Matter Content Of Sediment Research Articles

Efficacy of Phoslock® on the Reduction of Sediment Phosphorus Release in West Lake, Hangzhou, China

Famous as the world cultural heritage, West Lake in Hangzhou city has plenty of soft sediments with high organic matter content. To search the countermeasures for internal phosphorus release reduction from the sediment, the sediment core incubation was conducted to understand the efficacy of Phoslock® on internal phosphorus release in spring, summer and winter, respectively. The results showed that the internal phosphorus release fluxes in winter and spring were relatively low, with averaged values in the entire lake of 0.13 mg·(m2·d)-1 and 0.29 mg·(m2·d)-1, respectively, while the release flux was 3.29 mg·(m2·d)-1 in summer, more than ten times higher than those in spring and winter. It was estimated that 23.7 kg of phosphorus could be released from sediment in the entire lake every day in summer. Spatially, the phosphorus release flux was related to organic matter contents in sediments, but not the phosphorus or bioavailable phosphorus contents in sediments in West Lake. With Phoslock® added at the rate of 630 g·m-2, sediment phosphorus release was successfully controlled, which reduced the phosphorus concentration in the lake water to less than 0.010 mg·L-1. Especially during summer time, the sediment phosphorus release was reduced by 98% after Phoslock® application. The research suggested that Phoslock® is powerful for phosphorus control even for sediments with high organic matter content, which could be considered in ecological restoration of WEst Lake.

The impact of the kelp (Laminaria hyperborea) forest on the organic matter content in sediment of the west coast of Norway

ABSTRACTSediment cores were collected from an area off the west coast of Norway, where a well-established kelp community made up mainly of Laminaria hyperborea is found. Chemical analyses of the sectioned sediment cores were made, which included organic carbon, carbohydrates and phenols. These were used to collate the sediments in order to establish whether the different sites had a common origin and if this was kelp-related. The organic matter content in the surface sediments appears to be related to the water depth, which determines the degree of perturbation at the sediment-water boundary and hence the sedimentation of the organic matter. The relation between carbohydrates and phenols in the sediment appears to indicate a common origin. However, the carbohydrate and phenol content in the sediment organic fraction appears to closely resemble (to be analogous) to that of the kelp Laminaria hyperborea. Although there are some diagenetic and decomposition changes in the subsurface (historical) organic matter (that may alter its findings), this study provides good evidence that the deposits were supplied by the kelp forest in the region. The sedimentation and export of kelp-derived material is of particular significance in terms of benthic ecology and production and may also play a significant role in the global carbon budget.

Characterization of the New Status of Nador Lagoon (Morocco) after the Implementation of the Management Plan

The present study was carried out in 2011 with the aims of (1) evaluating the changes in sedimentary distribution that occurred in Nador lagoon seabed (Morocco) after the implementation of the lagoon management plan in 2009; and (2) characterizing its new sedimentary status in 2011. Due to the lack of a baseline, we used the 1992 sedimentary status for comparison. The seabed surface sediment distribution showed a great change between 1992 and 2011. We found the same four sediment facies, which were present in 1992, namely: mud, sandy mud, muddy sand, and fine sand. However, in 2011, mud covered more than 54% of the lagoon seabed surface, mostly located in the middle part of the seabed, whereas in 1992, more than 80% of the lagoon seabed was covered by sandy mud. The sediments’ characteristics showed moderately to poorly sorted facies (S0), ranging between platykurtic and leptokurtic (SK) and with various symmetry indices (SG). The organic matter content in sediment has strongly decreased, from values higher than 20% in most areas in 1992 to a mean value of 3.9% in 2011, ranging from 0.2% to 10.4%, thus confirming that the management actions implemented in 2009 were likely effective in reducing the organic pollution.

