中国农田重金属问题的若干思考

在对我国若干典型区域调研及资料分析的基础上,作出了当前我国耕地重金属“主产区基本安全,重点区域风险较大”的基本判断,提出了针对农田土壤采用“重金属含量超标”替代“重金属污染”的观点,指出我国农业主产区农田重金属存在明显的累积趋势.同时,在对我国土壤重金属钝化和活化、植物吸收和阻控、微生物转化和利用等研究成果进行总结和借鉴基础上,提出了强化重金属超标农田安全利用、重金属含量阈值制订、重金属污染源头和过程阻控、超标农田修复以及产地环境安全保障体系等系列建议.     

朝天委陵菜的重金属耐性与吸收性研究

利用植物生长室水培试验和温室土培盆栽试验的方法,研究了朝天委陵菜在不同浓度Pb水培条件下和Cu、Zn、Pb、Cd复合污染土壤条件下的重金属耐性和吸收性,结果表明,水培条件下随着处理浓度的增加,朝天委陵菜均生长良好,虽高浓度Pb处理下出现植株矮小、叶渐黄、根系变黑等毒害症状,但植株并未死亡,表明在水培条件下朝天委陵菜对Pb具有极强的耐性;在最高浓度3 600μmol/L Pb处理下地上部和根中Pb浓度达到最大值,分别为947 mg/kg和71 053 mg/kg。在温室土培盆栽条件下,朝天委陵菜在外加Cu、Zn、Pb和Cd分别为200、1 000、1 000和5 mg/kg的土壤上较对照生长受到抑制,地上部Cu、Zn、Pb和Cd浓度分别达到741±164、18 248±2 222、1 543±483和29.4±5.2 mg/kg;外加重金属更高时则导致植株死亡。朝天委陵菜对Pb胁迫和Cu、Zn、Pb、Cd复合污染土壤具有较强的耐受性,可作为重金属尤其是Pb污染土壤的修复植物。     

The use of microbial parameters in monitoring soil pollution by heavy metals

Microbial parameters appear very useful in monitoring soil pollution by heavy metals, but no single microbial parameter can be used universally. Microbial activities such as respiration, C and N mineralization, biological N₂ fixation, and some soil enzymes can be measured, as can the total soil microbial biomass. Combining microbial activity and population measurements (e.g., biomass specific respiration) appears to provide more sensitive indications of soil pollution by heavy metals than either activity or population measurements alone. Parameters that have some form of internal control, e.g., biomass as a percentage of soil organic matter, are also advantageous. By using such approaches it might be possible to determine whether the natural ecosystem is being altered by pollutants without recource to expensive and long-running field experiments. However, more data are needed before this will be possible. Finally, new applications of molecular biology to soil pollution studies (e.g., genetic fingerprinting) which may also have value in the future are considered.     

重庆三峡库区耕地土壤重金属含量的空间变异性研究

对重庆三峡库区耕地土壤重金属含量的空间变异性研究结果表明,Hg和Cr服从对数正态分布,拟合得到Hg与Cr的半方差函数模型分别为幂函数和球状模型,且在一定范围内存在空间相关性;采用Kriging内插法对未测点重金属进行最优估计,所绘制的Kriging插值图反映了该区耕地土壤重金属Hg和Cr的空间变异特征。     

土壤中重金属离子竞争吸附的研究进展

本文主要对土壤中重金属离子竞争吸附的研究现状进行了综述。讨论了影响重金属离子竞争吸附能力的一些主要因子、吸附平衡模型及吸附反应的动力学过程。重金属离子的一级水解常数、离子半径、电负性等性质及其外界环境条件,如pH值、离子强度、有机质含量等因素影响着离子选择性吸附的强弱。竞争的Langmuir方程和扩展的Freundlich方程被用来对竞争吸附过程进行描述,同时指出竞争吸附过程中存在着一个"过饱和点"。最后,对竞争吸附的发展方向进行了展望,指出应加强理论模型和多因子综合作用影响的研究。     

Combination effects of heavy metals and fluoranthene on soil bacteria

The effects of (1) Cd, Cu, Zn, and fluoranthene (FLA), separately applied, and (2) combinations of one of these heavy metals with FLA on the growth of bacteria were studied in agar plate experiments. The bacteria were extracted from A horizons of a Eutric Regosol and a Calcic Chernozem. Significant reductions of bacterial counts were observed for both soils at concentrations > 1.0 mg Cd l^–1, 0.5 mg Cu l^–1, and 0.5 mg Zn l^–1, respectively. Additions of FLA up to 100 mg l^–1 did not result in increasing reductions of bacterial growth in the Regosol. Only 0.5, 2, and 100 mg FLA l^–1 caused significant reductions of 22–27%. Bacterial counts were not affected by 0.2 mg FLA l^–1. Low concentrations of heavy metals which were not affective when added separately were found to reduce bacterial growth when applied in combination with 0.2 mg FLA l^–1. At higher levels of heavy metals up to 2.5 mg l^–1, addition of FLA also increased the toxicity of the metals. It is assumed that the enhancement of toxicity by FLA is due to an alteration of the permeability of bacterial cell membranes. Received: 19 July 1996     

