长三角和珠三角农业土壤对Pb、Cu、Cd的吸附解吸特性

研究了长江三角州和珠江三角州10种代表性农业土壤对重金属Pb、Cu和Cd的吸附与解吸特性。结果表明:大多数土壤对重金属有较强吸附能力,土壤性质对重金属吸附与解吸行为有很大影响。其中,pH值是影响土壤对重金属吸附与解吸的最重要因素,土壤重金属吸附量随pH值增加而增加。土壤pH值和有机质或粘粒含量较高的土壤(如乌栅土、青紫泥田、黄斑田),其对重金属吸附能力高于pH值和有机质或粘粒含量较低的土壤(如黄筋泥、粉泥田)。重金属解吸量随重金属吸附量和土壤重金属饱和度增加呈指数增加趋势;土壤对重金属的吸附能力从强至弱依次为Pb、Cu、Cd;当3种重金属共存时,重金属之间竞争能力强弱顺序与吸附能力顺序相同。重金属之间竞争作用随土壤酸度和重金属污染程度的增加而增强。     

酸雨对长江三角洲地区四种典型土壤中锌解吸的影响

近年来酸雨危害频繁发生,特别是长江三角洲地区,酸雨致使土壤中重金属锌的吸附和解吸发生了一定的变化。选取具有代表性的长江三角洲地区4种典型土壤,通过加入外源重金属锌培育污染土样,在不同pH的酸雨下对已污染土样进行解吸。通过实验探究土壤母质对于重金属锌的吸附及解吸的特点,为国家制定土壤标准提供可靠的数据支持。结果表明：土壤中锌的解吸量随着pH的降低而增加;比较不同母质发育而成的土壤,在pH=4.0、5.6模拟已污染土壤中锌的解吸量顺序为：沟沟堆积母质〉湖相沉积物母质〉河相沉积物母质〉海相沉积物母质。在pH=2.0、3.0时,河相沉积物母质、湖相沉积物母质解吸量迅速增加,超过海相沉积物母质锌的解吸量。     

壳聚糖对污染土壤中吸附态Pb（Ⅱ）的解吸作用

土壤中重金属的吸附-解吸直接影响重金属在土壤及其生态环境中的形态转化、迁移和归趋.利用螯合剂促进普通植物富集吸收土壤中重金属是一种新的土壤组合修复技术, 向污染土壤中施用螯合剂可增加土壤溶液金属的浓度和活度,有利于金属到根部而被植物吸收.通过吸附等温实验研究了壳聚糖对污染土壤中铅的解吸作用.将壳聚糖提取液加入含Pb土壤中结果表明,壳聚糖螯合剂能提高土壤中吸附态铅的解吸效率,增加解吸溶液中Pb2 的浓度.壳聚糖对污染土壤中铅的解吸作用随着壳聚糖加入量的增大而增大,用浓度为0.4 g·L-1的90%脱乙酰度壳聚糖做提取液,提取液pH＝3,提取平衡时间10 h达到最高提取率32.4%,该吸附过程遵从Langmuir等温吸附方程; 土柱淋溶实验表明壳聚糖对污染土壤中Pb2 的提取率为27.4%.研究结果为铅在环境中的迁移转化和治理技术等方面的实际应用提供有价值的参考.     

EDTA、茶皂素及其混剂对土壤中Pb、Zn的解吸效果

以广东大宝山尾矿库区土壤为研究对象,通过振荡提取实验,研究了不同pH值下EDTA、茶皂素及其混剂对土壤中重金属铅和锌的解吸效果,结果表明:(1)EDTA对土壤中铅、锌的解吸率最高可分别达到54.19%、48.75%;茶皂素对土壤中铅、锌的解吸能力远弱于EDTA,尤其在pH值大于3的条件下,茶皂素对土壤中铅的解吸效果非常有限;(2)EDTA与茶皂素的混剂对土壤中铅的解吸高于锌,最高可分别达到73.98%、65.78%,这主要与土壤中铅、锌的形态分布有关;(3)在pH值在3—6范围内,铅的解吸率随pH值减小而增加,在pH值为4—6,锌的解吸率随pH值减小而增加.实验结果表明,茶皂素能强化EDTA对重金属的洗脱效率,并且在pH值2—7范围内,二者的协同作用受pH的影响较小.     

