Fractionation of phosphorus in the sediments of a tropical estuary

Fractionation of phosphorus in the sediments of the Cochin estuary situated along the southwest coast of India was studied by applying sequential chemical extraction. The different forms of phosphorus were estimated seasonally (premonsoon, monsoon, and postmonsoon) under eight different schemes. The major forms of phosphorus analyzed were exchangeable P, anion exchangeable P, carbonate-bound P, labile and resistant organic P, Fe and Al P, calcium-bound P, and hydrolyzable surplus P. Quantitatively, the above fractions in isolation or in combination vary in content due to chemoestuarine variability and seasonal fluctuations. Changes in speciation have been noted in association with salinity variations in the waterway, especially following enhanced river runoff during the monsoon. The chemical forms of the sediment-bound phosphorus in the northern parts of this estuary have been shown to be modified by nonpoint sources. Sediment P fractionation defines the role of chemical speciation of phosphates (as nutrients) and is indicative of the processes controlling the pathways of P into the coastal waters. The changes in the exchangeable P, together with marked regional variations in calcium-bound P, exemplify the complex estuarine variability of phosphorus. Enhanced amounts of exchangeable P mark its appearence in high saline waters, signifying the presence of biologically available nutrient phosphorus. The calcium-bound P and hydrolyzable surplus P show significant relation with sediment organic carbon and Fe whereas other forms do not exhibit any marked covariation. The Ca and Na NTA extraction scheme is very specific in its selectivity.     

Enrichment of trace metals in surface sediments from the northern part of Point Calimere, SE coast of India

This study deals with the geochemical nature of distribution, enrichment of total trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) in bulk sediments and its association with sediment texture, carbonates and organic carbon. Sixty surface sediment samples were collected during two different seasons in 2002 and 2003 along the coastal regions in three transects from Nagapattinam town, north of Point Calimere in southeast coast of India. The sediments are mostly sandy silt and are dominated by the carbonate content. Organic carbon distribution indicates that they are brought in by the minor river input. Enrichment of trace metals is clearly identified by the domination of Pb, Zn, Cd with high values than the average crustal values and comparison of trace metals from other coastal regions in the southeast coast of India. Statistical analysis clearly indicates that Fe and Mn control the distribution of trace metals and are concentrated in the finer particles and organic carbon fraction. The increase in concentration signifies the need for regular monitoring of the offshore coastal region in southeast coast of India which was recently destroyed by the 2004 December tsunami event, and which is also located near the Sethu Samuthram Ship Canal Project.     

广西茅尾海入海河口表层沉积物重金属分布及风险评价

为揭示茅尾海入海河口表层沉积物中重金属分布特征及生态风险,在茅岭江、大榄江、钦江入海河口采集13件表层沉积物样品进行重金属分析。研究结果表明,茅尾海沉积物中重金属As、Cd、Cr、Cu、Hg、Pb、Zn含量平均值分别为7.78×10-6、0.14×10-6、37.6×10-6、18.9×10-6、0.004 8×10-6、22.5×10-6、54.7×10-6,均低于GB 18668—2002的一类标准。沉积物中重金属空间分布差异较大,茅尾海东部工业区和西部茅岭江附近具有较高的重金属含量。重金属污染分析表明,大部分重金属元素显示为无污染—轻度污染水平,Cr具有中等污染水平;生态风险分析显示,重金属总体处于较低潜在风险,东部工业区Hg、Cd显示出中等生态风险。通过相关性分析、聚类分析、主成分分析探讨重金属污染物来源,结果显示重金属污染主要受河流控制,Hg、As、Cd还受到临港工业区废水排放的影响。综合研究表明,茅尾海生态环境总体较好,但建议重点关注东部工业区重金属排污状况。     

Mobilization of trace metals in a tropical turbid estuary influenced by a monsoon season

The selective removal of trace metals by suspended matter in high turbidity zones plays a major role in the fluvial transport of terrigenous metals to the marine environment. The seasonal longitudinal variability of trace elements (Cu, Zn, Cd, Ni, Pb, Fe, and Mn) in Cochin estuary, a tropical positive estuary, was studied and the results were compared with the prevailing situation in other subtropical waterways. The hydrodynamical features showed increasing turbidity downstream with increasing salinities during both the seasons. In contrast with the temperate estuaries where the development of turbidity maxima causes the removal of metals, the estuaries of tropics modify the fluvial transport of metals by the way of redistribution between the dissolved and particulate fractions in the intermediate salinities. In Cochin estuary, the distributional features of trace metals are primarily influenced by the variations in salinities and river discharges. Consequently, this gives rise to two different types of distributional patterns: (1) during premonsoon, the estuarine reactivity is more pronounced and hence, mid-estuarine solubilization of the particulate metal appears to play a prominent role in controlling the fluxes of trace metals studied and (2) but during monsoon, the hydrological conditions influence the downstream transport of the metals more by physical dilution than chemical reactivity.     

