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.     

An assessment of contamination and ecological risk of metals in sediments of the Guaracara,Caparo and Couva rivers in Trinidad,West Indies

The presence of metals in an aquatic environment can serve as a biomarker for pollution and can be used to evaluate its contamination status. Rapid industrialisation in recent decades has propelled Trinidad and Tobago to be one of the most developed nations within the Caribbean region and has stimulated the awareness of potential ecological risks from various industrial activities affecting the rivers of Trinidad. Sediment samples from three rivers along the West coast of Trinidad were analysed for Cd, Cr, Cu, Mn, Ni, Pb and Zn. For all three rivers, the metal concentrations in sediments were in the range of 0.40–2.31?μg/g, 12.77–33.04?μg/g, 14.51–72.89?μg/g, 224.90–4472.83?μg/g, 8.20–43.08?μg/g, 22.63–38.34?μg/g and 92.0–5462.60?μg/g for Cd, Cr, Cu, Mn, Ni, Pb and Zn, respectively. Assessment of the pollution status indicated that all three rivers were considered polluted, with significant contributions from Cr, Cu, Mn, Ni and Zn. The potential ecological risk for all three rivers, however, was low and multivariate statistics revealed that mainly anthropogenic sources contributed to the metal concentrations in sediments of all three rivers.     

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.     

Vertical Distribution and Inventories of 239,240Pu in Deep Sea Sediments of the Mediterranean Sea (Algerian Basin, Ionian Sea)

Deep-sea sediments collected in two areas of the Mediterranean Sea having different sedimentological characteristics have been analyzed to determine present concentrations and inventories of ^239,240Pu and to study the main mechanisms controlling them. Plutonium distribution in the deepest part of a submarine canyon (Taranto Valley, Ionian Sea) is compared to that obtained in an abyssal plain (north Algerian Plain). in the latter case, sedimentation is mainly due to the sinking of biogenic particles, while in the former lateral transport of terrigenous material along the slope of the canyon can significantly contribute to sediment accumulation on the bottom.

^239,240Pu surface concentration in the canyon ranged from 0.2 to 1 Bq kg^-1 (dry weight) and this was lower in the abyssal plain. in this area, plutonium was detectable only in the first 4 cm, while in the canyon it was present down to 11-15 cm. ^239,240Pu inventories are 3 Bq m^-2 in the plain and 45-60 Bq m^-2 in the canyon, indicating considerable input of terrigenous material towards the final part of the Taranto Valley.     

Spatial distribution and ecological risk assessment of heavy metals in surface sediments from a typical plateau lake wetland, China

Surface sediment (0-15 cm) samples were collected from 31 different grid points throughout the Yilong Lake in April 2004. Samples were subjected to a total digestion technique and analyzed for As, Cd, Cr, Pb, Ni, Cu, and Zn in order to study spatial distribution characteristics based on Kriging method and assess their ecological risks posed by these heavy metals. Results showed that the mean concentrations of these heavy metals were lower than potential effect levels. Patches of higher heavy metal concentrations occurred in the inflow area of the Cheng River and northeast area nearby the road and railway. The higher concentrations of As and Cr also appeared in the east area (lake outlet), while the patches of lower concentrations were uniformly distributed at the southwest corner between Luosewan and Xiaoguoxi. The heavy metal loads such as As, Cd and Pb might come from the common sources due to industrial sewage and traffic pollution, while higher concentrations of Ni, Cr, and Zn in these sediments were dominated by parent rocks. However, Cu originated from both sources. Sediments with respect to As, Cd and Cu were grouped below the effect range low (ERL) at all sites, and with respect to Cr and Pb were grouped into the range from ERL to the effect range median (ERM) at more than 50% of sampling sites. The mean heavy metal toxic units in the Yilong Lake decreased following the order Pb > Cr > As > Ni > Zn > Cd > Cu, with higher contributions to the sum of toxic units of Pb, Cr and As.     

Zooplankton responses to hydrological and trophic variability in a Mediterranean coastal ecosystem (Lesina Lagoon,South Adriatic Sea)

Spatial and temporal variability in zooplankton was studied at eight stations located in the Lesina Lagoon (South Adriatic Sea) Salinity, temperature, dissolved oxygen and chlorophyll a (in the lagoon) at these stations were also assessed. The zooplankton community was characterised by clear seasonal oscillations and mostly represented by copepods and their larvae. The dominant copepod species were Calanipeda aquaedulcis and Acartia tonsa, which exhibited spatial–temporal segregation in the lagoon. C. aquaedulcis copepodites seemed to be better adapted to oligotrophic and oligohaline conditions compared with the A. tonsa population. The invasive species A. tonsa has completely replaced the formerly abundant Acartia margalefi. A positive correlation was found between abundances, total species numbers and trophic state. An increasing abundance trend was shown from the lagoon towards the sea. The highest diversity indices were recorded at the two channel inlets, during high tide due to the absence of a clear dominance of one or more coastal species and the co-occurrence of species of lagoon and marine origin.     