椰壳生物炭对多种重金属在广东水稻土中的吸附解吸特性影响

土壤中有毒有害重金属会造成环境污染并危害人体健康.本文基于OECD 106实验准则,采用批量平衡实验方法,研究了多种有效态重金属镉(Cd2+)、钴(Co2+)和铜(Cu2+)在广东省水稻土中的吸附解吸行为特征以及添加椰壳生物炭对吸附解吸行为的影响,并探讨了pH值、温度和添加炭含量对吸附率的影响.结果表明,3种重金属在土壤中的吸附平衡时间为25 h,解吸平衡时间为30 h,添加质量浓度5％椰壳生物炭可使土壤对3种重金属的吸附率提高11.6％ ～20.0％,重金属离子在土壤中的吸附为不可逆吸附,具有明显滞后效应,Cd2+、Co2+和Cu2+的解吸滞后系数分别为33.838、1.347和0.972.在本试验条件下,土壤溶液的pH值随椰壳生物炭含量的增加而增大,温度和含炭量对吸附率的影响呈良好的线性关系(r2>0.951).这表明,在土壤中施用椰壳生物炭能有效缓解土壤中的重金属污染.     

干旱区灰钙土和风沙土对Zn的吸附与解吸特性

以自然土壤灰钙土和风沙土作为试验供试土壤,研究了Zn在两种土壤样品中的吸附-解吸特性.结果表明:(1)当平衡液中Zn浓度较低时,土壤对Zn的吸附量随浓度的增加而增加,但增加速度较慢;平衡液中Zn浓度继续增加时,吸附量增加速率变大(曲线斜率逐渐增大),由于灰钙土有机质、碳酸钙、p H等高于风沙土,所以灰钙土对Zn的吸附量大于风沙土;(2)在实验设定的浓度范围内,Langmuir模型、Freundlich模型对实验数据的拟合线性相关均极显著,但总体来看Freundlich型吸附等温线方程适合描述土壤对Zn吸附过程;(3)两种土壤的高碳酸钙及有机质含量导致土壤吸附的Zn不容易被解吸,所以两种土壤的解吸量都很少,且灰钙土p H(8.65)大于风沙土(8.17),则风沙土解吸量大于灰钙土,土壤吸附Zn的解吸率与土壤Zn吸附能力呈反比,Zn在风沙土中的解吸率比灰钙土大,所以Zn在沙土的迁移和扩散的风险比灰钙土大,二次函数最为适合模拟土壤中Zn的吸附量与解吸量之间的关系,且随着Zn吸附量的增大,两种土壤对重金属Zn的解吸率均呈现出先增大后减小的趋势.     

无机阴离子对镉、铅解吸特性的影响

土壤中重金属的解吸直接影响重金属在环境中的形态转化和植物有效性.而地表水环境及土壤中的无机阴离子能与重金属离子络合,影响重金属在环境中的迁移和作物的吸收.因此,有关无机阴离子对重金属解吸特性影响的研究,将有利于了解重金属的吸附-解吸机制及其控制措施.文章以我国东北地区草甸棕壤作为研究对象,采用静态解吸实验研究无机阴离子(C1-、SO42-、F-)对土壤中镉、铅的解吸行为的影响.结果表明,土壤中镉、铅的解吸率与无机阴离子类型、浓度密切相关;随着解吸液中无机阴离子(C1-、SO42-、F-)浓度的增大,土壤镉、铅的解吸率随之提高.C1-、SO42-、F-这3种无机阴离子对解吸土壤中镉的影响力顺序是:C1- > SO42- > F-;对解吸土壤中铅的影响力顺序是:SO42- >C1- > F-.     

