Experimental Study on Surface Reactions of Heavy Metal Ions With Quartz—Aqueous Ion Concentration Dependence

Adsorption of divalent metal ions, including Cu²⁺, Pb²⁺, Zn²⁺, Cd²⁺ and Ni²⁺, on quartz surface was measured as a function of metal ion concentration at 30°C under conditions of solution pH= 6. 5 and ion strength I = 0. 1mol/L. Results of the experimental measurements can be described very well by adsorption isotherm equations of Freudlich. The correlation coefficients (r) of adsorption isotherm lines are > 0. 96. Moreover, the experimental data were interpreted on the basis of surface complexation model. The experimental results showed that the monodentate-coordinated metal ion surface complex species (SOM⁺) are predominant over the bidentate-coordinated metal ion surface complex species [(SO)₂M] formed only by the ions Cu²⁺, Zn²⁺ and Ni²⁺. And the relevant apparent surface complexation constants are lgK_M = 2.2–3.3 in order of K_Cd≥K_Pb > K_Zn > K_Ni≥K_Cu, and lgβ_M = 5.9-6.8 in order of β_Ni > β_Zn > β_Cu. Therefore, the reactive ability of the ions onto mineral surface of quartz follows the order of Cd > Pb > Zn > Ni> Cu under the above-mentioned solution conditions. The apparent surface complexation constants, influenced by the surface potential, surface species and hydrolysis of metal ions, depend mainly on the Born solvation coefficient of the metal ions. This project was financially supported by the National Natural Science Foundation of China (No. 49572091).     

土壤重金属元素迁移模拟方法在矿集区适用性比较

选择合适的模拟方法预测重金属的迁移对于防治重金属污染具有重要意义。介绍土壤重金属的垂向迁移和水平迁移2种方式,比较了垂向迁移中的经验模型、分相模型和整体模型,以及水平迁移中的SWAT模型、随风迁移模型的优缺点及其影响因素,探讨了这些模型在矿集区重金属迁移模拟中的适用性,为矿集区选择合适的土壤重金属迁移模拟方法提供了科学依据。     

土壤重金属元素迁移模拟方法在矿集区适用性比较

选择合适的模拟方法预测重金属的迁移对于防治重金属污染具有重要意义。介绍土壤重金属的垂向迁移和水平迁移2种方式,比较了垂向迁移中的经验模型、分相模型和整体模型,以及水平迁移中的SWAT模型、随风迁移模型的优缺点及其影响因素,探讨了这些模型在矿集区重金属迁移模拟中的适用性,为矿集区选择合适的土壤重金属迁移模拟方法提供了科学依据。     

Mathematical models to predict soil heavy metal toxicity in the 2012 Olympic site

Heavy metal concentrations in samples collected from the London 2012 Olympic Village were determined using a three-step sequential extraction and a rapid extraction method. Metal toxicity was measured by employing the Microtox^? solid phase analysis. Both extraction methods produced comparable results (p?=?0.996), but the rapid method produced higher readings. A number of heavy metals were detected using the two extraction methods, including aluminum, arsenic, cadmium, chromium, copper, iron, nickel, lead and zinc; beryllium, molybdenum, niobium and titanium were also found in low concentration ranging between 0.16 and 27.10?mg/kg in the total acid digestion. The total metal levels in all the soil samples were within the UK Soil Guideline Value (SGV) except for lead which ranged between 62.9 and 776.2?mg/kg. The 30?min EC₅₀ of different soil fractions was 2?C5.8?g/L. In the absence of any of heavy metals in the SGV, the Dutch Guideline values were referred. Mathematical models for a number of metals were generated based on the changes in EC₅₀ values between each (F1, F2 and F3) soil fractions and the initial toxicity in the non-fractionated samples. The resulting models produced good R² values (>96%) for predicting the change in toxicity of lead, cadmium, zinc and copper by measuring their changes in concentrations. These models could substantially reduce the time requires to determine the toxicity in the samples; they would be a useful tool in the clean up process where monitoring of metal toxicity is required.     

