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.     

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.     

稻麦轮作下水稻土重金属形态特征及其生物有效性

在成都平原稻麦轮作下86个土样中重金属全量和各形态含量分析的基础上,采集分析相应点位上种植的主要粮食作物小麦和水稻籽粒的重金属含量,通过描述性统计分析、相关性分析及线性回归方程的模拟,研究了土壤中重金属的形态分布特征及其生物有效性。统计分析结果表明：土壤中Cr、Cu、Pb、Zn各形态含量的分配顺序为：残渣态〉有机物结合态〉铁锰氧化物结合态〉碳酸盐结合态〉可交换态,而Cd各形态含量的分配顺序为：铁锰氧化物结合态〉残渣态〉碳酸盐结合态〉有机物结合态〉可交换态。若以活性态（非残渣态含量）而论,Cd的活性最高,Cr的活性最低。除Cr外,各元素全量与各活性形态之间的关系较为密切。土壤中全Cd含量与4种活性形态Cd含量间的相关性均达极显著水平;Cu、Zn全量分别与其铁锰氧化物和有机物结合态含量,Pb全量分别与其可交换态和铁锰氧化物含量间的相关系数达显著或极显著水平。用卫生部颁布的食品中重金属限量卫生标准评价稻麦籽粒重金属累积情况,其结果表明,小麦籽粒（旱作）中的Cd、Cr、Cu、Pb分别超标14.71%、8.70%、6.50%和17.40%,而水稻籽粒（水作）仅有Pb和Cd含量超标10.90%和8.70%。不同形态重金属对水稻和小麦籽粒中重金属累积的影响效应不同,从多元线性回归方程的回归系数来看：稻一麦籽粒中Cd含量受到土壤中各活性形态Cd含量的影响。除铁锰氧化态Cd和有机物结合态Cd含量分别对小麦和水稻籽粒中Cd的累积表现出负效应外,其余均为正效应。可交换态Cu含量对稻-麦籽粒Cu累积的效应最大,其次受碳酸盐结合态Cu含量的影响。稻一麦籽粒Pb含量的累积受土壤各活性态Pb含量影响效应的差异不甚明显。稻-麦籽粒Zn含量与土壤各活性态Zn含量间无显著线性关系。     

Quick sequential procedure for speciation analysis of heavy metals in soils by supersonic extraction

Abstract

In order to improve the extraction efficiency and reduce the operation time, supersonic energy by means of supersonic bath was used to the modified Tessier sequential extraction for speciation analysis of heavy metals in soils. Extractable contents of Cu, Fe, Mn, Ni, Pb and Zn were measured by flame atomic absorption spectroscopy. The merit of the supersonic extraction (SE) applied to the modified Tessier, method is not only that the operation time for the first 4 fractions was reduced from ca 18 h to 8 h, comparing with conventional extraction (CE), but also the extraction efficiency was higher. There were no significant differences between the data obtained by the proposed method using supersonic extraction and the reference values of the standard reference materials of EES-2 and EES-3. The results for both of SE and CE in the soil samples were consistent. The extractable Cu, Ni and Zn in the sample No. 1 were mainly associated with the third fraction (Fe-Mn oxides fraction), and fourth fraction (organic matter fraction) in the sample No. 2. The extractable Fe and Mn were all mainly associated with the third fraction, and Pb the fourth fraction in both of the samples. The effects of varying concentrations of hydroxylamine hydrochloride on the extraction of metals were also studied.     

硫对土壤重金属形态转化及植物有效性的影响研究进展

生源要素硫在土壤中的化学循环不仅会直接影响土壤重金属元素的环境行为,也可通过调控植物根际微环境间接影响植物对重金属元素的吸收累积.土壤中的硫被植物根吸收后在植株中合成的有机硫化合物如植物螯合素(PCs)和金属硫蛋白(MTs)可与重金属形成毒性较低的络合物,构成植物重金属解毒的重要机制之一.我国部分土壤缺硫现象严重,为保证作物高质高产,硫肥的使用逐渐被重视,而硫与重金属的交互作用机制也逐渐成为研究热点.本文综合相关研究,介绍了硫在土壤中的生物化学转化,探讨了土壤硫的化学转化对土壤重金属形态转化及植物有效性的影响,并对今后硫在土壤重金属控制的应用提出展望.
     