磷对褐土中锌镉次级吸附和解吸影响

通过吸附和解吸试验,研究了不同磷吸附量石灰性褐土对锌镉次级吸附和解吸的影响。结果表明,次级吸附锌和镉对不同吸附量磷土壤的磷解吸量随磷吸附量的增加而增加,而磷解吸量随次级吸附后锌、镉浓度的增加而降低,即随锌镉添加量的增加,磷的有效性有所降低。土壤对锌的次级吸附量和吸附率随磷吸附量的增加先降低后升高,并随添加镉浓度的增加而降低,解吸量和解吸率随磷吸附量的增加而增加,说明在正常施磷范围内,增加磷的施用量能提高土壤中锌的有效性,同时,土壤对高浓度锌的次级吸附率小于低浓度锌的次级吸附率,而土壤对高浓度锌的解吸量和解吸率要远大于对浓度锌的解吸量和解吸率;土壤对镉的次级吸附量、吸附率和解吸量、解吸率都随着磷吸附量的增加而增加,且吸附量随添加镉的量增加而增加,但镉次级吸附量和吸附率随添加锌浓度的增加而减小,解吸量和解吸率却增大,说明在磷吸附量相同的条件下,添加锌促进了镉的有效性。     

2种水稻土中Cu(Ⅱ)和Pb(Ⅱ)的解吸动力学

用一次平衡法研究了2种水稻土表面吸附态Cu(Ⅱ)和Pb(Ⅱ)的解吸动力学行为及柠檬酸和酒石酸对2种重金属离子解吸的影响。结果表明,虽然2种土壤对Pb(Ⅱ)的吸附量比Cu(Ⅱ)高得多,但无论在单一重金属体系还是Cu(Ⅱ)和Pb(Ⅱ)共存体系中,Cu(Ⅱ)的解吸量均大于Pb(Ⅱ),湖州水稻土Cu(Ⅱ)的解吸量大于嘉兴水稻土,说明土壤对重金属离子的吸附亲和力越大,吸附的重金属离子越不易解吸。用E lovich方程拟合动力学数据可以获得比较满意的结果。解吸速率与时间的关系曲线表明,Cu(Ⅱ)和Pb(Ⅱ)的解吸速率随时间的增加迅速减小。Cu(Ⅱ)的解吸速率大于Pb(Ⅱ),柠檬酸和酒石酸不仅使重金属的解吸量增加,而且使Cu(Ⅱ)和Pb(Ⅱ)的解吸速率大大提高。2种有机酸对Cu(Ⅱ)解吸的促进作用大于Pb(Ⅱ),柠檬酸的促进作用大于酒石酸。     

添加羟基磷灰石对土壤铅吸附与解吸特性的影响

采用羟基磷灰石对四种不同类型的土壤进行铅的吸附-解吸试验.结果表明:四种土壤对铅的吸附均可用Langmuir和Freundlich方程进行描述,土壤中加入羟基磷灰石明显增加了土壤对铅的吸附量和吸附亲和力,同时降低了土壤中铅的解吸百分数,在偏酸性的红壤上表现更为明显,其最大吸附量增加28%.羟基磷灰石对铅吸附的反应机理可能与磷灰石溶解后与铅形成磷酸盐沉淀及其对铅的表面吸附作用有关.土壤对铅的吸附量及吸附亲和力与土壤的有机质、阳离子交换量及粘粒含量有显著正相关,而与土壤砂粒的含量呈负相关.     

The adsorption of lead and copper from aqueous solution on modified peat-resin particles

Raw peat was modified with sulfuric acid, then mixed modified with resin to prepare the modified peat-resin particles. Using the batch experimental systems, the removal of heavy metals (copper and lead) on the modified peat-resin particles was investigated. The data of the adsorption isotherm could be fitted by the Langmuir equation well. The adsorption rate of heavy metals on modified peat-resin particles was very swift. The removal processes of heavy metals on modified peat-resin particles could be well described by pseudo-second order model. The adsorption rate of lead was affected by the initial heavy metal concentration, initial pH, particle size, agitation speed and particle mass. In the adsorption of heavy metals (lead and copper) on the modified peat-resin particles, ion exchange was the major reaction mechanism. Desorption data showed that the lead adsorbed by modified peat-resin particle could be desorbed by 0.5 N or 1.0 N HNO3. The desorption rate was swift. The experiments indicated that the modified peat-resin particles have great potential for the removal of heavy metals from wastewater.     

