Heavy metal bioavailability in a soil affected by mineral sulphides contamination following the mine spillage at Aznalcóllar (Spain)

A field experiment, lasting 14 months, was carried out in order to assess the effect of organic amendment and lime addition on the bioavailability of heavy metals in contaminated soils. The experiment took place in a soil affected by acid, highly toxic pyritic waste from the Aznalcóllar mine (Seville, Spain) in April 1998. The following treatments were applied (3 plots per treatment): cow manure, a mature compost, lime (to plots having pH < 4), and control without amendment. During the study two crops of Brassica juncea were grown, with two additions of each organic amendment. Throughout the study, the evolution of soil pH, total and available (DTPA-extractable) heavy metals content (Zn, Cu, Mn, Fe, Pb and Cd), electrical conductivity (EC), soluble sulphates and plant growth and heavy metal uptake were followed. The study indicates that: (1) soil acidification, due to the oxidation of metallic sulphides in the soil, increased heavy metal bioavailability; (2) liming succeeded in controlling the soil acidification; and (3) the organic materials generally promoted fixation of heavy metals in non-available soil fractions, with Cu bioavailability being particularly affected by the organic treatments.     

Metal tolerance and biosorption potential of filamentous fungi isolated from metal contaminated agricultural soil

Heavy metal analysis of agricultural field soil receiving long-term (>20 years) application of municipal and industrial wastewater showed two- to five-fold accumulation of certain heavy metals as compared to untreated soil. Metal-resistant fungi isolated from wastewater-treated soil belonged to genera Aspergillus, Penicillium, Alternaria, Geotrichum, Fusarium, Rhizopus, Monilia and Trichoderma. Minimum inhibitory concentrations (MIC) for Cd, Ni, Cr, Cu, and Co were determined. The MIC ranged from 0.2 to 5 mg ml(-1) for Cd, followed by Ni (0.1-4 mg ml(-1)), Cr (0.3-7 mg ml(-1)), Cu (0.6-9 mg ml(-1)) and for Co (0.1-5 mg ml(-1)) depending on the isolate. Aspergillus and Rhizopus isolates were tested for their metal biosorption potential for Cr and Cd in vitro. Biosorption experiments were conducted with initial metal concentrations of 2, 4, 6 and 8 mM with a contact time of 4 h and wet fungal biomass (1-5 g) at 25 degrees C. Maximum biosorption of Cr and Cd ions was found at 6 mM initial metal concentration. Aspergillus sp.1 accumulated 1.20 mg of Cr and 2.72 mg of Cd per gram of biomass. Accumulation of these two metals by very tolerant Aspergillus sp.2 isolate was at par with relatively less tolerant Aspergillus sp.1 isolate. Rhizopus sp. accumulated 4.33 mg of Cr and 2.72 mg of Cd per g of biomass. The findings indicated promising biosorption of cadmium and chromium by the Rhizopus and Aspergillus spp. from aqueous solution. There is little, if any, correlation between metal tolerance and biosorption properties of the test fungi.     

Willow growth in response to nutrients and moisture on a clay landfill cap soil. I. Growth and biomass production

The growth and biomass production by willow (Salix viminalis L.) was studied in lysimeters containing Oxford clay landfill cap soil with different amendments, bulk densities and watering regimes. Three years from planting, stem biomass in well-watered plants was least (0.28 kg plant(-1)) with high bulk density soil (1480 kg m(-3)) and no nutritional amendment but was increased 10-fold (2.53 kg plant(-1)) by reducing soil bulk density (1200 kg m3) and adding amendments. In comparison, on a sandy loam soil it was 6.23 kg plant(-1). There were similar differences in number of stems plant(-1), stem basal area plant(-1) and plant leaf area which can be attributed to low nitrogen and phosphorus levels in Oxford clay. Water stress reduced stem biomass production by 26-37% and caused higher root:stem ratios. These were also higher on Oxford clay than on the sandy loam. Successful biomass production from willow on Oxford clay landfill caps will therefore require nutritional amendment.     