Modelling the influence of environmental and weather factors on the density of the invasive polychaete Boccardia proboscidea

AbstractThe inter‐tidal zone around sewage discharges in a Southwest Atlantic shore (Mar del Plata, Argentina) is currently colonized by extensive inter‐tidal reefs of the invasive spionid Boccardia proboscidea. Understanding the links between both human and natural disturbances and the massive development of non‐indigenous species will help prevent marine bioinvasions, which are already favoured by global oceanic trade. We present herein predictive models for variations in the density of B. proboscidea around sewage discharges of Mar del Plata, using environmental (pH, turbidity, temperature, salinity and total organic matter content), weather (wind direction and storm records), spatial (sites) and temporal (season and year) variables. Density variations were modelled by generalized linear models, and model averaging (multimodel inference) was used to obtain predicted values. The highest predicted values of B. proboscidea density occurred at sites to the south of the sewage effluent in spring. These sites are more affected by urban effluent discharges and they showed increased B. proboscidea density when the north wind was predominant. In addition, B. proboscidea density values were higher in sites with 20–22 °C (seawater temperature), high total organic matter content in sediments and low salinity. The averaged model was only a good ‘predictive model’ for sites to the north of the outfall, but was useful as an ‘explanatory model’ in all sites. Such predictions may help to back up conservation and management policies and decisions.

Geographic patterns of biodiversity in European coastal marine benthos

Within the COST action EMBOS (European Marine Biodiversity Observatory System) the degree and variation of the diversity and densities of soft-bottom communities from the lower intertidal or the shallow subtidal was measured at 28 marine sites along the European coastline (Baltic, Atlantic, Mediterranean) using jointly agreed and harmonized protocols, tools and indicators. The hypothesis tested was that the diversity for all taxonomic groups would decrease with increasing latitude. The EMBOS system delivered accurate and comparable data on the diversity and densities of the soft sediment macrozoobenthic community over a large-scale gradient along the European coastline. In contrast to general biogeographic theory, species diversity showed no linear relationship with latitude, yet a bell-shaped relation was found. The diversity and densities of benthos were mostly positively correlated with environmental factors such as temperature, salinity, mud and organic matter content in sediment, or wave height, and related with location characteristics such as system type (lagoons, estuaries, open coast) or stratum (intertidal, subtidal). For some relationships, a maximum (e.g. temperature from 15–20°C; mud content of sediment around 40%) or bimodal curve (e.g. salinity) was found. In lagoons the densities were twice higher than in other locations, and at open coasts the diversity was much lower than in other locations. We conclude that latitudinal trends and regional differences in diversity and densities are strongly influenced by, i.e. merely the result of, particular sets and ranges of environmental factors and location characteristics specific to certain areas, such as the Baltic, with typical salinity clines (favouring insects) and the Mediterranean, with higher temperatures (favouring crustaceans). Therefore, eventual trends with latitude are primarily indirect and so can be overcome by local variation of environmental factors.

Superficial sediments and their relation to polyehaete families in a subtropieal embayment, Mexico

The soft bottoms in front of Mazatlan Bay and "Isla de la Piedra" Peninsula were studied to produce maps (depth, grain size and organic matter content in sediments). Sixty samples were óbtained with a 30 x 30 van Veen grab (4-21 m depth) and polychaetes were extracted from 21 subsamples. Grain size ranged from -1.05 phi (gravel) to 3 .81 phi (very fine sand), with fme sand predominl\ting. Organic matter content in sediment was 0.91-3.06 % (most values = 1-2 %). Thirty polychaete families (905 individuals/m2 in mean) were found, and Cirratulidae, Spionidae, Onuphidae, and Pilargiidae were domiuant. Pearson's correlation of grain size.