Heavy metals uptake from aqueous solutions using marine algae (Colpomenia sinuosa): kinetics and isotherms

The adsorption of copper, zinc, cobalt, lead and cadmium ions onto Colpomenia sinuosa was studied as a function of contact time, initial metal ion concentration and initial pH. In addition, desorption studies were performed. Characterisation of this adsorbent was also confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis. Batch adsorption experimental data were analysed using Langmuir, Freundlich and Dubinin–Raduschkevich (D–R) adsorption isotherms. The results indicated that the biosorption equilibrium was well described by both the Freudlich and D–R isotherms. Moreover, sorption kinetics was performed and it was observed that equilibrium was reached in<60 min, which could be described by the pseudo-second-order kinetic model for all heavy metals. The sorption of heavy metals onto the biomass was largely dependent on the initial solution pH. The elution efficiency for heavy metal ions desorption from C. sinuosa was determined for 0.1 M HCl, 1.0 M HCl and 1.0 M HNO₃. Desorption efficiency and also adsorption capacity were highest for Pb(II). The results indicate that C. sinuosa has great potential for the removal of heavy metals in an ecofriendly process.     

The Adsorption of Lead and Copper from Aqueous Solution on Modified Peat–Resin Particles

Raw peat was modified with sulfuric acid, then mixed modified with resin to prepare the modified peat–resin particles. Using the batch experimental systems, the removal of heavy metals (copper and lead) on the modified peat–resin particles was investigated. The data of the adsorption isotherm could be fitted by the Langmuir equation well. The adsorption rate of heavy metals on modified peat–resin particles was very swift. The removal processes of heavy metals on modified peat–resin particles could be well described by pseudo-second order model. The adsorption rate of lead was affected by the initial heavy metal concentration, initial pH, particle size, agitation speed and particle mass. In the adsorption of heavy metals (lead and copper) on the modified peat–resin particles, ion exchange was the major reaction mechanism. Desorption data showed that the lead adsorbed by modified peat–resin particle could be desorbed by 0.5 N or 1.0 N HNO₃. The desorption rate was swift. The experiments indicated that the modified peat–resin particles have great potential for the removal of heavy metals from wastewater.     

污染黑土中重金属的形态分布与生物活性研究

通过对污染和清洁黑土的耕层、非耕层分层采样分析,比较了Cd,Pb,Cu和Zn等在同一土壤耕层和非耕层以及不同采样点土壤中的形态分布和生物活性.结果表明,无污染黑土中这些重金属的形态分布一般为:残渣态>有机结合态>铁锰结合态>碳酸盐结合态>可交换态,外源污染则使可交换态重金属的含量增加.以生物有效性系数和迁移系数进行重金属生物活性评价,其在黑土中生物活性大小的顺序为:Cd>Cu>Zn>Pb.污染愈严重的土壤,重金属的生物活性和自身的淋溶能力相对较强,在非耕层中也表现出较高的生物活性.综合重金属在土壤中的含量和生物活性,发现2个污染点的黑土中Cd和Pb对当地农业生产和地下水安全已构成潜在的威胁.     

烟气脱硫石膏对滩涂围垦土壤重金属解吸及残留形态的影响

滩涂围垦土壤是重金属等难降解污染物的主要最终归宿场所之一,其重金属的解吸将影响重金属的迁移性、生物有效性和潜在毒性,研究重金属的解吸对土壤污染评价、修复及环境容量预测至关重要.研究了烟气脱硫石膏对广州市南沙滩涂围垦土壤重金属的解吸效果,并分析了烟气脱硫石膏对重金属形态的影响.在离心管中称取20.0 g过0.25mm筛土样,加入20 mL水和不同量的烟气脱硫石膏,在室温下于恒温振荡器振荡,风干研碎后用原子吸收分光光度法测定重金属全量,并用Tessier连续提取法研究了处理前后重金属形态变化.研究结果表明,随着脱硫石膏施用量的增加,经过振荡离心后的滩涂围垦土壤中重金属质量分数先急剧下降,之后变化趋于平缓.与原土相比各重金属最大解吸率分别为:Cd 30.38%,Cu17.73%,Ni 15.00%,Zn 14.19%,Pb 9.46%,Cr 8.89%.比较处理前后重金属的形态变化,发现各重金属的可交换态解吸率均达50%以上,并且重金属碳酸盐结合态质量分数也有减少.说明烟气脱硫石膏能降低土壤对重金属的吸附,经振荡离心后能降低土壤中重金属的毒性和生物可利用性.     