某化肥厂地块土壤重金属砷(As)污染特征与来源解析

在某化肥厂关闭企业地块,采集了0～6 m深度的土壤样品115件,分析了土壤样品中重金属砷的含量、污染特征及来源.结果表明,土壤样品中重金属砷(As)均有不同程度检出,超标样品54件,最大检测值为714 mg·kg-1,超出GB 36600-2018标准第二类用地筛选值(60 mg·kg-1)约10倍,超出第二类用地风险...     

Comparison on the phytoextraction efficiency of Bidens pilosa at heavy metal contaminated site in natural and electrokinetic conditions

The plant samples of Bidens pilosa were collected from a coal gangue vacant site and its surrounding area, located in central China, to study the remediation effect of the plant species on heavy metal(HM) contamination in both natural and electrokinetic(EK) conditions. The analytical results showed that the effect of phytoextraction and bioconcentration on the heavy metals in the sample of the EK group is more significant than those in the other control group. Compared with the results of natural condition, under the EK condition the concentrations of cadmium(Cd), lead(Pb), copper(Cu) and zinc(Zn) in the stems and leaves of the Bidens pilosa increased to 0.40 mg/kg, 4.23 mg/kg, 7.27 mg/kg, 830.24 mg/kg, respectively,with their increments of 292%, 1 731%, 141%, 2 076%. For root samples, the Cd, Pb, Cu and Zn concentrations increased to 0.52 mg/kg, 4.36 mg/kg, 10.87 mg/kg, and 98.12 mg/kg and the increase rates were 1 034%, 140%, 29%, and 181%, respectively. The phytoextraction efficiency of the Bidens pilosa was significantly higher than that of control group. The removal efficiency of Cd, Pb, Cu and Zn in soil increased to 26%, 72%, 27%, and 79% with the EK applied. In addition, the mechanism of HM migration,extraction and enrichment in Bidens pilosa under the EK condition was discussed.     

Effects of humic acid on heavy metal uptake by herbaceous plants in soils simultaneously contaminated by petroleum hydrocarbons

The effects of humic acid (HA) on heavy metal uptake by herbaceous plants in soil simultaneously contaminated with heavy metals and petroleum hydrocarbons were investigated. The results showed that HA reduced readily soluble and exchangeable forms of heavy metals in the contaminated soil but increased their plant-available forms. Potential bioavailability and leachability factors became larger than 1 after adding HA to the soil, except for those of Ni, suggesting that more heavy metals could be potentially phytoavailable for plant uptake. Furthermore, HA increased the accumulation of Pb, Cu, Cd, and Ni in the shoots and roots of selected plants. The greatest increase in the accumulation of heavy metals was 264.7 % in the shoot of Festuca arundinacea, with the bioconcentration factor (BCF) increasing from 0.30 to 1.10. Humic acid also increased the BCFs of the roots of Brassica campestris for Ni and Pb. These results suggest that HA amendment could enhance plant uptake of heavy metals, while concurrently reducing heavy metal leachability and preventing subsurface contamination, even in soils simultaneously contaminated with petroleum hydrocarbons.     

Suspended sediment concentration and particle size distribution,and their relationship with heavy metal content

This paper aims at assessing the feasibility of suspended sediment concentration (SSC) estimation by using predictor variables of heavy metal concentration (HMC, viz., iron, chromium, zinc and nickel) transported in solution and solid. The study was conducted in the Research and Educational Forest Watershed of the Tarbiat Modares University (Kojour) which comprises an area of ca. 50000 ha. For this study, suspended sediment samples were collected from the left bank of the Kojour River twice a week, as well as during runoff events from November 2007 to June 2008. The samples were then prepared through direct digestion and finally analyzed by atomic absorption spectrophotometry (AAS). The relationship between SSC and particle size distribution (PSD) were correlated with HMC by using bivariate and multivariate regression models. Proposed models were then selected based on statistical criteria. The results showed high correlation between dissolved and particulate chromium content with efficiency coefficients beyond 77% (P < 0.001). However, a lower relationship was found between SSC and nickel content. From these results, it is clearly shown that the HMC can practically be estimated by SSC in watersheds with different accuracy and vice versa. It is also understood that heavy metal pollution can be easily managed by controlling SSC.     

