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.     

Speciation of heavy metals in suspended particulates in urban air†

An anayltical procedure based on a sequential extraction scheme is applied to samples of suspended particulates from an urban area of Barcelona. This area presents high levels of air pollution owing to automotive emissions and industrial activity.

The procedure allows the partitioning of particulate trace metals into four fractions: soluble and exchangeable, bound to carbonates and iron‐manganese oxides, bound to organic matter and residual. In this work, the chemical associations of Fe, Pb, Cu, Mn, Cr and Cd have been investigated.

In the analysed samples, only the cadmium is predominantly in the first fraction whereas the other metals are largely associated to carbonates and Fe‐Mn oxides.     

Geochemical speciation of trace metals in sediments of the northern Nile Delta Lake by sequential extraction technique

ABSTRACT

The present study was performed to investigate surface sediment samples from Lake Edku of the Nile Delta Lagoons, Egypt. The Lake is important for fishing in the region. The importance of research is to understand the mobility and bioavailability of each studied metal. The study was carried out on 10 sampling sites during 2017. The sediments were subjected to the technique of sequential extraction to examine the chemical forms of some trace metals (Fe, Mn, Zn, Cu, Pb and Ni). Five stage extractions were done as the following order: soluble and exchangeable, carbonate, iron and manganese oxides, organic matter fraction and residual fraction. Attained results from the five fractions showed variations in the concentrations of metal contents of different sites under study. The overall metal concentrations (%) in the initial four extractable fractions (exchangeable, carbonate, oxides and organic matter fractions) were assessed to configure the mobility of each studied metal. The risk assessment code (RAC) represents the summation of exchangeable and carbonate fractions, it was between low and medium risk for aquatic environment. The range percentage of RAC for the metals was in the following order: 1.8–13, 4–23.5, 15–26, 5.7–19.5, 9–25 and 4.8–18.2 for Fe, Mn, Zn, Cu, Pb and Ni, respectively. Approximately 30% of the total copper was associated to the organic fraction, which may represent a high mobility of copper in these sediments. The highest mobility of metals in the sediments could be confirmed by its bioavailability factor (BF), which was within the ranges of 0.32–0.61, 0.36–0.59, 0.64–0.83, 0.36–0.72, 0.37–0.62 and 0.52–0.78 for Fe, Mn, Zn, Cu, Pb and Ni, respectively. The BF exhibited the following order: Zn > Ni > Cu > Pb ≈ Mn?>?Fe. The high levels of BF for the studied metals may represent the potentiality for toxic metals to be easily released into the aquatic environment.     

Comparative study of the fate and mobility of metals discharged in mining and urban effluents using sequential extractions on suspended solids

The fate, bioavailability and environmental impacts of metals discharged in municipal and mining wastewater discharge will depend to a large extent on chemical speciation and distribution. Previous studies on metal bioaccumulation have shown that total metal concentrations are not a good predictor of bioavailability in the dispersion plumes of municipal effluents. The objective of this study was to determine the solid phase speciation of metals in surface waters receiving urban and mining effluents in order to assess their fate and relative mobility in the receiving environment. Suspended particulate matter was sampled using sediment traps at several sites downstream of effluent outfall plumes as well as at reference upstream sites. Particulate metal in operationally defined fractions—exchangeable/carbonates, reducible, oxidisable and residual—were determined in suspended particulate matter with a series of selective chemical extractions. Metal enrichment in suspended particles was generally observed in both mining and urban effluent discharges. When compared to its receiving environment, the mining effluent appeared to release more particulate metals (Cu, Fe, Zn) in the most reactive fractions (i.e. exchangeable/carbonates + reducible forms, 23–43%), while other released metals, such as Cd and Mn, were predominantly in the least reactive forms (i.e., oxidisable + residual, 73–97%). In contrast, the reactivity of all particulate metals, with the exception of Mn, from the urban effluent was much higher, with up to 65, 42, 30 and 43% for Cd, Cu, Fe and Zn, respectively, in the two most reactive fractions. As expected in effluent dispersion plumes, parameters such as the organic carbon, Fe oxide and carbonate contents have specific effects on the partitioning of several trace metals, particularly Cd, Cu and Zn. Our results indicated that the relative distributions of metals among geochemical fractions varied in the effluent receiving waters where organic carbon and Fe oxides appeared as the most important parameters. This could therefore decrease the exposure for aquatic organisms that are exposed to those contaminated sediments as well as the risk to human health.     