Geochemistry of Cu, Co, Ni, Zn, Cd and Cr in the surficial sediments of a tropical estuary, southwest coast of India: a granulometric approach

 Geochemical characteristics of six trace metals – Cu, Co, Ni, Zn, Cd and Cr – in the bulk sediment and sand, silt and clay fractions of a tropical estuary on the southwest coast of India have been studied and discussed. In bulk sediment, the trace metal concentration is controlled mainly by the textural composition of the sample. Mud, sandy mud and sandy silt register higher concentrations of trace metals than that in sand-dominant sediments. The granulometric partitioning studies also re-affirmed the role of particle size in enriching the trace metals. The silt and clay fractions exhibit 7–8 times the enrichment of Cu and Cd compared to that in sand. The enrichment factors of Zn, Cr, Ni and Co in the silt and clay fractions, compared to that in sand, are 5–6, 4–5, 2–5 and 2–3 times, respectively. The trace metals in the sand fraction, particularly Ni and Cr, exhibit strong positive correlation with the heavy mineral content of the samples. It clearly indicates a heavy mineral pathway to the trace metals in the sand fraction. Cu and Co in silt and clay fractions exhibit a marked decrease towards the high saline zones of the estuary. This is attributed to the desorption of Cu and Co from particulate phases during estuarine mixing. Contrary to Cu and Co, the content of Zn in the clay fraction shows a marginal increase towards the estuarine mouth. This could be explained by the influx of Zn-rich contaminant discharges from Zn-smelting industries located slightly north of the estuarine mouth. The released Zn will effectively be held in the lattices of the clay mineral montmorillonite, which also exhibits a marked increase towards the estuarine mouth. The anomalously high values of Cd in some places of the Central Vembanad estuary is attributed to the local pollution. Received: 10 July 1995 · Accepted: 3 June 1996     

Geochemistry of Fe and Mn in surficial sediments of a tropical river and estuary,India—a granulometric approach

Geochemical characteristics of Fe and Mn in sand, silt, and clay fractions as well as in bulk sediments of the tropical perennial Muvattupuzha river and the Central Vembanad estuary of the southwest coast of India have been studied and discussed. The results of a physical fractionation study of Fe and Mn indicated a substantial increase in the content of these metals in silt and clay fractions above that in sand. The riverine silt and clay fractions account for two to three times the enrichment of Fe and Mn than the corresponding sand fraction; the estuarine counterparts indicate four to eight times the enrichment. The observed enrichment of Fe and Mn towards the more finer size grades is mainly due to the increased surface area of the finer clastics, which in turn increase the absorptive ability. However, the mineralogical diversities of the three size fractions also influence the enrichment of Fe and Mn. The spatial distribution of Fe and Mn indicates a marked decrease in the content of the latter than the former towards the high saline zones of the river and the estuary. This variation could be due to the higher solubility of Mn towards the high saline zones of the aquatic environment where reducing condition prevails most of the year.     

Pore water trace metal chemistry in polluted sediments of a tropical estuary of SE Brazil

The Sepetiba Bay is a shallow water body semi enclosed located on the west side of Rio de Janeiro City. Almost 80% of flesh water discharge, from the St Francisco canal, coming from the northern side of the bay develops an estuarine environment. Fishing and tourism are some of the most important economic activities in the area. During 35 years a zinc/cadmium smelter has polluted the bay. The objective of this investigation is to demonstrate the diagenetic processes and cadmium remobilization into pore water from the contaminated sediments. Two sites were selected to compare diagenetic processes. Site P1 is located next to domestic effluents discharge into the bay and approximately 20km away from the smelter. Site P2 is located near the same smelter and next to the Mazomba estuary, which is not influenced directly by domestic effluents. Peeper samplers of 25 cells with a resolution of 2.5 cm were deployed at both the sites. After a 3-weeks period of equilibrium, the pore waters were separated from the cells and analyzed immediately （within 24 h） for alkalinity, NH3 and reactive soluble phosphorus on a spectrophotometer. An ICP-AESΣH2S spectrometer was used to analyze Na, Mg, Li, Ba, Sr, Si, Fe and Mn. Total and labile dissolved Cd in pore waters were determined by differential-pulse stripping voltametry. The dissolved constituents in the pore waters have shown that the intensities of diagenetic reactions are different between sites. The reactions are stronger at site P1 site than at site P2, especially between 7.5 cm and 22.5 cm, which is evident by the organic rich sediment.     

