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1.
Heavy metal speciation and the associated ecological risks were investigated, using a European Community Bureau of Reference sequential extraction procedure, in sediments from the residential, mixed (residential and industrial), and agricultural areas of rural rivers in southern Jiangsu Province, China. Compared with the background values in Jiangsu Province soils, Cd was the metal with the highest contamination level, especially in the mixed area, followed by Cu and Zn. In the sediment samples from the agricultural area, the heavy metal concentrations were no more than two times greater than the background values. There were higher proportions of Cd in the acid-soluble fraction, Cr in the residual fraction, and Pb in the reducible fraction in the three areas. The heavy metal mobility was mainly controlled by the acid-soluble and reducible fractions. Cd could pose extremely high risks to the environment. In addition, the risks of heavy metal to the environment in the three areas followed the order: mixed area > residential area > agricultural area. Furthermore, a risk assessment code analysis showed that most of the sediment samples were classified as being of high to very high risk in the residential and mixed areas because of their Cd, Ni, and Zn concentrations. Heavy metal pollution in the residential and mixed areas is generally serious, and immediate remediation measures need to be taken.  相似文献   

2.
Five heavy metals (Cd, Cu, Ni, Pb, and Zn) in river sediments from Abshineh River, Hamedan, western Iran, were fractionated by a sequential extraction procedure. Cu, Ni, Pb, and Zn existed in sediments mainly in residual fraction (mean 92%, 86%, 77%, and 65%, respectively), whereas Cd occurred mostly as organic matter (mean 41%) and exchangeable (mean 25%) fractions. The mean percent of mobile fraction of Cd, Cu, Ni, Pb, and Zn in contaminated sediments was 25, 13, 4, 24, and 10, respectively, which suggests that the mobility and bioavailability of the five metals in sediments probably decline in the following order: Cd = Pb > Cu > Zn > Ni. The metal levels were also evaluated according to the contamination factor, which revealed significant anthropogenic pollution of Cd and Pb.  相似文献   

3.
Little is known on microbial activities in the sediments of large lowland rivers despite of their potentially high influence on biogeochemical budgets. Based on field measurements in a variety of sedimentary habitats typical for a large lowland river (Elbe, Germany), we present results on the abundance and production of sedimentary bacteria, the potential activity of a set of extracellular enzymes, and potential nitrification and denitrification rates. A diving bell was used to access the sediments in the central river channel, enabling us to sample down to 1 m sediment depth. Depth gradients of all measures of microbial activity were controlled by sediment structure, hydraulic conditions, as well as by the supply with organic carbon and nitrogen. Microbial heterotrophic activity was tightly coupled with the availability of carbon and nitrogen, whereas chemolithotrophic activity (nitrification rate) was related to the available surface area of particles. In the central bed of the river, bacterial production and extracellular enzyme activity remained high down to the deepest sediment layers investigated. Due to the large inner surface area and their connectivity with the surface water, the shifting sediments in the central channel of the river were microbially highly active There, vertically integrated bacterial production amounted to 0.95 g C m−3 h−1, which was 2.9 to 5.5 times higher than in the nearshore habitats. We conclude that carbon and nitrogen cycling in the river is controlled by the live sediments of the central river channel, which thus represent a “liver function” in the river's metabolism.  相似文献   

4.
Grain size distribution patterns along the East Frisian coast (German Wadden Sea) were evafuated with the aim of identifying potential effects of man-made structures (e.g. dikes) on the textural composition and sediment budget of the area. It was found that the distribution of various grain size fractions and settling velocities revealed a well-defined cross-shore energy gradient. Adjacent to the mainland dike the sediment is dominated by the 3.0–3.5 phi sand fraction (>70% by weight). In comparison to the sedimentary sequences normally observed in unobstructed backbarrier depositional environments, the sediments along the land-ward margin are in this case conspicuously depleted in grain sizes <3.5 phi, the corresponding size fractions contributing <20% by weight. This suggests that the dike interrupts the normal energy gradient, thereby inhibiting the deposition of sediments with settling velocities <0.5 cm s−1. This interpretation is confirmed when comparing individual cross-shore transects. The shorter the transect between the barrier island shore and the dike, the greater the fine sediment depletion. Since many faunal assemblages are grain-size specific, it is further suggested that the backbarrier ecosystem must have undergone significant modifications as a result of the substantial reduction in mud flats since the onset of dike construction some 1000 years BP. It is predicted that in the wake of the persisting and possibly accelerating sealevel rise this process of fine sediment depletion will continue and also affect progressively coarser sediments.  相似文献   

