水分条件对稻田土壤汞甲基化影响的模拟研究

通过培养实验,研究了70%田间持水量、干湿交替及淹水等3种水分管理方式对外源Hg在稻田土壤中甲基化的动态过程.外源添加浓度为5 mg·kg~(-1)Hg~(2+),培养时间为42 d.结果表明,70%田间持水量下,土壤甲基汞(Me Hg)含量基本保持稳定,平均为11.55μg·kg~(-1);淹水条件下,土壤Me Hg含量呈上升趋势,平均为30.70μg·kg~(-1),约为70%田间持水量的2.7倍;干湿交替条件下,土壤Me Hg呈现"涨-消"的波动趋势,平均含量为20.41μg·kg~(-1),约为70%田间持水量的1.7倍.培养结束后土壤Me Hg含量和占总Hg比例依次为:淹水(37.42μg·kg~(-1),0.76%)干湿交替(16.08μg·kg~(-1),0.33%)70%田间持水量(11.75μg·kg~(-1),0.25%),表明淹水条件有利于稻田土壤中汞的甲基化.Elovich方程可以拟合淹水条件下稻田土壤Me Hg含量变化的动力学过程,表明土壤中Me Hg含量在试验前期(7 d)快速升高,随后呈现缓慢增长的趋势.培养期间,各水分处理下稻田土壤中硫酸盐还原菌(SRB)数量均表现为上下波动式的周期性变化特征,均值分别为(533±31)cfu·g~(-1)(70%田间持水量)、(615±39)cfu·g~(-1)(淹水)和(509±43)cfu·g~(-1)(干湿交替).相关分析表明,土壤Me Hg含量与硫酸盐还原菌(SRB)数量、氧化还原电位(E_h)、土壤含水量之间的相关性达到了显著性水平(p0.05),与其他因素之间无显著相关性.可以推测,在稻田土壤淹水形成的厌氧环境中,SRB可能是生物汞甲基化的优势菌群.     

苏州地区水稻土重金属污染源解析及端元影响量化研究

利用国家土壤质量标准和当地背景值评价了苏州地区表层水稻土重金属(Pb、Cd、As、Hg、Cu、Zn、Ni、Cr)的污染(富集)状况.结果发现,苏州地区土壤Cd、Hg、As、Pb、Zn、Cu、Cr和Ni平均含量分别是0.23、0.23、9.14、35.36、103.36、35.75、77.12和33.18μg·g-1;除As外,其余7种重金属平均含量皆明显高于当地土壤背景值.通过与中国土壤环境质量标准(GB15618—1995)相比,发现苏州地区土壤中Cd和Hg是8种重金属中风险最高的.地质累积指数分析表明,苏州水稻土重金属Cd、Hg、Pb、Cu和Zn出现了污染,其中以Cd和Hg的污染程度最突出,约80%的土壤样品出现了Pb轻度污染.因子得分-多元回归法(PCS-MLR)估算表明,70%的土壤Cd来自与有色金属或磷有关的人为活动;土壤中约50%的Pb和72%的Hg源于大气沉降的贡献;土壤的Zn和Cu污染主要来自与有色金属或磷有关的人为活动,该端元对土壤Zn和Cu的影响率分别为53%和45%.     

我国南方四省集中连片水稻田土壤重金属污染评估研究

以2013—2014年南方湖南、江西、浙江、福建四省集中连片水稻田的63个采样数据为基础,利用单因子评价法和内梅罗指数评估南方水稻田土壤重金属的污染情况.结果表明:南方集中连片水稻田土壤Cd点位超标率为0;Hg、As和Ni 3种重金属含量超出《土壤环境质量标准》(GB15618-1995)二级标准的比例最大,分别为6.3%、4.8%和7.9%;研究区水稻田土壤重金属以清洁为主,70%以上符合农业生产和生活要求,但少量样点Hg为中度和轻度污染,As和Ni为轻度污染;从内梅罗综合指数看,研究区土壤重金属仅有3.18%和1.59%的为轻度污染和中度污染,主要分布在湖南和江西.     