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.     

Geochemical variations of major and trace elements in recent sediments,off the Gulf of Mannar,the southeast coast of India

The Gulf of Mannar along the Tuticorin coast is a coral base of the southeast coast of India. To obtain a preliminary view of its environmental conditions, geochemical distribution of major elements (Si, Al, Fe, Ca, Mg, Na, K, P), trace elements (Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) and acid leachable elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were analyzed in surface sediment samples from two seasons. Geochemical fractionation confirmed the lithogenic origin of metals, which were mainly associated with the detrital phase. The sediments in the gulf are sandy with abundant calcareous debris, which controls the distribution of total and acid leachable elements. Enrichment factors relative to crust vary by a magnitude of two to three and the presence of trace metals indicates the input of Cr, Pb, Cd, Cu and Zn in both forms through industrial activities. Factor analysis supports the above observation with higher loadings on acid leachable elements and its association with CaCO₃. The increase in concentration of trace metals (Cr, Pb, Cd, Cu, Co, Ni, Zn) along the Gulf of Mannar indicates that the area has been contaminated by the input from riverine sources and the industries nearby. The present study indicates that other sources should be evaluated in the long-term monitoring program.     

Geographical variations of trace elements in sediments of the major rivers in eastern China

 A total of 26 geographically and hydrologically diverse sediment samples were collected from 12 major rivers in eastern China. The <63-μm fraction of the sediments was analysed for both total concentrations of Cu, Zn, Pb and Cd, and their associations with various geochemical phases. The geographical variations of sediment-bound trace metals can be related to the bedrock types and weathering processes in the corresponding river basins. The rivers in southern China had notably higher concentrations of trace metals in sediments because of abundant non-ferrous mineral deposits and stronger weathering process in the region. A large proportion of trace metals in these sediments was associated with iron and manganese oxides and organic matter. Relative low levels of trace metals were found in river sediments in northern China, and a significant proportion of the metals was bound to organic matter, carbonates, and the residual fraction. The sediments in the Yellow River, originating from special loess, had the lowest concentrations of trace metals. Most of the trace metals were associated with the carbonates and residual phases. Received: 24 March 2000 · Accepted: 11 July 2000     

Competitive adsorption,release and speciation of heavy metals in the Yellow River sediments,China

The competitive adsorption and the release of selected heavy metals and their speciation distribution before and after adsorption in the Yellow River sediments are discussed. The adsorption of metals onto sediments increases with increasing pH value and decreases with increasing ionic strength. The competitive coefficient K _c and the distribution coefficient K _d are obtained to analyze the competitive abilities of selected heavy metals, which are ranked as Pb > Cu >> Zn > Cd. The competition among selected heavy metals becomes more impetuous with increasing ion concentration in water. Speciation analysis was done by an improved analytical procedure involving five steps of sequential extraction. Cu, Pb and Zn were mainly transformed into the carbonate-bound form (50.8–87.7%) in adsorption. Most of (60.7–77.3%) Cd was transformed into the exchangeable form, and the percentage of carbonate-bound Cd was 19.7–30.4%. The release reaction was so quick that the release capacity of selected heavy metals from sediments to aqueous solution reached half of the maximum value only in 30 s. As opposed to adsorption, the release capacities of selected heavy metals were ranked as Cd > Zn >> Cu > Pb. In this study, Cd produces the most severe environmental hazards, because its concentration in the release solution is 85.8 times more than the human health criteria of US EPA.     

Trace metals in acid sediments and waters, Pimpama catchment, southeast Queensland, Australia

The Pimpama River floodplain has developed over the last several thousand years as a result of sea-level fluctuations that shaped the lower catchment and enabled the formation of sedimentary pyrite. The subsequent production of sulfuric acid due to the oxidation of this pyrite enhances the breakdown of metal-bearing sediments and can lead to leaching of major and trace metals into the waters of the region. The seasonal pattern of rainfall and current land-use activities are important aspects that intensify the natural production of acid and influence the release and distribution of metals. To identify the source and migration of metals in the Pimpama catchment and to understand the impact of pyrite oxidation on the distribution of metals in sediments and waters, several components of the drainage system were analyzed: bedrock, sediments from river bed and bank, and water. The elements analyzed in this study (V, Cr, Co, Ni, Cu, Zn and Pb) are all present in the bedrock material which explains their occurrence in the unconsolidated sediments of the floodplain. These metals concentrate in the upper section of the sedimentary sequence and their presence is related to clay minerals such as smectite, organic matter and iron phases. However, Zn, Mo and Co occur in higher amounts than the local background and within standard shale. This comparison suggests that the diagenetic processes alone cannot explain the higher concentrations and it is concluded that these metals also have an anthropogenic source. The formation of sulfuric acid creates conditions for higher mobility of some metals, such as Cr, Co, Ni, Cu, Zn, but does not affect less mobile ones such as Mo and Pb. Over the longterm, the production of acid influences the breakdown of mineral phases and enhances the process of weathering. Over the short term, every rain event leaches acid from sediments and mobilizes metals resulting in a substantial reduction in the quality of river water. Received: 2 October 1998 · Accepted: 16 February 1999     