Heavy metals availability (Fe, Mn, Zn, Cu and Cr) in Aden Gulf sediments under aerobic and anaerobic conditions

The present study aims to analyse the chemical speciation of heavy metals in relation to aerobic and anaerobic conditions. Two sediment samples (from the Gulf of Aden, Yemen) were incubated under flooded conditions. In particular, the chemical forms of Fe, Mn, Zn, Cu and Cr under the experimental conditions were studied using a sequential chemical extraction method. The pH and Eh of the suspension were measured as critical parameters controlling the fate of the metals in the environment. The results showed that the metals concentration in the different forms varied with time incubation and affected by the variation of redox potential and pH value. Also, the changes in both redox potential (Eh) and pH values had evident effects on heavy metals transformation. It is obvious that the highest redox potential affected the amount of iron and manganese in the oxides form. When the redox potential decreased to-133 and-170 mV, it caused a significant transformation of the Fe-Mn oxide form to the water-soluble and exchangeable fractions. Under anaerobic conditions, the relative percentage of all five metals including the summation of four fractions (the water-soluble and exchangeable, carbonate, oxides and organic fractions) constituted 45-60% of the total amount of iron, 33-50% for manganese, 33-63% for Zn, 63-74% for Cu and 19-43% for Cr. Both zinc and copper among water-soluble and exchangeable fraction were high at the end of incubation period, this accompanied by a significant decrease in the content of the organically bound fraction. In general, the reducing conditions were more favorable for metal bound to water soluble and exchangeable fraction.     

Sequence of the main geochemical controls on the Cu and Zn fractions in the Yangtze River estuarine sediments

Metal speciation can provide sufficient information for environmental and geochemical researches. In this study, based on the speciation determination of Cu and Zn in the Yangtze Estuary sediments, roles of eight geochemical controls (i.e., total organic carbon (TOC), clay, Fe/Mn in five chemical fractions and salinity) are fully investigated and sequenced with correlation analysis (CA) and principal components analysis (PCA). Results show that TOC, clay and Fe/Mn oxides are key geochemical factors affecting the chemical speciation distributions of Cu and Zn in sediments, while the role of salinity appears to be more indirect effect. The influencing sequence generally follows the order: TOC>clay>Mn oxides>Fe oxides>salinity. Among the different fractions of Fe/Mn oxides, residual and total Fe content, and exchangeable and carbonate Mn exert the greatest influences, while exchangeable Fe and residual Mn show the poorest influences.     

Speciation of Heavy Metals in Floodplain and Flood Sediments: a Reconnaissance Survey of the Aire Valley, West Yorkshire, Great Britain

A five-step sequential extraction technique was used to determine the chemical association of heavy metals (Pb, Zn, Cu and Cd), with major sedimentary phases (exchangeable, surface oxide and carbonate, Fe and Mn oxides, organic and residual metal ions), in samples from floodplain and recent flood sediments of the River Aire, West Yorkshire. Analysis indicates that metals Pb and Zn are primarily associated with the Fe and Mn oxides, Cu with the organic fraction and Cd with exchangeable and surface oxide and carbonate metal ions. Knowledge of the chemical speciation of heavy metals in river sediment, despite the procedure's inherent limitations, facilitates an understanding of their bioavailability, storage and remobilisation in floodplain and river channel environments.     

土壤重金属化学形态的生物可利用性评价

重金属化学形态是近年来土壤化学、植物营养和环境科学研究领域的一个热点和难点,利用重金属的化学形态分布和含量变化来评价重金属的生物可利用性,有利于全面研究重金属的危害性和治理重金属污染土壤。结果表明,水溶态和交换态的重金属易被生物吸收利用,而残留态重金属一般不被生物利用,其它形态如碳酸盐结合态、铁锰氧化物结合态和有机物结合态的生物可利用性主要取决于外界环境的变化。     

