Heavy metal accumulation in the surficial sediments along southwest coast of India

Concentration and distribution of heavy metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface sediments collected from five stations located along the southwest coast of India were investigated seasonally to assess whether there is insidious buildup of heavy metals. Spatial variation was in accordance with textural characteristics and organic matter content. The concentration of the metals in sediments of the study area followed the order: Zn > Cr > Ni > Cu > Pb > Cd > Hg. The use of geochemical tools and sediment quality guidelines to account for the magnitude of heavy metal contamination revealed high contamination in monsoon and impoverishment during post-monsoon. Estimated total metal concentrations in the present investigation were comparable with other studies; however, concentrations of Ni and Zn were higher than that of other coastal regions. Concentrations of metals in sediment largely exceed NOAA effects range:low (e.g., Cu, Cr, Hg) or effects range:median (e.g., Ni) values. This means that adverse effects for benthic organisms are highly probable.     

Marine muds along the Guyana coast and their origin from the Amazon basin

The mineralogical composition of clay samples from the Amazon basin and the Guyana coast, including samples collected inland and on the continental shelf, was investigated by X-ray diffraction. Also humus content, specific surface and degree of potassium fixation were determined. The muds from the Guyana coast have virtually the same composition as those of the Amazon but are very different from the Guyanese soils and river muds. This suggests that most Guyanese coastal muds come from the Amazon which is confirmed by a consideration of the quantities involved. The only measurable effect of the sea water on the mud particles moving from the Amazon to Venezuela, which takes from one month up to 1000 years, is a decrease in potassium fixation, indicating that some potassium has been taken up from the sea water. The presence of large amounts of soil chlorite in shelf samples may be due to a prolonged contact with sea water but most probably is the result of subaereal conditions during the Pleistocene.     

Heavy metal concentrations in roadside-deposited sediments in Kuwait city

In the present study, roadside-deposited sediment samples collected from Kuwait city district, in Kuwait, were analyzed for specific heavy metals (As, Cr, Cu, Mn, Ni, Pb, and Zn). Contamination assessment status of heavy metals in roadside sediments was made using mathematical models in terms of enrichment factor (EF), geoaccumulation index (I _geo), and contamination factor (CF). The sediments showed remarkably high levels of all the metals, except Ni, above background concentrations in the following order (As, Cu, Pb, Zn, Mn, and Cr). CF and I _geo revealed overall moderately uncontaminated and moderate contamination, respectively, but the EFs for all metals ranged between moderate and significant enrichment.     

Heavy metal concentrations in sediments and in mussels from Argentinean coastal environments,South America

Among environmental contaminants, heavy metals are currently considered to be some of the most toxic ones present worldwide due to their harmful effects on organisms and ability to bioaccumulate in aquatic systems. In this work, the concentration of heavy metals (Cd, Cu, Pb, Zn, Ni and Cr) in Brachidontes rodriguezii and in the fine sediments of several coastal sites at the southwest of Buenos Aires Province, Argentina is analyzed. The Bahía Blanca Estuary and Pehuen-Có beach are located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing commercial species. An assessment, which involved analyzing distribution pattern of trace metals, comparative studies with sediment and ecological quality guidelines; and a sequential and integrated index analyses approach (containing Metal Pollution Index, Biosediment Accumulation Factor, Geo-accumulation Index (Igeo), Pollution Load Index and the mean Probable Effect Level quotients), was followed to estimate enrichment and risks of heavy metals in the sediments and in the mussels from these study areas. The results showed higher concentrations of some heavy metals (e.g., Cd, Cr and Ni) in mussels collected at Pehuen-Có, while no spatial differences in sediments were observed. According to the international environmental regulations, mean values of trace metals in mussels allowed to place both sites between “unpolluted and moderately polluted” and between the “low and medium category” of pollution. Furthermore, the mean concentrations found were within the detected ranges in other coastal sites worldwide.     

Heavy metal pollution assessment in marine sediments in the Northwest coast of Sabah,Malaysia

Heavy metal contents along the Northwest coast of Sabah were determined to interpret the pollution level in the marine sediment. The metal abundance is regulated by the physico-chemical properties such as the average sediment pH(7.82, 9.00 and 8.99), organic matter(0.62%, 1.60%, and 2.27%), moisture content(25.00%, 29.70%, and 15.00%) and sandy texture in Kota Belud, Kudat and Mantanani Island,respectively. The major elements show Ca>Fe>Mg>Al>Mn for all study sites, while the heavy m...     

