Distribution of cadmium, chromium, copper, lead and zinc in marine sediments in Hong Kong waters

Partitioning of heavy metals (Cd, Cr, Cu, Pb, Zn) in marine sediments collected from various sites in Hong Kong waters were determined using sequential extraction method. Sediments from Kellette Bank, located in Victoria Harbour, had higher metal concentrations especially Cu and Zn than most other sites. Slightly over 20% of total Cu and Cr existed as readily available forms in Peng Chau and Kellette Bank. At most sampling sites, over 15% of the Cu existed as the exchangeable form indicating that Cu could be readily released into the aqueous phase from sediments. A significantly higher percentage of Pb and Zn was associated with the three non-residual fractions. Hence, there is a greater environmental concern for remobilization of Pb and Zn compared with Cr. The high amount of residual Cd (>50%) and the relatively lower Cd content indicate that little environmental concern is warranted for the remobilization of Cd. Distribution of metals in sediments collected from different depth at Kellette Bank shows that metal concentrations decreased with profile depth. The levels of Pb and Zn associated with the two readily available fractions increased sharply in the surface sediment. These metals represented the pollutants, which were introduced into the area in the mid-eighties through early nineties as a result of rapid economic and industrial development in the territory. As significant portions of these metals were bound to the readily available phases in the surface sediments, metal remobilization could be a concern. An erratum to this article can be found at     

Land-based sources of pollution along the Izmit Bay and their effect on the coastal waters

The degree and the contribution of each point source to the pollution were determined in the Izmit Bay during the period 1999–2000. During 8 campaigns, samples from 11 points in the channels and water samples from 5 points in the coastal sea were collected for chemical analysis. The important pollutant parameters taken into account are inflow of total organic carbon (TOC), total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), nitrate, ortho-phosphate, ammonia and total polycyclic aromatic hydrocarbons (t-PAHs) in the discharge channels, and TOC, TSS, nitrate, ortho-phosphate, chlorophyll-a, temperature, dissolved oxygen (DO), and salinity in the coastal stations of the Bay. It should be pointed out that the industrial wastewaters entering the bay are partially treated but domestic wastes are discharged directly into the surface waters without any treatment. Of the pollution parameters measured in the channels, the highest concentrations, except TP, were observed in the Dil River and in the Eastern Channel. Concentrations of TOC, TSS, TN, TP, ammonia, nitrate and o-phosphate were found at concentrations of 231, 290, 152, 3.8, 16, 79, and 3.07 mg/L, respectively. Annual inflows of TOC were 21,301, 580, and 775 t/year and for TSS were 26,742, 585, and 1505 t/year in the western, central and eastern parts, respectively. The results show that the water quality of the bay has been deteriorated and 80% of the pollution was caused by Dil River for all parameters measured.     

Pb isotope signatures of sediments from Guanabara Bay, SE Brazil: Evidence for multiple anthropogenic sources

Sediments from Guanabara Bay and two rivers were analyzed for Pb isotope composition. The results define linear groups interpreted as different sources of Pb. The samples from Iriri and Surui rivers present different Pb compositions probably resulting from two active pollutants which are transported in the waters to the Guanabara Bay, where they are mixed. The ²⁰⁶Pb/²⁰⁷Pb values of 1.151 and 1.091 presented here are in the range of Brazilian galena ore signature.     

Metal pollution in coarse sediments of Tuticorin coast,Southeast coast of India

Indian coastal waters are subjected to considerable pressure from sewage and industrial wastes, which are responsible for the contamination of the coastal sediments with consequent loss in biosphere. The present investigation attempts to study the significance of coarse material (Sand fraction) in the distribution of metals in polluted marine sediments. The study revealed that coarse Sand component contains a relatively significant proportion of the anthropogenic metals (Cd, Cu, Pb and Zn) and therefore it cannot be neglected in metal pollution studies of coastal sediments. Further, the distribution of anthropogenic metals in both Silt + Clay and Sand fraction follow the same suit indicating similar pollution sources. From the total sediment type (Silt + Clay and Sand fraction) all anthropogenic metals had a noticeable amount (>50%) in the acid extractable (and potentially bio-available) fraction. This article stresses the importance of coarse fraction in metal pollution studies in Indian coastal system.     

