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1.
The concentrations of total mercury and methylmercury in sediments were determined at the dam of the Wujiangdu Reservoir in different seasons. Total mercury (HgT) levels in the whole sediment profile were 254.2±47.0 ng/g in winter, 254.2±31.6 ng/g in spring, and 256.7±60.8 ng/g in summer, without significant variations in different seasons or at different depths. In contrast, the methylmercury (MeHg) compounds were most abundant at the sediment-water interface and decreased progressively with depth. MeHg contents of the sediments during different seasons are highly dependent on microbial activity, and seem to be higher when Hg (II)-methylating microorganisms are active. Thus, MeHg levels tend to rise in the loci where nutrient supplies and biological productivity are favorable. The percentage of HgT that is present as MeHg in the sediments increased gradually from December 2003 to April 2004 and to July 2004.  相似文献   

2.
Based on the sedimentary geochemical studies of the Antarctic Ocean and the various geochemical parameters available,this paper deals with the process of emobilization of iodine in marine sediments during early diagenesis.The results showed that the process is not always controlled completely by organic matter as was expected previously.On average the adsorption and oxide phases of iodine account respectively for 23% and 32% of the total in continental-shelf and hemipelagic surficial sediments.Chemical analysis has revealed that the upward diffusion flux and redox conditions would play an important role in the concentration of iodine in the surface sediments.And the species of iodine in the surfial sediments characteristic of high I/Corg ratios would bepredominated by the oxide and adsorption phases.As experimentally evidenced,it is the early diagenetic remoibilization of iodine associated with the oxide and adsorption phases that led to the decrease of I/Corg with increasing depth.Calculations suggested that the diffusion flux of iodine from the deep parts of te sedimentary columum upwards is on the same order of magnitude as the deposition flux of it from sea water.This may be one of the important factors leading to the depletion of iodine in sedimentary rocks.On the basis of the above discussion and calculations the author has proposed a model for the remobilization of iodine in marine sediments during early diagenesis.  相似文献   

3.
Mineral and organic matter either soluble or suspended are transported by the rivers and when deposited in the bed of the river or in the water reservoir, sediments are formed, whose chemical composition may serve as a fingerprint of the history of the ecosystem. The results of the studies of sediments in water systems （river catchments, reservoirs） can be used not only for the evaluation of the current state of the ecosystem but also to prevent any dangerous environmental changes. Bottom sediments can in many ways accumulate both suspended and soluble components. The process is influenced by several factors like pH, red-ox potential, oxygen content, interactions, etc. The complexity of those phenomena causes that in order to study the accumulation processes of compounds in sediments the application of various analytical techniques is required. The authors participate in two big projects on sediment studies. The AquaTerra Project is the EU funded project on understanding river-sediment-soil-groundwater interactions for support of management of river basins and catchment areas. Our group＇s studies are focused on mercury determination and its speciation in sediments and fish from the Ebro River in Spain. The Dobczyce Project is the national project funded by the Ministry of Education and sciences of Poland which is also a EU member country. The latter covers many aspects of accumulation and fate processes of chemical compounds in sediments of the reservoir which supplies 60% of drinking water to about one million population in the city of Krakow in Poland.  相似文献   

4.
The water, pore water, sediment, and fish samples were collected from the Hongfeng Reservoir in November 2003 and February 2004 in accordance with trace metal protocols. The average concentrations of total mercury （THg）, dissolved mercury （DHg）, reactive mercury, dissolved gaseous mercury, total methylmercury, and dissolved methylmercury in the water columns were 8.00, 5.70, 0.63, 0.05, 0.16, and 0.07 ng/L, respectively. THg and DHg in the water columns, THg in pore water and THg in lake sediments of the Hongfeng Reservoir showed the level of mercury in the Hongfeng Reservoir was higher than in other natural waters in the world due to the loading of a lot of waste water with relatively high concentrations of mercury, whereas methylmercury concentrations in fish （wet weight） varied from 1.73-51.00 ng/g, much lower than in most remote lakes and reservoirs reported in northern Europe and North America. Methylmercury distributions in pore water and sediments showed methylation occurred mainly in the upper several centimeters of sediment cores in the Hongfeng Reservoir. The concentrations of dissolved organic carbon, total suspended particles, total Hg, and methylmercury were higher at Houwu than those at Daba in November 2003. It is suggested that other pollutants such as N and P from fishing farm and other waste water at Houwu, which resulted in deterioration of water quality, affected the concentrations and distributions of mercury species in the reservoir.  相似文献   