Contamination levels and state assessment in the lakes of the Oliveri-Tindari Lagoon (North-Eastern Sicily,Italy)

The Oliveri-Tindari Lagoon, located in North-Eastern Sicily (Italy) and composed of six lakes, is subject to continuous environmental changes. An integrated study focusing on sediment features and levels of contamination was carried out for three of the six lakes, which are of ancient origin: Verde, Mergolo della Tonnara and Marinello. A high primary production (26.89 μg l^?1) was detected at Lake Verde; texture classification showed a typical grain size in the sediments of all lakes; the study of macronutrients highlighted 17.08 of total carbon in sediments from Lake Mergolo della Tonnara; toxic elements were detected at higher concentrations in the sediments of Lake Marinello in comparison to the others, while arsenic was found in high concentrations in all the samples tested, especially in Lake Verde, with a mean value of 17.25 mg kg^?1 dry weight (d.w.). All the organic contaminants, except 4, 4′-dichlorodiphenyldichloroethylene, were below the detection limits in the sediments. Minimal microbiological contamination was found in both water and sediment samples. In the latter, we isolated several bacterial strains thriving in the presence of arsenic, which play a role in the biogeochemical cycle of arsenic. These preliminary results, obtained for the first time using a multidisciplinary approach, provide general information about the Oliveri-Tindari Lagoon area.     

Organochlorines in the surface sediments of the Bahiret el Bibane lagoon (Tunisia,Southwestern Mediterranean Sea)

Organochlorines (including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs)) were analysed in 10 surface sediment samples collected from the Bahiret el Bibane lagoon, which is one of the most productive lagoons and one of the most important active commercial fish traps in the southern Tunisia. The aim was to obtain information concerning the recent deposition of these compounds in this area, together with the levels, the distribution and any potential biological risk. Total concentrations of OCPs and PCBs in the sediments ranged from below the limit of detection (?1 and from 29.5 to 88.2?ng?g^?1?dw, respectively. The spatial distribution of PCBs suggested that the sources of these contaminants are probably located outside the lagoon and are transported by water currents and atmospheric deposition. Compared with some other regions of the world, the Bahiret el Bibane lagoon exhibited low to moderate levels of PCBs and OCPs. According to established sediment quality guidelines, PCBs and Lindane at most of the study sites would be more concerned for the ecotoxicological risk in the Bahiret el Bibane lagoon. The results of this study could provide a useful aid for the sustainable marine management of the region.     

Bioaccumulation of heavy metals in Octopus vulgaris from coastal waters of Alexandria (Eastern Mediterranean)

Heavy metal concentrations (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined in various tissues (hepatopancreas, branchial hearts, salivary gland, gills, genital tract, mantle, arms and skin) of Octopus vulgaris collected from three different contaminated sites in front of Alexandria (Egypt) during 2000. All collected tissues displayed high enrichment factors when compared to ambient levels. Heavy metal concentrations in most tissues displayed significant differences among sites, sizes and sex. This study suggests that hepatopancreas, and to a lesser extent branchial hearts, are better indicators of chronic Cu, Fe, Zn and Cd contamination than edible tissues. The enrichment factor (EF) for heavy metals in the hepatopancreas and in edible tissues allowed discriminating our samples into three main groups; (1) EF?>?55 (Cu), (2) EF ranging from 15 to 7.5 (Fe, Cd and Zn) and (3) EF?相似文献   

Geographical distribution and risk assessment of heavy metals: a case study of mine tailings pond

ABSTRACT

In China, a large number of tailings deposited on natural surfaces, the potential risk of tailings attracts people’s attention. In this study, heavy metals distribution, geo-accumulation index, ecological risk index, microbial diversity and community were examined to evaluate the risks of a tailings pond. Results indicated the tailings pH is about 8.17, and the redox potential was lower than zero. Heavy metals could be leached and migrate from the tailings. The tailings pond had more influence on the distribution of Pb, Zn, As, Cu, and S. The influence distance of Pb, Zn, and Cu was less than 10?m, and the influence distance of As and S was less than 50?m. S and As had stronger migration capability than other elements in the soil. The biggest potential ecological risk resulted from Pb, and the distances more than 100?m had low ecological risk. The tailings decreased microbial richness and diversity of the surrounding environment. Oxidising bacteria and reducing bacteria existed in both the tailings and the surrounding soils; however, there were more oxidising and reducing microbes in the tailings than in the surrounding soils. The tailings pond currently has little impact on the environment, but the potential risk still exists.     