Influence of acid rain and ozone on soil heavy metals under loblolly pine trees: A field study

A field growth chamber study was conducted to determine the effects of ozone and simulated acid rain (SAR) on soil heavy metals. Loblolly pine (Pinus taeda L.), grown in open-top chambers, was exposed to three concentrations of ozone (charcoal filtered air with 0.026 µL O₃ L^-1, and two non-filtered treatments in which ozone concentrations were 0.074 µL L^-1 and 0.147 µL L^-1, respectively) and two levels of SAR (pH 3.5 and 5.2). Ozone was applied for 12 h d^-1 for 9 months and acid rain deposition was 125 mm event^-1. After 9 months exposure, soil pH, organic matter and DTPA-extractable heavy metals (Cd, Pb, Zn, Mn, Fe, Cu) were determined on soil samples collected from exposed chambers at two depths (0–15 cm and 15–30 cm). Simulated acid rain decreased the original soil pH. The concentrations of Cd, Pb and Mn at SAR pH 3.5 were significantly higher than at SAR pH 5.2. Ozone did not affect Zn, Fe and Cu, but a significant interaction between pH and O₃ on Mn, Pb and Cd was observed. Due to the poor drainage capacity of this soil, leaching of heavy metals was not observed.     

施加改良剂对重度盐碱地土壤盐碱动态及草本植物生长的影响

为了探索内陆重度盐碱地的改良新方法,实验通过聚合有机酸(聚马来酸酐和聚丙烯酸)作为降盐碱剂,采用阻盐碱层、表土成膜剂以及土壤孔隙改善剂相结合的方法,对大庆市典型内陆盐碱土进行了改良实验,并在改良后的土壤及对照样地上种植不同植物--白菜、萝卜、菠菜、豚草和长春花,评价改良效果.结果发现:(1)通过施加降盐碱剂、阻盐碱剂及土壤孔隙剂,土壤的pH值和含盐量均有明显降低,下降幅度分别为pH:0.8～1.2、含盐量:0.2%～0.5%,而且表层改良效果优于深层;(2)在上述改良基础上施用表土成膜剂,使得土壤深层与表层盐碱运动减慢,即表层盐碱更低而深层更高,有利于保持表层适宜作物生长的条件;(3)2种聚合有机物比较来看,聚马来酸酐的改良效果好于聚丙烯酸;(4)从5种植物的生长状况来看,施用上述改良剂后较对照能够明显提高作物成活以及生长,特别是改良早期5种植物均呈现明显的生长趋势,而在后期存在生长力下降的趋势,因此,在大面积改良过程中需要考虑连续多次施加降盐碱剂以增强效果.     

Dynamics of C, N and P in soil amended with biosolids from a pharmaceutical industry producing cephalosporines or third generation antibiotics: a laboratory study

Large parts of the central highlands of Mexico are heavily eroded and the success of a planned reforestation program will greatly improve when the organic matter and nutrient content of the soil increases prior to the planting of the trees. This study investigated how the application of biosolids from a pharmaceutical company producing cephalosporines or third generation antibiotics could be used as a soil amendment and affect dynamics of C, P and N in soil. A sandy clay loam soil was sampled, amended with 24 g of dry biosolids kg(-1) dry soil or approximately 32 x 10(3) kg ha(-1) for the 0-10 cm layer, and incubated aerobically while production of carbon dioxide (CO(2)), dynamics of ammonium (NH(4)(+)),nitrite (NO(2)(-)), nitrate (NO(3)(-)), sodium bicarbonate (NaHCO(3)) extractable phosphorus (PO(4)(3-)), and microbial biomass carbon (C) were monitored. Results showed that the biosolid with pH 12, organic C content 162 g kg(-1), total N 21 g kg(-1), was of excellent quality considering its heavy metal content (USEPA) and a class "B" (USEPA) biosolid considering the amount of pathogens. No cephalosporines could be detected in the biosolid. Addition of biosolid to soil increased production of CO(2) 1.4 times and added >60 mg NH(4)(+) kg(-1). The application of biosolids did not significantly increase the concentration of NO(2)(-) which remained <2 mg N kg(-1) soil, but the concentration of NO(3)(-) did increase with 175 mg N kg(-1) soil. The microbial biomass C did not change when sewage biosolids was added and concentrations of extractable PO(4)(3-) only increased temporarily. Washing the biosolids reduced concentrations of NH(4)(+) and NO(3)(-), but also reduced pathogens and concentrations of chloride (Cl(-)), which might pose a treat to humans and the environment, respectively. Although the biosolid added valuable nutrients to the soil and did not inhibit C and N mineralization, further investigation into possible long-term environmental effects on soil processes and plant growth is necessary before this biosolid can be used in the field.     

