湘潭市土壤重金属地球化学特征的统计分析

运用相关性分析、聚类分析、因子分析及直方图分析对湘潭市土壤重金属地球化学特征进行了研究。结果表明：（1）As、Cd、Cu、zn与pH值呈显著正相关;As与Cd、Cu、Ph、zn呈显著正相关;Cd与As、Cu、Pb呈显著正相关;Cu与As、Cd、Pb、Zn呈显著正相关;Pb与As、Cu、zn呈显著正相关;Zn与As、Cd、Cu、Pb呈显著正相关;Hg与其他重金属及pH值不具有显著相关关系。（2）本区重金属分为两类,即Cr、pH、As、Zn、Cu、Cd;Hg、Pb。（3）区内重金属存在3种主要元素组合即As—Cd—Cu—Pb—Zn—pH;Cr—Hg;Cd—pH;（4）区内重金属As、Cd、Cr、Cu、Hg、Zn服从正态分布。（5）通过前人对湘潭市土壤重金属进行生态地球化学评价可知,区内Cd、Hg属重污染,从统计分析结果来看,Cd随着本区pH值变化而变化,并与As、Cu、Pb相关性显著;而Hg与pH值及其它重金属之间没有必然联系。     

模拟酸雨对土壤中铁、锰、锌的浸出特征

酸雨是指pH值小于5·6的大气降水,它不仅危害土壤,还通过土壤间接地危害整个生态系统,因此生态系统酸沉降的承受能力很大程度上取决于土壤对酸雨的敏感性〔1,2〕。我国能源以煤炭为主,大气中硫、氮含量较高,酸雨中SO42:-NO3-的比值范围大致在4:1到15:1之间〔3〕。同时,我国酸雨主要分布在长江以南地区,这正好与酸性土壤分布区相重叠,很大程度上加剧了对土壤的破坏程度。本文用ICP-AES法研究了在模拟酸雨作用下,土壤中生物必要元素Fe、Mn、Zn的释放水平和释放特征。1实验部分1.1仪器及工作条件电感耦合等离子体-原子发射光谱分析仪(IC…     

酸雨对苋菜中微量元素的影响

采用盆栽方法,研究了模拟酸雨(pH3．5)对苋菜中微量元素的影响。结果表明,酸雨使苋菜中K、Ca等营养元素严重流失,Al含量明显增高,Mn、Zn等微量元素的变化则因种植在不同原岩发育的土壤上而有所差异。在酸雨地区种植蔬菜,应增加K、Ca肥的施用,并预防由于土壤酸化使有害元素活化而被蔬菜吸收。     

长沙市公园土壤重金属调查与评价

根据对长沙市公园土壤的重金属含量测定结果,采用内梅罗综合污染指数对其进行了评价,并运用相关分析、聚类分析进行了统计分析。研究结果表明,岳麓山公园、烈士公园土壤重金属含量较低,月亮岛土壤重金属含量较高。通过内梅罗综合污染指数评价,认为岳麓山公园土壤属于安全级别,未发生重金属污染;烈士公园土壤中Cr、Hg、Cd属轻污染,其余重金属无污染;月亮岛中土壤重金属污染相对严重,其中Zn、Cd属重污染。通过相关分析表明,与pH值呈正相关的为Cr、Zn、Pb、As;聚类分析研究表明,在距离为20分为两大类Cr、Zn;Hg、Cd、Cu、As、Pb、pH。     

交流示波极谱滴定的研究——Ⅺ.锌和镉的连续滴定

利用Cd、Zn在示波极谱图上具有敏锐的切口及Cd、Zn与EGTA和与NH_3所生络合物稳定常数的差异,用交流示波极谱滴定法,在pH=10的NH_4OH-NH_4Cl缓冲溶液中,先用EGTA直接滴定Cd,用Cd切口的消失指示终点,再用EDTA直接滴定Zn,终点直观,方法简单、快速、准确、经济。连续滴定,测Zn时,Cd/Zn比达85,测Cd,Zn/Cd比达20,直接滴定大量Zn中Cd,Zn/Cd比可高达1000,比文献上已有的方法优越。     

无机盐存在下双水相体系萃取分离碘-乙基紫-镉(Ⅱ)缔合物

研究了在丙醇-水体系中加入表面活性剂乙基紫(EV)后,影响Cd2 分离的酸度、无机盐、卤离子种类等条件。实验表明,(NH4)2SO4存在下,无表面活性剂EV,一定量的I-,在酸性条件下,Cd2 的萃取率为68%,而同样条件下,加入mg级表面活性剂EV后,Cd2 与EV、г形成三元缔合物,被均相萃取、异相分离;缔合物进入丙醇相,Cd2 被完全萃取分离;在pH 1.0时,试验了Cd2 加入量为5μg/mL时与Fe3 、Co2 、Ni2 、Zn2 、Mn2 、Zn2 、Cr3 的二元或多元离子混合液的分离试验,分离完全。     