Speciation of heavy metals in sediments from the Scheldt estuary,Belgium

A simple three-step sequential extraction procedure was applied to study the speciation of heavy metals in sediment from Scheldt estuary, and their relationship to sediment grain size and organic matter content. The sedimentary metal content was fractionated into carbonate and exchangeable, metals bound to organic matter and residual fractions. Sedimentary total metal content was also determined using an industrial microwave (ETHOS 900) HF/HNO₃ extraction method. The extracts were analysed for metals using inductively coupled plasma atomic emission spectrometry. The bioavailable fraction (exchangeable and metals bound to organic matter) comprised less than the other forms. Residue metals were the dominant form of metals in almost all studied sites. The average total metal content for the studied sites decreased in the order Fe>Cr>Cu>Co>Zn>Pb>Cd. Based on average values for the studied sites, the highest bioavailable metals in sediments were Cd (38%) from Westkapelle, Zn (17%) from Yerseke, Co (12%) from Domburg, Cr (9%) from Vlissingen, Fe and Pb each (2%) from Yerseke, and Cu (1%) from Domburg. Metal recovery was good, with<10% difference between the total metal recovered through the extractant steps and the total metal determined using HF/HNO₃ extract.     

Geochemical distribution,bioavailability and potential toxicity of some trace metals in a complex micro-tidal estuary,Southwest India

The spatial and temporal variations of some trace metals in the surface sediments of Cochin Estuary were analyzed along with their geochemical associations to identify the possible sources, bioavailability and the health risks posed by them. The dominance of kaolinite and suggested that clay minerals distribution is influenced by sediment sorting. Total metal analysis revealed enrichment for Cd, Pb and Zn due to anthropogenic activities. The speciation analysis established that notwithstanding the large availability, carbonate as well as organic and sulfides bound fractions showed negligible associations with most of the metals. Hydrous Fe–Mn oxides appeared to play a major role in controlling the fate and transport of these metals in the sediments of Cochin Estuary. Lower contribution of the residual fractions for Cd (21%–26%), Pb (<60%) and Zn (24%–42%) indicated an obvious increase of other geochemical fractions. Risk assessment analysis revealed that regardless of total concentration, none of the analyzed metals were at safe levels in the estuary as appreciable percentages were found to be associated with mobile geochemical forms. The speciation study conspicuously established that the metals originating from non-geogenic sources are largely associated with the labile fractions and hence are more detrimental to the aquatic biota.     

外源铅铜镉在长三角和珠三角农业土壤中的转化

选择了我国经济发达地区的长江三角洲和珠江三角洲10个代表性农业土壤，采用室内培养和化学分级方法研究了加入外源铅、铜、镉在土壤中的动态变化及转化趋势，探讨了碳酸钙、粉煤灰、猪粪和钢渣等土壤改良剂对土壤重金属形态的影响。结果表明，随着土壤重金属负荷的提高，土壤中交换态重金属的比例增大，残余态比例下降，有效性提高，对环境威胁增大。当重金属加入最较低时，重金属优先向氧化物结合态、有机质结合态转化；而当加入最较高时，向交换态和碳酸盐结合态转化的比例明皿增加。pH和土壤组分对重金属在土壤中的转化有显著的影响，土壤pH下降可使交换态Cd、Cu、Pb的比例递增。加入碳酸钙、粉煤灰、猪粪和钢渣等改良剂可显著地降低土壤中交换态重金属比例，增加其它形态的重金属比例。     

Effect of acid rain on the fractionation of heavy metals and major elements in contaminated soils

Acid rain is a serious environmental problem worldwide. In the present study, we investigated the effect of acid rain (1:1 equivalent basis H₂SO₄:HNO₃) at pH values of 2.0, 4.0 and 7.0 on the fractionation of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb and Zn) and major elements (K, Na, Ca, and Mg) in contaminated calcareous soils over a 2084 h period. Heavy metals and major elements in soil samples were fractionated before and after 2084 h kinetic release using a sequential extraction procedure. Before kinetic studies the predominant fractions of K, Na, Ca, Mg, Cd and Ni were mainly associated with carbonate fraction (CARB), whereas Fe, Mn and Zn were associated with the Fe–Mn oxide fraction (Fe–Mn oxide). The highest percentage of Pb and Cu were found in the exchangeable (EXC) and organic matter (OM) fractions, respectively. After kinetic study using different simulated acid rain solutions, the major fractions of heavy metals (expect of Cu) and Na was the same as before release. Upon the application of different acid rain solutions, K and Mg were found dominantly in Fe–Mn oxide fraction, whereas Ca was in the EXC fraction. The results provide valuable information regarding metal mobility and indicated that speciation of metals (Cu and Zn) and major elements in contaminated calcareous soils can be affected by acid rain.     