Enhanced phytoextraction: II. Effect of EDTA and citric acid on heavy metal uptake by Helianthus annuus from a calcareous soil

High biomass producing plant species, such as Helianthus annuus, have potential for removing large amounts of trace metals by harvesting the aboveground biomass if sufficient metal concentrations in their biomass can be achieved However, the low bioavailability of heavy metals in soils and the limited translocation of heavy metals to the shoots by most high biomass producing plant species limit the efficiency of the phytoextraction process. Amendment of a contaminated soil with ethylene diamine tetraacetic acid (EDTA) or citric acid increases soluble heavy metal concentrations, potentially rendering them more available for plant uptake. This article discusses the effects of EDTA and citric acid on the uptake of heavy metals and translocation to aboveground harvestable plant parts in Helianthus annuus. EDTA was included in the research for comparison purposes in our quest for less persistent alternatives, suitable for enhanced phytoextraction. Plants were grown in a calcareous soil moderately contaminated with Cu, Pb, Zn, and Cd and treated with increasing concentrations of EDTA (0.1, 1, 3, 5, 7, and 10 mmol kg(-1) soil) or citric acid (0.01, 0.05, 0.25, 0.442, and 0.5 mol kg(-1) soil). Heavy metal concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted heavy metals decreased at high EDTA concentrations, due to severe growth depression. Helianthus annuus suffered heavy metal stress due to the significantly increased bioavailable metal fraction in the soil. The rapid mineralization of citric acid and the high buffering capacity of the soil made citric acid inefficient in increasing the phytoextracted amounts of heavy metals. Treatments that did not exceed the buffering capacity of the soil (< 0.442 mol kg(-1) soil) did not result in any significant increase in shoot heavy metal concentrations. Treatments with high concentrations resulted in a dissolution of the carbonates and compaction of the soil. These physicochemical changes caused growth depression of Helianthus annuus. EDTA and citric acid added before sowing of Helianthus annuus did not appear to be efficient amendments when phytoextraction of heavy metals from calcareous soils is considered.     

Copper phytoextraction in tandem with oilseed production using commercial cultivars and mutant lines of sunflower

Use of sunflower (Helianthus annuus L.) for Cu phytoextraction and oilseed production on Cu-contaminated topsoils was investigated in afield trial at a former wood preservation site. Six commercial cultivars and two mutant lines were cultivated in plots with and without the addition of compost (5% w/w) and dolomitic limestone (0.2% w/w). Total soil Cu ranged from 163 to 1170 mg kg(-1). In soil solutions, Cu concentration varied between 0.16-0.93 mg L(-1). The amendment increased soil pH, reduced Cu exposure and promoted sunflower growth. Stem length, shoot and capitulum biomasses, seed yield, and shoot and leaf Cu concentrations were measured. At low total soil Cu, shoot Cu mineralomass was higher in commercial cultivars, Le., Salut, Energic, and Countri, whereas competition and shading affected morphological traits of mutants. Based on shoot yield (7 Mg DW ha(-1)) and Cu concentration, the highest removal was 59 g Cu ha(-1). At high total soil Cu, shoot Cu mineralomass peaked for mutants (e.g., 52 g Cu ha(-1) for Mutant 1 line) and cultivars Energic and Countri. Energic seed yield (3.9 Mg air-DW ha(-1)) would be sufficient to produce oil Phenotype traits and shoot Cu removal depended on sunflower types and Cu exposure.     

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.     

黄土性土壤固化对黑麦草生长和根系活力的影响

采用盆栽试验,研究了安塞黄绵土不同容重、不同固化剂(路邦EN-1固化剂)掺量对黑麦草生长和根系活力的影响.结果表明:黄绵土容重在1.2～1.4 9·cm-3范围内,随土壤容重的增加,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均降低;各土壤容重条件下,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均高于对照,且随着固化剂掺量的增加均呈先增加后降低的趋势.土壤容重和固化剂掺量交互作用对根生物量和总生物量的影响均显著(P＜0.05).总体来看,土壤容重1.3 g·cm-3、固化剂掺量0.15％处理下,各指标值均最高.     