土壤水分对稻田土壤有效砷及碱性磷酸酶活性影响

采用室内模拟方法,在35%、65%和110%最大饱和持水量（WHC）条件下,系统地分析了稻田土壤有效砷及碱性磷酸酶活性变化规律.结果表明：砷污染稻田土壤后有效砷含量随砷污染浓度增加而增大,随培养时间延长逐渐降低,15d后趋于稳定;淹水降低了土壤有效砷含量及碱性磷酸酶活性;采用U=A/（1+B×C）模型较好拟合了不同水分下土壤碱性磷酸酶活性（U）与砷浓度（C）关系,表明碱性磷酸酶活性在一定程度上可表征不同水分下稻田土壤砷污染程度;计算得到稻田土壤砷轻度污染临界浓度（ED₁₀）为总砷67mg/kg和有效砷11mg/kg.研究表明适当调控土壤水分含量是控制稻田土壤砷毒性的有效方法之一.     

电镀污泥中重金属溶出动力学及其在土壤中的归趋

电镀污泥是电镀工业中重金属的"汇",在降水的作用下可能向环境释放大量的重金属.本文通过连续浸出实验和动力学拟合探究了电镀污泥中重金属的溶出特性,并分析了重金属在土壤中的吸附、迁移转化及淋出行为.结果表明,在淋溶初期,重金属从电镀污泥中大量释放,且土壤中Cr （Ⅵ）、Ni的淋出浓度分别高达0.102、0.222 mg·L^-1.淋溶后,表层土壤中Ni、Cu的总量及可交换态/碳酸盐结合态含量均显著增加;由于专性吸附作用,Cu的铁锰氧化物结合态含量也大量增加,Cu在土壤中的吸附率高达89.32%~97.67%,降低了其从土壤中的淋出风险.Cr、Ni、Cu更易在红壤中发生吸附并转化为稳定的有机结合态,降低了重金属的潜在迁移性;相应地,电镀污泥中释放的Cr、Ni、Cu在栗钙土中具有较高的淋出风险.     

重金属污染的稻田土中总有机碳和颗粒态碳的变化

从广东大宝山矿区横石河下游受重金属污染的水稻田采集6个土壤剖面样品,研究了土壤中总有机碳(TOC)、颗粒态有机碳(POC)和POC/TOC比率的垂直分布特征,并探讨不同污染程度对土壤有机碳含量及稳定性的影响.结果表明,与轻度污染和中度污染采样点相比,在重度污染的各土层中,TOC含量显著下降,其垂直分布有显著改变.POC含量在不同土层间的变化与TOC表现出相似的规律,但差异更显著.重金属污染会影响土壤有机碳不同组分在土壤剖面上的垂直分布特征及分配比例,从而影响土壤有机碳的稳定性和可利用性.中度重金属污染使POC含量显著增高,土壤有机碳变得易于分解和损失;重度污染使TOC含量显著降低,不利于土壤有机碳的固定和积累.不同重金属对土壤有机碳稳定性的影响不同,Pb表现出与Cu、Cd的拮抗作用,Pb使有机碳稳定性增加;而Cu和Cd则相反.但多种重金属联合效应使土壤有机碳稳定性呈降低趋势.     

锰促进稻田生物结皮固定灌溉水中镉

为了解在不同浓度的锰盐作用下生物土壤结皮对稻田灌溉水中镉的固定作用及机制,将不同浓度的硫酸锰、镉溶液与稻田生物土壤结皮混合,并在实验室内培养15 d.通过分析生物土壤结皮中不同形态的锰、镉的量,探究不同浓度锰盐对土壤结皮中镉的固定及分布的影响.结果表明:锰盐能有效地促进生物土壤结皮固定镉,随着锰盐浓度的增加,生物土壤结皮对镉的去除效率增加.在20.00 mg·L~(-1)硫酸锰条件下,生物土壤结皮对水中镉离子去除率达到98.20%,镉主要以非乙二胺四乙酸可提取的矿物形态存在.通过扫描电子显微镜-电子散射能谱及X射线光电子能谱分析,锰被锰氧化菌氧化成类似水钠锰矿的多孔海绵状物质,镉富集固定在晶格中.本研究对利用生物土壤结皮净化镉污染灌溉水提供了新的思路.     