5.
Heavy metal discharge has become one of the most serious environmental problems due to extensive industrialization. Sixty eight sediment samples from four wetlands were collected to analyze the regional factors affecting metal deposition. Meanwhile, a national sediment data collection based on relevant publications was developed covering the period from 2000 to 2016 to study the metal distribution in China. Principal metals assessed in this study are Cr, Cd, Cu, Pb, Zn, As, and Ni. At regional scale, the accumulation of Pb and Cd is significantly higher in surface than in subsurface sediments. At the national scale, heavy metals tend to increase with the increase in precipitation from 600 to 1500 mm. Further, metal deposition in the main river basins in China shows an increase trend from northern to southern China, and follows the order of: Pearl River > Yangste River > Yellow River > Hai River and Liao River. Cluster analyses show that these river basins contribute a large proportion of heavy metals to coastal metal deposition, which follows the order of: South Sea > East Sea > Bohai Sea > Yellow Sea. In general, metal deposition in sediments of water systems increases from northern to southern China irrespective of in-land area or coastal seas.  相似文献   

6.
To understand the effect of submerged macrophytes on P in sediment, P fractions in the surface sediments (0–20 cm) of Potamogeton crispus, Potamogeton maackianus and non-vegetated areas were investigated. In the submerged macrophytes areas, the concentrations of HCl-P, NaOH-P, IP, OP and BD-P were significantly lower than in the non-vegetated area. NH4Cl-P did not differ significantly among areas.

In the submerged macrophyte distribution areas, TP was significantly correlated with IP and OP. However, in the non-vegetated area, TP was significantly correlated with NH4Cl-P and OP. In all of the areas sampled, IP was the major phosphorus fraction in the sediments, which consists largely of NAOH-P and HCl-P. The decreasing order of P fractions was: IP > HCl-P > NaOH-P > OP > BD-P > NH4Cl-P. These results show that submerged macrophytes can decrease the concentrations of all P fractions and imply that submerged macrophytes play a key role in the retention of P nutrients.  相似文献   


7.
Sediment samples from the Ave river basin were collected with the aim of determining metal total pollution contents. Cr, Cu, Fe, Mn, Pb, Zn and VM at 550 °C were determined. Some physico-chemical parameters were also quantified in water samples collected in the water column just above the sediments.

Metal contamination factors (CF) indicated that sediments were not contaminated with Cu and Pb, slightly with Zn and moderately with Cr.

For sediments with high metal pollution loadings, the original BCR (Community Bureau of Reference) metal speciation protocol was also applied. Speciation studies showed that chromium was mainly associated with the oxidisable plus residual fractions (>85%). These results suggest that changes in the physico-chemical properties of the river water (e.g. pH, Eh) should not be accompanied by a significative release of chromium from sediments.

The relationships between chromium speciation fractions, physic-chemical parameters of the sediments and water samples were studied by Principal Component Analysis, and allowed to reduce the dimensionality of the data matrix from 14 to 3 significant components accounting for 89% of the variance. It was found that hydrous Fe/Mn oxides and organic matter are the “carriers” of chromium associated to fractions exchangeable and oxidable.  相似文献   


