The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads,such as soluble reactive phosphorus(SRP)and total phosphorus(TP),as well as the main elements of s...The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads,such as soluble reactive phosphorus(SRP)and total phosphorus(TP),as well as the main elements of sediment extracts in Dianchi Lake.Several strongly reducing substances in sediments,which mainly originated from anaerobic decomposition of primary producer residues,were responsible for the lower redox potential.In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water.Redox potentials exceeding 320 mV caused increases in TP,whereas SRP maintained a relatively constant minimum level.The concentrations of Al,Fe, Ca^(2+),Mg^(2+),K^+,Na^+ and S in interstitial water were also related to the redox potential of sediments,suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.展开更多
Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn）...Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.展开更多
Lake eutrophication has increasingly become a major environmental issue in China. Although significant efforts have been made towards its resolution in the last decade, most of the implemented control strategies are f...Lake eutrophication has increasingly become a major environmental issue in China. Although significant efforts have been made towards its resolution in the last decade, most of the implemented control strategies are fragmented, and the formation of policy lacks of sound scientific basis and long\|term objectives. Taking the well\|known Dianchi Lake as a case study, this paper presented a comprehensive assessment for the effectiveness of various eutrophication control strategies. It is expected that the concluding lessons would have a major implication to future eutrophication control.展开更多
Water-quality deterioration and eutrophication of the Lake Dianchi have acquired more and more attention in the last few decades. In this paper, the spatial and temporal eutrophication status of the Lake Dianchi was a...Water-quality deterioration and eutrophication of the Lake Dianchi have acquired more and more attention in the last few decades. In this paper, the spatial and temporal eutrophication status of the Lake Dianchi was assessed. The comprehensive trophic state index was chosen to assess the trophic status of the Lake Dianchi in the past 13 years. The result reveals that the trophic condition of Caohai is more serious than that of Waihai. Most of time Caohai was in extremely hypereutrophic state from 1988 to 2000. The trophic condition of Waihai had a worsening tendency from 1988 to 2000. Waihai was in eutrophic state before 1995, but it got in a hypereutrophic state after 1995. It was pointed out that TN and TP were the two biggest contributors of CTSIM in both Caohai and Waihai.展开更多
Background:Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats.Much research has been carried out on the impacts on birds of wetland res...Background:Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats.Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands,while inland wetlands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake,south-west China. Methods: The line transect method was performed at 26 sampling plots.Three of these were in the city,and to acquire all wild bird data 23 plots were located every 2-8 km along the shore of Dianchi Lake, between December 2011 and November 2013.We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration.To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables. Results: We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disappeared from the shore of Dianchi Lake.CCA results indicated that waterbirds could be divided into four categories based on their habitat preference:synanthropic (wintering gulls), special habitat (shorebirds),semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species.Conclusions:Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake.Distinct habitat requirements of different waterbird groups were detected in our study,suggesting different types of restoration and management should be impleme展开更多
The fish Sinocyclocheilus grahami is one of the indicative and endemic species in the Dianchi Lake ecosystem. As a result of pollution and invasion of exotic fishes, the fish had disappeared from Dianchi Lake since 19...The fish Sinocyclocheilus grahami is one of the indicative and endemic species in the Dianchi Lake ecosystem. As a result of pollution and invasion of exotic fishes, the fish had disappeared from Dianchi Lake since 1986 and only a few small populations survive in springs and streams around the lake. Due to the endangered status and special scientific value, S.grahami was listed as the second class protective animal of China in 1989. The importance of S. grahami and the indigenous biodiversity of Dianchi Lake were recognized by the Global Environment Foundation （GEF） /World Bank and Yunnan Development ＆ Reform Committee. Therefore a special grant was set up to restore and conserve the indigenous biodiversity of Dianchi Lake. The artificial breeding of S. grahami is a part of the targeted activities. Two successful breeding experiments were achieved using five females plus six males up to early March 2007. Approximately 1600 eggs were collected, of which 1320 eggs fertilized using the dry-fertilizing method. The mean fertilization rate was 73%. Approximately 480 fish fry was hatched and the mean hatching rate was 36%. After 10 days of cultivation, 95% fingerlings survived and their body lengths were up to 8- 12 mm. The importance of the artificial breeding success of S. grahami could be summarized as following： effectively protecting the fish from extinction; releasing the fish fry back to appropriate water body of the lake could help to restore the indigenous biodiversity of Dianchi Lake; facilitating the shift of local fish cultivation from the present non-indigenous to the future indigenous fishery.展开更多
基金Project supported by the National Natural Science Foundation of China(No.40401029).
文摘The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads,such as soluble reactive phosphorus(SRP)and total phosphorus(TP),as well as the main elements of sediment extracts in Dianchi Lake.Several strongly reducing substances in sediments,which mainly originated from anaerobic decomposition of primary producer residues,were responsible for the lower redox potential.In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water.Redox potentials exceeding 320 mV caused increases in TP,whereas SRP maintained a relatively constant minimum level.The concentrations of Al,Fe, Ca^(2+),Mg^(2+),K^+,Na^+ and S in interstitial water were also related to the redox potential of sediments,suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.
