Modelling the potential mobility of Cd,Cu, Ni,Pb and Zn in Mollic Fluvisols

European floodplain soils are frequently contaminated with potentially toxic inorganic substances. We used a multi-surface model to estimate the aqueous concentrations of Cd, Cu, Ni, Pb and Zn in three Mollic Fluvisols from the Central Elbe River (Germany). The model considered complexation in solution and interactions with soil organic matter (SOM), a clay mineral and hydrous Al, Fe and Mn oxides. The amounts of reactive metals were derived from extraction with 0.43 M HNO₃. Modelling was carried out as a function of pH (soil pH ± 1.4) because it varies in floodplain soils owing to redox processes that consume or release protons. The fraction of reactive metals, which were dissolved according to the modelling, was predominantly <1%. Depending on soil properties, especially pH and contents of SOM and minerals of the clay fraction, the modelled concentrations partially exceeded the trigger values for the soil–groundwater pathway of the German soil legislation. This differentiation by soil properties was given for Ni, Pb and Zn. On the other hand, Cd was more mobile, i.e., the trigger values were mostly exceeded. Copper represented the opposite, as the modelling did not predict exceeding the trigger values in any horizon. Except for Pb and partially Zn (where oxides were more important), SOM was the most important adsorbent for metals. However, given the special composition and dynamics of SOM in mollic horizons, we suggest further quantitative and qualitative investigations on SOM and on its interaction with metals to improve the prediction of contaminant dynamics.     

北方常见农作物根际土壤中铅、锌的形态转化及其植物有效性

采用盆栽试验结合形态分析技术研究了北方地区常见农作物对污染土壤中铅(Pb)、锌(Zn)的形态转化及其植物有效性的影响。土壤Pb、Zn形态分析结果显示,与非根际土壤相比,多数作物根际可交换态、碳酸盐结合态、有机质结合态Pb比例降低,而铁锰氧化物结合态、残渣态Pb则显著增加;Zn则表现为可交换态比例略呈降低趋势,碳酸盐结合态、铁锰氧化物结合态与有机质结合态升高,残渣态Zn则大幅下降。这提示,作物根际土壤Pb存在由松结合态向紧结合态转化的现象,从而植物有效性降低;而根际土壤Zn的形态变化则与Pb相反,即由紧结合态向松结合态转化,相应地提高了Zn的植物有效性。     

Modelling the concentrations of dissolved contaminants (Cd,Cu, Ni,Pb, Zn) in floodplain soils

Central European floodplain soils are often contaminated with potentially toxic metals. The prediction of their aqueous concentrations is a prerequisite for an assessment of environmental concerns. We tested the aqueous concentrations of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) derived from multi-surface adsorption modelling (on hydrous iron, aluminum and manganese oxides, clay and soil organic matter) against those analyzed in situ in the soil solution of four horizons of floodplain soils at the Elbe River, Germany. The input data for the reactive metals were derived from a seven-step sequential extraction scheme or from extraction with 0.43 M nitric acid (HNO₃) and evaluated in four modelling scenarios. In all scenarios, measured and modelled concentrations were positively related, except partially for Pb. Close reproduction of the measured data was obtained using measured data of accompanying cations and anions together with amounts of reactive metals from both the sequential extraction or from 0.43 M HNO₃ extraction, except for Cu, which was often strongly overestimated, and partially Cd. We recommend extraction with 0.43 M HNO₃ to quantify reactive metals in soil because the modelling results were metal-specific with better or equal results using the single extractant, the application of which is also less laborious. Approximations of ion concentrations and water contents yielded similar results. Modelled solid-phase speciation of metals varied with pH and differed from that from sequential extraction. Multi-surface modelling may be an effective tool to predict both aqueous concentrations and solid-phase speciation of metals in soil.     

