Spatial Variations And Pollution Characteristic Of Heavy Metals In Sediments Of Poyang Lake At The Inlet Of Raohe River And Le'an River

The pollution of the environment problem is one of the important problems which is global to face for 21 centuries. Heavty metal pollution, owing to the characteristics of permanet,eco-toxicity and biological, has long been an important subject in the international environmental science field.There are numerous lakes in China; however the Poyang Lake is the unique and famous for its largest area in our country. It is the largest fresh lake in China. It holds water from the five rivers—Ganjiang River, Fuhe River, Xingjiang River, Raohe River and Xiushui Rive, and emptied into Changjian River, the No.1 River in China, at Hukou after storing up. Among them ,Raohe River has the subsidiary current——Le'an River ,there has the biggest copper mine of our country——DeXing copper mine in the downstream of Le'anRiver and the its mineral mountain acidity waste water resulted in to influence very greatly to the ecosystem of Raohe River and Poyang lake.So, we take Le'an River and the estuary of Poyang Lake as the typical area, choose several kind of main heavy metal element such as Cu, Pb, Zn and so on is the object of study, analyzes in receives the nature and the high strength humanity exercises under the combined action the rivers and in the Hukow tidal flat ecosystem, the heavy metal element in deposit distribution, the accumulation, the migration and the transformed rule and the ecology effect, discusses Le'an River and the Hukow heavy metal main origin and the input way, finally enters the Poyang Hukow body heavy metal to the entire Le'an River and Rao River to carry on the environment quality and the ecology risk assessment, provides the scientific basis for the Poyang Lake resources reasonable development use and the environmental protection.River waters, suspended solids (SS) and surface sediments were sampled at 17 sites along Le An River mainstream and its 14 tributaries in October of 2005. In Ji River, the largest tributary, samples were collected at 4 sites. Because riverbeds in some sites are full of stones and rocks, sediments over there are not available, the samples were obtained and studied by investigation and assessment on heavy metals pollution of aquatic plants and its relevant water, soils and sediments in the estuary of the Poyang lake in July of 2006 .The content of Cu, Zn, Pb, Cd and their speciation in the samples were determined by atomic absorption spectrophotometer (AAS) and graphite furnace atomic absorption spectrophotometer(GFAAS), then dates were analyzed by Statistical Package for the Social Sciences(SPSS).The results were as follows:1. Le An River has been seriously contaminated by copper, lead and zinc heavy metals originating from AMD of two large-sized mines (Dexing Copper Mine and Yinshan Lead-zinc Mine), Surface waters and heavy metal distribution in Le An River catchments can be divided into four groups. In Dawu River and downstream of Ji River (the two tributaries received AMD respectively from the two mines), concentrations of heavy metals and sulfate were the highest, and other tributaries showed the lowest concentrations (un-polluted). The upstream zone of Le An River had water chemistry and heavy metal concentrations similar to the un-polluted tributaries. The highest concentrations of sulfate and heavy metals in Le An River was found in the middle stream zone and flowing downstream they decline significantly. Unlike the previous findings, copper contamination in Le An River began at the mixing location with Dawu River (R13) and showed two obvious sources (another located at the mixing location with Ji River, R20). However, the first contamination of lead and zinc occurred at R20 and only one source was found. Sulfur isotope of sulfate in surface waters evidenced that sulfur in middle stream zone of Le An River was mainly from Dexing Copper Mine and Yinshan Lead-zinc Mine. The investigation indicated that a highly localized distribution pattern was closely associated with the two pollution sources along the Le An River.2. Topsoils and barnyardgrass of three tributaries contain high Cd (Ji River), Cu (Dawu River and Ji River), Pb (Ji River) and Zn (Tiquan River and Ji River) contents. Heavy metal contents in topsoils and barnyardgrass of other 11 tributaries are low, close to the abundance in parent rocks. For Cd and Ni, their contents are similar in all tributaries.Spatial variations of enrichment factors and contamination indices for these heavy metals in topsoils show four Cu content peaks, three Pb and Zn content peaks along Le'An River. These content peaks are in keeping with the anthropogenic contamination sources. Cadmium, Cr and Ni shows little contamination in the entire river. Heavy metal contamination can be found after their sources have been abandoned for over ten years.Barnyardgrass only shows strong Cd absorption character. Relative to those in topsoils, Cr, Ni, Cu, Pb and Zn contents are all low in the plant, especially for Pb, Ni and Cr. Although most sites containing high contents of Cd, Cu, Pb and Zn in topsoils also find high contents in barnyardgrass, there is no significant correlation between topsoils and barnyardgrass.3. Although compares with the national soil environment quality, Rao River enters in the estuary of Poyang Lake type spot bottom putty Cu, Pb, the Zn content target conforms to three levels of standards. But compares with the Poyang Lake basin bottom putty background value, these 3 metallic element average content surpasses the background value separately 28.9 times of 8.3 time of 4.8 times. This had indicated, as a result of Le'an Jiang's influence, Rao River enters in the estuary of Poyang Lake deposit Cu, Pb, the Zn pollution already quite serious.The highest content of heavy metal elements all appears in the dragon buccal groove nearby (R2); in Poyang Lake (R3) next best, Rao River enters the lake river road junction (R1) is instead smallest. This spatial distribution characteristic possible and river mouth current of water relative anxious, affects the deposit granularity spatial distribution to concern. Rao River enters in the estuary of Poyang Lake deposit Cu, Pb, Zn mainly is by organic condition and the residual condition (S4) primarily, may exchange condition (S1) and the carbon union condition (S2) and so on the biological effective conditions relative fern, may exchange condition (S1), the carbon union condition (S2) and the ferromanganese oxidation state (S3) compares other elements to be high, therefore its biological hazardous nature is big.The findings indicated the Poyang Lake heavy metal pollution mainly is the Cu pollution. The Poyang Lake heavy metal pollution main origin is the Dession copper mine, in which Cu is certainly the main pollutant, therefore, the findings and the actual situation are tally.At the same time, leaves the conclusion not rarely. Must govern the Poyang Lake heavy metal pollution to have first to govern the Dession copper mine waste water pollution.As the Cu associated minerals, the Zn pollution simultaneously the existence is unavoidable, therefore, in to source of pollution main pollutant government time must simultaneously consider other pollutant. The Pb pollution except comes from outside the Dession copper mine, the Mt. yinshan lead-zinc mine, possibly more comes from the industry and the sanitary sewage, also possible and the lake district ships dye the oil related, therefore, next Poyang Lake Pb pollution preventing and controlling will be a difficulty.