成都市河流表层沉积物重金属污染及潜在生态风险评价

根据流经成都市内的三条河流（府河、南河、沙河）表层沉积物重金属数据，采用Hakanson潜在生态危害指数法对重金属的潜在生态风险进行了评价。结果表明（1）重金属潜在的生态危害因子（Er^i）说明大多属于轻微生态危害范畴，产牛生态危害的主要重金属是Hg、Cd，Cu、Pb次之，As影响最小；（2）多种重金属的生态系统的潜在生态风险指数（RI）表明河流重金属污染属于轻微生态危害和接近中等生态危害，其受危害程度由强至弱的次序为：府河，南河，沙河。     

Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts,Mediterranean Sea)

To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By contrast, the lowest polluted zones showed a high population density and the highest percentages of epiphytes. Epiphytes were abundant where a Posidonia oceanica meadow was present and decreased in the most polluted zones. Sediments of the Gulf of Termini and Lampedusa exhibited high percentages of benthic foraminifera typical of well-oxygenated waters and low concentrations of metals, with the exception of sites located near sewage outfalls and harbour areas. Furthermore, even though deformed tests are commonly known in natural stressed environmental conditions, this study shows that in the most polluted zones, benthic foraminifera were characterised by the highest percentages of deformed individuals.     

Mercury distribution,speciation and potential ecological risk assessment in sediments from Lake Taihu,China

Abstract

Twenty-one surface sediments collected from seven surroundings areas of Lake Taihu in two different years were analyzed for total mercury (THg) concentrations, physicochemical characteristics and speciation using a sequential extraction method to assess spatial distribution, sources, and potential ecological risk. Surface sediments from Lake Taihu contained elevated levels of Hg in two sampling years with THg levels ranging from 77 to 346?ng/g (mean 145?ng/g) in October 2010 and ranging from 122 to 573?ng/g (mean 266?ng/g) in November 2012, respectively. The mean THg concentrations in all studied surface sediments exhibited an increasing trend over time. The oxidizable fraction (F3) and residual fraction (F4) were the predominant Hg species in sediments, while more mobile Hg phases of acid-soluble fraction (F1) and reducible fraction (F2) made up less than 0.5% THg. Significant relationships were found between total organic carbon (TOC) and THg and geochemical speciation indicating an important role for organic matter in affecting distribution, mobility, and bioavailability of Hg in sediments. As evidenced by Hakanson’s potential risk index the total ecological risk of Hg was low in the entire Lake Taihu in 2010 but considered moderate in Zhushan Bay, West Coast, and Meiliang Bay in 2012. These findings provide conservation managers with information needed to more effectively regulate the environment of Lake Taihu.     

镇江市古运河河岸沉积物重金属分布特征及潜在生态风险评价

对镇江市古运河河岸7个表层沉积物中重金属As、Cu、Pb、Cd、Zn、Cr含量进行测定,并通过富集系数、地累积指数法、潜在生态风险评价以及主成分分析等对沉积物重金属的分布特征进行综合分析与评价.结果表明:(1)古运河河岸带沉积物Cr、Cu、Zn、As、Pb和Cd元素的含量平均值分别为45.07、41.70、254.06、19.67、45.88、0.75 mg·kg-1,p H平均值为7.98.对比《国家土壤环境质量标准》可知,沉积物中Cu、Zn、Pb、As属于超一级标准,而Cd属于超二级标准.(2)6种重金属的富集系数表现为:AsCdPbZnCuCr,且综合富集系数在空间上表现为:G2G5G1G4G3G7G6;(3)古运河河岸表层沉积物地累积指数表现为AsCdPbCuZnCr,6种重金属中As富集量最大,Cr的富集量最小.(4)单项潜在生态危害系数结果表明,Cr、Cu、Zn、Pb均为轻微生态危害程度,As和Cd处于中等生态危害程度.从RI值判断,古运河河岸沉积物总体处于轻微生态危害.(5)相关性和主成分分析结果表明,Pb、Cu、Cr、Cd是决定第一主成分的4个主要因子,且Cu与Pb、Cd以及Pb与Cd元素具有相同的污染源.As、Zn在第二主成分中具有较高的载荷值,且As与Zn之间的相关性较弱,表明这两种重金属并非来自同一污染源.     