Simultaneous determination of mercury and organic carbon in sediment and soils using a direct mercury analyzer based on thermal decomposition–atomic absorption spectrophotometry

The purpose of this work was to study the feasibility of using a direct mercury analyzer (DMA) to simultaneously determine mercury (Hg) and organic matter content in sediment and soils. Organic carbon was estimated by re-weighing the sample boats post analysis to obtain loss-on-ignition (LOI) data. The DMA-LOI results were statistically similar (p<0.05) to the conventional muffle furnace approach. A regression equation was developed to convert DMA-LOI data to total organic carbon (TOC), which varied between 0.2% and 13.0%. Thus, mercury analyzers based on combustion can provide accurate estimates of organic carbon content in non-calcareous sediment and soils; however, weight gain from moisture (post-analysis), measurement uncertainty, and sample representativeness should all be taken into account. Sediment cores from seasonal wetland and open water areas from six oxbow lakes in the Mississippi River alluvial flood plain were analyzed. Wetland sediments generally had higher levels of Hg than open water areas owing to a greater fraction of fine particles and higher levels of organic matter. Annual loading of Hg in open water areas was estimated at 4.3, 13.4, 19.2, 20.7, 129, and 135ngcm−2yr−1 for Beasley, Roundaway, Hampton, Washington, Wolf and Sky Lakes, respectively. Generally, the interval with the highest Hg flux was dated to the 1960s and 1970s.

Biodiversity of polychaete assemblages in a highly productive lagoon located in Baja California Sur, México

Polychaetes are key components of marine ecosystems. Their diversity of ecological niches is enormous, playing a significant role in sedimentary habitats. This study broadens the biodiversity information for the west coast of Baja California and particularly for Bahía Magdalena. Polychaete diversity and structure were assessed at 21 stations. Polychaetes were the dominant macrofaunal group with 30 families and 102 species identified in samples collected during two cruises in December 1996 and October 1999.Best-represented families were Capitellidae, Cirratulidae, Nephtyidae, Nereididae, Onuphidae, Paraonidae, and Spionidae. In 1996, densities ranged from 90 to 3460 individuals/m2 and Shannon index varied between 1.76–3.12 with the highest diversity values located in the northwestern area of Bahía Magdalena. In 1999, densities ranged from 70 to 1440 individuals/m2 and Shannon index was 1.72–2.83, and the highest values occurred in the north area of the bay. Organic matter content in sediments varied between 0.87–5.70%. Four functional feeding groups (carnivores, herbivores, deposit-feeders, and suspension-feeders) were found with deposit-feeders and carnivores as the most abundant. Multivariate analyses performed with abundance data showed different polychaete assemblages in 1999 compared to 1996. This work can serve as a base-line study to determine future changes in polychaete assemblages.

Sediment Carbon Storage of Two Main Wetlands in Pondicherry, India

Assessing the carbon storage patterns in the sediments of Oussudu and Kaliveli, considered as potential wetlands for conservation under RAMSAR convention and declared bird sanctuaries by the government was the objective of the study. Dissolved oxygen and CO2 diffusion rates in the 'surface waters' was analyzed and the relationship between the sediment carbon storage and oxygen/carbon dioxide in the waters was presented. The mean dissolved oxygen content for the study period (2009 - 2011) was 17.28 ± 3.25 mg/l for Oussudu and 35.5 ± 7.23 mg/l for Kaliveli respectively. The rate of CO2 diffusion was high (13.31±2.71 mg/l) in Kaliveli than in Oussudu (6.48±1.21 mg/l). High level of CO2 diffusion causes acidification forming carbonic acids which might be the cause of high levels of sediment calcium in Kaliveli. The mean calcium carbonate and organic matter content of sediment was 2.11±0.51% and 1.51±0.59% for Oussudu and 36.21±4.51% and 0.46±0.16% for Kaliveli respectively. The total organic carbon and phosphate content were 0.87±0.34% and 27.38±0.56 (mg/L) for Oussudu and 0.27±0.09% and 4.13±0.67 (mg/L) for Kaliveli respectively. There existed a significant inversely proportional relationship between calcium carbonate and organic matter and a strong positive relationship between organic matter and phosphate in the sediments. Our study reveals that majority of the carbon storage is through organic matter in Oussudu lake and through calcium carbonate in Kaliveli.

