in metal contaminated treatments, independent of the subsoil type and acidity of the irrigation water. This effect corresponded to an even stronger reduction in root growth in the metal treatments. In the first two growing seasons, evapotranspiration was higher on the calcareous than on the acidic subsoil. In the third year the difference disappeared. Acidification of the irrigation water had no significant effect on water consumption, although a tendency to enhance evapotranspiration became increasingly manifest in the second and third year. Soil water potentials indicated that the increasing water consumption over the years was fed primarily by intensified extraction of water from the topsoil in the lysimeters with acidic subsoil, whereas also lower depths became strongly exploited in the lysimeters with calcareous subsoil. These patterns agreed well with the vertical profiles of fine root density related with the two types of subsoil. Leaf transpiration measurements and biomass samples showed that different plant species in part responded quite differently and occasionally even in opposite ways to the metal treatments and subsoil conditions. They suggest that the year-to-year changes in treatment effects on water consumption and extraction patterns were related to differences in growth dynamics, as well as to shifts in competitiveness of the various species. Results showed that the uncontaminated subsoil offered a possibility to compensate the reduction in root water extraction in the topsoil under drought, as well as metal stress.     

NATURAL REVEGETATION OF ALKALINE TAILING HEAPS AT TAXCO,GUERRERO, MEXICO

The aim of this research was to identify adapted native plant species with potential for use in phytoremediation of a metalliferous mine tailings heap in Guerrero, Mexico. Physico-chemical characterization, total, DTPA-extractable and fractionation of metals in rhizospheric and non-rhizopheric samples were carried out to gain information about their potential risks. Metal concentrations in plant and bioconcentration factors (BCF) were also determined. Organic matter (OM) and total N contents were higher in the rhizospheric samples, which could improve the conditions for plant establishment. Total Cu, Zn, and Pb concentration were above those for normal soils. The highest metals concentration was found in the residual and organic fractions. Eleven plant species were recorded at the site; three behaved as metal accumulator plants: Gnaphalium chartaceum (accumulator of Cu, Mn, Zn, and Pb), Wigandia urens and Senecio salignus (1027 and 2477 mg kg^?1 of Zn). These species and Brickellia sp. presented high Pb-BCF; they may be suitable for metals phytoextraction. Seven species behaved as excluder plants; Guardiola tulocarpus, Juniperus flaccida, and Ficus goldmanii, presented low BCFs. These species are well suited to cope with the toxic conditions, and they could be propagated for revegetation and stabilization of these residues and to decrease metal bioavailability.     

牡蛎对重金属生物富集动力学特性研究

应用半静态双箱模型室内模拟了牡蛎对四种重金属 (As、Hg、Cd、Pb)的生物富集实验 ,通过非线性拟合得到了牡蛎富集重金属的吸收速率常数 k1 、排出速率常数 k2 、生物富集因子 BCF、生物学半衰期 B1 /2 等动力学参数。结果表明 :吸收速率常数 k1及生物富集因子 BCF均随着外部水体浓度的增大而减小而平衡状态下生物体内金属含量 CAmax随着外部水体浓度的增大而增大 ,且成显著正相关 ,这说明牡蛎比较理想的重金属 Hg、Cd、Pb污染的指示生物。     

长期重金属胁迫对农田土壤微生物生物量、活性和种群的影响

调查了沈阳张士灌区长期污水灌溉造成的原位农田土壤重金属污染状况,从土壤微生物生物量、微生物活性和微生物种群数量的角度评价了长期重金属污染对农田土壤生态系统的影响.结果表明,张士灌区土壤存在严重的Cd污染,土壤Cd含量达1.75～3.89 mg·kg ^-1,部分区域还伴有Cu、Zn复合污染.在目前污染程度下,土壤微生物生物量碳(C_mic)、微生物商(qM)、土壤脱氢酶活性以及自生固氮菌数量随土壤重金属含量增加呈下降趋势,代谢商(qCO₂)随土壤重金属含量增加显著升高,而底物诱导呼吸强度(SIR)、纤维素酶活性以及细菌、放线菌和真菌数量无明显变化.相关性分析表明,土壤Cd含量变化是影响微生物参数变化的主要因素,在微生物参数中微生物商和代谢商对重金属污染最敏感.     

重金属污染区土壤酶活性变化——以福建龙岩新罗区特钢厂污水灌溉区为例

从福建龙岩新罗区特钢厂污灌区农田采集土壤,测定土壤基本理化性质及脲酶、纤维素酶、碱性磷酸酶、多酚氧化酶、过氧化氢酶活性和Cu、Cd、Pb、Zn含量,探讨重金属污染和土壤性质对土壤酶活性的影响.结果表明:4种全量或有效态重金属与土壤脲酶、纤维素酶、碱性磷酸酶和多酚氧化酶活性呈显著正相关,与过氧化氢酶活性呈显著或极显著负相关;土壤pH与碱性磷酸酶活性呈极显著正相关,粉粒含量与过氧化氢酶活性呈显著负相关.经通径分析,重金属污染刺激了脲酶、多酚氧化酶和纤维素酶活性,但对碱性磷酸酶活性的影响较小.有效态Cu、Cd、Pb、zn对过氧化氢酶活性的直接影响并不大,但通过间接途径抑制了过氧化氢酶活性.土壤理化性质对5种土壤酶活性的影响较大,碱解氮直接抑制了脲酶活性;全磷直接刺激了碱性磷酸酶和过氧化氢酶活性,并通过有效磷刺激了纤维素酶活性;有效磷直接刺激了纤维素酶活性,直接抑制了碱性磷酸酶和过氧化氢酶活性;全钾直接抑制了碱性磷酸酶和多酚氧化酶活性;速效钾通过有效磷刺激了纤维素酶活性;土壤颗粒组成明显影响多酚氧化酶和过氧化氢酶活性.5种酶活性与土壤Cu、Cd、Pb、Zn含量之间的关系不明确,因此其活性不是指示土壤Cu、Cd、Pb、Zn污染的良好指标.     

