Behaviour of trace metals in surface sediments of the Black Sea

Early diagenetic processes control the behavior, and more specifically the dissolved‐solid phase distribution of heavy metals in sediments. The depth distribution of Co, Mn, Cu, Zn, Ni, and Fe in sediment were determined in box cores from the Black Sea. The sequential analyses results of these metals indicate contrasting behavior of Mn and Co during early diagenesis, consistent with their respective chemistries and particle‐associations. The profiles of extractable trace metals in the cores are clearly related to sediment type or depositional environment. Topmost sections of the profiles for these elements are generally similar, i.e. rapid decrease in concentration below the sediment surface.     

Geochemical forms of trace metals in mangrove sediments—Red Sea (Egypt)

Seven sediment samples from mangrove sediments of the Red Sea were taken in order to evaluate the possible contamination of the sediments by trace metals (iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), lead (Pb) and cadmium (Cd)). Sequential extraction techniques were performed to study the different geochemical forms of these metals. X-ray diffraction analysis has been performed to correlate the mineralogical composition with the geochemical forms of the studied elements. The results of Fe and Mn contents indicate that they are in large part from lithogenous origin. The elevated concentrations are associated with the residual form ranged from 70 to 93% for Fe and 46 to 70% for Mn. The percentage of Zn, Cu, Cd and Pb in the non-residual form was much greater than that of the residual fractions. This reflects the high mobility and bioavailability of these metals in mangrove sediments of the Red Sea. X-ray diffraction analysis revealed the presence of silicate components including quartz, feldspars and clay minerals in some locality. Non-silicate components recorded in the study area as calcite as well as, Mg-calcite. Quantitatively both components i.e. silicate and carbonate varied according to their source material.     

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.     

Sediment-associated trace and major metals in the headwaters of a tropical reservoir

Bed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72?±?6.82?µg/g); Mn (9.34?±?2.57?µg/g); Na (6.20?±?2.29?µg/g); K (0.65?±?0.57?µg/g); Mg (8.07?±?1.36?µg/g); Ca (13.92?±?2.85?µg/g); Ba (0.17?±?0.17?µg/g); Al (106.54?±?5.55?µg/g); and Se (0.6?±?0.19?µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in the bed sediments of the two headstreams had not reached pollution status with the exception of Se.     

Sediments distribution of trace metals in a coastal lagoon (Southern Sardinia,Mediterranean Sea): assessment of contamination and ecological risk

Coastal lagoons are subject to several sources of contaminations. To shade light on the contamination level of the Santa Gilla lagoon (Tyrrhenian Sea) we investigated the spatial distribution of Cr, Ni, Pb, Zn and Hg in sediments and their correlation with grain size and organic matter contents. Moreover, sediment contamination levels and the ecological risk associated with metal concentration were assessed using different abiotic indicators. The lagoon is characterised by low levels of contamination, with exceptions for Pb and Hg, whose distribution reflects the position of an old chlor-alkali plant and that of an airport. These results indicate that the restoration put in place 30 years ago have not reached the expected target and that the presence of the airport deserves further attention. In the outer section of the lagoon, where clam fishery occurs, we observed low levels of contamination suggesting that such artisanal fishery could somehow help mobilising metals. We conclude that the area exposed to Hg pollution, though tentatively restored, still suffers of a potential risk of ecosystem deterioration. We pinpoint that further investigations on the mobility, bioavailability and toxicity of metals are needed to finally address the actual impairment of the Santa Gilla lagoon.     