Factors controlling spatial distributions and relationships of carbon, nitrogen, phosphorus and sulphur in sediments of the stratified and eutrophic Gulf of Gdansk

Spatial distribution and coupling of carbon, nitrogen, phosphorus and sulphur were studied in sediments of the Gulf of Gdansk, southern Baltic Sea. We report data on sedimentary contents of total and organic carbon (TC and OC), total nitrogen (TN), total and organic phosphorus (TP and OP) and total sulphur (TS), as well as pore water concentrations of ammonium, phosphate and hydrogen sulphide. The lowest values of all the investigated parameters were observed in coastal area, while the highest were noted in sediments below halocline which is attributed to changing hydrodynamic conditions and sedimentation regimes with depth. The contents of TC, OC, TN, TP, OP and TS in sediments and their molar ratios were also noted to vary spatially in relation to distance from land and oxygen conditions in near-bottom water. As a result of high organic matter supply to the sediments caused by eutrophication we observed increased contents of TC, OC, TN, TP and OP in the upper few centimetres of sediment. Results obtained for the Gdansk Deep indicate that sediments in this area are site of accumulation of sulphur and redox-dependent phosphorus release.We analysed relationships between the investigated parameters and organic matter content in sediments measured as loss-on-ignition (LOI). Regression analysis indicated that LOI was a good estimator of contents of OC, TN and OP in the Gulf of Gdansk sediments and may be used as a screening tool when planning geochemical investigations. However, calculated equations can only be applied to LOI results obtained at similar temperature and exposure time (550°C, 6h). In addition to this, the method was unreliable for prediction of TS content in euxinic environments where, as in the Gdansk Deep sediments, accumulation of sulphur occurs due to the formation of iron (II) sulphides.

Palaeoclimate inferred from δ18O and palaeobotanical indicators in freshwater tufa of Lake Äntu Sinijärv, Estonia

We investigated a 3.75-m-long lacustrine sediment record from Lake Äntu Sinijärv, northern Estonia, which has a modeled basal age >12,800 cal yr BP. Our multi-proxy approach focused on the stable oxygen isotope composition (δ18O) of freshwater tufa. Our new palaeoclimate information for the Eastern Baltic region, based on high-resolution δ18O data (219 samples), is supported by pollen and plant macrofossil data. Radiocarbon dates were used to develop a core chronology and estimate sedimentation rates. Freshwater tufa precipitation started ca. 10,700 cal yr BP, ca. 2,000 years later than suggested by previous studies on the same lake. Younger Dryas cooling is documented clearly in Lake Äntu Sinijärv sediments by abrupt appearance of diagnostic pollen (Betula nana, Dryas octopetala), highest mineral matter content in sediments (up to 90 %) and low values of δ18O (less than −12 ‰). Globally recognized 9.3- and 8.2-ka cold events are weakly defined by negative shifts in δ18O values, to −11.3 and −11.7 ‰, respectively, and low concentrations of herb pollen and charcoal particles. The Holocene thermal maximum (HTM) is palaeobotanically well documented by the first appearance and establishment of nemoral thermophilous taxa and presence of water lilies requiring warm conditions. Isotope values show an increasing trend during the HTM, from −11.5 to −10.5 ‰. Relatively stable environmental conditions, represented by only a small-scale increase in δ18O (up to 1 ‰) and high pollen concentrations between 5,000 and 3,000 cal yr BP, were followed by a decrease in δ18O, reaching the most negative value (−12.7 ‰) recorded in the freshwater tufa ca. 900 cal yr BP.