Quantitative speciation of heavy metals in soil and crops of agricultural fields of Islamabad,Pakistan

Abstract

Two root crops: carrot (Daucus carota) and spring onion (Allium fistulosum) and soil samples were selected from the agricultural fields located near Islamabad, Pakistan to determine their elemental content. Field soil speciation of the two crops was also carried out to analyse the correlation of the elements in field crop and soil. Concentrations of selected elements were evaluated in the leaf, stem, root and flowering part of the crops using flame atomic absorption spectrophotometry. The results showed that elements are mostly concentrated in soil rather than crop parts following the sequence Zn>Cu>Pb>Ni>Cr>Cd. Furthermore, soil speciation showed that Ni and Cr are more prevalent in the Fe–Mn oxide fraction, Zn and Cd as the carbonate bound fraction and Cu is found in the organic bound form. However, concentrations of Pb are similar across the carbonate, Fe–Mn oxide and organic bound fractions. The highest average concentration of Zn is found as the carbonate bound fraction (2.09 ± 0.005 mg kg^?1) and Cu as the organic bound (1.51 ± 0.029 mg kg^?1) in soil samples taken from the agricultural field of Daucus carota.     

鄂尔多斯地区公路沿线土壤重金属形态与生物有效性

采用TessierA连续提取法对鄂尔多斯地区公路沿线土壤重金属（Pb、Zn、Cu、Ni、Cr）化学形态进行了测定。同时对土壤pH值、重金属含量和公路绿化植物重金属（Cd、Hg、Pb、Cu、Zn、Ni、Cr、As和Se）含量进行了分析,对该区域重金属的生物有效性与潜在生态风险进行预测。结果表明：土壤重金属有效态占总量百分比的大小序列为Zn〉Pb〉Ni、Cr〉Cu,与重金属元素在绿化植物中含量大小序列Zn〉Cu〉Ni、Cr、As、Pb〉Cd〉Hg并非完全趋于一致。不同公路段土壤重金属与其不同形态存在较大的变幅。公路沿线表层土壤中重金属的有效态占其总量为G109（东胜-准格尔段）15．7％～46．1％,G210（达拉特-东胜段）8．0％-40．9％,G109（东胜-鄂托克段）9．1％～33．9％,而且以有机态和Fe—Mn氧化结合态的比例较大,为各元素有效态的主要形态特征。Cu在不同植物不同器官中的含量较高,可能在鄂尔多斯地区特定环境条件下随植物的蒸腾拉力、水分和营养盐运移的生理生态作用下使其在植物体中富集。土壤重金属Zn的有效态含量较高,而残渣态含量低,须特别注意其对区域生态系统的潜在影响。     

Effects of biochar amendments on speciation and bioavailability of heavy metals in coal-mine-contaminated soil

An incubation experiment was executed on applying biochar as a soil remediation amendment to discuss an effect of the various addition rates on the speciation and bioavailability of heavy metals in mining-contaminated soil. The result showed that the content of Cd in soil was 9.51 times higher than the Huainan soil background values. The contents of Cu, Zn and As were 2.97, 1.60 and 1.42 times the background values, respectively, and the total contents of all heavy metals were higher than the standard values of soil environment quality GB15618-1995 set by the China Ministry of Environmental Protection. Speciation analysis indicated that Cu and Cd were mainly associated with the reducible fraction, while Zn and As were dominated by the residual fraction. After biochar was added to contaminated soil, the residual fractions of heavy metals increased, while the acid-soluble fractions reduced. According to the results of CaCl₂ extraction experiment, CaCl₂-extractable concentrations of Cu, Zn, As, and Cd were observed with a biochar dosage rate of 10%, which were 57.26%, 51.37%, 6.94% and 42.04% lower than those of control soil samples, respectively, but there were no obvious changes of CaCl₂-extractable As.     

重金属与农药污染的农业土壤脱毒过程研究进展

农业土壤环境自身脱毒过程是极其复杂的生态化学过程,对于土壤健康质量的维持和改善具有重要意义。然而,一直以来,人们对污染物的致毒过程研究得较多,对农业土壤自身脱毒能力及机制未给予足够重视。本文就农业土壤环境中,重金属与农药污染物的吸附脱毒、非生物降解(水解、光解)脱毒、微生物降解脱毒、土壤酶学脱毒、根际环境中的降解和转化脱毒以及植物富集固定进行了综述,并分析了各脱毒过程中所涉及到的反应机理。     