干旱区绿洲土壤中重金属的形态分布及生物有效性研究

测定了Cd、Pb、Zn和Ni等重金属在不同处理土壤中的全量和各赋存形态,以及它们在盆栽试验油菜（Brassica cole）中的质量分数,并利用Pearson相关系数分析了该区土壤-油菜体系的生物有效性。结果表明,供试绿洲土壤原状土中,Cd、Pb、Zn和Ni均以稳定的残渣态形式存在;而在处理土壤中,重金属被钝化的量有限,Cd的存在形式主要以碳酸盐态为主,Pb、Zn和Ni则主要以铁锰氧化态为主。根据相关性分析,油菜根部和叶部的Ni质量分数均与土壤中Ni的各非残渣态分布系数有相关性,表明当土壤中Ni以非残渣态存在时,活动性Ni的质量分数较高,其被生物吸收利用的可能性也较大;油菜根部的Zn质量分数与土壤中Zn的碳酸盐结合态分布系数显著的正相关性;油菜各部位Cd和Pb的质量分数与土壤中Cd和Pb的各形态分布系数之间无显著相关关系。     

风沙土不同有机组分对氨氮的解吸特征影响

采用平衡解吸法研究了风沙土不同有机组分对氨氮的解吸特征影响。结果表明,去除腐殖质后的风沙土氨氮解吸比例增加（由0.58增加到0.68）,同时,解吸迟滞性指数显著降低（由0.067降低到0.021）,说明腐殖质是影响风沙土氨氮解吸特征的重要因素;氨氮在轻组有机组分上的表面分配作用吸附是导致解吸比例增大,解吸迟滞性指数减小的原因;重组有机组分中的紧结态腐殖质（胡敏素）对氨氮的解吸起关键作用,它不但解吸比例较低（Dr=0.23）,而且解吸迟滞性指数较大（TⅡ=0.458）;氨氮在紧结态和稳结态腐殖质所形成的团聚体颗粒微孔隙中的不可逆吸附是导致解吸比例降低、解吸迟滞性指数增大的根本原因;考查土壤对氨氮的解吸特征不但要考虑有机质的含量,更要考虑有机质的存在形态,它也是影响土壤氨氮解吸特征的重要因素,轻组有机组分、重组有机组分及重组有机组分中的稳结态加紧结态腐殖质（HⅡ＋HⅢ组）和紧结态腐殖质（HⅢ组）携载的吸附态氨氮进入水体后,对上覆水体的扩散通量可分别按其饱和吸附量的0.94、0.58、0.33和0.23倍估算。     

Heavy metals,occurrence and toxicity for plants: a review

Metal contamination issues are becoming increasingly common in India and elsewhere, with many documented cases of metal toxicity in mining industries, foundries, smelters, coal-burning power plants and agriculture. Heavy metals, such as cadmium, copper, lead, chromium and mercury are major environmental pollutants, particularly in areas with high anthropogenic pressure. Heavy metal accumulation in soils is of concern in agricultural production due to the adverse effects on food safety and marketability, crop growth due to phytotoxicity, and environmental health of soil organisms. The influence of plants and their metabolic activities affects the geological and biological redistribution of heavy metals through pollution of the air, water and soil. This article details the range of heavy metals, their occurrence and toxicity for plants. Metal toxicity has high impact and relevance to plants and consequently it affects the ecosystem, where the plants form an integral component. Plants growing in metal-polluted sites exhibit altered metabolism, growth reduction, lower biomass production and metal accumulation. Various physiological and biochemical processes in plants are affected by metals. The contemporary investigations into toxicity and tolerance in metal-stressed plants are prompted by the growing metal pollution in the environment. A few metals, including copper, manganese, cobalt, zinc and chromium are, however, essential to plant metabolism in trace amounts. It is only when metals are present in bioavailable forms and at excessive levels, they have the potential to become toxic to plants. This review focuses mainly on zinc, cadmium, copper, mercury, chromium, lead, arsenic, cobalt, nickel, manganese and iron.