Comparative analysis of heavy metal concentration in secondary treated wastewater irrigated soils cultivated by different crops

The use of treated urban wastewater for irrigation is a relatively recent innovation in Botswana and knowledge is still limited on its impact on soil heavy metal levels. The aim of this study is to analyze and compare heavy metal concentration in secondary wastewater irrigated soils being cultivated to different crops: olive, maize, spinach and tomato in the Glen Valley near Gaborone City, Botswana. The studied crop plots have been cultivated continuously under treated wastewater irrigation for at least 3 years. Most crop farms have sandy loam, loamy sand soils. Based on food and agriculture organization, heavy metal threshold values for crop production have been studied. Results showed that the wastewater irrigated soils in the Glen Valley have higher cadmium, nickel and copper than desirable levels, while the levels of mercury, lead and zinc are lower than the maximum threshold values recommended for crop production. The control sites show that the soils are naturally high in some of these heavy metals (e.g copper, zinc, nickel) and that crop cultivation under wastewater irrigation has actually lowered the heavy metal content. Comparing between the crops, mercury and cadmium levels are highest in soils under maize and decline linearly from maize to spinach to olive to tomato and control site. By contrast, concentrations of the other metals are at their lowest in maize and then increase from maize to spinach to olive to tomato and to control site.     

Countermeasures of heavy metal pollution

This article gives a review on heavy metal pollution prevention and control,and it also discusses heavy metal pollutant discharge,prediction and evaluation of environmental impact,and pollution prevention and monitoring.     

Assessing the concentration and potential dietary risk of heavy metals in vegetables at a Pb/Zn mine site,China

Cd, Pb, Cu and Zn were measured in vegetables in Xiguadi village around Lechang Pb/Zn mine in Guangdong province, South China. The daily intake (DI) of these metals from vegetables by local people was also determined. The respective Cd, Pb, Cu and Zn concentration was 0.05–0.90 (mean 0.25), 1.04–5.82 (2.64), 0.53–7.07 (2.00) and 3.87–25.20 (11.68) mg kg⁻¹, of which Cd concentration in all vegetables exceeded the safe limit given by FAO/WHO. The DI was found to be 49.76, 475.56, 360.36 and 2,102.63 μg, respectively. The present results indicated local mining activity caused vegetable heavy metal contamination and Cd concentration exceeding the stipulated standards for all vegetables indicating potentially serious dietary risks for local people.     

Sorption of heavy metal ions by a hydrous manganese oxide

Sorption of Co, Zn, Ca and Na by δ-MnO₂ was studied at 24.0 ± 0.5°C and pH 4. During the sorption of Co and Zn, Mn was released to the solution phase; however, Mn release was not detected during the sorption of Ca and Na. On the basis of crystal field theory, it is proposed that Zn may interchange with Mn²⁺ in the δ-MnO₂ structure, whereas Co may interchange with both Mn²⁺ and Mn³⁺. It is suggested that the interchangeable Mn²⁺ and Mn³⁺ sites were in the disordered layers in the δ-MnO₂ structure.Sorption of Co, Zn and Ca at pH 4 fitted single-site Langmuir isotherm expressions at all Ca concentrations, but only at concentrations greater than 10^?4 M for Co and Zn. Mn release by δ-MnO₂ at pH 4 during Co and Zn sorption also fitted single-site Langmuir isotherms. An expression for the case of multisite Langmuir sorption was derived and applied to the cases of Co and Zn sorption and to the case of Mn release during Co sorption. The data of these cases were used to calculate statistically the coefficients of multiple regression equations from which the sum of the capacities of all sites in each case were obtained. From all of these derived capacities, it is proposed that there was only one site where Ca interchanged with surface bound H. Zn was postulated to interchange not only with these bound H sites, but also with another site where it interchanged with structural Mn²⁺. Co was postulated to interchange with both of these sites, and additionally, with a third site where it interchanged with structural Mn³⁺.Using a pH-stat set at pH 4, it was determined that approximately 2 moles of H were released per mole of Co or Zn sorbed at bound H sites.     