丹-锡高速公路两侧土壤中重金属元素污染的测定与评价（英文）

论文对丹-锡高速公路两旁土壤中重金属Pb、Cd、Cr、Cu、Zn、Fe、Ni和Mn元素的含量进行了采样调查。分别用单项污染指数、内梅罗指数和地累积指数对土壤中重金属元素的污染状况进行了评价。结果表明:高速公路两旁栽种防护林对土壤重金属污染起到一定的防护作用。随着距路基中心距离的增加,土壤pH值变化范围不大,土壤略呈弱酸性,土壤中Pb、Zn、Mn、Cd和Cu的含量呈现下降的趋势,Fe、Cr、Ni的含量在距路基10~30m范围内略有增加。公路两侧土壤中Pb含量超过背景值,但没有引起污染,Zn、Cr和Cd含量处于轻度到中度污染。土壤中Pb、Cd、Zn、Fe和Cu来自于同一类污染源。     

铜质水表中重金属溶出的研究

利用ICP-MS光谱仪,探讨铜质水表中重金属的溶出,分析了水质、浸泡时间、pH值对重金属溶出的影响。各元素在模拟自来水中的溶出量是超纯水的1．5-2倍,溶出量由大到小依次为Cu,Pb,Cr（VI）,Cd;一般在0．5d时出现溶出拐点,在4d时达基本饱和;在pH4的酸性水质中,各元素的溶出量为极大值。该方法适于铜质水表中重金属溶出的分析。     

基于长期定位监测的稻田土壤理化变化和镉污染风险评价

土壤镉(Cd)污染及由此造成的水稻籽粒Cd超标是近年来我国农业环境和农产品安全领域面临的一项重要问题,对人体健康造成严重威胁。为明确Cd在稻田土壤理化变化和镉污染风险评价及相互关系,通过51个定位监测点连续5年对水稻籽粒和其对应的根系土壤进行协同监测。结果表明,监测区域内土壤酸化比较严重,土壤养分含量较高,年度之间差异不明显。土壤总Cd变化范围为0.067~1.260 mg·kg-1;土壤有效Cd含量变化范围为0.018~0.992 mg·kg-1;水稻籽粒Cd含量变化范围为0.003~1.170 mg·kg-1,籽粒Cd富集系数变化范围为0.013~2.396。5年内总体上土壤Cd与水稻籽粒Cd污染、潜在生态风险指数(Ei)及健康风险评价(HQ)较低并呈下降趋势,但土壤Cd生物活性较高。随机森林模型(Random forest mode)分析显示土壤性质显著影响土壤总Cd和有效态Cd,土壤交换能力是影响水稻籽粒对Cd吸收的主要因子。当pH≤6.5时,随着土壤pH值升高,土壤总Cd含量、土壤有效Cd含量及水稻籽粒Cd含量均升高,但当pH值≥6.5时,随着土壤pH值升高,土壤总Cd含量、土壤有效Cd含量及水稻籽粒Cd含量却均下降。研究结果可为受污染耕地分类管控和水稻安全生产提供科学依据。     

土壤中镉对酸雨的敏感性研究

模拟土壤在自然酸雨淋洗条件下镉的释放行为,研究了不同酸度、不同酸雨成分、不同流量的酸雨对土样中镉淋出的影响,以及镉在不同碳酸根含量的土样对酸雨淋洗的敏感性。     

Assessment of mobility of heavy metals in two soil types by use of column leaching experiments and chemometric evaluation of elution curves

The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of soils (acidic forest soil and neutral agricultural soil) by leaching with calcium chloride solution in column experiments. The screening properties of neutral agricultural soil towards pollution by heavy metals (Ni, Cu, Zn and Cd) are approximately 10 times higher than those of acid forest soil. The neutral agricultural soil, polluted artificially by one pore volume (PV) of an HMs solution of concentration 200 mg L^?1, can screen the leaching of these metals over several hundreds of years. The higher apparent desorption rate and per cent desorption of HMs (especially Cd) in acid forest soil indicated a higher potential of intensive migration of the metals across the profile and indicated potential risk of Cd pollution for this type of soil. The latest approach of artificial neural networks to describe transport of HMs in soil has been also evaluated. Using a simple three-layer perceptron topology with three hidden neurons, the experimental data could be simulated. The results suggested that the pH of soil is a major factor controlling the retention of the heavy metals in the soils.     