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

• The concentrations of 13 heavy metals in Taihu Lake were analyzed. • Aquatic vegetables intake was first included in deriving human health AWQC. • The human health AWQC for 13 heavy metals in Taihu Lake were derived. • Human health risk assessment for 13 heavy metals were conducted in Taihu Lake. Heavy metals are widely concerning because of their toxicity, persistence, non-degradation and bioaccumulation ability. Human health ambient water quality criteria (AWQC) are specific levels of chemicals that can occur in water without harming human health. At present, most countries do not consider the effects of aquatic vegetables in deriving human health AWQC. Therefore, the intake of aquatic vegetables (Brasenia schreberi) was added to the derivation of human health AWQC and a health risk assessment for 13 heavy metals in Taihu Lake. The human health AWQC (consumption of water, fish and aquatic vegetables) values of 13 heavy metals ranged from 0.04 (Cd) to 710.87 μg/L (Sn), and the intake of B. schreberi had a very significant effect on the human health AWQC for Cu, with a more than 62-fold difference. The hazard quotients of As (2.8), Cd (1.6), Cr (1.4) and Cu (4.86) were higher than the safe level (HQ= 1), indicating that As, Cd, Cr and Cu in Taihu Lake posed a significant health risk. Sensitivity analysis showed that the contribution rate of B. schreberi intake to the human health risk from Cu was 91.6%, and all results indicated that the risk of Cu in B. schreberi to human health should be of particular concern. This study adds the consideration of aquatic vegetable consumption to the traditional method of human health AWQC derivation and risk assessments for the first time, and this approach can promote the development of risk assessments and water quality criteria.     

Soil pollution by trace metals derived from animal feed and manure in the Bursa region of Turkey

The Bursa region of Turkey has important agricultural production areas. Animal producers use agricultural fields in this region for disposal of manure. Therefore, in this study the concentrations of the seven trace metals Zn, Mn, Cu, Ni, Cr, Pb, and Cd in 324 animal feed and manure samples from three dairy cattle, three laying hens farms, and three broiler farms have been determined. The average concentrations in dairy cattle manure were 130 (Zn), 150 (Mn), 4.2 (Cu), 6.8 (Ni), 44 (Cr), 0.8 (Pb), and 0.09 (Cd) mg kg^?1 dry weight; for laying hens manure 240 (Zn), 190 (Mn), 0.63 (Cu), 3.8 (Ni), 30 (Cr), 0.55 (Pb), and 0.12 (Cd) mg kg^?1 dry weight; and for broiler manure 240 (Zn), 280 (Mn), 1.4 (Cu), 3.8 (Ni), 35 (Cr), 3.4 (Pb), and 0.16 (Cd) mg kg^?1 dry weight. The calculated trace metal loading rate indicated that manure application might pose a potential risk to agricultural fields according to the current soil protection regulations of Turkey.     

AVS-SEM relationships and potential bioavailability of trace metals in sediments from the Southeastern Mediterranean sea,Egypt

In risk assessment of aquatic sediments, much attention is paid to the difference between acid volatile sulfide (AVS) and simultaneously extracted metals (SEM) as indicators of metal bioavailability. Distribution of AVS and SEM (Cd, Cu, Ni, Pb and Zn) were determined in 20 representative sampling sites collected along the Egyptian Mediterranean coast. Total SEM concentration [ΣSEM] ranged from 0.012 to 0.241 μmoleg^?1. AVS concentrations were much more variable, showing significant spatial variations. The values ranged from 0.015 to 31.326 μmoleg^?1. The different relationships between AVS and SEM to establish mechanical models such as the ratio of ΣSEM and AVS [ΣSEM/AVS], the difference between the ΣSEM and AVS [ΣSEM–AVS], or the organic carbon normalised difference between SEM and AVS [ΣSEM-AVS]/f_oc models were used as parameters to evaluate potential bioavailability. Considering SEM/AVS model, sediments at the Western Harbour, Eastern Harbour, Ras El-Burr, El-Gamil East, and Port Said stations are occasionally toxic, while according to SEM-AVS model, no indication of associated adverse toxic effect would occur at any of the sampling sites. Calculated [ΣSEM-AVS]/f_oc was<130 μmoleg^?1 in the sediments indicating that sediments should pose a low risk of adverse biological effects owing to cadmium, copper, lead, nickel and zinc. Association of adverse effects to aquatic organisms was determined, using the classification of the sediments according to the Sediment Quality Guidelines (SQGs). The marine Threshold Effect Levels (TEL) and Probable Effect Levels (PEL) were used in this work and in order to obtain a more realistic measure of predicted toxicity, mean PEL quotients (PELq) were calculated. The mean PELq calculated for the sampling sites was (0.11–1.5) and categorised as slightly toxic at all stations except Baghoush, Nobarreya and western harbour, which had PELq<0.1 and categorised as non-toxic. The obtained data concluded that the remobility and bioavailability of trace metals contained in surfacial sediments of the Egyptian Mediterranean coastal area are low.     