5.
With the rapid development of industrialization and urbanization in the Pearl River Delta region, organic as well as inorganic pollution is becoming a major environmental concern. Urban deposits including road dusts, corresponding gully sediments and topsoils proved to be useful tools for assessing the level and distribution of contaminants in metropolitan areas. Most of the previous studies utilizing urban deposits, however, focused on inorganic pollutants, while data on organic pollutants are rare. In this study, therefore, the organic pollutants in urban deposits of Hong Kong and Guangzhou were systematically investigated in terms of their abundance, composition and distribution. The road dusts, gully sediments and vehicular tunnel dusts as well as soils from different urban locations with variable traffic volumes （less than 1000 to more than 75000 AADT） were examined. The results indicated that vehicle-emitted particles were the major source of organic pollutants, while the contributions from background soils were very limited. Surprisingly, the soil in a remote island of Hong Kong with no vehicular traffic has also shown signs of pollution from vehicular particles likely through dry-wet atmospheric deposits. In general, the characteristics of organic pollutants in urban dusts from both cities are comparable although there were also some significant differences. For example, the amount of extractable organic matter in urban deposits of Hong Kong was significantly higher than that of Guangzhou. Differences in their extractable asphaltene contents not only reflected the differences in quality and types and fuels used in these cities, but also sample residence times, and thus different extents of weathering processes.  相似文献   

6.
Damming effect on the distribution of mercury in Wujiang River   总被引：2，自引：0，他引：2  
Seasonal changes in total mercury concentrations in surface water were observed for the Wujiang River, with higher values at the time of greater flow. The total mercury in this river was mostly associated with suspended particles, particulate mercury accounting for 84% of the total mercury flux on average during the high flow period, and 52% of the total mercury flux on average in the low flow period. Significant losses of Hg from the water were observed in the downstreams of the reservoir. In addition, the concentrations of particulate mercury in the downstreams of reservoir appeared to have been enhanced by sediment re-suspension and shoreline erosion caused by flood discharge, while the filtered portion decreased. These observations suggested that reservoirs played an important role in controlling the transport and fate of mercury in the Wujiang River.  相似文献   

7.
Dissolved organic matter （DOM）, a mixture of numerous organic compounds of 30 to 300000 D, exists in all natural water resources including rivers, lakes and oceans, and plays a very important role in global carbon cycle and ecology. The DOM molecules absorb UV light strongly in short wavelengths and prevent microorganisms from being damaged by solar UV irradiation. Meanwhile, the large DOM molecules are then photodegraded into inorganic carbon and smaller organic molecules which are easier for bacterioplankton to digest. The Arkansas River is one of the largest rivers in the US, and a major input of organic materials to the Mississippi River and Gulf of Mexico. However, the photochemical properties of the DOM in the river water have not been investigated. To study this photodegradation process of the Arkansas River, water samples from the river were collected, filtered, sealed into quartz flasks, and exposed to sunlight for up to 15 hours. Some samples were retrieved from the flasks at certain time intervals. The intensity of the sunlight was measured during the exposure process at 30 min to 1 hr intervals. UV-vis absorption, fluorescence emission, 3D fluorescence spectra and DOM concentrations were determined for all retrieved samples. It was found that the total DOM concentration decreased while the dissolved inorganic carbon （DIC） concentration increased in the samples. UV absorption and fluorescence intensity of DOM decreased exponentially. The disappearance rate of UV absorption varied with wavelength. The loss of integral fluorescence was about 2.6 times that of the UV absorption at the excitation wavelength. In addition, the quantum yields also decreased, and the peak position of 3D fluorescence scan shifted to shorter wavelength.  相似文献   