湖州市土壤重金属元素分布及潜在生态风险评价

在对湖州市土壤重金属污染状况进行调查后,按照有关标准和方法对该市土壤重金属潜在生态风险进行了评价。结果表明:单因子污染指数最小的是Pb,最大的是Cd。土壤中Pb含量均达标,其余各重金属元素有部分土壤超标。68.9%的土壤处于安全等级,21.6%的土壤处于警戒限,轻污染土壤占8.1%,重污染土壤占1.4%。68.9%的土壤处于低风险等级,27.0%的土壤处于中等风险等级,强风险等级土壤占2.7%,很强风险等级土壤占1.4%。林地的重金属含量变化幅度普遍大于耕地。耕地土壤污染程度轻于林地。土壤中各重金属对污染的贡献大小为:CdNiCrHgZnCuAsPb。     

南京栖霞重金属污染区植物富集重金属效应及其根际微生物特性分析

以南京栖霞重金属污染区5种植物及其根际土壤为研究对象,对植物富集重金属特征以及重金属含量与根际土壤细菌数量、土壤酶活性等的相关性进行了调查分析。结果发现,植物根际重金属污染物以Zn和Cd为主;重金属污染地区的植物有较强的吸收重金属能力,龙葵和茼草具备了超积累植物的基本特征;植物根际细菌和Pb抗性细菌的数量达到了107CFU g-1土;根际土壤酶活性未受到重金属的毒害或受到的毒害很小;植物体中重金属含量与土壤重金属含量及其存在状态、土壤酶、土壤重金属抗性细菌有显著的正相关性。根际土壤细菌尤其是具有重金属抗性的活性细菌可能会促进土壤重金属的活化,由此促进植物体对重金属的吸收和转运。     

重金属污染农田安全利用:进展与展望

我国耕地土壤污染面积广,污染情况复杂,农产品重金属超标问题已经关系到国计民生。常用的物理化学修复方法成本高,不适用于大面积的中低污染农田。植物提取修复方法成本低,环境友好,但修复时间长,推广困难。总的来讲,基于重金属移除的诸技术在解决农田重金属污染方面还没有太大优势。相较而言,农田安全利用在不移除或缓慢移除土壤重金属的条件下,以生产安全农产品为目标,具有更加坚实的现实意义和推广价值。种植低吸收农作物是安全利用的重要措施,基因工程手段在低吸收农作物品种筛选中具有巨大的潜力,但其可能带来的生态环境风险使得这些通过基因工程得到的低吸收作物的田间种植面临着巨大挑战。土壤添加剂可以改变土壤重金属形态,降低重金属的生物有效性,但会对土壤质量产生影响。微生物尤其是土著微生物的利用越发受到关注,改变微生物的生存环境与基因工程手段能够强化微生物的钝化效果。施肥、水分管理、间作等农艺措施也能改变土壤重金属的形态,抑制作物对重金属的吸收。未来以加强推广为目的,多种技术手段的联合应用是重金属污染农田安全利用的重要发展方向,其中以生物技术为核心的利用模式具有十分重要的意义。     

Bio-indicators to assess impacts of heavy metals in land-applied sewage sludge

Soils from a pastoral farm that had received large amounts of heavy metal contaminated sewage sludge 6-10 years previously were investigated to determine the impact of heavy metals on Rhizobium. The 8 ha application area was originally divided into five different-sized blocks (blocks 1-5), which received sludge at different times between 1991 and 1994. The response of a lux biosensor based on R. leguminosarum bv. trifolii (Rhizotox-C), was compared with more traditional techniques for measuring the presence of effective strains of Rhizobium (MPN) and nitrogen fixation (δ¹⁵N natural abundance). Although population size (MPNs), nitrogen fixation and biosensor response varied between treatment blocks, linear regression analysis determined that this block effect could not be directly linked to soil heavy metal concentrations, but was probably due to biological, physical, chemical and environmental compounding factors at the site. In this type of uncontrolled field application, the lux bioassay may provide the most useful information as it measures toxicity to any microorganism exposed to the soil solution, for example, the free living rhizobia.     