4种重金属污染对稻田土反硝化细菌的影响

在实验室条件下,研究Cd²⁺、As⁵⁺、Cu²⁺和Pb²⁺处理黄松稻田土、紫色稻田土和红壤稻田土后,4周内重金属污染对反硝化细菌种群数量及其反硝化活性的影响.结果表明,在1kg干土中加入0.5mg Cd²⁺、30mg As⁵⁺、50mg Cu²⁺和200mg Pb²⁺时,对稻田土反硝化细菌种群数量及其活性有促进作用,加入Cd²⁺、As⁵⁺、Cu²⁺和Pb²⁺分别超过1.0,60,500,400mg/kg干土时,对稻田土反硝化细菌种群数量及其活性有明显抑制作用.但反硝化细菌种群数量及其活性能逐渐恢复并接近对照水平,重金属污染越重,恢复所需的时间也越长.同一种重金属元素对不同水稻田土的反硝化细菌种群数量及其活性的影响也有差异.     

Application of ultrasonic to speciation analysis of heavy metals in soil

In order to reduce the operation time and improve the extraction efficiency, ultrasonic energy by means of ultrasonic bath was used to the modified Tessier sequential extraction for speciation analysis of heavy metals in soil. Extractable contents of Cu, Fe, Mn, Ni,Pb and Zn were measured by atomic absorption spectroscopy(hAS). The merit of the ultrasonic extraction (UE) 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. The results for both of UE and CE 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 concentration of hydroxylamine chloride on the capability for the extraction of studied metals were also studied.     

Microbial diversity of soil bacteria in agricultural field contaminated with heavy metals

In this study we evaluated the bacterial diversity in a soil sample from a site next to a chemical industrial factory previously contaminated with heavy metals. Analysis of 16S rDNA sequences amplified from DNA directly extracted from the soil revealed 17 different bacterial types （genera and/or species）. They included Polyangium spp., Sphingomonas spp., Variovorax spp., Hafina spp., Clostridia, Acidobacteria, the enterics and some uncultured strains. Microbes able to tolerate high concentrations of cadmium （500μmol/L and above） were also isolated from the soil. These isolates included strains of Acinetobacter （strain CD06）, Enterobacter sp. （strains CD01, CD03, CD04 and CD08） （similar strains also identified in culture-independent approach） and a strain of Stenotrophomonas sp. The results indicated that the species identified from direct analysis of 16S rDNA of the soil can be quite different from those strains obtained from enrichment cultures and the microbial activities for heavy metal resistance might be more appropriately addressed by the actual isolates.     

新河污灌区土壤中重金属的形态分布和生物有效性研究

通过野外采样调查和实验分析,对北京市新河污灌区土壤中Cu、Pb、Zn、Cd 4种重金属的含量、形态分布和生物有效性进行了研究.首次尝试运用体外消化法研究了土壤中重金属的生物有效性问题,并与经典的Tessier五步连续提取法的结果进行了对比.结果发现,新河污灌区土壤中,Cd的浓度超过国家二级标准,Cu、Pb、Zn的浓度未超标.土壤中Cu、Pb、Zn主要以残渣态存在,Cd主要以有机结合态存在,且Cd的可交换态比例最高,生物有效性也最高.体外消化法分析得到的重金属生物有效性成分的含量要比利用化学形态分析法分析得到的高,但Cu、Pb、Zn、Cd 4种重金属的生物有效性排序是相同的,即Cd＞Zn＞Pb＞Cu.两种方法提取的重金属含量之间有相关关系.     