8.
The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO3-N concentrations in the mainstream are 147.5 μM in the high-flow period and 158.0 μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are 6.43 μM in the high-flow period and 4.18 μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ( 62.9%) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are 85.4, 84.6 μM in the high-flow period and 60.8, 53.9 μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng'an River on the mainstream.  相似文献   

9.
The Daning River is a very important tributary in the Three Gorges Reservoir area. It is also a famous scenic spot. Anomalies appeared after water storage of the reservoir in June, 2003. In September, 2003, eutrophication monitoring in the 135-m backwater reach of the Daning River was conducted and the data were simply analyzed. The assessment result is that water body in the segment from Shuauglong to Longmen was mesotrophic or eutrophic. At the same time, the causes of its nutritional change were discussed, and counter-measures have been proposed.  相似文献   

10.
Concentrations and loads of nitrate and total phosphorus and the sources of these two nutrients were investigated at the Panjiakou and Daheiting Reservoir system in northern Hebei Province, the People＇s Republic of China. The Luanhe River is the primary source of water to these reservoirs. The response of the reservoir system from the phosphorus loading, with respect to chlorophyll-a production from algae, was fitted to a model of normalized phosphorus loading which regresses the average summer-time chlorophyll-a concentration to the average annual phosphorus concentration of the reservoir. The reservoirs have a primary use for drinking water and partially supplies the city of Tianjin with its annual supply, but secondary uses include flood control and aqua culture （fish cages）. Comparison of the normalized phosphorus loading and chlorophyll-a response of this system to other reservoirs throughout the world from similar studies indicates an elevated level of eutrophication, which will require an approximate 10-fold decrease in phosphorus load reduction to bring the system to a more acceptable level of algal productivity. Isotopes of nitrogen and oxygen in dissolved nitrate were measured from the headwater streams and at various locations along the major river system that provides the majority of water to this reservoir, and within the two reservoirs.  相似文献   

11.
Nitrogen and phosphorus are the major nutrients to cause eutrophication to degrade water quality of the Miyun Reservoir,a very important drinking water source of Bijing,China,and they are mainly from non-point sources.The watershed in Miyun County was selected as the study region with a totoal area of 1400km^2.Four typical monitoring catchments and two experimental units were used to monitor the precipitation,runoff,sediment yield and pollutant loading related to various land uses in the meantime.The results show that the total nutrient loss amounts of TN and TP are 898.07t/a,and 40.70t/a,respectively,in which nutrients N and P carried by runoff are 91.3% and 77.3%,respectively.There is relatively heavier soil eroson in the northern mountain area whereas the main nutrient loss occurs near the northeast edge of the reservoir.Different land uses would influence the loss amounts of non-point source pollutants.The amount of nutrient loss from the agricultural land per unit is highest,that from forestry comes next that from grassland is lowest.However,due to the variability of land use areas,agricultural land contributes a lot to TP and forestry lands to TN.  相似文献   

12.
Settling particles were collected from six stations at the Okinawa Trough and the East China Sea continental margin. Activities of U, Th, Pu isotopes and ^210Pb were determined for the particles to elucidate their transport processes. Surface sediment samples were also analyzed for their isotopes. There was a tendency for ^210Pb activities to increase almost linearly with depth from 72 m on the continental shelf edge to 1019 m in the Okinawa Trough. Increasing ^210Pb activities in settling particles with depth on the continental margin may be attributable to enhanced ^210Pb scavenging by particles and removal near the front. There also was a clear tendency for total mass fluxes and the radionuclide fluxes to increase with depth, with an especially large increase near the bottom. The ratio of the observed ^210Pb flux to the ^210Pb deficiency flux in the near-bottom traps ranged between 8.9 and 46. These high values show a strong ^210Pb excess which would be attributable to large advective import to the near-bottom and resuspended particles that have settled through the water column but have not been incorporated into the sediments. High variability of radionuclide fluxes occurred in very short time periods. Activities of ^238U, ^232Th, ^230Th, ^228Th, ^210Pb and ^239Pu＋^240Pu in settling particles were significantly higher than those in the underlying surface sediments.  相似文献   