Phytomass change in natural phytocenosis as an indicator of technogenic pollution of soils with heavy metals

This study considered the possibility of using plant community phytomass for the assessment of soil pollution with heavy metals (HM) from industrial wastes. The three-year-long field experiment was run under the regional natural meadow vegetation; the polymetallic galvanic slime was used as an industrial waste contaminant. It is shown that soil contamination primarily causes decrease of phytomass in the growing phytocenosis. The vegetation experiments determined nonlinear dependence of cultivated and wild plant biomass on the level of soil contamination; it is described by the equations of logistic and Gaussian regression. In the absence of permanent contaminants, the soil is self-cleaned over time. It reproduces phytomass mainly due to the productivity increase of the most pollution-tolerant species in the remaining phytocenosis. This phenomenon is defined as environmental hysteresis. Soil pollution by industrial waste leads to the loss of plant biodiversity. The research shows that the study of the HM impact on ecosystems is expedient given the consideration of the “soil–phytocenosis–pollutant” complex in the “dose–response” aspect. The reaction of phytocenosis on HM showing decline in phytomass leads to serious limitations in the choice of accumulating plants, because the adsorbed HM are rejected through phytomass.     

Modeling of phytoextraction efficiency of microbially stimulated Salix dasyclados L. in the soils with different speciation of heavy metals

Bioaugmentation of soils with selected microorganisms during phytoextraction can be the key solution for successful bioremediation and should be accurately calculated for different physicochemical soil properties and heavy metal availability to guarantee the universality of this method. Equally important is the development of an accurate prediction tool to manage phytoremediation process. The main objective of this study was to evaluate the role of three metallotolerant siderophore-producing Streptomyces sp. B1–B3 strains in the phytoremediation of heavy metals with the use of S. dasyclados L. growing in four metalliferrous soils as well as modeling the efficiency of this process based on physicochemical and microbiological properties of the soils using artificial neural network (ANN) analysis. The bacterial inoculation of plants significantly stimulated plant biomass and reduced oxidative stress. Moreover, the bacteria affected the speciation of heavy metals and finally their mobility, thereby enhancing the uptake and bioaccumulation of Zn, Cd, and Pb in the biomass. The best capacity for phytoextraction was noted for strain B1, which had the highest siderophore secretion ability. Finally, ANN model permitted to predict efficiency of phytoextraction based on both the physicochemical properties of the soils and the activity of the soil microbiota with high precision.     

Total and speciation analyses of heavy metals in the sand fraction of Nigerian oil sands for human and ecological risk assessment

Total metal analysis and metal speciation of sand fraction of Nigerian oil sands were done to extract and partition heavy metals into six operationally defined fractions in order to assess environmental and health implications of the oil sand development. Soxhlet extraction of bitumen from the oil sand was done using toluene. Traces of water and extracting solvent were removed at 70°C from the sand fraction using oven. Elemental analysis was performed by Atomic Absorption Spectrophotometry. The heavy metals except Cu have low Pollution index values. Negative geo-accumulation index was obtained for the metals except Cu, indicating that the oil sands were uncontaminated with the metals. Strong and significant positive correlations existed between Fe/Pb, Zn/Cu, Cd/Pb, Ni/Cd, Ni/Pb, Cd/Fe, Ni/Fe and Cr/Zn, while strong and significant negative correlations existed between Mn/Pb and As/Mn, indicating common sources or chemical similarities and vice versa. T-test results indicated significant differences between the concentrations of the metals. Cross-plot analysis showed strong positive correlation between the sand fraction and Nigerian bitumen. Speciation analysis indicated highest and lowest indices of metal mobility for Zn and Pb, respectively. This study concluded that the sand fraction may not pose any environmental risks from elemental point of view.     

重金属污染土壤修复技术研究的现状与展望

目前重金属污染土壤的修复主要采用物理化学技术和植物修复技术,根据其作用和过程和机物,物理化学技术主要包括化学固化,土壤淋洗和动电修复;植物修复技术包括植物稳定,植物挥发和植物提取,本文就各种修复技术的原理,优缺点,实用性及其国际研究与发展动态作一简述。     

Zinc and cadmium uptake by the hyperaccumulator Thlaspi caerulescens in contaminated soils and its effects on the concentration and chemical speciation of metals in soil solution