太湖地区水稻土颗粒中重金属元素的分布及其对环境变化的响应

采用原状土样分离技术，研究了太湖地区几种主要水稻土示同颗粒中重金属元素Pb、Cr、Cd的分布，结果表明这些元素在不同粒径的土壤颗粒中分配迥异，重金属含量在＞0．25mm的粗颗粒和＜0．002mm的细颗粒中较高，且与土壤有机碳有密切的关系；重金属元素主要积累于＞0．25mm的粗颗粒中，Cd的粗颗粒积累比Pb、Cr更强烈，耕层土壤重金属的颗粒分配因土壤种类不同而异，并响应于土壤环境变化，提出以分馏系数表示重金属在土壤颗粒的分配特点。     

2种组配改良剂对稻田土壤重金属有效性的效果

为研究2种组配改良剂LS(碳酸钙+海泡石)和HZ(羟基磷灰石+沸石)对土壤重金属的生物有效性以及水稻吸收累积重金属的影响,在湘南某矿区附近污染稻田中施用了不同添加量(0,2,4,8g/kg)的两种组配改良剂,并进行了水稻种植的田间试验.结果表明,施用2~8g/kg组配改良剂LS和HZ均能使土壤pH值和CEC含量显著增加,有机质含量变化不明显,LS比HZ更能提高土壤pH值和CEC含量.施用2~8g/kg组配改良剂LS能使土壤中Pb、Cd、Cu和Zn的TCLP提取态含量分别降低25.7%~52.2%、12.7%~25.7%、6.4%~17.2%和8.6%~23.4%,施用2~8g/kg HZ使土壤中Pb、Cd、Cu和Zn的TCLP提取态含量分别降低57.6%~80.1%、7.0%~40.9%、2.3%~22.7%和4.5%~33.2%.两种组配改良剂能显著降低土壤中Pb、Cd、Cu和Zn的生物有效性,抑制水稻植株对Pb和Cd的吸收,土壤Pb、Cd和Cu的TCLP提取态含量与水稻根系和糙米中Pb、Cd和Cu的含量之间存在显著或极显著的正相关关系,TCLP提取态含量能较好的表示重金属在土壤中的生物有效性.     

Effect of combined pollution by heavy metals on soil enzymatic activities in areas polluted by tailings from Pb-Zn-Ag mine

Some enzymatic activities were determined in the areas polluted by tailings from Tiantai Pb-Zn-Ag Mine in Zhejiang Province of China. The results indicated the soil enzymatic activities decreased significantly with increase of concentrations of heavy metals or the distance away from mining tailing center, especially dehydrogenase and urease activities. Multivariate regression analysis between heavy metal contents and soil enzymatic activities indicated that single dehydrogenase activity was very significantly correlated to combined effect of soil heavy metals in mine area. Moreover, single urease, protease and acid phosphatase activities were significantly related to the combined effect of heavy metals. The results suggest it is feasible to use soil enzymatic activities to indicate the pollution situation by combined heavy metals in the soil of mine area.     

超声辅助EDDS/EGTA淋洗对土壤重金属形态、环境风险的影响及响应面优化

采用响应面法实验设计研究了超声辅助EDDS/EGTA淋洗对Cu、Zn、Pb和Cd等不同重金属的洗脱效果和对残留重金属化学形态分布的影响,以超声功率、初始pH、EDDS投加量、EGTA投加量作为考察对象,以各重金属去除率及其环境风险削减率为响应值进行了模拟和优化.结果表明,EDDS对Pb的洗脱效率最高,Cu、Zn次之,Cd最低;EGTA对Cd的洗脱效率最高,Pb、Zn次之,Cu最低;超声功率对Cu、Pb去除强化效果明显,对Cd影响小,对Zn无显著影响;初始pH值为酸性时,Cu和Zn去除率高,碱性时Pb去除率较高,Cd去除率有所下降.EDDS与EGTA投加量及EGTA投加量与初始pH值对环境风险总削减率存在交互作用.超声辅助EDDS/EGTA对可还原态重金属洗脱效果较好,但容易导致弱酸提取态Cu和Pb残留率有所升高.响应面优化结果表明,当EDDS和EGTA投加量分别为重金属总摩尔数的1.92和2.56倍、超声功率为600 W、淋洗液初始pH值为5.27时,环境风险总削减率达到77.58%,与模拟值相近,模型具有较好的模拟和预测能力.     