Desorption of Heavy Metals from Typical Soil Components (Clay,Peat) with Glycine

Abstract

Natural organic chelating agents take part in the mobilization and translocation of heavy metals in unpolluted and polluted soils. They also have to be considered as possible extracting agents for the decontamination of heavy metal polluted soils. For an assessment of the desorption capability of glycinc, heavy metals (Cd, Cu, Ni, Pb, Zn) were adsorbed onto typical soil components (bentonite and peat). The metal loaded sorbents were resuspended in aqueous solutions of glycine at pH 7.0 and 4.5 and the quantities of the desorbed metals were analysed in the liquid phase. Furthermore, the dependency of the desorption rate on the duration of experiments and the metal content were investigated. The remobilization of heavy metals from bentonite by glycine at pH 7.0 decreases following the order Cu > Ni > Zn > Cd > Pb and ranges from 95% to 9.5%. The desorption rate was significantly lower at pH 4.5 and in suspensions of peat.     

"Acid extractable" metal concentrations in solid matrices: a comparison and evaluation of operationally defined extraction procedures and leaching tests

Different frequently used methods to determine the influence of acid conditions on heavy metal release from soils, sediments and waste materials, namely pH_stat leaching tests and acid extractions with acetic acid (HOAc) (0.11 M and 0.43 M) and sodium acetate (NaOAc) (1 M) were compared for 30 samples (soils, sediments and waste materials) with different physico-chemical properties and a different degree of contamination. However, no distinct relationship was found between physico-chemical sample characteristics, total element concentrations and acid-extractable metal concentrations in the presented dataset.

pH played an important role in explaining the release of metals from the contaminated soils, sediments and waste materials. The pH-shift after extraction with the different acetic acid solutions (0.11 M and 0.43 M) was both explained by the initial pH of the sample and its acid neutralizing capacity. The pH of the NaOAc extract was well buffered and the release of elements from solid matrices by NaOAc was both the result of the complexation with acetate and pH (pH 5). Generally, a linear correlation was found between the amount of Zn and Cd extracted by 0.11 M HOAc, 0.43 M HOAc and 1 M NaOAc. The amounts of Zn and Cd extracted with HOAc (0.11 M and 0.43 M) were comparable with amounts of respectively Zn and Cd released during pH_stat leaching at pH 4. However, for Cu, Pb and As, it was often not possible to relate the results of a pH_stat leaching test to the results of single extractions with acetic acid solutions.     

Model study of acid rain effect on adsorption of trace elements on soils using a multitracer

Using a radioactive multitracer and model acid rain (HCl or H₂SO₄ solution), batch experiments were performed to examine the pH effect on the adsorption-desorption equilibrium of 16 elements on soils as a model study of an acid rain effect. Kaolin, black soil (original and with organic matter almost removed) and Kureha soil (original and with organic matter almost removed) were used as adsorbents. Characteristic dependence on the pH value of the suspension was observed for the adsorption of the elements on kaolin and the soils. The results of this model study indicate that acid rain decreases the retention of cations, while it increases or does not change the adsorption of anions on soils. Organic matter in soils has a positive effect on the extent of adsorption of most elements investigated.     

杭州西郊茶园土壤重金属的积累特点与来源分析

选择了杭州市西部近郊、远郊和农村等3个受人为不同程度影响的区块,分析了同为第四纪红土母质发育的茶园与附近林地土壤剖面中重金属垂直分布的特点,探讨了茶园土壤重金属的来源。结果表明,相同区块的茶园与附近林地土壤重金属Pb、Cd和Hg剖面分布相似,均随剖面深度下降,表土Pb、Cd和Hg含量随离城市距离增加而下降,说明研究区茶园土壤中重金属Pb、Cd和Hg的积累主要与大气沉降有关;茶园与附近林地土壤重金属Cu和Zn也随剖面深度而下降,但同一区块中茶园表土重金属Cu和Zn含量明显高于附近林地土壤,说明施肥等农业措施对茶园土壤Cu和Zn的积累有较大的影响;茶园土壤中Cu和Zn的积累与地理位置关系不大。茶园土壤中Cr和Co的积累不明显,并有淋失的趋势。     

Adsorption of cadmium ions from aqueous solutions using nano-montmorillonite: kinetics,isotherm and mechanism evaluations