Assessing Risks of Heavy Metal Toxicity in Agricultural Soils: Do Microbes Matter?

Deleterious effects of heavy metals on soil microorganisms are reviewed in relation to the complexities involved in their study. There is strong evidence that soil microbes are more sensitive to heavy metals than animals or crop plants. Decisions concerning limits considered to be ‘safe’ in terms of protection of soil microorganisms or soil microbial processes from metal toxicity depend on the organisms considered and value judgements as to their importance. At present there is a large discrepancy in actual concentrations of heavy metals that are allowed to accumulate in agricultural soils between different countries. The approach of attempting to achieve zero accumulation of heavy metals in soils is undoubtedly the most conservative, but will severely restrict the recycling of sewage sludges to agricultural land.     

植物修复──重金属污染土壤整治有效途径

系统论述了重金属污染土壤植物修复的概念、原理、方法与研究动态,列举了污染土壤植物修复的一些实例。探讨了土壤重金属超富集植物的类型、特点、应用潜力以及基因工程等现代生物技术的应用、效果与最新展望,为土壤污染的综合整治及生态修复提出了新的思路。     

Laboratory study of heavy metal phytoremediation by three wetland macrophytes

Detention ponds and constructed wetlands have proven to be effective in reducing peak stormwater runoff volume and flow, and recent interest has extended to utilizing them to improve stormwater runoff quality. A review of stormwater runoff studies indicated that lead, zinc, copper, cadmium, phosphorus, and chloride are contaminants of primary concern. In laboratory settings, the uptake of contaminants by three wetland plant species, Glyceria grandis, Scirpus validus, and Spartina pectinata, was examined and removal rates from nutrient solutions inflow and nonflow reactors were measured. The removal rates varied by plant species and target contaminant, and no one species was the best accumulator of all six contaminants. Belowground tissues of all three species accumulated higher concentrations of the four heavy metals and aboveground tissues accumulated higher concentrations of phosphorus and chloride. Plants grown in flow reactors showed significantly higher accumulation rates than those grown in nonflow reactors. Also, plants grown hydroponically accumulated higher concentrations of the six target contaminants than those grown in sand reactors. However, those grown in sand had a much greater increase of biomass and removed a greater mass of the six target contaminants. Removal rates measured in these experiments can be used to design detention ponds to maximize stormwater remediation.     

Inhibition of photosynthesis by heavy metals

Inhibition of photosynthesis by heavy metals is well documented. In this review the results are compared between in vitro experiments on isolated systems (chloroplasts, enzymes ­.), experiments on excised leaves and intact plants and algae in vivo. In vitro experiments suggest potential sites of heavy metal interaction with photosynthesis at several levels of organisation, which are not necessarily confirmed in vivo. Analytical data on subcellular heavy metal level are generally missing to discuss their mechanism of action in the intact organism. In the field factors such as soil characteristics and air pollution have to be taken into account for assessing the mechanism of action of heavy metals on photosynthesis in plants, growing in a polluted erea.paper presented at the FESPP meeting in Strasbourg (1984)     

基于文献计量的细菌-生物炭协同修复重金属污染土壤研究进展

为提高重金属污染土壤可持续修复效能,研究生物炭与细菌对重金属污染土壤的协同修复作用。基于文献计量学分析及重金属污染土壤修复背景,总结了细菌与生物炭对土壤重金属的稳定化特征及菌炭间的相互作用,分析了单一生物炭或细菌对重金属污染土壤修复的局限性,强调了细菌-生物炭协同修复技术的优势,阐述了细菌与生物炭主要通过离子交换、固定作用、氧化还原作用和迁移作用等重要机制有效修复重金属污染土壤,揭示了细菌-生物炭协同作用在重金属污染土壤修复中的巨大应用价值。文献计量学研究表明,生物炭与细菌对重金属污染土壤的协同修复已得到广泛关注。目前认为:生物炭与细菌的协同作用可有效改良土壤理化性质及提高土壤修复效率,也可促进植物生长及植物修复进程;生物炭对细菌影响具有双重性质,可促进细菌生长,也可能对细菌产生毒害;细菌可改变生物炭的理化性质,进而强化生物炭的重金属固定性能;细菌协同生物炭联合修复重金属污染土壤过程中,生物炭主导吸附和固定,细菌则发挥活化和解毒等功能;优化细菌-生物炭组合形式,发展混合细菌与多种类生物炭协同技术,是复合重金属污染土壤可持续修复亟待解决的重要问题;进一步揭示细菌与生物炭对重金属污染土壤的耦合作用及长效作用机制,规避生物炭生产和应用中的潜在生态健康风险,研发新型高效能细菌与生物炭复合体是细菌协同生物炭可持续修复重金属污染土壤应用领域面临的挑战。