N2 fluxes in sediments of the Elbe Estuary and adjacent coastal zones

ABSTRACT: The conversion of reactive nitrogen species to N 2 during denitrification in sedimentsmay be one of the most valuable ecosystem services provided by estuarine and intertidal environ-ments near river discharge areas. To quantify the rates and limiting factors of denitrification in theestuary of the Elbe River and adjacent Wadden Sea (SE North Sea), we measured sediment N 2 fluxes across subtidal and intertidal sediments, and along gradients in nitrate and organic matterconcentrations. We conducted 2 sampling campaigns, in March and September 2009, duringwhich N 2 fluxes were quantified by N 2 /Ar measurements in sediment core incubations, and com-pared to isotope pairing results in September 2009. At ambient nitrate concentrations, sediments inthe inner Elbe Estuary produced N 2 fluxes of up to 156 µmol N m −2 h −1 . In September, nitrate con-centration in bottom water and organic matter content in sediments limited N 2 production; suchlimitations were not observed in March. We extrapolated the estuarine sediment nitrogen removalof March and September to the present-day area of intertidal and subtidal sediments in the ElbeEstuary between the port of Hamburg and the transition to the North Sea. Our estimate suggeststhat 3.3 ± 1.2 kt nitrate-N are removed in sediments in this region in spring and summer. This im-plies that reactive nitrogen removal in the inner Elbe Estuary reduces the spring/summer load ofthe Elbe River (47 kt N) by around 7%, a reduction that is much lower than commonly assumed forestuaries, and significantly lower than nitrate removal in the Elbe was in historical times.KEY WORDS: Denitrification · Nitrogen cycle · Eutrophication · Elbe Estuary

Environmental Factors Influencing the Prevalence of a Clostridium botulinum Type C/D Mosaic Strain in Nonpermanent Mediterranean Wetlands

Between 1978 and 2008, 13 avian botulism outbreaks were recorded in the wetlands of Mancha Húmeda (central Spain). These outbreaks caused the deaths of around 20,000 birds from over 50 species, including globally endangered white-headed ducks (Oxyura leucoceophala). Here, a significant association was found between the number of dead birds recorded in each botulism outbreak and the mean temperature in July (always >26°C). The presence of Clostridium botulinum type C/D in wetland sediments was detected by real-time PCR (quantitative PCR [qPCR]) in 5.8% of 207 samples collected between 2005 and 2008. Low concentrations of Cl(-) and high organic matter content in sediments were significantly associated with the presence of C. botulinum. Seventy-five digestive tracts of birds found dead during botulism outbreaks were analyzed; C. botulinum was present in 38.7% of them. The prevalence of C. botulinum was 18.2% (n = 22 pools) in aquatic invertebrates (Chironomidae and Corixidae families) and 33.3% (n = 18 pools) in necrophagous invertebrates (Sarcophagidae and Calliphoridae families), including two pools of adult necrophagous flies collected around bird carcasses. The presence of the bacteria in the adult fly form opens up new perspectives in the epidemiology of avian botulism, since these flies may be transporting C. botulinum from one carcass to another.

Deposit-Feeding Sea Cucumbers Enhance Mineralization and Nutrient Cycling in Organically-Enriched Coastal Sediments

BackgroundBioturbators affect multiple biogeochemical interactions and have been suggested as suitable candidates to mitigate organic matter loading in marine sediments. However, predicting the effects of bioturbators at an ecosystem level can be difficult due to their complex positive and negative interactions with the microbial community.Methodology/Principal FindingsWe quantified the effects of deposit-feeding sea cucumbers on benthic algal biomass (microphytobenthos, MPB), bacterial abundance, and the sediment–seawater exchange of dissolved oxygen and nutrients. The sea cucumbers increased the efflux of inorganic nitrogen (ammonium, NH4 +) from organically enriched sediments, which stimulated algal productivity. Grazing by the sea cucumbers on MPB (evidenced by pheopigments), however, caused a net negative effect on primary producer biomass and total oxygen production. Further, there was an increased abundance of bacteria in sediment with sea cucumbers, suggesting facilitation. The sea cucumbers increased the ratio of oxygen consumption to production in surface sediment by shifting the microbial balance from producers to decomposers. This shift explains the increased efflux of inorganic nitrogen and concordant reduction in organic matter content in sediment with bioturbators.Conclusions/SignificanceOur study demonstrates the functional role and potential of sea cucumbers to ameliorate some of the adverse effects of organic matter enrichment in coastal ecosystems.