8.
We aimed to identify the environmental factors which significantly affect metal uptake by reed plants in the intertidal marshes along the river Scheldt. Transfer coefficients, defined as the ratio of metal concentrations in reed stems to the metal contents in specific sediment fractions (i.e. the exchangeable Cd and Zn fraction and total Cr, Cu, Ni and Pb content), were calculated for each sampling site. They were inversely related to the sediment clay and/or organic matter content. Metal mobility and thus plant availability is higher in sediments with a lower clay or organic matter content. Moreover, the plants might actively accumulate in particular essential elements when concentrations in the sediments are rather low, which is the case in sediments low in clay and organic matter contents. Finally, more sandy sediments are expected to be susceptible to occasional oxidation of sulphides, which leads to an increased metal availability. A higher salinity promoted the uptake of Cu, Cr and Zn.  相似文献   

9.
Heavy metal distribution, bioavailability, and ecological risk in the surface sediment of Taihu Lake were evaluated. Samples were collected from eight representative sites in September 2011 and February 2012. In the surface sediment, average metal contents were in the order of Cr > Zn > Ni > Pb > Cu. Spatially, Zhushan Bay maintained higher Cu, Ni, and Zn contents and Xiaomeikou maintained higher Cr and Pb contents than other sites. Spatial and temporal variation were observed in the bioavailable metals determined by acid-soluble fraction of BCR extraction. The labile metals in Zhushan Bay and Xiaomeikou were quantified by diffusive gradients in thin films (DGT) and DGT-labile concentrations of Zn, Ni, Cu, Pb, and Cd were in descending order, indicating the inconsistence of labile concentrations of different heavy metals with the total metal contents and that the toxic effect of Cd in sediment should be given attention. The ecological risk assessed by Hakanson potential ecological risk index showed that Zhushan Bay suffered the most serious pollution and should be given special attention. Bioavailability of metals should be taken into account during risk assessment for more accurate estimation.  相似文献   

10.
Columnar sediment samples were collected from five representative estuaries of Dianchi Lake, China. And the vertical distribution of each fraction of nitrogen (IEF-N, CF-N, IMOF-N, OSF-N) were tested. The results showed that the TN content in sediments from areas A, B, C, D and E gradually decreased with depth between 0 and 15 cm, then sharply decreased with depth between 15 and 30 cm and stabilized at depth below 30 cm, indicating the exogenous input of N in these areas has not been controlled effectively. The proportion of TN occupied by various N fractions in the sediments ranked as follows: OSF-N > IMOF > CF-N > IEF-N. Correlation analysis results showed both IEF-N and IMOF-N were significantly correlated with the content of TFe2O3 + MnO + Al2O3 in deeper sediments, while no correlation in superficial sediments. The areas A and B have extremely high release risks for N in superficial sediments. However, the N in the sediments of areas C, D and E were in relative equilibrium with the overlying water, indicating release potential risk was relatively low.  相似文献   

11.
Respiratory electron transport system (ETS) activity and oxygen consumption in the interstitial water, and in the fine (i.e. silt) and coarse (sand) sediment fractions from the hyporheic zone of the prealpine river Bača (W Slovenia) have been measured in order to estimate the intensity of potential and actual carbon mineralization through microbial communities. Hyporheic samples from the river bed (RB) and gravel bars (GB) were compared. ETS activity and oxygen consumption of all fractions from the RB did not differ significantly from those from the GB. ETS activity and oxygen consumption of biofilm attached to 1 g of the silt were higher than of that attached to the same mass of the sand. A significant correlation between ETS activity and oxygen consumption indicated that the former should be a good indicator of intensity of bioactivity in hyporheic sediments. The ratio of ETS activity to oxygen consumption (ETS/R ratio) revealed that the oxygen consumption of microorganisms is responsible for approximately 60% of the metabolic potential in the hyporheic sediments. The contributions of different fractions of sediment to the total ETS activity differed between RB and GB. The contribution of microorganisms in the interstitial water and silt was higher in GB than in the RB, but the sand fraction contributed less to potential carbon loss in GB than in the RB. Average total respiratory carbon loss per volume through the hyporheic zone was higher in the RB than in GB. The main reasons suggested are the different intensity of exchange of surface water with the hyporheic zone, and the rate of consolidation of sediments, which is primarily a function of river hydrology and geomorphology. Handling editor: J. Padisak  相似文献   