With increasing industrial development, heavy metal pollution, e.g., cadmium (Cd) pollution, is increasingly serious in soil and water environments. This study investigated the sorption performance of nano-montmorillonite (NMMT) for Cd ions. Adsorption experiments were carried out to examine the effects of the initial metal ion concentration (22.4–224 mg/L), pH (2.5–7.5), contact time (2–180 min) and temperature (15–40 °C). A simulated acid rain solution was prepared to study the desorption of Cd adsorbed on NMMT. After the adsorption or desorption process, the supernatant was analyzed using a flame atomic absorption spectrometry method. The Cd removal rate increased as the pH and contact time increased but decreased as the initial metal ion concentration increased. The maximum adsorption capacity was estimated to be 17.61 mg/g at a Cd²⁺ concentration of 22.4 mg/L. The sorption process can be described by both the Langmuir and Freundlich models, and the kinetic studies revealed that the pseudo-second-order model fit the experimental data. The Cd desorption rate when exposed to simulated acid rain was less than 1%. NMMT possesses a good adsorption capacity for Cd ions. Additionally, ion exchange was the main adsorption mechanism, but some precipitation or surface adsorption also occurred.     

Saturated hydraulic conductivity of a volcanic ash soil affected by repulsive potential energy in a multivalent anionic system

Acid rain is supposed to influence soil structures, because soils have pH-dependent charges. The adverse effects of acid rain on soils must be assessed. Although repulsive potential energy among soil clay particles generates swelling and dispersion, thereby changing the soil’s hydraulic conductivity, the relationship between hydraulic conductivity and repulsive potential energy has not been evaluated. Moreover, research into repulsive potential energy in multivalent counterionic systems has been rare. In this paper, repulsive potential energies for a volcanic ash soil (allophanic Andisol), which is characterized by a number of pH-dependent charges, were evaluated in a multivalent counterionic system. Changes in saturated hydraulic conductivity (K) of volcanic ash soil during dilute acid leaching and their relationship with the repulsive potential energies were examined. When nitric acid at pH 3 or 4 was leached, K decreased rapidly. On the other hand, the decrease in K attenuated as the proportion of sulfate in the dilute acid increased. Electrophoretic mobilities were measured and the zeta potentials were estimated. From the zeta potentials and the calculation of repulsive potential energies between the clay particles in the NO₃–SO₄ system, we concluded that the decrease in K for an acid solution with a high proportion of nitrate was due to swelling and dispersion of the soil induced by electrostatic repulsive potential energy. Because sulfate formed complexes on the clay surface, the repulsive potential energy decreased as the proportion of sulfate in the dilute acid increased. Then, the flocculation of the soil was maintained, thereby inhibiting the decrease in K.     

As, Cd, Cr, Ni and Pb pressurized liquid extraction with acetic acid from marine sediment and soil samples

Rapid leaching procedures by Pressurized Liquid Extraction (PLE) have been developed for As, Cd, Cr, Ni and Pb leaching from environmental matrices (marine sediment and soil samples). The Pressurized Liquid Extraction is completed after 16 min. The released elements by acetic acid Pressurized Liquid Extraction have been evaluated by inductively coupled plasma-optical emission spectrometry. The optimum multi-element leaching conditions when using 5.0 ml stainless steel extraction cells, were: acetic acid concentration 8.0 M, extraction temperature 100 °C, pressure 1500 psi, static time 5 min, flush solvent 60%, two extraction steps and 0.50 g of diatomaceous earth as dispersing agent (diatomaceous earth mass/sample mass ratio of 2). Results have showed that high acetic acid concentrations and high extraction temperatures increase the metal leaching efficiency. Limits of detection (between 0.12 and 0.5 μg g^− 1) and repeatability of the over-all procedure (around 6.0%) were assessed. Finally, accuracy was studied by analyzing PACS-2 (marine sediment), GBW-07409 (soil), IRANT-12-1-07 (cambisol soil) and IRANT-12-1-08 (luvisol soil) certified reference materials (CRMs). These certified reference materials offer certified concentrations ranges between 2.9 and 26.2 μg g^− 1 for As, from 0.068 to 2.85 μg g^− 1 for Cd, between 26.4 and 90.7 μg g^− 1 for Cr, from 9.3 to 40.0 μg g^− 1 for Ni and between 16.3 and 183.0 μg g^− 1 for Pb. Recoveries after analysis were between 95.7 and 105.1% for As, 96.2% for Cd, 95.2 and 100.6% for Cr, 95.7 and 103% for Ni and 94.2 and 105.5% for Pb.