Assessment of heavy metals in a soil contaminated by oil spill: a case study in Nigeria

Surface and subsurface soil samples contaminated with crude oils were collected from an impacted site at Bodo City in the Niger Delta, Nigeria, after a field reconnaissance survey. An uncontaminated soil sample collected 100 m from the impacted site, but within the same geographical area, was used as a control. Trace elements such as, As, Cu, Cr, Cd, Fe, Pb, Ba, Ni, V, Hg and cation-exchange capacity constituents of the contaminated and uncontaminated soils were determined by atomic absorption spectroscopy. Trace element concentrations were: Cu, 0.5–13.4 mg kg^{? 1}; Cr, 0.2–0.8 mg kg^{? 1}; Fe, 6.2–8.7 mg kg^{? 1}; Ba 80.0–108.0 mg kg^{? 1}; Ni, 0.6–4.8 mg kg^{? 1}; and V, 4.0–9.4 mg kg^{? 1}; cation-exchange capacity ranged from 43.6 to 57.2 mg kg^{? 1} in surface and subsurface soils. Results showed that eigenvalues for the two first principal components represent up to 49% of the total variance. A positive correlation of the first principal component with Cu, Cr and cation-exchange capacity shows pollution from oil spillage, while a positive correlation of the second principal component with Cr, Fe, V, and dissolved oxygen (DO) shows both oil pollution and allochthonous inputs.     

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.     

Temporal variation and distribution of trace metals in freshwater and fish from Calabar River, S.E. Nigeria

An investigation on the abundance and distribution of trace metals (Fe, Cu, Zn, Mn, Cr, Cd and Pb) in water, and nine species of fish samples from Calabar river was carried out in 1992. The concentrations of iron (6000–7240gl^–1), zinc (4910–7230gl^–1), and cadmium (3–7gl^–1) showed moderate pollution while those of copper (420–630gl^–1), manganese (23–48gl^–1), chromium (<10–20gl^–1) and lead (<1–10gl^–1) in water were well below WHO permissible levels. Significant seasonal changes (0.001p0.25) were obtained for iron, copper, zinc, manganese and cadmium in water. Furthermore, iron, zinc and cadmium showed statistically significant spatial changes (0.005p0.10). Of the nine fish species studied, no statistically significant relationship between body weight and the concentrations of the metals was observed. The concentrations of the metals per mean total body weight apparently decreases in the order Fe>Zn>Cu>Mn>Pb>Cd=Cr and were within the limits that were safe for consumption.     

Uptake of seven metals by two macrophytes species: potential for phytoaccumulation and phytoremediation

Aquatic macrophytes can be used in the studies of quality of water ecosystems and in monitoring of metals and other pollutants. The aim of this study was to assess concentration levels, accumulation and distribution of seven metals in selected plant parts of Typha angustifolia L. and Iris pseudacorus L., in comparison with sediment and water samples of a reservoir. Metal content in the samples was determined by optical emission spectrometry (ICP-OES iCAP 6500). The concentrations of all examined metals were higher in the sediment than in the water samples. In plants, metal concentrations depended on plant species and organs. The roots/rhizomes were primary organs for metal concentration and accumulation. T. angustifolia L. accumulated Mn and Cu, and I. pseudacorus L. accumulated Cd and Cu in the fruits. T. angustifolia L. hyperaccumulated As. The values of enrichment coefficients and translocation factors were: 0 to 3.31 and 0 to 2.39, respectively. The plant species investigated absorb, translocate and accumulate metals in their organs differently, which provides advantages in combining them for remediation of wasted aquatic ecosystems.     

Trace metals in fish,sediment and water from the south west coast of the Arabian sea,Pakistan

Concentrations of ten metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg) in the edible muscle of Arius maculatus captured from eight different near‐shore and off‐shore sites off the south west coast of the Arabian Sea, Pakistan, were determined by atomic absorption spectrophotometry. Relevant water and sediment samples from the sites were also analysed for the metals. Zinc showed the highest metal concentration (6.763 μg/g, wet weight) in the muscle of the fish, while Mn and Hg showed lowest level (0.019 μg/g, wet weight). Of all the metals investigated, largest scatter (measured as σ) was observed for Zn (σ = 2.058 /μg/g) in fish muscle, for Fe and Mn in sediment (σ = 27481 and 44.50 μg/g) and for As in water (σ = 0.270 μg/L). The metal distribution data pertaining to water, fish and sediment were examined on the basis of simple metal correlations. The statistical study revealed that Ni, Cr, Pb and Cu had significant positive correlations (r > 0.830 at ρ = 0.01). The finding substantiated a trace metal concentration gradient in the area, thereby indicating that the local marine environment is contaminated by anthropogenic sources.     