12.
The mobility and bioavailability of copper (Cu) depends on the Cu sorption capacity of soil and also on the chemical form of Cu in soils. Laboratory batch experiments were carried out to study the sorption and distribution of Cu in nine soils differing in their physicochemical properties from the oasis in the middle reaches of Heihe river basin, China: desert soil (S-1), agricultural soils (S-2, S-3, S-8, and S-9), marshland soil (S-4), and hungriness shrub soils (S-5 and S-6). Copper sorption behavior was studied using the sorption isotherm and sequential extraction procedure. In general, the sorption capacity for Cu decreased in the order: S-4 > S-9 > S-2 > S-8 > S-3 > S-6 > S-5 > S-7 > S-1. The correlation results suggest that soils with higher CEC, silt, clay, CaCO3, and organic matter will retain Cu more strongly and in greater amounts than soils that are sandy with lower CEC, CaCO3, and organic matter. pH is not an important impact factor to Cu sorption in experimental soil samples because pH in soils used in this study had a narrow range. The distribution of sorbed Cu varied between nine soils studied and depended on both soil properties and initial added Cu concentration. There are significant differences in the distribution of Cu in each soil with the increase of initial Cu concentration. The predominance of Cu associated with the available fraction, which was over 50% of the total sorbed Cu in most cases, indicates that the change of geochemical conditions might promote the release of Cu back into soil solution thus impacting organisms in the soils. The added Cu has also the tendencies to locate in the residual fraction, which was larger than 5% of the total amount extracted from the four fractions in most soils.  相似文献   

13.
The Salton Sea is a hypersaline lake located in southeastern California. Concerns over the ecological impacts of sediment quality and potential human exposure to dust emissions from exposed lakebed sediments resulting from anticipated shrinking of shoreline led to a study of pesticide distribution and transport within the Salton Sea Basin, California, in 2001–2002. Three sampling stations—upriver, river mouth, and offshore—were established along each of the three major rivers that discharge into the Salton Sea. Large-volume water samples were collected for analysis of pesticides in water and suspended sediments at the nine sampling stations. Samples of the bottom sediment were also collected at each site for pesticide analysis. Sampling occurred in October 2001, March–April 2002, and October 2002, coinciding with the regional fall and spring peaks in pesticide use in the heavily agricultural watershed. Fourteen current-use pesticides were detected in water and the majority of dissolved concentrations ranged from the limits of detection to 151 ng/l. Diazinon, EPTC and malathion were detected at much higher concentrations (940–3,830 ng/l) at the New and Alamo River upriver and near-shore stations. Concentrations of carbaryl, dacthal, diazinon, and EPTC were higher in the two fall sampling periods, whereas concentrations of atrazine, carbofuran, and trifluralin were higher during the spring, which matched seasonal use patterns of these pesticides. Current-use pesticides were also detected on suspended and bed sediments in concentrations ranging from detection limits to 106 ng/g. Chlorpyrifos, dacthal, EPTC, trifluralin, and DDE were the most frequently detected pesticides on sediments from all three rivers. The number of detections and concentrations of suspended sediment-associated pesticides were often similar for the river upriver and near-shore sites, consistent with downstream transport of pesticides via suspended sediment. While detectable suspended sediment pesticide concentrations were more sporadic than detected aqueous concentrations, seasonal trends were similar to those for dissolved concentrations. Generally, the pesticides detected on suspended sediments were the same as those on the bed sediments, and concentrations were similar, especially at the Alamo River upriver site. With a few exceptions, pesticides were not detected in suspended or bed sediments from the off-shore sites. The partitioning of pesticides between water and sediment was not predictable from solely the physical–chemical properties of individual pesticide compounds, but appear to be a complicated function of the quantity of pesticide applied in the watershed, residence time of sediments in the water, and compound solubility and hydrophobicity. Sediment concentrations of most pesticides were found to be 100–1,000 times lower than the low-effects levels determined in human health risk assessment studies. However, maximum concentrations of chlorpyrifos on suspended sediments were approximately half the low-effects level, suggesting the need for further sediment characterization of lake sediments proximate to riverine inputs. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005  相似文献   