蚯蚓-秸秆及其交互作用对黑麦草修复Cu污染土壤的影响

以高沙土为供试土壤,加入Cu^2＋以模拟成：0,100,200,400mg／kgCu^2＋的Cu污染土壤,设置接种蚯蚓（E）、表施秸秆（M）,同时加入蚯蚓和秸秆（ME）及不加蚯蚓和秸秆的对照（CK）4个处理,并种植黑麦草。研究蚯蚓、秸秆相互作用对黑麦草吸收、富集铜的影响。结果表明：加入秸秆显著提高了蚯蚓的生物量,一定程度上缓解了重金属对蚯蚓的毒害,同时蚯蚓显著提高了秸秆的分解率,较无蚯蚓对照提高了58．11％～77．32％。接种蚯蚓（E,ME）还提高了土壤有效态重金属（DTPA-Cu）含量,秸秆处理（M）则降低了土壤有效态重金属含量。研究还发现,E处理促进了黑麦草地上部生长,而M和ME处理均显著提高了黑麦草地下部的生物量。E和ME处理同时提高了植物地上部和地下部的Cu浓度及Cu吸收量,M处理则只对植物的地下部Cu浓度和Cu吸收量有显著促进作用。总体来看,E处理、M处理及ME处理分别使黑麦草地上部Cu富集系数提高了31．22％～121．07％．2．12％～61．28％和25．56％～132．64％。     

Amendment of vanadium-contaminated soil with soil conditioners: A study based on pot experiments with canola plants (Brassica campestris L.)

We performed pot experiments with canola plants (Brassica campestris L.) to evaluate the effect of eight soil conditioners on the amendment of vanadium (V)-contaminated soil based on analysis of the growth of canola plants and the uptake, bioaccumulation, and translocation of heavy metals. Tested soil conditioners included polyacrylamide (PAM), sepiolite, humic acid (HAC), peat, sludge compost (SC), bentonite, lime, and fly ash. Results from the analysis of the growth of canola plants and the analysis of variance showed that the best soil conditioners for V-contaminated soil were 0.05–0.1 wt% PAM, 1 wt% peat, 1 wt% HAC, and 1 wt% SC; moderately effective soil conditioners included sepiolite and lime. The best combination of soil conditioners was 0.1 wt% PAM, 1 wt% HAC, and 0.15 wt% lime, in addition of 1% ZVI, which increased the biomass and height of canola plants by 1.18-fold and 59.49%, respectively. We conclude that the best combination of soil conditioners determined from this study is promising for mitigating V contamination in soil.     

Phytostabilization of polymetallic contaminated soil using Medicago sativa L. in combination with powdered marble: Sustainable rehabilitation

This study uses an ecotoxicology approach to evaluate the effectiveness of combining powdered marble as an amendment, with phytostabilization by Medicago sativa L. on the neutralization of acidic mine tailings, and the stabilization of heavy metals. The mine tailings were collected from an abandoned polymetallic mine in Southern Morocco, and mixed with powdered marble as the following proportions, 25%, 50%, and 75%. Laboratory immobilization/stabilization tests showed that the application of powdered marble in the treatments led to a significant increase in pH, and significant reductions of Cu, Zn (99%), Pb (98%), and Fe (45%). Greenhouse experiments showed that plant growth in all treatments was significantly (p ≤ 0.05) less than growth in agricultural soil. Plant growth significantly (p ≤ 0.05) decreased as the proportion of powdered marble increased. The concentration of metals in plant roots were significantly (p ≤ 0.05) higher than those of shoots. Combining immobilization by powdered marble with phytostabilization by M. sativa L. could represent a viable method of rehabilitating acidic polymetallic mine tailings.     