A multi-method approach for the study of lanthanum speciation in coastal and estuarine sediments

Two independent analytical methods (sequential extraction and kinetic extraction methods) were applied in order to understand the distribution and speciation of La in the coastal and estuarine sediments from the central east coast of India. Sequential extraction study revealed that La was primarily present as inert complexes (~ 50–60% of the total La) in all the sediments. Amounts of ~ 20–30% of the total La in all the sediments were found to associate with the total organic carbon (TOC) in the sediments. The dissociation rate constants of La–sediment complexes obtained from kinetic extraction studies revealed that the concentration of thermodynamically weak complexes of La gradually increased with the increasing La/TOC ratio in the sediments.     

Soil and groundwater pollution of an urban catchment by trace metals: case study of the Addis Ababa region, central Ethiopia

Analysis of the total heavy metal (Cr, Cd, Pb, As, Cu, Ni, Zn, Co) concentration was performed on 33 soil samples taken from different profiles and soil types in a highly urbanized and industrial sector of Addis Ababa, central Ethiopia. They were analyzed using aqua regia extraction coupled with a four-stage sequential extraction (SE) procedure. The objectives of the analysis were to investigate the degree of soil heavy metal contamination, its binding forms, mobility and the implications for the groundwater resource. The results show a relatively high content of the analyzed trace metals in the soil attributed to anthropogenic and geogenic sources. Although most of the trace metals are found in the upper few centimeters of the residual soils, because of churning processes within the black cotton soils, vertical distribution of the trace metals is complex. According to the heavy metal SE analysis, the major heavy metal contribution is from the residual followed by the hydroxide phases. Groundwater heavy metal contamination is present with more than 90 and 50% of the analyzed groundwater samples exceeding WHO guidelines for Cr and Cd, respectively. Since the degree of soil heavy metal contamination has apparently not surpassed the soil’s buffering capacity, it appears that the transport path of these toxic metals to the groundwater is through fractures, joints, and related preferential flow paths.     

Spatial distribution,environmental assessment and source identification of metals content in surface sediments of freshwater reservoir,Pakistan

Surface sediments were collected from different sites of a freshwater reservoir, Pakistan, and analyzed for eight metals (Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn) using flame atomic absorption spectrometry. The estimated metals levels were found higher than other reported studies. The environmental indices including geoaccumulation index, enrichment factor and contamination factor identified Cd, Co, Pb and Zn as the priority pollutants of concern. Chromium, Cu and Mn were also found to be enriched in some areas. The pollution load index (≥1) indicated progressive deterioration of the sediments quality. Principal component and cluster analyses revealed that Cd, Co, Pb and Zn were mainly originated from agricultural activities, domestic wastes, road runoffs and recreational activities. Chromium, Cu, Fe and Mn were mainly derived from natural sources though Cr, Cu and Mn were partially contributed by human inputs. Based on spatial distribution, inlet and middle sites of the reservoir were found more contaminated. This study would drive urgent attention to develop preventive actions and remediation processes for aquatic system protection and future restoration of the reservoir.     

Distribution of trace elements in the coastal sea sediments of Maslinica Bay, Croatia

Spatial distributions of trace elements in the coastal sea sediments and water of Maslinica Bay (Southern Adriatic), Croatia and possible changes in marine flora and foraminifera communities due to pollution were investigated. Macro, micro and trace elements’ distributions in five granulometric fractions were determined for each sediment sample. Bulk sediment samples were also subjected to leaching tests. Elemental concentrations in sediments, sediment extracts and seawater were measured by source excited energy dispersive X-ray fluorescence (EDXRF). Concentrations of the elements Cr, Cu, Zn, and Pb in bulk sediment samples taken in the Maslinica Bay were from 2.1 to over six times enriched when compared with the background level determined for coarse grained carbonate sediments. A low degree of trace elements leaching determined for bulk sediments pointed to strong bonding of trace elements to sediment mineral phases. The analyses of marine flora pointed to higher eutrophication, which disturbs the balance between communities and natural habitats.     