The effects of soil properties and temperature on the adsorption isotherms of lead on some temperate and semiarid surface soils of Iran

Sorption of metal ions by soil and clay minerals is a complex process involving different mechanisms, and controlled by different variables that can interact. The aim of this work was to study the retention mechanisms of Pb ions on different soil samples. Surface soils were sampled from Guilan and Hamadan provinces in north and northwest of Iran with temperate and semiarid climates. The adsorption isotherms of Pb on the soils have been studied at 15, 27 and 37°C. The adsorption data for different soils were fitted into Langmuir and Freundlich models. Temperate soil samples had higher clay content, cation exchange capacity, dichromate (oxidable) organic carbon, total Kjeldahl-nitrogen, biological activity, amorphous and crystalline Fe and Al, but semiarid soil samples had higher sand content, pH, equivalent calcium carbonate, available P and K. Lead adsorption data obtained from semiarid soils against those obtained from temperate soils were better fitted in both Langmuir and Freundlich models. Langmuir constants Q ₀ for Pb adsorption in semiarid soils were considerably lower than those for Pb adsorption in temperate soils. However, the binding energy (K _L) of Pb and Freundlich constant n were higher for data of semiarid soils. The effect of temperature on the Pb adsorption was positive especially in temperate soils; however, soil properties had higher effects on Pb adsorption.     

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.     

多氯联苯在土壤中的吸附规律及其影响因素研究

为了建立定量描述土壤中多氯联苯（PCBs）迁移规律的数学模型,以采自现代黄河三角洲地区的土壤为研究对象,针对类二噁英类多氯联苯PCB81及阻转类多氯联苯PCB95在土壤中的吸附行为进行了研究,获得了其吸附等温方程并分析了土壤有机质含量、颗粒组成、pH、矿物质含量等特性参数对吸附量的影响。结果表明,PCBs在土壤中的吸附行为符合Langmuir吸附等温方程;PCBs的吸附量与土壤中有机质含量和土壤粘粒含量呈正相关关系,与土壤pH值及土壤矿物质含量无明显相关关系。     

Sorption of heavy metals on organic and inorganic soil constituents

Sorption of heavy metals to organic matter and mineral soil constituents can hardly be separated experimentally. Here we studied the retention capacity of organic matter and minerals from soils in a long-term field experiment in which the organic carbon content had been altered, but the mineral phase had remained constant over time. The sorption of Cu, Cd and Zn showed a non-additive contribution of soil organic matter and minerals to the sorption capacity of soil. Sorption on organic matter exceeded mineral sorption from 6 to 13 times. This is the first time that sorption to soil organic matter is quantified in bulk soils.     

沉积物的逐级分离与硝基苯的吸附

采用逐级分离法将大连近海海底沉积物进行分级处理，每级相继去除碳酸盐、有机质和金属水合氧化物，最后一级为粘土矿物。每级沉积物的电子显微镜形态观察结果与逐级分离的预期结果基本吻合。硝基苯在各级沉积物上的吸附行为符合Ｆｒｅｕｎｄｌｉｃｈ等温式，同时证明本文所用的逐级分离法对大连近海海底沉积物的分离有较好的适用性。     

Changes in chemical forms of lead in temperate and semiarid soils in sterile and unsterile conditions