14.
We combined sediment and faunal data to explore the role of the sedimentary regime in shaping the distribution of subtidal sandbank environments and the associated meiofaunal nematode communities at Broken Bank and Swarte Bank, in the southern North Sea. A variety of sediment transport processes occur in the area, differing in the frequency and magnitude of sediment mobility, and the continuum between erosion, translation and sediment accumulation. The seabed contained a variety of bedforms, including longitudinal furrows, and small to very large sandwaves. The bed sediments were dominated by fine and medium sands, with admixtures of silt and gravel. Based on sedimentary bedforms and grain size analysis, a total of 11 sedimentary facies were delineated, of which 8 were analysed in detail for their relationships with the meiofauna. The sedimentary facies fell clearly into groups of facies, respectively representing high, high-moderate and moderate, and episodic sediment mobility. For those sedimentary facies where daily movement of sediments and bedforms occurred (‘high’ sediment mobility), the resulting spatially homogeneous environments were dominated by an impoverished nematode community comprising small deposit feeders and large predators. Resistance to sediment movement and the ability to exploit alternative food sources were prominent functional features of the successful colonisers. Those facies characterised by relatively infrequent sediment mobility (‘episodic’ and ‘high-moderate and moderate’ sediment mobility) comprised a heterogeneous suite of benthic habitats, containing taxonomically and functionally diverse assemblages of nematodes of various sizes, feeding types and reproductive potential. Faunal distribution patterns here indicated trade-offs between the resistance to sediment movement, environmental tolerance and competitive abilities. Our focus on diverse assemblages of organisms with high turnover times, inhabiting highly dynamic sedimentary environments, has revealed new animal-sediment relationships of relevance to pure and applied science.  相似文献   

15.
1. Nutrient concentrations in interstitial water springs at the downstream ends of two gravel bars in the River Rhône were measured in order to estimate the importance of nutrient inputs [nitrate, dissolved organic carbon (DOC), biodegradable and refractory fractions of DOC] from the parafluvial zone (saturated sediments adjacent to the wetted channel, i.e. interstitial habitats of gravel bars) to the river as well as seasonal variations in these inputs.
2. Compared with surface water, parafluvial water had lower concentrations of DOC (especially the refractory fraction) and generally higher concentrations of nitrate. These differences were at their lowest during winter.
3. The influence of gravel bar geomorphological heterogeneity (grain size and spatial distribution of fine sediments) on parafluvial inputs was studied in terms of nutrient content and biofilm characteristics along transects across the gravel bars.
4. A gravel bar located in a stable area of the river had low transversal heterogeneity and acted as a sink for DOC and as a source of nitrate. The low fine sediment content and the high oxygenation of interstitial water must have enabled aerobic processes such as mineralization of organic matter and nitrification to occur.
5. In contrast, gravel bars located in a degradation zone of the river had a spatially variable structure, acting as a sink for DOC and nitrate because localized accumulation of fine sediment and ensuing hypoxic conditions induced anaerobic processes such as denitrification.
6. This study highlights the important influence of geomorphological heterogeneity in gravel bars for nutrient transformations as well as nutrient exchanges between parafluvial interstitial systems and the adjacent river over a seasonal cycle.  相似文献   

16.
A flood event in a river will redistribute the bed sediments and may bury benthic insect larvae. To test the responses of case-building caddis larvae under such circumstances, we buried fourth instar larvae of Potamophylax cingulatus (Limnephilidae) in sediment of various grain size diameters (<1, 1–4, 4–10, >10 mm) to a depth of 1 or 2 cm. Depth of burial significantly affected time taken to emerge, individuals buried to 2 cm requiring longer to emerge, particularly if buried in fine (<1 mm) or coarse (>10 mm) sediment. Two thirds of those buried 2 cm deep in fine sediment abandoned their cases before emerging, whereas very few of those buried in coarser sediments and none buried to 1 cm depth emerged without a case. Burial in fine sediment is detrimental to P. cingulatus individuals, to the extent that they will abandon their cases, increasing the risk of predation, in order to facilitate escape. The case mass probably acts as a physical impediment to movement in fine matter, particularly if the animals experience respiratory stress. In coarse sediment, weight of sediment particles may slow down emergence, but not to the extent that individuals resort to case abandonment.  相似文献   