Hydrocarbons in surficial sediments from the Scotian Shelf

Surface sediments from 20 stations on the Scotian Shelf, collected on a transect from Halifax to Emerald Bank and around Sable Island, have been analyzed for hydrocarbon content and composition by gas chromatography and fluorescence spectrophotometry. Some samples were taken near abandoned exploratory drilling sites in the Sable Island area. Hydrocarbons appear to be mainly derived from biogenic terrestrial sources as evidenced by an inverse correlation of concentration with increasing distance from the mainland and a strong odd carbon preference in the n-alkanes. Contribution from petroleum sources, while minor, was most noticeable between Halifax and Emerald Bank. There is also evidence that the hydrocarbon composition at abandoned exploratory drilling sites has been slightly altered.     

Methane flux from mangrove sediments along the Southwestern coast of Puerto Rico

Although the sediments of coastal marine mangrove forests have been considered a minor source of atmospheric methane, these estimates have been based on sparse data from similar areas. We have gathered evidence that shows that external nutrient and freshwater loading in mangrove sediments may have a significant effect on methane flux. Experiments were performed to examine methane fluxes from anaerobic sediments in a mangrove forest subjected to secondary sewage effluents on the southwestern coast of Puerto Rico. Emission rates were measured in situ using a static chamber technique, and subsequent laboratory analysis of samples was by gas chromatography using a flame ionization detector. Results indicate that methane flux rates were lowest at the landward fringe nearest to the effluent discharge, higher in the seaward fringe occupied by red mangroves, and highest in the transition zone between black and red mangrove communities, with average values of 4 mg CH₄ m^?2 d^?1, 42 mg CH₄ m^?2 d^?1, and 82 mg CH₄ m^?2 d^?1, respectively. Overall mean values show these sediments may emit as much as 40 times more methane than unimpacted pristine areas. Pneumatophores ofAviciennia germinans have been found to serve as conduits to the atmosphere for this gas. Fluctuating water level overlying the mangrove sediment is an important environmental factor controlling seasonal and interannual CH₄ flux variations. Environmental controls such as freshwater inputs and increased nutrient loading influence in situ methane emissions from these environments.     

The geostatistics of the metal concentrations in sediments from the eastern Brazilian continental shelf in areas of gas and oil production

Geostatistical techniques were used to evaluate the differences in the geochemistry of metals in the marine sediments along the Eastern Brazilian continental margin along the states of Ceará and Rio Grande do Norte (Northeastern sector) and Espírito Santo (Southeastern sector). The concentrations of Al, Fe, Mn, Ba, Cd, Cu, Cr, Ni, Pb, V, Hg, and Zn were obtained from acid digestion and quantified using flame atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The metals showed a similar order of concentration: Al > Fe > Ba > Mn > V > Ni > Pb > Cr > Zn > Cu, in both the Ceará; and Rio Grande do Norte shelf regions but different in the Espírito Santo shelf (Fe > Al > Mn > Ba > Zn > V > Cr > Ni > Pb > Cu. The concentrations of Hg and Cd were below the detection limit in all areas. A multivariate analysis revealed that the metals of siliciclastic origin on the continental shelf of Ceará are carried by Al. In addition, a large portion of metal deposits is connected to the iron and manganese oxides on the continental margin of Rio Grande do Norte. The metals from the continental supply on the coast of Espírito Santo (Cu, Ni, Ba, and Mn) are associated with Al; whereas Cr, Pb, V, and Zn are associated with iron in this southern area. Geochemical evaluations are needed to distinguish the origin and mineralogical differences of marine sediments within the regions. Scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) applied to the sediments from the coast of Ceará showed the morphological diversity of sediment grains: biological fragments, multifaceted particles, aggregates, and crystals occurred in the three regions analyzed. Among these grains, calcite, Mg-calcite, and aragonite were predominant in the northeastern sector, whereas silicates and other minerals were predominant the southeastern sector. Mg, K, Ti, and Zr as well as the lanthanides La and Ce were identified using SEM/EDS and added to the geochemical analysis of the data.     