Radiological characterization and environmental impact in northwestern coast of Egypt

A study of environmental radioactivity along the northwestern coast of Egypt was performed by the Central Laboratory for Environmental Radioactivity Measurements Inter-comparison and Training within the framework of the research project: Radiological Studies/Measurements of Natural and Man-made Radionuclides in the Environment. The present paper contains important conclusions, correlations and interpretations of the environmental measurements. The samples collection and measurements were conducted according to the Egyptian Atomic Energy Authority monitoring plan for locations along the northwestern coast of Egypt and its main tributaries of interest. The specific activities of 226Ra (238U series), 228Ra (232Th series), 40K and 137Cs (Bq/kg dry weight) were measured using gamma-ray spectrometers based on hyper-pure germanium detectors. The absorbed radiation dose rates in air (nGy/h) due to natural radionuclides in shore sediment and radium equivalent activity index (Bq/kg) were calculated. The specific activity ratios of 228Ra/226Ra were calculated for evaluation of the geo-chemical behavior of these radionuclides. Samples textures and CaCO3 and total organic matter contents of sediments were also determined while the pH, major cations and anions such as Na+, K+, Ca++, Mg++and Cl−, SO4 – and HCO3, respectively were also determined in water samples.

Distribution of Organic Matter in Sediment of Lakeside Belt in East Dongting Lake

Distribution of organic matter and effect of wetland types and pH on organic matter were studied in sediment of lakeside belt in east Dongting Lake according to taking 56 samples from surface to 20cm and 52 samples from 20cm to 40cm. The results showed that the average content of organic matter was 15.40g/kg from surface to 20cm and 12.02g/kg from 20cm to 40cm in sediment of lakeside belt in east Dongting Lake. Spatial distribution of organic matter could be expressed as middle variation. Wetland types were classed into silt beach, lake marsh beach and reed beach in Dongting Lake region and influenced distribution of organic matter because of difference variance on hydraulic dynamics condition and retarding effect of vegetation on water flow velocity. Order of organic matter content in sediment was the lake marsh beach &gt; reed beach &gt; silt beach in 0-20cm and 20-40cm layers in lakeside belt in east Dongting Lake. Organic matter contents decreased in turn from 0-20cm to 20-40cm in lake marsh and reed beaches and increased in silt beaches. Values of pH in sediment were slightly alkaline in whole studied region. Negative correlation was established between organic matter content and pH value. The results will provide base data and science reference for controlling and recovery of sediment pollution in east Dongting Lake.

Influential factors on the levels of cation exchange capacity in sediment at Langat river

An exploratory study was carried out at 22 sampling stations along the Langat River, Selangor in order to investigate on the vitality of cation exchange capacity (CEC) in sediment (0–5 cm). Parameters such as pH, Eh, salinity, and electrical conductivity (EC) were determined. The CEC in sediment has been calculated by the determination of Ca2+, Na+, Mg2+, and K+ using the flame atomic absorption spectrophotometer, while the organic matter content in sediment was ascertained using the loss on ignition method. The characteristic of the sediment shows that pH (3.09–7.46), salinity (0.02–10.71 ppt), EC (3.39–517 μS/cm) and Eh (−16.20–253.10 mV) were substantially high in variation. This study also revealed that exchangeable Ca2+ and Mg2+ were controlled by organic matter contents, while exchangeable Na+ and K+ were influenced by salinity. Salinity was observed to play a major part in controlling all the exchangeable cations, as it gives strong significant correlations with Na+, K+, Mg2+, CEC, and organic matter at p < 0.01. The presence of seawater, clay mineralogy, and organic matter proves that it does play an important role in determining the CEC and soon relates to the pollution magnitude in the sediment.