Sequential extraction has been used as a suitable method for fractionation of chemical forms of trace elements and study of their plant availability. Surface soils were sampled from Guilan and Hamadan provinces in north and northwest of Iran with temperate and semiarid climates. The chemical forms of Pb in the Pb(NO₃)₂-treated (400 μg Pb g⁻¹) soils have been studied in solid state incubation (FC) at 27°C in sterile and unsterile conditions. After 20 min and 3600 h a sequential extraction scheme was also used to fractionate Pb of incubated samples into soluble-exchangeable (Sol-Exch), carbonates associated (ACar), organic matter associated (AOM), Mn oxide associated (AMnOx), Fe oxide associated (AFeOx), and residual (Res) forms. Temperate soil samples had higher clay content, cation exchange capacity (CEC), dichromate oxidable organic carbon (OC), total Kjeldahl-nitrogen (TN), biological activity, amorphous and crystalline Fe and Al, but semiarid soil samples had higher sand content, pH, equivalent calcium carbonate (ECC), available P and K. Soil lead fractionation revealed that in both groups of soils Pb largely changed to exchangeable, carbonates associated and organic associated forms after 20 min. The chemical forms of Pb differed widely among soils after 3600-h incubation. The conversion rate of Pb from more available forms to less available forms was higher in temperate soils with higher Fe–Mn oxides and OM contents compared to semiarid soils. In temperate soils after 3600-h incubation, greater content of Pb was observed in Res (68%), AOM (14%), ACar (7%), and AMnOx (5%) fractions. However, in semiarid soils greater content of Pb was observed in Res (61%), ACar (16%), Sol-Exch (8%), and AOM (8%) fractions. The sum of AMnOx and AFeOx chemical forms for Pb in semiarid soils compared to temperate soils was lower. It was only 7% against 9% in temperate soils. Soil microorganisms in unsterile soils had significant effect on AOM, AFeOx and Res fractions of Pb. They not only increased AOM and AFeOx fractions of Pb in soils but also decreased Res fraction of Pb significantly.     

Mobility of toxic elements in carbonate sediments from a mining area in Poland

The Boles?aw–Bukowno mining area in Poland is highly polluted by elements such as Zn, Pb, Cd and As. The reactivity and mobility of toxic elements such as Tl are poorly known. Here, we studied by sequential extraction the mobility of As, Cd, Co, Cr, Cu, Mn, Mo, Pb, Tl and Zn in sediments from two water reservoirs near Bukowno. Results show that available As, Co, Mn, Pb and Zn are found in carbonate minerals. Available Cd, Cu and Tl are found in sulphides and organic matter. The extractability of As, Cr, Mo and Tl was rather poor. By contrast, 85 % of total Cd, Pb and Zn was mobile. We discuss Tl and Mo association in carbonate sediments from ore deposits.     

Lead redistribution in a mine soil treated with three manures and incubated at two different temperatures

The study of heavy metals’ redistribution between different fractions allows to know their bioavailability and mobility in soils. Soil samples were collected from a lead mine in Hamadan provinces, NW Iran. In a factorial experiment soil was treated with cow, sheep and poultry manures (20?g?kg^?1 soil) separately and incubated near field capacity at 10°C and 37°C. An untreated soil (as control) was also incubated at the same temperatures. After 0 and 120 days, a sequential extraction scheme was used to fractionate Pb of incubated samples into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), carbonates associated (ACar), and residual (Res) forms. Soil Pb in Sol-Exch and AOM fractions were increased by manure application significantly. The AOM and ACar forms of Pb were higher in soils treated with the manures and incubated in lower temperature. In contrast, the Sol-Exch and Res chemical forms of Pb were higher in the soils incubated at 37°C. These results may be related to the higher calcium carbonate dissolution and organic matter decomposition because of better biological activity in the soils incubated in higher temperature. The increase of the Res fraction (stable form) in this condition may resulted in lower toxicity and mobility in soil environment.     

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。     

Metal distribution in urban soil around steel industry beside Queen Alia Airport,Jordan