深圳沿海表层海水与地表水关系的地球化学分析

依据深圳沿海所取31件表层海水样品的水化学数据,对主要离子Ca2+、Mg2+、Na+、K+、SO42-和HCO3-与C l-以及B r-与C l-的关系作散点图分析。西海岸表层海水Ca2+、K+、SO42-和HCO3-与C l-的比偏离海水稀释线,源于其位于珠江河道影响范围,与珠江水有不同程度的混合;东海岸表层海水Ca2+、K+和HCO3-与C l-的比主要围绕海水稀释线波动,表明沿海表层海水流动缓慢,受表层海水蒸发和当地沿岸污染河水排泄的长期累积影响;靠近深圳湾的5件西海岸海水样品成分与东海岸表层海水相似。     

Effect of waves in the redistribution of sediments along the Konkan coast

From the wave refraction diagrams it is delineated that the Jaigad Head and Warori Bluff are the zones of wave energy convergence and the Narvan and Ambwah bays the areas of wave energy divergence. The presence of two distinct mineral phases noticed at the Jaigad, Ambwah and Varvade bays shows that there are two different circulations of sediment movements. The presence of natural barriers restricts the movement of sediment along the coast. The sand bar at the mouth of the Jaigad Bay has different orientations during the monsoon and non-monsoon periods causing obstruction to navigation during the former period.     

Normalization of metal concentrations in estuarine sediments from the Gulf of Mexico

Metal concentrations were examined in sediments from 497 sites within the estuaries of the Gulf of Mexico by the United States Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP). Data were normalized for extant concentrations of aluminum to isolate natural factors from anthropogenic ones. The normalization was based on the hypothesis that metal concentrations vary consistently with the concentration of aluminum, unless metals are of anthropogenic origin. Strong linear correlations (>75% variation explained) were observed between Al and Cr, Cu, Pb, Ni, and Zn. Moderate correlations (50–75% variation explained) were observed between Al and As or Ag. Weak but significant correlations (30–40% variation explained) were observed between Al and Hg or Cd. Based on these results, the spatial extent of contamination was examined. About 39% of sites with contamination by at least one metal occurred near population centers, industrial discharge sites, or military bases. The remainder of the observed contamination represented a dispersed pattern, including the lower Mississippi River (7%) and numerous agricultural watersheds (54%), suggesting that the contamination might be from nonpoint sources.     

Heavy metal distribution in surface sediments of the Tirumalairajan river estuary and the surrounding coastal area, east coast of India

Surface sediments collected at the Tirumalairajan river estuary and their surrounding coastal areas were analyzed for the bulk metal concentration. The sediments were collected from post- and premonsoon seasons. Dominances of heavy metals are in the following order: Fe > Mn > Zn > Pb > Cu in both seasons from estuary and coastal area. The results reveal that Fe, Mn, Cu, Pb, and Zn demonstrated an increased pattern from the estuary when compared to the coastal area. The heavy metal pattern of the sediments of the Tirumalairajan river estuary and its surrounding coastal area offered strong evidence that the coastal area was a major source of heavy metals to the estuarine region. For various metals, the contamination factor and geoaccumulation index (I _geo) have been calculated to assess the degree of pollution in sediments. The contamination factor and geoaccumulation index show that Zn, Pb, and Cu unpolluted to moderately pollute the sediments in estuarine part. This study shows the major sources of metal contamination in catchment and anthropogenic ones, such as agriculture runoff, discharge of industrial wastewater, and municipal sewage through the estuary and adjoining coastal area.     

Heavy metal distribution in sediments from Calabar River, southeastern Nigeria

The concentration and areal distribution of selected metals (Pb, Zn, Cu, Cd, Ni, Fe, and Cr) in the sediments of the Calabar River were studied to determine the extent of anthropogenic input and to estimate the effects of dumping industrial waste materials into the river. The concentrations of Pb, Zn, and Cu indicate relatively moderate pollution mainly on the left-hand side of the river while Ni, Cr, Co, Cd, and Fe levels are below values found to have adverse effects on the lives of marine biota. High metal contents are found close to industrial establishments and so enhanced metal concentrations are related to industrial sewage and metal leaching from garbage and solid waste dumps.     

Heavy metal concentrations in water and surface sediments of Maharlou Lake, SE of Shiraz, Iran

The main objective of this study is to evaluate trace metal distribution and identify their sources in the Maharlou Lake. Trace metals （Cr, Co, Ni, Cu, Zn, Cd, Pb） and major elements （A1, Ca, Fe, K, Mg, Mn, Na, P） were investigated in water and surface sediments. There was a negative relationship between the depth of water and heavy metal concentration. Metal concentrations in water and sediment samples show a high variability and decrease in this order： Al〉Fe〉Ni〉Co〉Pb〉Zn〉Cu〉Mn〉Cd. In the northern parts of the lake, especially at the inflow of drains and the Khoshk River of Shiraz City, metal concentrations are higher in both water and sediment samples. In order to assess the heavy metal enrichment in sediment samples, trace metal concentrations were normalized for Al. Except for Mn, all metals are enriched relative to average crust and average sedimentary rocks. Also, the results showed that stations located at the northern coast of the lake, have higher enrichment factors （EF） than the other stations. The results of this study showed that the Khoshk River and other drains are the main pollutant sources of the Maharluo Lake.     