The hyperaccumulator Thlaspi caerulescens J & C Presl. was grown in seven different soils collected from around Europe that had been contaminated with heavy metals by industrial activity or the disposal of sewage sludge to land. Zinc accumulation factors (shoot concentration/initial soil solution concentration) ranged from 3500–85 000 with a mean value of around 36 000. This compares with mean accumulation factors of 636, 66 and 122 for Cd, Ca and Mg, respectively. The concentration of Zn in the shoots was much greater than in the roots. The total removal of Zn and Cd ranged from 8 to 30 and from 0.02 to 0.5 mg kg^-1 soil, respectively. The Zn concentration in shoots of T. caerulescens correlated, using a curvilinear relationship, with the initial Zn concentration in soil solution (R² = total Zn 0.78; Zn²+ 0.80). There was no relationship between the uptake of Zn and the total Zn concentration in the soil. In most soils, solution pH increased only slightly after growth of T. caerulescens, indicating that acidification was not the mechanism used to mobilise Zn in the soil. Dissolved organic carbon concentrations generally increased but characterisation of the component organic compounds was not attempted. The concentrations of Zn and Cd in soil solution decreased considerably after growth of T. caerulescens. The percentages of Zn and Cd in soil solution present as free ions also decreased. However, the decrease of Zn in soil solution after growth accounted for only about 1% of the total Zn uptake by T. caerulescens. This was much lower than for Cd, Ca and Mg. The results suggest that either T. caerulescens was highly efficient at mobilising Zn which was not soluble initially, or the soils used had large buffering capacities to replenish soil solution Zn within a short time. This work highlights the need to investigate the role of root exudates on the mobilisation of Zn and Cd in soils by the hyperaccumulator T. caerulescens.     

重金属污染土壤原位化学固定修复研究进展

重金属污染土壤原位化学固定修复是通过添加不同外源物质固定土壤中重金属元素,达到降低重金属迁移性和生物有效性的一种重要方法.由于操作方便和效果快速,使其在污染土壤治理过程中有着不可代替的作用,尤其对于耕作土壤中的面源污染.许多具有俘获土壤中重金属离子能力的自然物质和工业副产品如磷矿石、泥炭土、石灰和有机肥等都可用在实地的固定修复中.采用实验室评价和实地应用评价,一方面可以评估这些固定物质在土壤中对重金属离子的固定效率;另一方面可以评估重金属的溶出、释放和生物毒性等生态风险.本文对原位修复过程中采用的不同固定物质的来源和分类进行了概述,对化学固定过程的机理进行了探讨,同时阐述了重金属污染土壤化学固定修复应用过程中的实验室评价和实地应用评价方法,分析了化学固定修复的局限性并提出了今后的发展方向.     

Microbial community structure in soils with decomposing residues from plants with genetic modifications to lignin biosynthesis

Lignin is a major determinant of the decomposition of plant materials in soils. Advances in transgenic technology have led to the possibility of modifying lignin to improve the pulping properties of plant materials for papermaking. Previous studies have shown that lignin modifications also affect the rate of plant material decay in soil. The aim of this work was to investigate short-term changes in soil microbial community structures when tobacco residues with reduced activity of enzymes in the monolignol pathway decompose. The residues from lignin-modified plants all decomposed faster than unmodified plant materials. The relative proportions of some of the structural groups of microbial phospholipid fatty acids were affected by genetic modifications, especially the proportion of double unsaturated chain fatty acids, indicative of fungi.     

阜新市农田土壤重金属含量及其分布特征

通过对辽宁省阜新市城郊区县180处农田土壤的取样调查分析,初步了解了农田土壤重金属As、Cu、Zn、Ni的含量特征及其空间分布,并探讨了当地矿业开采活动对农田土壤重金属积累及空间分布的影响.结果表明,研究区域内农田土壤Cu、Zn和Ni的几何平均含量均高于背景值,且这3种重金属存在普遍累积的现象;不同种植类型土壤中,菜地土壤Cu、Zn、As含量显著高于粮田,且重金属积累更为明显;4种重金属的空间分布均呈城区高于郊县的趋势;重金属含量较高的区域与矿山开采区域基本重叠.研究区域内采矿活动是农田重金属的重要来源,同时畜禽养殖业所产生的畜禽粪便可能对农田土壤中Cu、Zn和As的增加有一定作用.当地农牧业生产和布局应适当考虑土壤污染的风险.     