The influence of physicochemical parameters on bioavailability and bioaccessibility of heavy metals in sediments of the intertidal zone of Asaluyeh region,Persian Gulf,Iran

In this research, we have worked on the evaluation of heavy metal contamination in the sediments taken from the intertidal zone of Asaluyeh region using Modified Community Bureau of Reference sequential extraction method (mBCR), the simplified bioaccessibility extraction test (SBET), and calculated enrichment factor (EF). Also, potential influencing factors including sediment characteristics that may affect the heavy metals bioavailability and bioaccessibility were investigated. mBCR extraction analysis indicated that among the metals, Mn, Zn, V, Cu, and Cd exhibit relatively higher mobility, while Ti, Pb, Cr, and Ni occur mainly in the residual fractions. Based on the mean values, the bioaccessibility of metals decreased in the order: Mn (50.01%)>Cd (46.26%)>Zn (14.61%)>V (13.97%)>Pb (10.88%)>Ni (9.2%)>Ti (8.43%)>Cr (6.66%)>Cu (6.23%). The obtained results from the principal component analysis (PCA), EF and mBCR extraction showed that most anthropogenic-derived metals with higher solubility are more bioaccessible compared to those of natural origin. Multiple linear regression analysis demonstrated that the main physicochemical variables of the sediment influencing the bioaccessibility of metals include cation exchange capacity (CEC), pH, and particle size fraction.     

Assessment of mercury mobility and bioavailability by fractionation method in sediments from coastal zone inundated by the 26 December 2004 tsunami in Thailand

The 26 December 2004 tsunami covered significant portion of a coastal zone with a blanket of potentially contaminated sediments. In this report are presented results on mercury concentrations in sediments deposited by the tsunami in a coastal zone of Thailand. Since the total mercury concentrations are insufficient to assess mercury mobility and bioavailability in sediment, its fractionation was applied. Sediments were sampled within 50 days after the event and analyzed by sequential extraction method. The procedure of sequential extraction involved five subsequent stages performed with solutions of chloroform, deionized water, 0.5 M HCl, 0.2 M NaOH, and aqua regia. The mean concentration of total mercury in sediments was 119 ± 50 ng g⁻¹ dry mass (range 66–230). The fractionation revealed that mercury is mainly bound to the least bioavailable sulphides 75 ± 6% (range 62–86), organomercury compounds 14 ± 7% (range 4–26), and humic matter 9 ± 7% (range 1–27). The lowest contributions bring fractions of water-soluble mercury 0.8 ± 1.0% (range 0.1–3.6) and acid soluble mercury 0.9 ± 0.5% (range 0.2–2.1). Although, the total mercury content is similar in a reference sample and in the tsunami sediments, the highly toxic organomercury fraction contribution is higher in the latter. The results were compared with chemical and sedimentological properties of the sediments but no significant correlations were obtained between them.     

Distribution and sources of phosphorus in tidal river sediments in the Washington, DC, Area

 Sediments in the rivers and basins around Washington, DC, have high concentrations of phosphorus, which, based on geographic distributions, is largely derived from urban runoff and municipal sewage. Dissolved-particulate phosphate exchange reactions and biological uptake of dissolved phosphorus from the water column may be an added source of phosphorus to the sediments. Concentrations of total sedimentary phosphorus ranged from 24 to 56 μm P/g-dw, and were highest in areas near combined sewer outfalls. As a part of this study, sedimentary phosphorus was fractionated into Fe-P, Ca-P, Al-P, and organic phases using a selective-sequential leaching procedure. The distribution of the phases in all sediments analyzed follow the order , Fe-P>Ca-P>Al-P. Spatial variations in the amounts of phosphorus in the different phases is related to the sources of phosphorus to the area. The proportions of occluded Al-P and organic P are 10–20% of the total P, respectively. This suggests that phosphorus from natural sources is small compared to anthropogenic inputs in this area. The high leachable Fe-P and Ca-P in these sediments might contribute a substantial amount of P to the water column under conditions of remobilization. Received: 20 February 1996 · Accepted: 2 April 1996     