Phyto-availability and speciation change of heavy metals in soils amended with lignin as micro-fertilizer

Lignin is a primary byproduct from the black liquor treatment in paper making industries, its application as micro-fertilizer in agricultural land might provide a promising alternative to sewage discharge. However, application of such a micro-fertilizer might affect the soil properties and result in soil pollution. In this study, the effects of lignin application on phytoavailability and speciation change of heavy metals in soils were investigated. Greenhouse experiments showed that lignin application improved the growth of winter wheat (Triticum aestivum L.) in all three soils investigated. The increase of the biomass for wheat shoot was 59.7%, 39.8% and 12.3% for Beijing soil, Jiangxi soil and Dongbei soil, respectively. In contrast, lignin amendment decreased the concentrations of heavy metals in wheat shoots from 2.2% to 61.0%. Sequential extraction procedure of a three-step BCR was used to investigate the fraction distribution. The extractable fractions were specified as fraction B1: water soluble, exchangeable and carbonate bound or weakly specifically adsorbed; B2: Fe-Mn oxide bound; B3: organic matter and sulfide bound. The results showed that lignin application led to the redistribution of heavy metals in each fraction. Generally, heavy metals decreased in B1 and B2 fractions and increased in B3 fraction. Upon the results short-term application of lignin in agricultural land not only improves the growth of wheat but also reduces the phyto-abailability of heavy metal in wheat.     

Conocarpus biochar as a soil amendment for reducing heavy metal availability and uptake by maize plants

The objective of this study was to assess the use of Concarpus biochar as a soil amendment for reducing heavy metal accessibility and uptake by maize plants (Zea mays L.). The impacts of biochar rates (0.0, 1.0, 3.0, and 5.0% w/w) and two soil moisture levels (75% and 100% of field capacity, FC) on immobilization and availability of Fe, Mn, Zn, Cd, Cu and Pb to maize plants as well as its application effects on soil pH, EC, bulk density, and moisture content were evaluated using heavy metal-contaminated soil collected from mining area. The biochar addition significantly decreased the bulk density and increased moisture content of soil. Applying biochar significantly reduced NH₄OAc- or AB-DTPA-extractable heavy metal concentrations of soils, indicating metal immobilization. Conocarpus biochar increased shoot dry biomass of maize plants by 54.5–102% at 75% FC and 133–266% at 100% FC. Moreover, applying biochar significantly reduced shoot heavy metal concentrations in maize plants (except for Fe at 75% FC) in response to increasing application rates, with a highest decrease of 51.3% and 60.5% for Mn, 28% and 21.2% for Zn, 60% and 29.5% for Cu, 53.2% and 47.2% for Cd at soil moisture levels of 75% FC and 100% FC, respectively. The results suggest that biochar may be effectively used as a soil amendment for heavy metal immobilization and in reducing its phytotoxicity.     

Biosorption of cadmium(II), lead (II) and copper(II) with the filamentous fungus Phanerochaete chrysosporium

The biosorption from artificial wastewaters of heavy metals (Cd(II), Pb(II) and Cu(II)) onto the dry fungal biomass of Phanerochaete chryosporium was studied in the concentration range of 5-500 mg l(-1). The maximum absorption of different heavy metal ions on the fungal biomass was obtained at pH 6.0 and the biosorption equilibrium was established after about 6 h. The experimental biosorption data for Cd(II), Pb(II) and Cu(II) ions were in good agreement with those calculated by the Langmuir model.     

蚯蚓和秸秆对铜污染土壤微生物类群和活性的影响

试验设置4个Cu浓度水平：0、100、200和400 mg·kg^-1 Cu²⁺,每个Cu浓度水平设置4个处理：对照(CK)、表施秸秆(M)、接种蚯蚓(E)、同时加入蚯蚓和秸秆(ME),研究了在Cu污染土壤中加入蚯蚓和秸秆对土壤微生物数量及活性的影响.结果表明：Cu污染、秸秆和蚯蚓均明显影响土壤微生物类群; Cu污染对细菌、放线菌具有抑制作用,而对真菌没有影响;秸秆显著提高了真菌数量;蚯蚓使土壤细菌、放线菌数量显著增加,而对真菌数量影响不大.Cu污染浓度＞200 mg·kg^-1处理对微生物量碳具有抑制作用;加入秸秆或蚯蚓,可显著提高土壤微生物量碳,而且同时加蚯蚓和秸秆处理土壤微生物量碳增加最显著.加入蚯蚓和秸秆后,土壤呼吸值显著增高.Cu<200 mg·kg^-1时,蚯蚓处理土壤呼吸值最大,平均比对照高3.06～5.58倍;Cu≥200mg·kg^-1时,蚯蚓、秸秆同时加入处理土壤呼吸值最高.4个处理土壤代谢商大小顺序为：ME>E>M>CK.蚯蚓和秸秆处理对土壤NH₄⁺-N没有影响,而对土壤NO₃^--N影响各异.接种蚯蚓,可显著提高土壤NO₃^--N含量;加入秸秆,可显著降低土壤NO₃^--N含量;同时加入蚯蚓和秸秆处理NO₃^--N含量最低.相关分析表明,土壤有效态Cu(DTPA-Cu)与土壤放线菌、细菌呈显著负相关,而与土壤呼吸、土壤NO₃^--N、NH₄⁺-N含量呈显著正相关.引入秸秆和蚯蚓,可在一定程度上减缓Cu污染对微生物数量和活性的影响.     