The objective of this study was to assess the extent and severity of metal contamination in urban soil around Queen Alia Airport, Jordan. Thirty-two soil samples were collected around steel manufacturing plants located in the Al-Jiza area, south Jordan, around the Queen Alia Airport. The samples were obtained at two depths, 0–10 and 10–20 cm, and were analyzed by atomic absorption spectrophotometry for lead (Pb), zinc (Zn), cadmium (Cd), iron (Fe), copper (Cu) and chromium (Cr) levels. The physicochemical factors believed to affect the mobility of metals in the soil of the study area were also examined, including pH, electrical conductivity, total organic matter, calcium carbonate (CaCO₃) content and cation exchange capacity. The high concentrations of Pb, Zn and Cd in the soil samples were found to be related to anthropogenic sources, such as the steel manufacturing plants, agriculture and traffic emissions, with the highest concentrations of these metals close to the site of the steel plants; in contrast the concentration of Cr was low in the soil sampled close to the steel plants. The metals were concentrated in the surface soil, and concentrations decreased with increasing depth, reflecting the physical properties of the soil and its alkaline pH. The mineralogical composition of the topsoil, identified by X-ray diffraction, was predominantly quartz, calcite, dolomite and minor minerals, such as gypsum and clay minerals. Metal concentrations were compared using one-way analysis of variance (ANOVA) to compute the statistical significance of the mean. The results of the ANOVA showed significant differences between sites for Pb, Cd and Cu, but no significant differences for the remaining metals tested. Factor analysis revealed that polluted soil occurs predominantly at sites around the steel plants and that there is no significant variation in the characteristics of the unpolluted soil, which are uniform in the study area.     

Fractionation of trace metals (Mn,Zn, Cu,Pb) in Red Sea sediments,Gulf of Aden,Yemen

A sequential extraction technique was applied to estimate the chemical association of Mn, Zn, Cu and Pb in five chemical phases (exchangeable, carbonate, Fe–Mn oxides, organic matter and residual) in sediments of the Gulf of Aden, Yemen. The results indicated that a higher level of Mn was associated with the residual fraction (natural sources) than the non-residual fraction (anthropogenic sources). Zn fractionations revealed that it was associated more with Fe–Mn oxides and organic fractions than exchangeable and carbonate fractions. Most of the Cu was present in the residual form (60–72%) except for in the main port area (zone III), where it was associated with the organic phase (77% of the total Cu content, the organic matter content was 5%). Similarly, most Pb was bound in the residual fraction (56–71%) except the main port area where ～ 62% of the total Pb was bound in non-residual fractions. It was also found that the Pb concentration in the exchangeable fraction was very high compared with other metals. The risk assessment code for the metals showed a low risk for Zn and Cu, but low to medium risk for Mn. Fractionation of Pb showed medium risk at most of the regions except at the eastern area, which revealed a high risk for the aquatic environment.     

Adsorption anionischer Azofarbstoffe an Boden/Sediment

The adsorption behavior of three anionic azo dyes (Acid Orange 6, Acid Orange 10 andAcid Orange 12) on different soil/sediment components (quartz sand, clay and organic matter) was investigated with a flow-through method using a simplified HPLC apparatus. Organic matter had the highest adsorption capacity for all three dyes, followed by clay and sand. The adsorption on different components in mixtures was not additive. The adsorption of similar aniomic azo dyes decreased with increasing negative charge. The affinity of equally charged dye molecules to the adsorbents was also strongly influenced by the remaining chemical structure. While adsorption on organic matter could always be described by Freundlich isotherms, S-shaped isotherms were often measured with quartz sand and clay. For that reason one must assume different adsorption mechanisms for organic matter and mineral adsorbens. Lower pH values always led to stronger adsorption of the anionic azo dyes. On the other hand, ionic strength effects cannot be characterized so clearly. Adsorption was generally lowered by decreasing ionic strengths but sometimes the opposite effect was observed. Moreover, there were some unusual cases of partly irreversible adsorption on quartz sand and organic matter when the dyes were not dissolved in an aqueous solution containing additional inorganic ions but in double distilled water. The adsorption of anionic azo dyes on soil and sediment materials turned out to be a very complex process. Although some interesting coherences could be pointed out, much more research is required to recognize general principles, concerning for example the influence of the chemical structure or the surrounding aqueous solution.     