Historical record of heavy metal pollution deduced by lead isotope ratios in core sediments from the Osaka Bay,Japan

Three marine sediment cores from Osaka Bay were analyzed for ²¹⁰Pb geochronology, heavy metal concentrations (Zn, Cu, and Pb) and stable lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb) in order to reconstruct high-resolution heavy metal pollution history from 1900–2006. Anthropogenic metal accumulation in sediments peaked in 1970 in agreement with the high economic growth period in Japan. The comparison of temporal patterns of ²⁰⁶Pb/²⁰⁷Pb ratio with other areas of Japan suggested that the heavy metals, imported from several different countries during the periods of economic growth (1955 to 1973), are the main pollution source for the country. For the period 1970–2006, the sediment data reflect the result of stricter environmental regulations applied after the late 1960s. However, heavy metal concentrations in the surface sediments are still elevated to levels several times higher than the levels at the bottoms of the cores. Additionally, the lead isotope ratio does not show significant change after the 1980s. Secondary heavy metal pollution through the mixing of deeper polluted sediment appears to be the likely reason for the deterioration of present time submarine sediment environments. In conclusion, this study has demonstrated that it is difficult to recover over a period of several years the benthic quality of a bay, once it is heavily polluted.     

Historical environmental pollution trend and ecological risk assessment of trace metals in marine sediments off Adyar estuary,Bay of Bengal,India

Geochemical, mineralogical and textural analyses were carried out in core sediments off Adyar estuary, Bay of Bengal, India to record the contamination trend from urban and industrial activities during the historical past. Quartz, feldspar, kaolinite, chlorite and illite were the main lithogenic and clay minerals; carbonate was the predominant biogenic mineral. Trace metals (Fe, Al, Cu, Cr, Ni, Pb and Zn) indicate more enrichment in the surface sediment layers due to recent anthropogenic activities. The mean anthropogenic factor (AF) values for trace metals in core sediments decreased in the following order: Cr > Ni > Zn > Cu > Pb. The pollution load index (PLI) values in Adyar core sediments ranged from 1 to 1.25 with an average of 1.07. Based on AF, PLI, and sediment quality guidelines values for trace metals, significant metal enrichment and ecological risk were obtained in upper-most sediment layer. Multivariate statistical methods such as correlation matrix, principal component analysis and cluster analysis were carried out to find the relationships among the texture size, metals and minerals. The pollution of Adyar estuarine sediments was started in the 1960s, responding to the rapid economic development in Chennai coastal and Adyar estuarine region in the last five decades. Despite these high concentrations in the upper layer, development and expansion of industries are still continuing. The stricter regulations for the discharge and remediation of sediments are urgent for the conservation of environments and human health.     

Speciation and mobility of heavy metals in mud in coastal reclamation areas in Shenzhen,China