Particulate metal speciation in surficial sediments from Loch Dee, southwest Scotland, U.K.

The geochemical partitioning of ten elements in stratified Holocene sediments from Loch Dee, southwest Scotland, has been established by use of a five-stage sequential extraction procedure. Samples from below 15 cm sediment depth show minimal evidence of modification by anthropogenic contamination or active diagenesis and hold Fe, Mg, Cu, Cd, Co, Pb, and Ni primarily in detrital silicates or organic complexes, while Mn, Ca, and Zn reside largely in adsorbed and reducible oxide phases. In the uppermost ca 15 cm of sediment, enhanced total concentrations of Zn, Cu, and Pb reflect increased atmospheric deposition during the postindustrial period. Of these metals, only Pb displays any notable adjustment of partitioning in the enriched zone, showing disproportionate accumulation in labile oxides and organic-Pb phases. The lack of Pb and Zn carbonates in the contaminated horizon may reflect inherent thermodynamic instability under the acid surface and pore-water conditions of Loch Dee. Increments to total Mn and Co in the surficial ca 5 cm of sediment are attributable to the accumulation of secondary oxides and adsorbed species, consistent with precipitation from the interstitial pore-waters across a sedimentary redox front. The presence of metals such as Zn and Cd in soluble or acid-volatile phases in the interfacial sediment has implications for the future management of the Loch Dee basin, with leaching into the overlying waters likely, given the continuation of current trends of lake acidification.     

Remobilization of transition metals in surficial pelagic sediments from the eastern Pacific

The top thirty centimeters of sediment at two sites in the eastern equatorial Pacific contain evidence of post-depositional remobilization of Mn, Fe, Co, Ni, Cu, and Zn. Remobilization takes place as Mn and Fe oxyhydroxides are released to the pore water during the microbially-mediated decomposition of organic matter. Precipitation of the dissolved metals in near-surface more oxic strata controls the solid-phase distribution of Mn, Fe, and Zn. The solid-phase redistribution of Co and Ni requires only suitable material for readsorption. Comparison of pore water fluxes with solid-phase metal distributions in the solid sediment indicates no loss of dissolved metal to the overlying water column at the present time. Loss of Mn during the Quaternary is indicated by the composition of the sediments, however. Leaching experiments suggest that portions of the mobile Mn, Fe, Co, Ni, and Cu are fixed by incorporation in authigenic smectite in the surficial sediments.     

Heavy metal concentrations in marine sediments impacted by a mine-tailings spill, Marinduque Island, Philippines

A mine-tailings spill occurred on the island of Marinduque, Philippines, on 24 March 1996. Originating from the Marcopper Mine, tailings sludge flowed down the Boac River abruptly and during subsequent storm events. Most of the tailings material has since accumulated in the nearshore environment along the western coast of the island. Nineteen sediment cores were collected from this site and analyzed for heavy metals. Elevated concentrations of Cu (706-3,080 ppm), Mn (445-1,060 ppm), Pb (43-56 ppm), and Zn (131-276 ppm) are present in the tailings. Two horizons of high metal concentrations in the marine sediment profile are interpreted to correspond to two distinct tailings input events. The lower horizon corresponds to the original 1996 spill, whereas the spike near the surface is thought to be a combination of input due to dredging of the river in 1997 and reworking of sediments. A previous history of contamination is also deduced from the metal profiles. The volume of tailings material released into the marine environment due to the spill is estimated to be 180,000 to 260,000 m³.     

REE Geochemistry of Surficial Sediments from the Yellow Sea of China

REE geochemical studies of surficial sediment samples from the Yellow Sea of China have shown:(1)The average content of RE2O3 in the Yellow Sea sediments is 175 ppm,close to that in the East China Sea sediments.The REE distribution patterns in the Yellow Sea sediments are also similar to anomalies.These REE characteristics are typical of the continental crust.(2)The contents of REE are controlled mainly by the sediment grain size,i.e.,REE contents increase gradually with decreasing sediment grain size.REE are present mainly in clay minerals.In addition,REE contents are controlled obviously by heavy minerals.REE abundances in heavy minerals are much greater than those in light minerals.(3)Correlation analysis shows that REE have a close relationship with siderophile elements,especially Ti,which has the largest correlation coefficient relative to REE.Terrigenous clastic materials subjected to weathering and transport are suggested to be the main source of REE in the Yellow Sea sediments.