基金Project supported by the Science and Technology Program for Social Development of Jiangsu Province,China (No.BS2006060)Startup Fund of Nanjing University of Information Science & Technology, the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University (No. 2005406711)the Jiangsu Key Laboratory of Environmental Change and Ecological Construction, Nanjing Normal University.
文摘Fractionation of heavy metals in sediments can help in understanding potential hazards of heavy metals. The present study analyzed total concentrations and fractions of selected heavy metals （Cd, Cr, Cu, Pb, and Zn） in surface sediments from Dianchi Lake, Yunnan Province, China, as well as factors that may affect distributions of the various heavy metal fractions. Total concentrations of the heavy metals decreased in the order Zn 〉 Cu 〉 Pb 〉 Cr 〉 Cd. These heavy metals, except Cr, were much higher than their background levels, indicating that Dianchi Lake was polluted by Cd, Zn, Pb, and Cu. Cadmium occurred mainly as the non-residual fraction （sum of the HOAc-soluble, reducible, and oxidizable fractions） （97.6%）, and Zn （55.7%） was also predominantly found in the non-residual fraction. In contrast, most of the Cr （88.5%）, Pb （81.8%）, and Cu （59.2%） occurred in the residual fraction. Correlation analysis showed that total heavy metal concentrations, organic matter and reducible Fe were the main factors affecting the distributions of the various heavy metal fractions. In the Walhai section of Dianchi Lake （comprising 97% of the lake area）, the concentrations of Cd, Zn, Pb, and Cu in the non-residual fraction were significantly lower （P ≤ 0.01 or 0.05） than those of the Caohal section （3% of the lake area）. This indicated that potential heavy metal hazards in the Caohai section were greater than the Waihai section.
文摘Lake eutrophication has increasingly become a major environmental issue in China. Although significant efforts have been made towards its resolution in the last decade, most of the implemented control strategies are fragmented, and the formation of policy lacks of sound scientific basis and long\|term objectives. Taking the well\|known Dianchi Lake as a case study, this paper presented a comprehensive assessment for the effectiveness of various eutrophication control strategies. It is expected that the concluding lessons would have a major implication to future eutrophication control.
文摘Water-quality deterioration and eutrophication of the Lake Dianchi have acquired more and more attention in the last few decades. In this paper, the spatial and temporal eutrophication status of the Lake Dianchi was assessed. The comprehensive trophic state index was chosen to assess the trophic status of the Lake Dianchi in the past 13 years. The result reveals that the trophic condition of Caohai is more serious than that of Waihai. Most of time Caohai was in extremely hypereutrophic state from 1988 to 2000. The trophic condition of Waihai had a worsening tendency from 1988 to 2000. Waihai was in eutrophic state before 1995, but it got in a hypereutrophic state after 1995. It was pointed out that TN and TP were the two biggest contributors of CTSIM in both Caohai and Waihai.
基金The National Natural Science Foundation of China(41471149 and 31060079)
文摘Background:Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats.Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands,while inland wetlands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake,south-west China. Methods: The line transect method was performed at 26 sampling plots.Three of these were in the city,and to acquire all wild bird data 23 plots were located every 2-8 km along the shore of Dianchi Lake, between December 2011 and November 2013.We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration.To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables. Results: We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disappeared from the shore of Dianchi Lake.CCA results indicated that waterbirds could be divided into four categories based on their habitat preference:synanthropic (wintering gulls), special habitat (shorebirds),semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species.Conclusions:Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake.Distinct habitat requirements of different waterbird groups were detected in our study,suggesting different types of restoration and management should be impleme
文摘The fish Sinocyclocheilus grahami is one of the indicative and endemic species in the Dianchi Lake ecosystem. As a result of pollution and invasion of exotic fishes, the fish had disappeared from Dianchi Lake since 1986 and only a few small populations survive in springs and streams around the lake. Due to the endangered status and special scientific value, S.grahami was listed as the second class protective animal of China in 1989. The importance of S. grahami and the indigenous biodiversity of Dianchi Lake were recognized by the Global Environment Foundation （GEF） /World Bank and Yunnan Development ＆ Reform Committee. Therefore a special grant was set up to restore and conserve the indigenous biodiversity of Dianchi Lake. The artificial breeding of S. grahami is a part of the targeted activities. Two successful breeding experiments were achieved using five females plus six males up to early March 2007. Approximately 1600 eggs were collected, of which 1320 eggs fertilized using the dry-fertilizing method. The mean fertilization rate was 73%. Approximately 480 fish fry was hatched and the mean hatching rate was 36%. After 10 days of cultivation, 95% fingerlings survived and their body lengths were up to 8- 12 mm. The importance of the artificial breeding success of S. grahami could be summarized as following： effectively protecting the fish from extinction; releasing the fish fry back to appropriate water body of the lake could help to restore the indigenous biodiversity of Dianchi Lake; facilitating the shift of local fish cultivation from the present non-indigenous to the future indigenous fishery.