重金属的土水分配行为研究——根际土壤溶液采样器的应用

采用根际土壤溶液采样器(Rhizon-SMS)原位采集河南平原耕地土壤溶液.用土壤溶液中重金属浓度对数作为因变量、土壤溶液理化性质作为自变量,进行多元线性逐步回归,结果表明:只有有机碳进入Cu的相关方程,pH进入Cd的相关方程.土壤溶液pH和土壤中的Zn都作为自变量进入Zn的相关方程.土壤溶液中的Cu与pH没有线性关系,而Cd和Zn与土壤溶液pH有显著的线性关系(p＜0.01).计算了土壤中Cu、Cd、Zn在土壤与土壤溶液中的分配系数Kd.本研究中,3种重金属的Kd大小顺序为:Cu＞Zn＞Cd.根据Freeze 和Cherry模型,联合log(Kd-Cd)、log(Kd-Zn)与pH的线性关系,估计了Cd和Zn在土壤中的迁移速度.     

重金属与土壤环境质量及食物安全问题研究

As、Cd、Hg、Pb和Se是对食物链造成污染的最重要元素。简述了土壤环境质量的内涵,讨论了重金属污染的现状、特性、来源以及重金属与食物安全的关系,并提出治理重金属污染的途径与方法。     

化肥施用对土壤中重金属生物有效性的影响研究

本研究综述了化学肥料施用对土壤中重金属生物有效性的影响,土壤施肥能改变土壤理化性质如pH、溶液中的离子组成、阳离子交换量等,或直接与重金属离子发生反应,影响重金属的生物有效性。故施用化肥时要考虑到所施化肥的种类和施用量可能会导致重金属的植物可利用性发生改变,从而对人体健康产生影响。     

Geochemical fluxes in forested acidified catchments

The atmospheric deposition of some major components (e.g., NO₃-N 6.6 and 14.5; SO₄-S 17.8 and 42.4 kg ha^–1 a^–1) and trace elements (e.g., Cd 0.4 and 1.1, Cu < 1.9=" and=" 15,=" pb=" 43=" and=" 48=" g=">^–1 a^–1) in bulk and throughfall deposition respectively, shows a pronounced decline in recent measurements of total deposition in the eastern Erzgebirge (Germany). This is true for both bulk and throughfall deposition in 1992–1994 as compared to similar data from 1985–1989. The decline is a result of successful emission control strategies in central Europe and the shut down of plants and factories in the former GDR.The dry deposition at the highest (influenced by long-range transport) and the lowest station (local influences) shows distinct differences (e.g., Cd 0.6 and 0.3; Cu 17.4 and 7.3; Pb 13 and 31 ng m^–3). A comparison between total and dry deposition exhibits the different behavior of elements in respect to atmospheric concentrations and solubility in (rain)water. Anthropogenically released elements are mainly immited via wet deposition.     

Short- and long-term effects of heavy metals on urease activity in soils

Summary The inhibitory effects of cadmium, chromium, copper, lead, nickel and zinc on urease activity of five different soils during two different periods were investigated, in order to obtain information on the change in heavy metal toxicity with time. The results are presented graphically as logistic dose-response curves. When the ecological dose range was used as a measure of toxicity this value decreased significantly only for copper in the sandy soil. Considering toxicity as the ecological dose-50% (ED50) value, toxicity tended to increase over 1 1/2 years for cadmium, copper and zinc. For nickel and lead, however, the toxicity stabilized in all soils, except in sand and clay. The average ED 50 value of zinc varied between 100 and 300 mg kg^–1 and its toxicity was highest. It is emphasized that these data may help to set limits for the heavy-metal pollution of soils.     

Influence of heavy metals on the functional diversity of soil microbial communities

Three soil types-Calcaric Phaeozem, Eutric Cambisol and Dystric Lithosol-in large container pots were experimentally contaminated with heavy metals at four different levels (light pollution: 300 ppm Zn, 100 ppm Cu, 50 ppm Ni, 50 ppm V and 3 ppm Cd; medium pollution: twofold concentrations; heavy pollution: threefold concentrations; uncontaminated control). We investigated the prognostic potential of 16 soil microbial properties (microbial biomass, respiration, N-mineralization, 13 soil enzymes involved in cycling of C, N, P and S) with regard to their ability to differentiate the four contamination levels. Microbial biomass and enzyme activities decreased with increasing heavy metal pollution, but the amount of decrease differed among the enzymes. Enzymes involved in the C-cycling were least affected, whereas vartous enzyme activities related to the cycling of N, P and S showed a considerable decrease in activity. In particular, arylsulfatase and phosphatase activities were dramatically affected. Their activity decreased to a level of a few percent of their activities in the corresponding unpolluted controls. The data suggest that aside from the loss of rare biochemical capabilities-such as the growth of organisms at the expense of aromatics (Reber 1992)-heavy metal contaminated soils lose very common biochemical propertities which are necessary for the functioning of the ecosystem. Cluster analysis as well as discriminant analysis underline the similarity of the enzyme activity pattern among the controls and among the polluted soils. The trend toward a significant functional diversity loss becomes obvious already at the lowest pollution level. This implies that concentrations of heavy metals in soils near the current EC limits will most probably lead to a considerable reduction in decomposition and nutrient cycling rates. We conclude that heavy metal pollution severely decreases the functional diversity of the soil microbial community and impairs specific pathways of nutrient cycling.Dedicated to Professor J. C. G. Ottow on the occasion of his 60th birthday     