连续浸提技术测定土壤和沉积物中硒的形态

本文建立了土壤和沉积物中硒的形态分析方法，应用连续化学浸提技术将土壤和沉积物进行连续五次抽提，根据不同形态硒的溶解度，将土壤和沉积中的硒分为可溶态（水溶态）、可交换态及碳酸盐结合态、铁－锰氧化物结合态、有机物－硫化物结合态及元素态、残渣态五种结合形态。种形态硒分级浸提的相对标准偏差均小于４．０％，总回收率（即：五种形态和与总硒的比值）为９３．２－９４．４％。     

Annual production and molecular weight as an influential factor for environmental distribution of chemicals — a case study in Japan

The changes promoted by treatment of a highly polluted soil with sulphuric acid or calcium hydroxide for changing its pH value are studied by controlling physical properties (particle size, TGA and DTA curves), evolution of metal species (exchangeable, as carbonates, related to Fe‐Mn oxides, linked to organic matter and residual) and metal uptake by plant cultures. Metal contents were determined, after wet digestion with HF—HNO₃—HC1O₄ when necessary, by AAS (Ca, Mg, Cu, Pb, Mn, Fe, Zn) or emission (Na, K). The treatment of soil with successive amounts of sulphuric leads to changes in particle size, hydration properties and exothermic peak for organic matter combustion. Very small changes were, however, detected in the alkaline treatment of soil. Soil treatments do not have practical influence on speciation of some metals (Na, K, Mg, Pb, Mn, Fe), but the intensity of the acid treatment leads to both an increase in the Cu extraction and a decrease in the Ca solubilization, probably through gypsum formation. In the case of zinc a maximum solubility in the middle of the range of acid treatment was observed. The comparison among extractants shows solubilities high for two pollutants (Pb, Cu), associated mainly to Fe—Mn oxides and organic matter, and low for two macrocomponents (Fe, K). The rest of metals, basically present in soil as carbonates or oxides, have intermediate extractions. Pot cultures weights depended mainly on both the treatment of soil (poor development in the more acid sample and drainage difficulties in the rest of acid treatments) and the situation (very low weights in laboratory runs as compared with outside), but the irrigation with water or a diluted sulphuric acid solution (at pH = 4.0) did not produce significant weight changes. Tendencies to increase plant pollution were observed for smaller soil pH, acid irrigation and probably for outside cultures, due to uptake by leaves.     

Aluminum fractionation in acidic soils and river sediments in the Upper Mero basin (Galicia,NW Spain)

This study aims to determine aluminum fractions in the fine earth of acidic soils under different land uses (forest, pasture and cultivation) and in the river bed sediments of the headwater of the Mero River in order to identify and quantify Al-bearing phases to assess Al mobility and potential bioavailability (environmental availability) in the monitoring area. Sequential extraction is used to evaluate the Al partitioning into six fractions operationally defined: soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, aluminum bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction (aluminum within the crystal lattices of minerals). The mean concentration of total aluminum (24.01 g kg^?1) was similar for the three considered uses. The mean percentage of the aluminum fractions, both in soils and sediments, showed the following order: residual fraction ? amorphous compounds ≈ crystalline iron oxides > water-soluble/exchangeable/specifically adsorbed > bound to oxidizable organic matter ≈ Mn oxides. However, in the soils, the amorphous compounds and water-soluble/exchangeable/specifically adsorbed fraction showed considerable differences between some types of uses, the percentage of aluminum linked to amorphous compounds being higher in forest soils (16% of total Al) compared to other uses (mean about 8% of total Al). The highest values of water-soluble/exchangeable/specifically adsorbed Al were also found in forest soils (mean 8.6% of the total Al versus about 4% of pasture and cultivation), which is consistent with the lower pH and higher organic matter content in forest soils. Nevertheless, the potentially bioavailable fraction (sum of the first three fractions) is low, suggesting very low geoavailability of this element in both soils and sediments; hence, the possibility to affect the crops and water quality is minimal.     