13.
Environmental pollution is one of the vertical problems faced in the 21 century. There are numbers of lakes located in China. Poyang Lake, which is the largest freshwater lake in China, is the famous representation. The environmental geochemistry of trace and ultra-trace element As in the sediment-water interface （SWI） of Poyang Lake was investigated in detail. Solutions presented in the project can be summarized as follows： it is the first time to discover that the ：nasking agent of 8-hydroxyquinoline was found to be an efficient agent to eliminate the interference of transition metals in the determination of arsenic species, especially to eliminate As （Ⅴ） emission with high selection in the matrix of As （Ⅲ） and As （Ⅴ） coexisting solution. A sensitive and interference-free procedure has been successfully established for the arsenic speciation on As （Ⅲ）, As （Ⅴ）, Asorg in pore water samples using flowing injection hydride generation atomic fluorescence spectrometry （FI-HG-AFS）. It was observed that the concentrations of arsenic species in porewaters were relatively high. With the variation of the redox in sediments, it is easy to cause the second pollution in overlying waters for their upward diffusion. Arsenic is mainly absorbed onto iron and manganese oxyhydroxides in controlling the behavior of As. The effect factors of the transfer, cycle of arsenic are the redox condition at SWI, disturbance, and microbial action, etc.  相似文献   

14.
We investigated in more detail the adsorption phenomenon which was described earlier. It was clearly established that the hydroxyl apatite was not participated in P adsorption. This phenomenon takes place because of ferric hydroxide film. Modem sediments from the Southem Basin of Lake Baikal were taken and stirred with Baikal water. Carrier-free [^32p]-orthophosphate was added in this system. Similar experiments were made with carrier-free [^35S]-sulphate. Sulphate stayed in supematant completely. The influence of pH on the system with inorganic phosphate was also studied. In low alkali conditions phosphate migrated in supematant, in low acid, in sediments. Baikal sediment was stripped of iron-hydroxous film by treatment with 1% oxalic acid. Investigation of striped sediment shown that phosphate stays in supematant only. Hence, hydroxyl apatite cannot be the phase of the sediments of Lake Baikal which binds phosphate. This all showed by our group before. Now we have found the limit of phosphate sorption in Lake Baikal sediments and the stehiometry of the sorption. The sorption limit of Lake Baikal sediments was studied. An experiment with inorganic ^31P phosphate was made. 0.025% K2HPO4 solution with adding ^32P radioactive mark into it was prepared. 100 μL of mixture of ^31PO4^3- and ^32PO4^3- seven times were added in a ＂Baikal water-Baikal sediment＂ system and blank （100 ml BW only）. Concentrations of inorganic ^31PO4^3- were very low so the bend dot on the diagram was found and sorption limit of sediment was estimated. Baikal sediment stopped assimilating phosphate in the bend dot. The stehiometry of sorption was estimated by supematant-sediment radioactive ratio, which equals 3, that is, three Fe （Ⅲ） atoms associate one PO4^3- anion. The only Fe （Ⅲ） substance which could associate P is -Fe-O-Fe- polymer film. It also dissolves in acid conditions.  相似文献   

15.
Dongping Lake area, located in the lower reaches of Yellow River, is an ideal place to study the changes of modern river and lake sedimentary environment. The sediment samples of Dawen River, Yellow River, and Dongping Lake were collected, and the major elements, trace elements and organic matter geochemical composition of the samples were analyzed. Cluster analysis, characteristic element ratio method and graphic method were used to explore the geochemical characteristics of sediments and their environmental implication. The results show that the contents of SiO_2, Na_2O, TiO_2 and Zr in sediments of Dawen River and Yellow River are relatively high, and the contents of iron and manganese oxides, organic matter, CaO, P_2O_5 and Sr in lake sediments are relatively high. That reveals the differences of sedimentary environments between the rivers and the lake. The contents of Sr and Zr in Dawen River are affected by the rapid migration of clastic materials in the upstream carbonate source area during the flood season; the δCe,ΣREE and REE's ratios in the sediments of the Yellow River reflect the influence of the Loess source; and the distribution of elements changes along the flow direction during the flood season. The characteristics of p H, element composition and LREE HREE fractionation of the lake sediments indicate that the sediment source is complex, and the lake environment is affected by the flood season. The study shows that the geochemical content and its variation characteristics of sediments effectively reveal the sedimentary environment, material composition and characteristics of flood season of rivers and the lake in the study area.  相似文献   