畜禽粪便有机肥中重金属在水稻土中生物有效性动态变化

通过土壤淹水培养试验和土壤淹水培养不同时间后同时开始的水稻生物盆栽试验,研究不同畜禽粪便有机肥中Cu、Zn、Cd、Pb在水稻土中生物有效性动态变化以及与等量重金属无机盐的差异,明确不同畜禽粪便有机肥中不同重金属生物有效性差异及动态变化规律.结果表明,水稻土施入畜禽粪便有机肥后30~60 d内,畜禽粪便有机肥处理土壤溶液中重金属含量显著低于等量重金属无机盐处理,重金属无机盐处理土壤溶液中Cu、Zn、Cd、Pb的含量分别是鸡粪处理的2.4倍、3.1倍、3.9倍和327.3倍,分别是猪粪处理的2.0倍、2.2倍、15.6倍和4.0倍.60d后畜禽粪便有机肥处理和对应等量重金属无机盐处理土壤溶液中Cu、Zn、Cd、Pb的含量变的无差异.不同施用时间的畜禽粪粪便有机肥处理水稻体内Cu、Zn、Pb含量均显著低于对应的等量重金属无机盐处理,施用畜禽粪肥处理降低了土壤中Cu的生物有效性.畜禽粪便有机肥中重金属的生物有效性随施用后不同时间的变化呈现先升高后降低再升高规律,在施用后2个月时畜禽粪便有机肥中重金属的生物有效性最低,只相当于对应的等量重金属无机盐的13.0%~30.0%.     

Mobilities and teachabilities of heavy metals in sludge with humus soil

Chemical forms of Zn, Ni, Cu, and Pb in municipal sewage sludge were investigated by adding humus soil to sludge and by performing sequential extraction procedures. In the final sludge mixtures, Zn and Ni were mainly found in Fe/Mn oxide-bound (F3) and organic matter/sulfide-bound (F4) forms. For Zn, exchangeable (F1), carbonate-bound (F2), and F3 forms were transformed to F4 and residual forms (F5). For Ni, Fl and F2 forms were transformed to Fl, F2, and F3 forms. Both Cu and Pb were strongly associated with the stable forms F4 and F5. For Cu, F2 and F3 forms were major contributors, while for Pb, F3 and F4 forms were major contributors to F5. Humus soil dosage and pH conditions in the sludge were strongly correlated with the forms of heavy metals. Five forms were used to evaluate metal mobilities in the initial and final sludge mixtures. The mobilities of the four heavy metals studied decreased after 28 days. The metal mobilities in the final sludge mixtures were ranked in the following order: Ni > Zn > Cu = Pb. Leaching tests showed that the mobilities of Zn and Ni in lower pH conditions (pH 4) were higher than those in higher pH conditions (pH 8).     

构树修复对重金属污染土壤环境质量的影响

通过温室盆栽试验,研究构树（Broussonetia papyrifera）生长对重金属污染土壤酶活性和微生物群落结构的影响.结果表明,构树修复污染土壤中酶活性和微生物多样性明显提高.经270d培养后,构树生长土壤中蔗糖酶和酸性磷酸酶活性与种植土壤相比分别显著（P<0.05）提高3.12倍和2.29倍;土壤脱氢酶与有效态As、Cd、Pb、Zn和Cu含量,蔗糖酶与有效态Cd含量,以及磷酸酶与有效态Cd和Cu含量之间呈显著负相关（P<0.05）.根据16S和18S rDNA PCR-DGGE分析表明,构树修复可提高污染土壤中细菌和丛枝菌根真菌多样性.上述结果表明,构树修复可有效改善重金属污染土壤的环境质量.然而,污染土壤中重金属有效态含量下降不明显,必须辅助物理和化学措施来强化构树对重金属污染土壤的生态修复潜力.     

土壤重金属测定的前处理的方法的改进

本文根据美国EPA的微波消解标准方法,结合了我国传统的土壤消解方法,解决了传统的土壤消解方法的时间长,试剂消耗量大的问题。     

Speciation and fractionation of heavy metals in soil experimentally contaminated with Pb,Cd, Cu and Zn together and effects on soil negative surface charge

Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water-soluble and exchangeable(SE), weakly specific adsorbed( WSA),Fe and Mn oxides-bound(OX) and organic-bound( ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic-bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH4CI, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.