有色矿业区耕作土壤、蔬菜和大米中重金属污染

有色金属矿业区周边土壤重金属污染严重,对我国生态环境质量、食品安全和人体健康构成了一定威胁,研究典型矿业区周边复合污染地带的土壤环境质量及其食物安全对促进其可持续发展具有深远的意义。从湖南省的长沙、株洲、衡阳、郴州等有色金属矿业区收集耕作土壤、蔬菜和大米样品,结合主成分分析、聚类分析和相关分析,研究其中重金属元素的累积和迁移特征,评估蔬菜和大米中重金属元素对人体健康的潜在危害程度。研究结果表明,耕作土壤中主要重金属污染元素为Cd、As、Pb、Cu、Zn等;主成分分析表明,菜地土中第一主成分主要反映了Pb、Zn、Cd、As的复合污染信息以及与土壤pH的相关关系;水稻土中第一主成分主要反映了Cu、Zn、Pb、Cd的复合污染信息;聚类分析进一步阐明耕作土壤以Cd、Pb、As、Cu、Zn为主的复合污染特征。研究区蔬菜中Cd、Pb、As、Cu、Zn、Cr含量,大米中Cd、Pb和Zn含量均明显超过我国食品卫生标准;蔬菜中Cd、Pb、As和大米中Cd、Pb对人体健康的潜在危害较大。     

工业城市不同功能区土壤和蔬菜中重金属污染及其健康风险评价

为了研究和评价工业城市不同功能区的土壤和蔬菜中重金属污染和健康风险状况,以株洲市为例,在工业区（石峰区）、农业区（芦淞区）和旅游区（大京风景区）分别采集土壤和蔬菜样品,分析重金属Cd、As、Pb、Hg、Zn、Cr和Cu的质量分数,并采用地质累积指数法（Igeo）和健康风险评价模型分别对土壤和蔬菜中重金属进行评价。结果表明：工业区、农业区和旅游区土壤中Cd、As、Pb、Hg、Zn、Cr和Cu的平均质量分数都超出湖南省土壤背景值,部分重金属甚至超出国家土壤环境质量二级标准。不同功能区土壤中重金属的地质累积指数（Igeo）表明：工业区、农业区和旅游区土壤受到不同程度的重金属污染,其中Cd和Hg的污染最为严重,污染程度依次是工业区〉农业区〉旅游区。不同功能区蔬菜中Cd、As、Pb和Zn的危害商（HQ）值都大于1.0,而Cu和Cr的危害商（HQ）都小于1.0。不同功能区蔬菜中重金属危害指数（HI）都大于10.0,尤其是工业区蔬菜的危害指数（HI）〉100.0,当地成年人食用受到重金属污染的蔬菜会导致严重的健康危害,其中Cd和As,是危害指数（HI）的主要贡献者,两者贡献率之和的范围为75%~89%,而Cr的贡献率几乎为0。     

Seasonal variation and partition of trace metals (Fe, Zn, Cu, Mn, Cr, Cd and Pb) in surface sediments: relationship with physico-chemical variables of water from the Calabar River, South Eastern Nigeria

The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are reported. Chemical partition of the metals in the sediments reveals that 2–30% of the total metal load was contributed by the non-detrital (acid-soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70–98%). Using multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physio-chemical changes (dissolved oxygen, pH, salinity and conductivity) in the water column. Fe–Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and detrital trace metals in the sediments. On the basis of index of geoaccumulation (I-geo) and comparison with previous studies, the Calabar River surface sediments have been classified as unpolluted.     