16.
Although eutrophication and trace element contamination are two key environmental problems in Dongting Lake, a systematic study of the distribution of trace elements in sediments of this lake has not previously been undertaken. In order to identify the current levels of trace metal contamination in Dongting Lake, the concentrations of trace elements （Cd, Cr Cu, Ni, Pb, Zn, As and Hg） in the sediments at 53 locations were investigated in this study. The lake, the second largest fresh-water lake in China, boasts three China wetlands of international importance. Dongting Lake which lies in the south of the middle Yangtze River is the most important reservoir lake in the Yangtze River drainage area, and is characterized by fast flow-through water, large runoff volume and short period of exchanging water （no more than 20 days）. The granulometric analysis result of sediments shows that a large proportion of the sediments measures at 2-63 μm in size; the result of mineralogical analysis shows that original mineral is the main composition of the sediments, followed by clay mineral and carbonate. The contents of copper, lead, zinc, cadmium, arsenic and mercury are higher than the background levels of soil （ Ⅰ Soil） in China, but lower than the threshold values for severely polluted soil （Ⅲ Soil） in China except Cd higher than that in Ⅲ Soil. The concentrations of trace elements analyzed are higher than the Threshold Effect Level of Interim Sediment Quality Guideline by Canada EPA and are lower than the Probable Effect Level. The assessment by geoaccumulation index shows that the contamination of Cd reached strong level in Dongting Lake. Study on speciation of metals by a BCR procedure indicates that the trace elements （Cu, Zn, Cr, and Ni） analyzed are mainly distributed in residual phases but Pb in Fe/Mn oxhydroxide phase and Cd in soluble and carbonate-bound fraction. The potential risk was the highest in East Dongting Lake based on the calculated contamination factors which are mostly probably caused by the deposition of the trace element pollutants via the Xiangjiang River and the discharge of the pollution sources in the vicinity of East Dongting Lake.  相似文献   

17.
The impact of water quality changes of the Changjiang River on dissolved CO2 and silicate concentration and seasonal flux in the water column for the past decades were evaluated, based on monitoring data from hydrographic gauge. It was found that dissolve…  相似文献   

18.
The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe^2 and Mn^2 ,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe^2 increased later and decreased earlier than that of Mn^2 .Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe^2 ,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system.  相似文献   

19.
Mechanism of Seasonal Deterioration of Water Quality in Lake Baihua,China   总被引：3，自引：1，他引：3  
Water quality of Lake Baihua was found worsening in the autumn of 1994.Studies have shown that the decomposition of organic matter in the upper-level sediments resulted in seasonal anoxia with the release of P,Mn,and S^2- from the sediments to the overlying water column,and the increase of NO2^- concentration led to blackening of the water column,deat of fishes and secondary Mn pollution.  相似文献   

20.
Lakes along the middle and lower reaches of the Yangtze River are unique shallow lake group faced with serious problems of eutrophication. In shallow lakes, there are strong interactions between surface sediment and overlying water, and the chemical, biological processes are complicated in the system. The mechanism of shallow lake eutrophication is still insufficient to instruct the harness practice. Water samples were collected quarterly in each lake center from 2000 to 2003. Chemical variables and ionic concentrations were measured in laboratory. This paper focused on the seasonal variations of NO2-N, NO3-N, NH4-N, DIP, chlorophyll a and TN ： TP ratios in 49 lakes along the middle and lower reaches of the Yangtze River. The cooperating mechanisms between N and P were investigated through the analysis of their relationships at different nutrient levels.  相似文献   

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