Sediment budget-based estimates of trace metal inputs to a Chesapeake estuary

This article evaluates whether a sediment budget for the South River, Maryland, can be coupled with metals data from sediment cores to identify and quantify sources of historic metal inputs to marsh and subtidal sediments along the estuary. Metal inputs to estuarine marsh sediments come from fluvial runoff and atmospheric deposition. Metal inputs to subtidal sediments come from atmospheric deposition, fluvial runoff, coastal erosion, and estuarine waters. The metals budget for the estuary indicates that metal inputs from coastal erosion have remained relatively constant since 1840. Historical variations in metal contents of marsh sediments have probably resulted primarily from increasing atmospheric deposition in this century, but prior to 1900 may reflect changing fluvial sources, atmospheric inputs, or factors not quantified by the budget. Residual Pb, Cu, and Zn in the marsh sediments not accounted for by fluvial inputs was low to moderate in 1840, decreased to near zero circa 1910, and by 1987 had increased to levels that were one to ten times greater than those of 1840. Sources of variability in subtidal cores could not be clearly discerned because of geochemical fluxes, turbulent mixing, and bioturbation within the cores. The sediment-metal budgeting approach appears to be a viable method for delineating metal sources in small, relatively simple estuarine systems like the South River and in systems where recent deposition (for example, prograding marshes) prevents use of deep core analysis to identify background levels of metal. In larger systems or systems with more variable sources of sediment and metal input, however, assumptions and measurement errors in the metal budgeting approach suggest that deep core analysis and normalization techniques are probably preferable for identifying anthropogenic impacts.Field and laboratory research conducted at the Department of Geography, University of Maryland, College Park, Maryland, 20742, USAField and laboratory research conducted at the Marine and Estuarine Environmental Science Program, University of Maryland, College Park, Maryland, 20742, USA     

Trace metals in sediments near offshore oil exploration and production sites in the Alaskan Arctic

Increased offshore development in the Alaskan Arctic has stimulated interest in assessing potential impacts to the environment before the onset of any adverse effects. Concentrations of trace metals in sediments are used in this paper to provide one sensitive indicator of anthropogenic inputs from offshore activity over the past several decades. Sediments in coastal waters of the western Beaufort Sea are patchy with respect to sediment granulometry, organic carbon content, and concentrations of trace metals. However, results for surface sediments and age-dated cores show that nearly all samples contain natural concentrations of Ag, Ba, Be, Co, Cr, Cu, Hg, Ni, Pb, Sb, Tl, V and Zn, with metal/Al ratios that have been constant for many decades. Metal concentrations for incoming river-suspended matter compare well with sediment metal values and, along with vertical distributions in sediments, show no discernible diagenetic impacts that distort the sedimentary record for metals, except for Mn, As and possibly Cd. Slightly elevated concentrations of Ba, Hg, Ag, Sb and Zn were observed in a total of eight instances or in only 0.7% of the 1,222 data points for metals in surface sediments.     

Heavy metals in freshly deposited sediments of the Gomati River (a tributary of the Ganga River): effects of human activities

 The concentrations of various metals (Cr, Cu, Co, Fe, Mn, Ni, Pb, Zn, and Cd) were determined in recently deposited surface sediments of the Gomati River in the Lucknow urban area. Markedly elevated concentrations (milligrams per kilogram) of some of the metals, Cd (0.26–3.62), Cu (33–147), Ni (45–86), Pb (25–77), and Zn (90–389) were observed. Profiles of these metals across the Lucknow urban stretch show a progressive downstream increase due to additions from 4 major drainage networks discharging the urban effluents into the river. The degree of metal contamination is compared with the local background and global standards. The geoaccumulation index order for the river sediments is Cd>Zn>Cu>Cr>Pb. Significant correlations were observed between Cr and Zn, Cr and Cu, Cu and Zn and total sediment carbon with Cr and Zn. This study reveals that the urbanization process is associated with higher concentrations of heavy metals such as Cd, Cu, Cr, Pb, and Zn in the Gomati River sediments. To keep the river clean for the future, it is strongly recommended that urban effluents should not be overlooked before their discharge into the river. Received: 16 February 1996 · Accepted: 29 February 1996     