Removal of trace metals by Sorghum bicolor and Helianthus annuus in a site polluted by industrial wastes: a field experience.

Using the perspective of full scale application of phytoremediation techniques, research is focusing on the optimization of agronomic practices. Two annual high biomass yield crops, Sorghum bicolor and Helianthus annuus, were grown in a polymetallic soil. The experimental site, polluted by pyrite cinders, is located in an industrial site that has been listed in the clean-up national priority list since 2001. Specific aims of this work were to observe the concentration of metals in plants during the crop cycle and to establish the amount of metal removed by the crops. The field trial, arranged in a randomized block design, started in 2005. The concentrations of heavy metals in the soil were: As 309, Cd 4.29, Co 50.9, Cu 1527 and Zn 980mg kg(-1). The crops grown on the polluted soil received mineral fertilization (Fert) and organic amendment (Org), while plants in control soil (Ctrl) did not receive anything. The plots were watered during the crop cycle during two drought periods, using a sprinkler irrigation system. The phytoextraction potential of crops was estimated during the whole growth cycle and the plant biomass that was collected in each sampling date was ICP-analyzed. Plant-biomass growth curves were obtained. The concentrations of the metals in the shoots and in the total plant biomass were recorded. Finally, the metal removal was calculated for the harvestable parts of the crops. The amelioration of the nutritive status of the substrate that resulted, was highly effective for the biomass yield. However, fertilization and soil amendment did not heighten the concentration of metals in the harvestable tissue of the plants during the crop cycle. In some cases, organic matter appeared to bind the elements making them less available for the plants. The evaluation of the potential of phytoremediation of our plants compared to other crops in terms of metal removal was positive. Our results of metal removal are consistent with the results from other in situ experiments. The Zn removal by S. bicolor and H. annuus reached about 2000g ha(-1) and 1000g ha(-1), respectively.     

利用乙二胺四乙酸淋洗修复重金属污染的土壤及其动力学

通过室内模拟试验,采用振荡淋洗的方法研究了乙二胺四乙酸(EDTA)浓度、pH、淋洗时间对重金属去除效果的影响.利用一级反应动力学模型对试验数据进行拟合,并测定了EDTA处理前后土壤中重金属形态的变化.结果表明,EDTA溶液在浓度为0.1 mol·L^-1、pH 7、淋洗时间1 d的条件下能达到对污染土壤重金属的最大去除率,去除率分别为Cd 89.14%、Pb 34.78%、Cu 14.96%、Zn 45.14%.模型拟合结果表明,Cd的质量转移系数最大,其次是Zn、Pb和Cu.说明在土壤淋洗过程中,Cd和Zn最先达到质量转移的平衡状态,然后是Pb和Cu.形态分级结果表明,EDTA能有效地去除交换态、碳酸盐结合态和氧化物结合态重金属,而对有机态和残余态部分重金属作用效果不明显.     

有机物料对污染土壤上水稻生长和重金属吸收的影响

采用盆栽试验,研究了施用有机碳源、菜籽饼和猪粪对污染土壤上水稻生长和重金属吸收特性的影响.结果表明： 施用菜籽饼和猪粪均能缓解重金属对水稻的毒害作用,促进水稻生长,显著增加地上部生物量和籽粒产量,降低糙米中重金属浓度;而有机碳源抑制水稻生长.与施用化肥相比,施用菜籽饼和猪粪处理的水稻籽粒产量分别增加128.3%和67.9%;施用菜籽饼处理的糙米Cd、Cu和Zn浓度分别降低47.6%、35.2%和21.5%,施用猪粪处理分别降低9.5%、21.2%和9.3%.土壤中DTPA提取态重金属浓度与水稻地上部生物量和重金属积累总量呈显著负相关.