我国北方典型日光温室蔬菜生产系统土壤重金属积累趋势

本文以山东省寿光市日光温室蔬菜生产系统为例,研究了As、Cd、Cu、Hg、Pb和Zn等重金属元素在土壤中的积累趋势。结果表明：有机肥中Cu、Zn元素含量较高,而无机肥中Cd、Zn元素含量较高,但所有元素均未超过目前的相关标准。表层土壤中上述元素的平均含量均未超出《温室蔬菜产地环境质量评价标准》(HJ333-2006)相应的标准限值,但Cd平均含量已接近评价标准。除了As和Pb元素外,表层土壤中Cd、Cu、Hg和Zn的含量随着种植年限的增长而增加,出现积累。在目前的重金属积累状况下,主要蔬菜可食部分的重金属含量明显低于中国食品污染物限量标准,处于安全级别。由于蔬菜生产最初均是在底层土壤上开始的,加之封闭的生产环境,表明土壤中重金属主要来自各种农用投入品的输入,而各种肥料的高量输入是其积累的主要原因。今后对该地区设施蔬菜生产的环境管理,除了制定更严格的肥料重金属含量标准外,更重要的是要严格控制各种肥料的施用量,这样既可降低系统养分过量盈余,又可控制土壤重金属的积累。     

Experimentally induced effects of heavy metal on microbial activity and community structure of forest mor layers

This study compared the toxic effects of adding chromium (Cr), zinc (Zn), lead (Pb), molybdenum (Mo), nickel (Ni), and cadmium (Cd) at three dose levels to mor layer samples in laboratory experiments. Microbial activity in the form of soil respiration was monitored for 64 days. At the end of the experimental period, the composition of the soil microbial community structure was analysed by phospholipid fatty acid (PLFA) analysis. The metals added induced changes in the microbial community structure and affected respiration negatively, indicating toxicity. The microbial community structure (principal component analysis of the PLFA pattern) for all metals was significantly related to microbial activity (cumulative respiration), indicating intimate links between microbial community structure and activity. The most striking result in this study was that the shift in the microbial community because of metal stress was similar for all metals. Thus, the PLFA i16:0 increased most in relative abundance in metal-polluted soils, followed by other PLFAs indicative of Gram-positive bacteria (10Me16:0, 10Me17:0, 10Me18:0, a17:0 and br18:0). The PLFA 16:1ω5 was consistently negatively affected by metal stress, as were the PLFAs 18:1, 18:1ω7 and 19:1a. However, a significant separation between Cr- and Cd-polluted soils was observed in the response of the PLFA cy19:0, which decreased in abundance with Cr stress, and increased with Cd stress. Furthermore, the PLFA 18:2w6, indicating fungi, only increased with Cr and Zn stress. The effective doses of the metals, ranked with regard to background metal concentrations, decreased in the order: Zn > Cr > Pb > Mo > Ni > Cd. We concluded that interpretation of results of microbial activity from experiments of metal toxicity should include microbial structural patterns and background metal concentrations.     

Impact of heavy metals on the degradative capabilities of soil bacterial communities

The degradative capabilities of six heavy-metal-affected and six unaffected bacterial communities from Canadian and German soils were determined by enumerating colony-forming units on 20 specific media. Each of these contained an aromatic substrate as the sole source of C and energy. Comparisons of plate counts revealed that heavy metal stress caused a decrease in the eveness of the distribution of the 20 degradative capabilities This suggests that in heavy-metal-affected bacterial communities, relatively rare degradative capabilities, irrespective of their nature, are even rarer than in unaffected communities, while the reverse is true for more common capabilities. The results are discussed with respect to the ease with which aromatic substrates can serve as C and energy sources.     

徐州市北郊农业土壤重金属污染评价

研究评价徐州市北郊农业土壤重金属污染状况结果表明,该区农业土壤中Cu、Cd、Pb、Zn和Cr 5种重金属平均含量均高于土壤背景值,其农业土壤Cd、Cr为重污染,土壤Zn为污染警戒级(尚清洁水平),其他2种元素为安全级(清洁水平),其综合污染指数为Cr>Cd>Zn>Cu>Pb。