Struktur Komunitas Gastropoda Di Perairan Pesisir Kecamatan Genuk Kota Semarang

Gastropods have an important role in aquatic environments, especially in food and energy cycles. This aim of study determine the abundance and structure community of gastropods and physical parameters of the water, the type of substrate sediments and organic matter content in sediments that serve to optimize the utilization analysis and estimation of the abundance of gastropods conditions contained in the Genuk Coastal Waters, the city of Semarang. The method used in this research descriptive method by means of sampling stations gastropods includes 6 points. The study results for all sampling points had 260 individuals, that comprise of 10 species, namely Turricula javana, Thaislacera, Murex trapa, Bufonaria rana linnaeus, Nassarius sp, Natica tigrina, Babylonia spirata, Turritella terebra, Pseudoneptunea varicosa, and Conus sp. Sum abundance of species ranging between 0,08 to 2,37 individu/m2. Value index of diversity (H') ranged from 0,000 to 2,026 in the category of low and moderate, and values of uniformity index (e) ranged from 0,000 to 1,461 are included in the high category and the dominance index (c) between 0,255 to 1 in the category of not no dominance (TAD) and no dominance (AD), and for the distribution patterns are dominated by the uniform distribution pattern from the clumped distribution patterns whereas community similarity (S) category was up to the height ranges between 44,44% - 88,89%.

Fugacity approach to evaluate the sediment–water diffusion of polycyclic aromatic hydrocarbons

Diffusion is an important process for sediment-water exchange and plays a vital role in controlling water quality. Fugacity fraction (ff) was used to estimate the sediment-water diffusion of polycyclic aromatic hydrocarbons (PAHs) between seawater and surficial sediment. A total of 33 surface sediment and sea water samples were collected concurrently from the northeast coastal area in China and 25 PAHs were analyzed including the alkylated and chlorated PAHs. Fugacity fraction was calculated based on the PAH concentrations in water and sediment, octanol-water partition coefficient of PAHs, organic matter content in sediment, and density of sediment. The calculated results showed that ff increased with decreasing molecular weight of PAHs. The low molecular weight PAHs (2-3 rings) transferred from sediment to water and the sediment acted as a secondary source to the water. The medium molecular weight PAHs (4-5 rings) were close to the sediment-water equilibrium and the transfer tendency shifted between sediment and water. The high molecular weight PAHs (5-6 rings) transferred from water into sediment and the sediment acted as a sink. Soot carbon and the difference of PAH concentrations between sediment and water were found to be important factors affecting the sediment-water diffusion. This study provided new insight into the process of sediment-water diffusion, which has a great influence on the quality of water, especially in severely-polluted sediment areas.

Distribution and bioaccumulation of organochlorine pesticides in surface sediments and benthic organisms from Taihu Lake, China

The spatial distribution and bioaccumulation of organochlorine pesticides (OCPs) in surface sediments and benthic organisms from Taihu Lake were studied. OCPs were detected in all sediment samples with total concentrations ranging from 4.22 to 461 ng g −1 dry weight (dw). The ratios of certain metabolites to their parent compounds indicated there are still new inputs of parent DDT (dichlorodiphenyltrichloroethane) to Taihu Lake, while the highest residues of HCHs (hexachlorocyclohexanes) mainly came from earlier usage and fresh γ-HCH (lindane). No positive correlation was found between the distribution of OCPs and organic matter contents in sediments. Concentrations of OCPs and lipids in typical large benthic organisms, Bellamya aeruginosa ( B. aeruginosa) and Corbicula fluminea ( C. fluminea) , increased with body weight. HCHs, DDTs, chlordanes and heptachlors were the dominant compounds detected in organisms and C. fluminea accumulated much more OCP than B. aeruginosa. Higher values of biota-sediment accumulation factor (BSAF) were detected in C. fluminea, which was both affected by biological characteristics of the organisms and physicochemical properties of the compounds.