Coastal reclamation has been carried out along the coastal areas near Shenzhen, China in a large scale since 1980s by dumping fill materials over the marine mud at the sea bottom. Usually the area to be reclaimed is drained first and some of the mud is air-dried for a few weeks before it is buried by fill. After reclamation, the terrestrial groundwater, which is relatively acidic and with high dissolved oxygen, gradually displaces the seawater, which is alkaline with high salinity. The changes in the burial conditions of mud and the properties of the pore water in the mud may induce the release of some heavy metals into the mud. Field survey confirms that the pH and salinity of the groundwater in the reclamation site are much lower than the seawater. Chemical analyses of mud and groundwater samples collected from the reclamation sites reclaimed in different years indicate that most of the heavy metals in the mud decrease gradually with time, but the heavy metals in the groundwater are increased. The release of heavy metals into pore water due to reactivation of heavy metals in the mud is of environmental concern. To understand why some of the heavy metals can be released from the mud more easily than others, a sequential extraction method was used to study the operationally determined chemical forms of five heavy metals (Cu, Ni, Pb, Zn, and Cd) in the mud samples. Heavy metals can be presented in five chemical forms: exchangeable, carbonate, Fe–Mn oxide, organic, and residual. Ni and Pb were mainly associated with the Fe–Mn oxide fraction and carbonate fraction; Zn was mainly associated with organic fraction and Fe–Mn oxide fraction, while Cu and Cd were associated with organic fraction and carbonate fraction, respectively. If the residual fraction can be considered as an inert phase of the metal that cannot be mobilized, it is the other four forms of heavy metal that cause the noticeable changes in the concentration of heavy metals in the mud. On the basis of the speciation of heavy metals, the mobility of metals have the following order: Pb (36.63%) > Cu (31.11%) > Zn (20.49%) > Ni (18.37%) > Cd (13.46%). The measured metal mobility fits reasonably well with the degree of concentration reduction of the metals with time of burial observed in the reclamation site.     

Metals in sediments of springs and cave streams as environmental indicators in karst areas

The content of heavy metals and arsenic in sediments of karst streams in southern Missouri was investigated for its potential use as an indicator of pollution. A three-step sequential extraction procedure was utilized for this purpose. The amount of trace elements bound to each extraction phase gives insight of its availability and geochemical dependence. These results were complemented with analyses of correlation and spatial variability. Although sediments collected in this study remained below EPAs critical value guidelines, concentration in the mobile phases and higher normalized Mn values successfully identified sites with concentrations higher than background levels. Correlation among elements was poor in most cases; among the trace metals only Cu and Zn correlated while Pb correlated with Ca, Al, Mn and Fe. Spatial variability analysis confirmed that natural variation among adjacent sediment samples is a common occurrence. The urban spring Ward Branch showed the highest levels of Cr, Zn, Pb and As.     

广西珍珠湾红树林湿地沉积物重金属分布及评价

沉积物中的重金属属于持久性污染物,具有富集性、难降解性和毒性,长时间累积会对生态环境和人体健康造成威胁。为研究珍珠湾红树林湿地表层沉积物中的重金属含量分布特征及质量现状,2021年9月在珍珠湾红树林分布区采集13件表层沉积物样品,分析测试重金属含量。结果表明: 与国内其他红树林湿地相比,珍珠湾红树林湿地表层沉积物中的重金属含量处于相对较低水平; 地累积指数法显示大部分表层沉积物样品无重金属污染,仅有2个站位受到Cd和Hg的轻微污染,潜在生态风险指数法表明湾内各站位均为低生态风险; 相关性分析和主成分分析表明,Cd主要受江平江输入和珍珠湾东南部海水养殖的影响,其他元素主要为自然背景的岩石风化沉积,利用主成分-多元线性回归模型对重金属的来源进行解析认为,表明江平江输入的重金属贡献率为57%,海水养殖影响的重金属贡献率为43%。综上所述,珍珠湾红树林湿地整体生态状况良好,但仍需重点关注Cd的输入。     

A comparison of the early diagenetic environment in intertidal sands and muds of the Manukau Harbour,New Zealand

The early diagenetic environment of intertidal sandy sediments (sands) and muddy sediments (muds) is described and compared from two cores taken from an unpolluted part of the Manukau Harbour, New Zealand. Extraction techniques characterized the form of the trace elements (Fe, Mn, S, C, Pb, Zn, Cu) at different depths in the sediment. Dissolved forms of Fe, Mn, and S were measured in interstitial water. Nonresidual metal concentrations, humic acid, FeS, and FeS₂ are an order of magnitude higher in the muds than in the sands because of dilution by unreactive sand particles. Muds contain a larger proportion of metals in the mobile fractions; exchangeable (Mn), carbonate (Mn, Fe, Zn), and easily-reducible oxide (Fe, Mn, Zn, Pb). This is due to greater surface area (for Mn adsorption); the favorable conditions for MnCO₃, FeCO₃, and FeS precipitation; and higher concentrations of easily reducible iron oxide and humic acid. Therefore, compared to the sands, muds are more important as reservoirs for toxic metals, both in terms of quantity and availability. At either site there was very little difference between the forms of Zn, Pb or Cu identified by sequential extraction as sediments changed from oxic to anoxic conditions. One reason for this is that the amounts and proportions of some of the important components that bind metals, viz., amorphous iron hydrous oxides, humic acids, and FeS₂, do not change much. Other components that do change with redox conditions, for example, manganese phases and FeS, are only minor components of the sediment. Redox conditions, then, have relatively little effect on trace-metal partitioning in the sediment matrix of these unpolluted sediments.     