贵州兴仁煤矿区农田土壤重金属化学形态及风险评估

为了解煤矿区周边农田土壤重金属污染状况,采集了贵州省兴仁县某典型煤矿区农田土壤样品64份,测定了土样中重金属(As、Cr、Pb、Zn、Cd、Hg、Cu、Ni)总量及各形态含量,采用单因子指数法、潜在生态风险指数法(Hkanson法)和风险评估编码法(RAC)对研究区主要土壤利用类型(水稻土、薏米地、植烟土和菜园土)中重金属进行潜在生态风险评估和环境风险评价.结果表明： 不同利用类型土壤中重金属含量除Zn外,其他元素均明显超过贵州省背景值.单因子指数法评价结果表明,As、Pb、Hg和Cu污染较为严重,均属重度污染.形态分析表明,土壤中重金属形态构成差异明显,酸可提取态As、酸可提取态Cd所占比例较高;Cr、Zn、Cu、Ni主要以残渣态为主;Pb主要以可还原态和残渣态为主;而Hg的酸可提取态、可还原态、可氧化态均占有相当比例,三者之和大于55%.重金属可利用度大小顺序为:As(63.6%)>Hg(57.3%)>Cd(56.4%)>Pb(52.5%)>Cu(45.7%)>Zn(32.8%)>Ni(26.2%)>Cr(13.2%).潜在生态风险指数表明,各类型土壤潜在生态风险(RI)〖JP2〗为:菜园土(505.19)>薏米地(486.06)>植烟土(475.33)>水稻土(446.86),均处于较高风险.风险评估编码法结果显示,As在水稻土、薏米地及植烟土中均处于高风险,在菜园土中处于中等风险;Cd、Hg均处于中等风险,Cr、Pb、Zn、Cu和Ni均处于低风险.因此,对该区域农田土壤进行管控时应重点考虑As、Cd和Hg污染.     

大型水生植物对重金属的富集与转移

通过野外调查和室内分析,研究了云南阳宗海南北两区域自然生长的17种水生植物的生长状况及植物和对应水样、根区底泥中重金属(As、Zn、Cu、Cd、Pb)的含量。结果表明:植物长势良好,未发现受害症状。水体As严重污染,Pb轻度污染,Zn、Cu和Cd均未超标。9种沉水植物同时对As、Zn、Cu、Cd、Pb的富集系数(植物全株重金属含量与水中该元素含量的比值)远大于1,具有共富集特征。在平均含As0.175mg/L的水中,金鱼藻、黑藻、小眼子菜、八药水筛全株As平均含量分别为(150±7.3)、(179±35)、(92±31)、(265±21)mg/kg(干重),对As具有较强富集能力;对于8种湿生和挺水植物,北部采样点的喜旱莲子草、田栖稗、细叶小苦荬和长芒稗对As,长芒稗、细叶小苦荬、圆果雀稗、水蓼和风车草对Cd,海芋和圆果雀稗对Zn的富集系数(植物地上部重金属含量与底泥中该元素含量的比值)以及圆果雀稗对Cd和Zn转移系数(植物地上部重金属含量与根中该元素含量的比值)均大于1。聚类分析结果表明,金鱼藻、黑藻、八药水筛、小眼子菜、穗状狐尾藻5种水生植物同时对As、Zn、Cu、Cd、Pb具有较强的吸收和富集能力,在重金属复合污染水体修复中具有较大潜力。     

Source apportionment and health risk assessment of heavy metals in agricultural soils in Xinglonggang,Northeastern China

Heavy metals in soil can affect human health through the exposure pathways of oral ingestion, dermal contact, and inhalation. In this study, to assess the health risk of heavy metals in the agricultural area of Xinglonggang, 52 soil samples were collected and tested to obtain the concentrations of As, Cd, Cr, Cu, Ni, Pb, V, and Zn in the soil. The enrichment factor indicated that the heavy metals of the agricultural soils were enriched, but the degree of enrichment was mild for all of the heavy metals. Coefficient analysis and principal component analysis indicated that V, Cr, Ni, and Pb were mainly from natural sources, As was from irrigation, Cu and Cd tended to be from chemical fertilizers and pesticides, and Zn was from mixed sources including irrigation, chemical fertilizers, and pesticides. A human-health risk assessment indicated that the residents in the study area face high risk from carcinogens and low risk from noncarcinogens; As and Cr are the major heavy metals affecting human health. This study provides a reference and a basis for formulating effective measures to prevent and control heavy metal enrichment in agricultural soils.