焦化厂污染场地表层土壤有机-矿质复合体中多环芳烃的分布

采用湿法物理分级方法将湖南省某焦化厂遗留场地表层土壤分成4种粒级的有机-矿质复合体组分,即粘粒(<2μm)、粉粒(2—20μm)、细砂(20—200μm)和粗砂(>200μm),并研究了美国EPA优先控制的16种多环芳烃(PAHs)在其中的分布特征及土壤不同有机-矿质复合体组分中有机质和矿物质组成的差异对PAHs赋存分布的影响.研究结果表明,不同粒级有机-矿质复合体中PAHs的含量顺序为粗砂>粉粒>细砂>粘粒,低环PAHs(环数≤3)在粘粒中的含量较高,达到56.3%,而高环PAHs(环数≥4)在粉粒、细砂和粗砂中的分布较高含量分别是79.37%、72.7%和71.63%,各粒级矿质复合体中PAHs含量与土壤有机碳有较好的相关性.通过对有机-矿质复合体进行X射线衍射分析发现,场地土壤粘粒和粉粒中粘土矿物含量较高,这也在一定程度上影响了污染物质在其中的分布.     

土壤中铅的吸附-解吸行为研究进展

铅是重要的土壤重金属污染元素之一，了解铅在土壤中的物理化学行为，有利于预防和修复土壤的铅污染。土壤中铅的吸附-解吸行为，依吸附机理的不同，分为专性吸附和非专性吸附。土壤铅吸附的机理还存在不同的观点，如水解吸附／非水解吸附机理，单分子吸附／双分子吸附机理等。影响土壤中铅吸附-解吸行为的主要因素，有土壤矿物组成、土壤有机质、pH、温度、竞争离子等。文章最后对描述土壤铅吸附过程的主要数学方程(Langmuir方程、Freundlich方程和Temkin方程)作了论述。     

武当山土壤的粘粒矿物与表面电荷性质

本文研究了湖北省武当山风景区石英云母片岩发育的７个土样的粘土矿物组成、粘粒氧化物含量。土壤电荷量及电荷零点．结果表明：（１）供试土壤粘土矿物均以２∶１型矿物占优势，在海拔４４０ｍ以下的土壤中主要是水云母和蛭石，在海拔６７０ｍ以上的土壤中主要是１．４ｎｍ过渡矿物、绿泥石和水云母；（２）土液粘粘中氧化铁和氧化铝的含量、粘粒硅铝率及氧化铁的游离度随海拔的变化而变化的趋势不甚明显，但非晶形铝铁氧化物的含量及氧化铝和铁的活化度随海拔升高而趋于增加；（３）土壤可变负电荷量、阴离子吸附量和电荷零点随海拔升高而趋于增加。     

A Petrographic Investigation of two Sequential Extraction Techniques Applied to Anaerobic Canal Bed Mud

The application of sequential extraction procedures to determine metal speciation in sediments is fraught with uncertainty regarding what is actually dissolving or re-precipitating at each stage. In order to choose an appropriate scheme for the investigation of contaminated anaerobic mud two different sequential extraction procedures (Kersten and Förstner, 1986; Quevauviller, 1998) were investigated using a Cryogenic SEM (CryoSEM) technique coupled with energy dispersive X-ray analysis (EDXA). This enabled assessment of the degree of reagent selectivity and any re-precipitation associated with the respective methods. Analysis of the non-leached sediment revealed the most abundant authigenic minerals in order of decreasing abundance to be Fe²⁺-phosphate vivianite (Fe₃(PO₄)₂·8H₂O), mixed Fe, Zn, Cu sulphides, pyrite and calcite. After each stage of the sequential extraction the sediment residue was examined using CryoSEM. After extraction of the exchangeable fraction no obvious evidence of mineral dissolution was observed. Calcite was not completely dissolved during the carbonate extraction stage of either procedure. Vivianite began to dissolve in the carbonate extraction stage of both procedures and was completely dissolved by oxide extraction stage of both procedures. The sediment leached by acidified ammonium oxalate, contained abundant Fe oxalate crystals, suggesting that a large proportion of the Fe released from the vivianite has been re-precipitated. The Fe oxalate was then dissolved with the subsequent sulphide fraction. The technique used to extract the sulphide and organic fraction is the same in both schemes and no sulphide or metal rich organic matter was found in either residue.     

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.