Retrospective analysis of the impacts of major hurricanes on sediments in the lower Everglades and Florida Bay

A record of the impacts of major hurricanes on sediment stratigraphy and composition in subtropical ecosystems has been preserved in the lower Everglades and Florida Bay. These impacts were observed in discontinuous layers of sediment that were identified from high-resolution, vertical profiles of excess ²¹⁰Pb and ¹³⁷Cs. Discontinuities were found at different geographic locations and at two to three different depths in the sediment column; however, the layers were each deposited within time periods that corresponded with the passing of category 3–5 hurricanes during 1960, 1948 and 1935. A simple mass balance model for excess ²¹⁰Pb was used to show net changes of ±20–100% in excess ²¹⁰Pb inventory that resulted from sediment disturbances of <1 to >22 cm. Abrupt shifts in sediment composition were often observed in hurricane-impacted layers. Ratios of organic (C/P) were four- to fivefold higher than normal in post-hurricane layers of sediment at open bay sites. These layers are phosphorus poor and seem to reflect preferential decomposition of organic P relative to organic C in association with hurricanes. The net effect is for major hurricanes to redistribute sediment, organic matter and nutrients.This revised version was published online in July 2003.     

广西防城港近岸表层沉积物重金属分布特征及污染评价

为了解防城港近岸海域表层沉积物重金属分布及污染特征,系统采集了19件研究区的表层沉积物样品,检测了7种重金属元素的含量.测试结果表明:研究区表层沉积物中Cu、Pb、Zn、Cd、Cr、Hg和As含量均符合政府制定的海洋功能区划要求.单因子潜在生态危害指数法评价结果显示,不同重金属潜在生态危害排序为Hg>Cu>Cd>As>...     

A predictive modeling approach to assessing the groundwater pollution susceptibility of the Paluxy Aquifer, Central Texas, using a Geographic Information System

The Paluxy aquifer in north-central Texas is composed primarily of Lower Cretaceous clastics. This aquifer provides water for both domestic and agricultural purposes in the region. The study area for this investigation incorporates the outcrop and recharge areas, as well as the confined and unconfined portions of the aquifer. The purpose of this investigation is to develop a predictive modeling approach for evaluating the susceptibility of groundwater in the Paluxy aquifer to contamination, and then compare this susceptibility evaluation to water-chemistry data collected from wells completed within the aquifer. Using such an approach allows one to investigate the potential for groundwater contamination on a regional, rather than site-specific scale. Based on data from variables such as land use/land cover, soil permeability, depth to water, aquifer hydraulic conductivity and topography, subjective numerical weightings have been assigned according to each variables' relative importance in groundwater pollution susceptibility. The weights for each variable comprise a Geographic Information System (GIS) map layer. These map layers are combined to formulate the final pollution susceptibility map. Using this method of investigation, the pollution susceptibility map classifies 32% of the study area as having low pollution susceptibility, 41% as having moderate pollution susceptibility, 25% as having high pollution susceptibility, and 2% as having very high pollution susceptibility. When comparing these modeling results with water-chemistry data from wells within the Paluxy aquifer, the four wells with the highest concentration of nitrate contamination are all found within regions of very high pollution potential. This confirms the accuracy and usefulness of the predictive modeling approach for assessing aquifer pollution susceptibility. Received: 1 June 1999 · Accepted: 30 August 1999