广州城市水体沉积物中重金属形态分布研究

选取广州城市水体中的４ 个污染沉积物样品,采用连续提取法研究沉积物中重金属元素（ Ｐｂ 、 Ｚｎ 、 Ｃｕ 、 Ｎｉ 、 Ｃｒ 、 Ｍｎ） 的形态分布,结果表明：重金属元素主要以残渣态、有机结合态和氧化铁结合态存在,其中 Ｐｂ 、 Ｎｉ、 Ｍｎ 以残渣态和氧化铁结合为主, Ｚｎ 以残渣态和有机结合态为主, Ｃｕ 以有机态和氧化铁结合态为主, Ｃｒ 以氧化铁结合态为主。沉积物中固相组分对重金属的富集能力为：无定型氧化锰＞ ＞ 碳酸盐＞ 氧化铁＞ 有机质,而富集量则是后两者大于前两者。     

长春市土壤微生物生化作用与重金属化学形态关系研究

研究了长春市土壤微生物的生化作用强度（氨化作用强度、固氮作用强度,纤维素分解强度和土壤基础呼吸）与重金属（Pb、Cd、Cu、Zn和Ni）化学形态的关系。通过科学采样和实验室测试分析了不同功能区土壤中,重金属含量和化学形态与微生物生化作用强度,并使用相关分析、偏相关分析多种数据统计方法进行数据处理。结果表明：各功能区因土地利用方式的差别和土壤中重金属的各种化学形态对土壤微生物生化作用强度有不同的影响。其中氨化作用与交换态Cd、Zn和Ni含量呈显著正相关;固氮作用与土壤重金属各化学形态相关性均不显著;呼吸作用与铁锰氧化物结合态Pd和交换态Cu呈显著正相关;纤维素分解作用强度与交换态Pd含量呈显著负相关。在土壤理化性质等相关变量受控时,重金属化学形态对微生物生化作用强度的影响有较明显的变化。其中与无控制变量相比,在控制变量作用下,纤维素分解作用强度受交换态Pd影响上升了0.0314,表现为交换态Pd抑制纤维素分解作用强度。呼吸作用与交换态Pd的相关系数在无控制因素情况下为-0.1425,在有控制因素情况下为-0.3230,表明交换态Pd促进呼吸作用强度。而有机结合态Ni表现为抑制固氮作用。因此可利用交换态Pd与纤维素分解作用强度、呼吸作用强度的相互关系,有机结合态Ni与固氮作用的相互关系等相结合来评价城市土壤重金属污染状况。文章为评价长春城市土壤重金属污染提供了微生物学指标的理论依据。     

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。     

填埋场内重金属总量及其形态分布对迁移性的影响

以杭州市天子岭填埋场为例,对不同深度填埋层中的重金属总量、重金属迁移率和重金属形态分布进行了研究．结果表明,尽管填埋层中的重金属总量是土壤背景值的数十倍,超出土壤环境质量标准,但是重金属的迁移率却很低．另外,重金属迁移率与可交换态含量相关;Cd,Cu,Pb,Cr,Ni和Zn在填埋层中均以残渣态为主,填埋场中重金属都得到了有效固定,迁移性很差;各元素的易还原态与难还原态是重金属除残渣态之外主要的结合态(除Cr),铁锰氧化物循环是控制填埋场中重金属转化行为的主要机制之一;Cu的酸可溶态与易还原态具有较好的相关性,说明cu这两种形态的转化行为相似．     

典型城市污染水体底泥中重金属形态分布和相关性

采用Tessier五步连续提取法,研究了南京市莫愁湖、玄武湖、秦淮河13个底泥样品中的重金属的形态分布情况,分析了重金属浸出量与各形态间的相关性及有机质与有机结合态的相关性,并通过红外谱图分析了有机质与重金属结合的机理.结果表明:底泥中Pb,cu,zh,Ni,Cr主要以有机结合态和残渣态俘在,两种形态的含量占总量70%以上,Zn和Cd的可交换态和碳酸盐结合态含量相列较高,Zn约占20%,Cd约占30%;Zn,Cu,Cd,Ni,Cr的浸出量均与可交换离子态呈现显著的相关性,因此可通过减小可交换离子态含量控制底泥重金属污染的风险性;研究还表明,有机质与有机结合态呈现显著的正相关,因此增加底泥中有机质含量有助于重金属向有_棚结合态转化,有机质与重金属的结合主要是由于其中-些官能团和重金属形成稳定的络合物.