Sources and Distribution of Heavy Metals in East China Sea Surface Sediments

Box cores and surficial sediments collected from the shelf, slope and Okinawa Trough of the East China Sea were analyzed for loss on ignition, and concentration and speciation of Al, Fe, Mn, Pb, Cd, Cu and Zn. in general, concentrations of these metals are higher in the inner shelf and lower in the midshelf, but the highest LOI, Cd and Mn levels are found in the Okinawa Trough. Spatial distributions of these metals in surficial sediments indicate that the Yangtze River is the major source for materials deposited in the inner shelf. the results of a six-stage sequential leaching experiment indicate that the fluvial input includes natural (e.g., Al and Fe) and anthropogenic (e.g., Pb) materials. the depletion concentration of these metals in the midshelf sediments reflects the dominance (～ 70%) of coarse, relict sand, while the enrichments in the inner shelf and the Okinawa Trough sediments are due to the fine grained, organic-rich sediments. the speciation of Mn in the sediments of the Okinawa Trough indicates that its distribution is diagentically or hydrothermally controlled.     

Metal distribution in marine sediments of the Mar Piccolo in Taranto (Ionic Sea,southern Italy)

The spatial distribution of selected metals (Fe, Ni, Mn, Zn, Cu, Pb, Hg and Cd) and their partition in the different chemical forms (speciation) were determined in benthic sediments from Mar Piccolo, Taranto (Ionic Sea, southern Italy). The aim of this study was to assess the degree of sediment contamination and bioavailability of metals, very important for Italian mussel culture, in a semi-enclosed marine ecosystem. In sediments, grain size distribution, total organic carbon (TOC), and humic (HA) and fulvic (FA) acids contents were also determined. The compounds TOC, HA and FA, in fact, have a great influence on metal complexation. High concentrations of copper, lead, zinc and mercury were found, especially in sediments of the first inlet of Mar Piccolo. Statistical analysis of results shows significant correlation among Cu, Pb and Zn concentrations and the influence of organic matter on the sediment distribution of Cu, Pb and Zn. Metal speciation analysis, carried out with sequential extraction method, shows that Fe and Ni are present in sediments mainly as sulphides. Mn and Pb are present principally in an ion-exchangeable form or bound to carbonate and Cu is associated to organic matter. Metal pollution index (MPI), calculated as a weighed mean of the metal contamination factors in each station, shows that with regard to Cu, Ni, Pb and Zn, some stations investigated are unpolluted (MPI <1), whereas in other areas, pollution level is not very high. On the contrary, for mercury, the pollution level in the first inlet of the basin is very high.     

Sources and Distribution of Heavy Metals in East China Sea Surface Sediments

Box cores and surficial sediments collected from the shelf, slope and Okinawa Trough of the East China Sea were analyzed for loss on ignition, and concentration and speciation of Al, Fe, Mn, Pb, Cd, Cu and Zn. in general, concentrations of these metals are higher in the inner shelf and lower in the midshelf, but the highest LOI, Cd and Mn levels are found in the Okinawa Trough. Spatial distributions of these metals in surficial sediments indicate that the Yangtze River is the major source for materials deposited in the inner shelf. the results of a six-stage sequential leaching experiment indicate that the fluvial input includes natural (e.g., Al and Fe) and anthropogenic (e.g., Pb) materials. the depletion concentration of these metals in the midshelf sediments reflects the dominance (∼ 70%) of coarse, relict sand, while the enrichments in the inner shelf and the Okinawa Trough sediments are due to the fine grained, organic-rich sediments. the speciation of Mn in the sediments of the Okinawa Trough indicates that its distribution is diagentically or hydrothermally controlled.     

The distribution of heavy metals in deposited urban dusts and sediments, Coventry, England

Samples of urban dusts and sediments have been collected and categorised into three compartment those which act mainly as sources, those undergoing transport and those which have been deposited. The sediments were fractionated into <63m to match similar sized lacustrine sediments and <2mm to represent natural and anthropogenic fluvially transported sediments. Preliminary results of total heavy metals analysis show that the <2mm fraction of the source group exhibits the greatest variabilty in metal concentrations. Overall, however, the <63m fraction dominates regardless of compartment. Some heavy metal concentrations decrease through the sourcetransportdeposit process, possibly due to selective onward transport of finer material or other anthropogenic processes unique to the urban environment (e.g. street cleansing). Sitespecificity is indicated in a comparison with other similar studies.