Bioaccessibility of metals in soils: comparison between chemical extractions and in vitro tests

It is well-known that the total metal content in soils is not a good indicator of their harmful effects, leading to an overestimation of risks. Toxicological and environmental hazards depend on the chemical species and on its bioavailability to target organisms. Because a good estimation of bioavailability is difficult, a good compromise is to assess bioaccessibility, defined as the maximum amount of a pollutant which is potentially absorbable by a target organism. This study presents a comparison of different strategies to measure metal bioaccessibility in soils. Three procedures were applied to real soil samples with different levels of metal contamination: pseudo-total metal attack, selective sequential extractions and in vitro tests (deliberately developed to simulate human or mammals digestion). Considering the first step of the selective extraction procedure, which can provide the bioaccessible fraction for deposit-feeder organisms, data obtained for each metal were lower than those obtained from in vitro tests. Therefore, it is possible to highlight that this extraction tends to underestimate metal bioaccessibility in soils for humans, while in vitro tests certainly will overestimate bioaccessibility for organisms as invertebrates. If the sum of first and second step of sequential procedure is considered, results are quite similar to those obtained from in vitro tests, but this kind of procedure would require two days of work rather than a few hours required to perform an in vitro test. Results highlight the diversity among the differently defined bioaccessible fractions and the need to apply the most suitable procedure depending on the target organism.     

Toxicity and bioaccumulation of heavy metals in mullet fish Liza klunzingeri (Mugilidae: Perciformes)

The mullet fish, Liza klunzingeri, commercially important and widely relished by Kuwaiti residents, and the stressed ecosystem in Kuwait Bay instigated us to conduct toxicity and bioaccumulation tests on heavy metals (Pb, Ni, V, Cu and Fe). Among five metals, Pb had the lowest observed effect concentration (LOEC) at 1 μg?l ^?1. Using multi-factor Probit analysis, toxicity tests (72 h) on L. klunzingeri reared in filtered sea water in the laboratory showed Pb with maximum effect at median lethal concentration (LC₅₀) followed by V, Ni, Cu and Fe. Their bioaccumulation factor (BAF) was in the sequence Pb>V>Fe>Cu and Ni. For fish exposed for 30 d, bioaccumulation exhibited increasing metal levels in liver followed by gills and muscles. These results suggest the potential use of L. klunzingeri as a bioindicator of metal pollution in the future.     

长岛岸滩及岩石附着油污指纹特征比对

选择长岛典型的两个旅游景点的岩石和岸滩附着的8个溢油样品,对样品中的饱和烷烃、萜烷、甾烷及多环芳烃化合物的分布特征及典型生物标志物诊断比值进行了比对分析.t检验结果表明,置信度为95%时,8个油样的生物标志物诊断比值指标均不能够完全匹配,不可判定其来自同一油源.九丈崖溢油样品之间差异性高于月牙湾.可见,长岛九丈崖岩石和月牙湾岸滩附着溢油样品之间具有较大相似度,但指纹特征各不相同,部分样品差别较大,具有混合油的指纹特征,为多次溢油的混合油样.     

Occurrence and health risk assessment of trace heavy metals via groundwater in Shizhuyuan Polymetallic Mine in Chenzhou City,China

The Shizhuyuan Polymetallic Mine in Chen-zhou City is an important multi-metal deposit in China. After a dam accident in 1985, there are still a number of mining plants, smelters and tailing ponds in this area. These had the potential to pollute the surrounding groundwater. In this study, groundwater samples were collected from 20 residents’ wells in this area during both dry and wet seasons. In particular, this study focused on the exposure and the health risk assessment of trace heavy metal in groundwater. Multiple statistical analysis and fuzzy comprehensive method were employed to reveal the distribution characteristics of heavy metal and to assess the groundwater quality. Results indicated that Cr, Fe, Ni, Cu, Zn, As, Cd, Ba, Hg and Pb were widespread with low exposure levels. There were 19 wells with low level exposure and one well with a moderate level exposure in the dry season. All of the wells were in low level exposure during the wet season. As and Mn exhibited potential non-carcinogenic concern, because their maximum hazard quotient (HQ) was higher than 1.0. This may cause adverse health effect on adults in dry season or on children in both seasons. Only As, showed that the maximum carcinogenic risk was more than 10⁻⁴, suggesting a high cancer risk for children in both dry and wet seasons. Therefore, analysis and reduction the concentrations of As and Mn in groundwater are needed in order to protect the health of residents and especially children in the area.