17.
Some results of a 2-year study of mercury pollution of the Katun river (Siberia) are summarised. Measurements of water flow, sediment transport and mercury concentrations were made and used to calculate the amount of mercury transported by the river. The distribution of transport between water phase and suspended material is calculated. It is concluded that suspended sediments play the main role in this process. The significance of different fractions of suspended sediment is also discussed.  相似文献   

18.
We investigated the distribution and diversity of tetracycline resistance genes encoding ribosomal protection proteins (RPPs) in river and channel sediments of the Mekong Delta in Vietnam. The sediment samples were taken from nine sites in the Hau River in southern Vietnam and from 1 site in a channel in Can Tho City in May 2004 using an Ekman-Birge sediment surface sampler. The RPP genes were amplified using PCR with DNA templates obtained directly from the sediments. The tet(M), tet(S), and tet(W) genes were detected by PCR in most sediment samples. Denaturing gradient gel electrophoresis analysis of these genes and sequencing of the resulting bands showed that tet(S) and tet(W) had only one genotype each, but that tet(M) had at least two, which were tentatively called type 1 and type 2. Type 1 tet(M) was identical to the gene encoded in various plasmids and transposons of gram-positive and gram-negative bacteria, and type 2tet(M) was similar to the gene encoded in Tn1545 of Enterococcus faecalis (99% identity, 170 bp/171 bp). This study showed that various RPP genes were widely distributed in the river and channel sediments of the Mekong Delta.  相似文献   

19.
Different phosphorus fractions and metal element composition of surficial sediments were measured on three occasions in 2005 and 2006 along a transect between Nyanza Gulf and offshore Lake Victoria, in order to assess the potential for sediments to contribute to the water column P concentrations in Lake Victoria. Total phosphorus (TP), apatite phosphorus (AP), inorganic phosphorus (IP) and organic phosphorus (OP) increased in sediments along the gulf towards the main lake while the non-apatite inorganic phosphorus (NAIP) increases were less defined. The longitudinal gradient of sediment TP and its fractions in Nyanza Gulf is a result of high rates of terrigenous input and resuspension and transport of the light, phosphorus rich inorganic and organic matter towards the main lake. TP in the sediment ranged from 812.7 to 1,738 mg/kg dry weight (DW) and was highest in the Rusinga Channel, the exchange zone between the gulf and the main lake. AP was the most important TP fraction, contributing between 35 and 57.3% of TP. Ca content in the sediment was strongly associated with TP and AP in the sediment (r2 = 0.92 and 0.98, respectively) in the gulf and the channel, indicating the importance of apatite in controlling P availability in these zones. In the gulf and the Rusinga Channel, the less bioavailable apatite phosphorus dominated, whereas in the deeper main lake OP was the major fraction illustrating the importance of anaerobic release of P from sediments and acceleration of internal P loading in the main lake.  相似文献   

20.
The present research was conducted to determine heavy metals in agricultural soils from Çanakkale, Turkey, using a sequential extraction procedure (acid soluble, reducible, oxidizable, and residual) as proposed by the Community Bureau of Reference (BCR) of the European Commission. Soil samples were taken from 12 different cultivated sites and analyzed for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn concentrations. The results revealed an order of Mn > Cd > Pb > Co > Ni > Cu > Zn > Cr for the heavy metals based on the sum of the first three fractions (acid soluble + reducible + oxidizable). The relationships between soil properties and each metal fraction were identified through Pearsons's correlation analysis. Hierarchical cluster analysis was performed to determine the behaviors and similarities of metals in each fraction. While Mn, Pb, and Zn exhibited subjective behaviors in the acid-soluble fraction, Cd, Co, Cu, Cr, and Ni exhibited similar behaviors with each other.  相似文献   

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