Trace metals in surface seawaters and sediments from various habitats of the Red Sea coast of Yemen

The purpose of this study was to determine and assess the concentrations of trace metals in surface seawaters and sediments from different coastal habitats of the Red Sea coast of Yemen. Surface seawater and sediment samples were collected, treated and analyzed for cadmium, cobalt, manganese, chromium, lead, iron, nickel, copper, zinc and vanadium by the atomic absorption spectrometric analysis. The concentrations were high for cadmium, cobalt and lead and low or consistent with the natural background concentrations for the rest of the metals. However, the coastal habitats of the Red Sea coast of Yemen are still considered unpolluted, it is concluded that the cadmium cobalt and lead levels in surface seawaters are high and could have negative effects on marine life of the sites. Further studies are needed to characterize the sources fate, biogeochemical processes and impacts of these trace metals on coastal habitats and marine life of the region.     

Spatial distribution features and environment effect of heavy metal in intertidal surface sediments of Guanhe estuary, Northern Jiangsu Province

In northern Jiangsu coastal zone area, Guanhe River is the biggest river and has the best navigation conditions among rivers which flow into the Yellow Sea. The grain sizes show gradual increase from the high intertidal zone to lower intertidal zone. The heavy metal values have slight changes along both sides of the river mouth, but show an evident change perpendicular to the tidal flat. In the latter case, they show a good correlation with grain size fluctuation, that is, the heavy metal values gradually decline when the grain size increases from the high intertidal zone to the lower intra-tidal zone. Analyses of the heavy metal elements show that on the Guanhe estuary surface sediment, the content of the elements Hg, As and Cu is above background values; Pb and Zn contents are rather close to the background values; and Cd content is less than the background values. The element Hg comes out to be harmful in a medium level to ecological environment, while the elements of Cr, As, Cu, Pb, Zn and Cd fall in a safe range of MPL. On the whole, Guanhe estuary tidal flat is not very harmful to the ecology in terms of the heavy metals. __________ Translated from Marine Geology & Quaternary Geology, 2007, 27(5): 23–32 [译自: 海洋地质与第四纪地质]     

Geological factors affecting the distribution of trace metals in glacial sediments of central Newfoundland

 In central Newfoundland (NTS 12A/10, 15, 16, 2H/1), As, Pb, and Zn concentrations in the clay-sized (<0.002 mm) and silt and clay-sized (<0.063 mm) fractions of till reflect compositional differences among and within rock terranes at scales of kilometers to tens of kilometers. In those fractions, till derived from volcanic bedrock of Victoria Lake Group (Tulks Hill) is notably enriched in As (50–>1000 ppm), exceeding levels commonly set for purposes of environmental protection. Near Pb-Zn mines at Buchans, geochemical variation with depth reflects the dispersal of detritus from mineralized bedrock, and differences in sediment type and provenance. There, surface sediments are rich in granitic debris derived from the Topsails igneous terrane 5 km north of Buchans and contain low concentrations of trace metals. These sediments are compositionally unrelated to either Buchans Group volcanic rock or an underlying, older till enriched in sulphide minerals and trace metals. Metal-rich till extending up to 10 km southwest of Buchans results from combined glacial and debris flow transport related to two distinct geological events. Trace metals are enriched (two- to fourfold) in the clay-sized fraction of till compared to the silt and clay-sized, and are associated with Al- and Mg-bearing minerals that preferentially concentrate in the clay fraction. The geochemistry of the silt and clay-sized fraction can approximate that of the <2-mm fraction. Background variations in till illustrate the important role of a geological framework to the interpretation of geochemical surveys and the origins of trace metals in the environment. Received: 31 October 1996 · Accepted: 27 May 1997     

Pyritization of trace metals in mangrove sediments

The present study investigates the levels of Mn, Zn, Ni, and Co pyritization in mangrove sediments along distinct sedimentary zones in Enseada das Gra?as, a lagoon-type estuary located on the southeastern coast of Brazil. The coastal geology is characterized by intense interactions of trace metals, forming pyrite minerals. Specific orders of DOP (degree of pyritization) and DTMP (degree of trace-metal pyritization) are shown: supratidal flat?<?mangrove forest?<?mud flat. Distinct changes in content along the sediment profiles are noted, where a supratidal flat presented low levels of DOP and DTMP with little variance along the sedimentary depths. The mangrove forest showed relatively high values of DOP and DTMP in the lower depths, while the mud flat showed the highest levels of DOP and DTMP.