矿山开发过程中重金属污染研究综述

矿山固体废物和酸性废水已成为矿山资源开发的两大环境公害,与此产生的矿山重金属污染也成为人们关注的焦点。矿山重金属和类金属元素在人类改造过的环境中发生的活化、迁移和再分配,必然对矿山开发区和邻近区的地球化学平衡带来新的扰动。研究重金属元素在这种地球化学过程中的扰动与平衡,可以揭示污染元素的迁移循环、形态转化规律及其对生态环境的危害,对矿山重金属的污染治理、环境影响评价和生态修复具有重要的指导意义。     

植物修复在治理矿区重金属污染土壤中的应用

矿业活动是环境中污染土壤的重金属的主要来源,采用植物修复技术具有物理、化学修复方法所无法比拟的费用低廉、不破坏场地结构、不造成地下水的二次污染等优点。文章从植物稳定、植物提取和植物一微生物以及动物的协同修复等三个方面简要介绍了对矿区污染土壤进行植物修复的研究进展。     

重金属离子在胡敏酸-高岭石复合体上的吸附

本文研究了胡敏酸存在下高岭石对重金属离子的吸附行为。实验结果表明:①胡敏酸和Cu2 溶液按先后顺序或同时加入高岭石中反应,在Cu2 平衡浓度<10mg/L时,3种加入顺序对Cu2 的吸附量基本相同,当Cu2 平衡浓度>10mg/L时,(K Cu) HA和(K Cu HA)两种加入顺序对Cu2 的吸附量比(K HA) Cu的略大。②在pH=5时,胡敏酸-高岭石复合体对Cu2 的吸附量明显大于纯高岭石。这是由于胡敏酸含有大量的羧基和酚羟基等活性基团,吸附在高岭石上的胡敏酸增加了其表面吸附位,在复合体表面形成了S—HA—Cu三元配合物,且Cu2 的吸附量与复合体中胡敏酸的含量在一定范围内成正相关;③溶液pH值在4～7之间变化可调控复合体对Cu2 的吸附机制。④在Cu2 和Cd2 共存时,随着金属离子初始浓度的增大,Cu2 的吸附量呈直线上升,而Cd2 的吸附量增加缓慢,表明复合体对Cu2 的吸附能力比对Cd2 强。     

改性沸石对重金属离子竞争吸附特性研究

以钠型改性沸石为吸附剂,以含有单一的镉、锌、铅溶液以及镉、锌、铅的混合溶液为吸附质,开展了改性沸石中重金属离子的竞争吸附及其影响因素等实验研究。结果表明,当溶液中有多种二价重金属离子存在时,各离子之间存在竞争吸附,竞争能力为Pb2+>Cd2+>Zn2+;Zn2+-Cd2+表现出显著的协同吸附效应,而Zn2+-Pb2+、Cd2+-Pb2+表现出拮抗吸附。     

土壤重金属污染评价方法研究进展

从技术应用的角度,将土壤重金属污染评价方法分为传统的方法和基于GIS的评价方法两大类.本文阐述了评价方法的研究进展,分析了主要评价方法的优缺点,最后对评价方法做出了展望.     

土壤中重金属形态分析方法研究

介绍了一种重金属形态分析连续多级提取新方法,用国家一级标样进行试验研究,并用国际标样做对比研究,表明该方法具有分组合理、更接近自然状态、操作简便易行、数据稳定可靠的特点,可为土壤环境中的重金属形态的研究及其环境危险评价提供更精确的元素信息。