Prediction of the concentration of chlorophyll-α for Liuhai urban lakes in Beijing City

The weekly water quality monitor data of Liuhai lakes between April 2003 and November 2004 in Beijing City were used as an example to build an artificial neural networks （ANN） model and a multi-varieties regression model respectively for predicting the fresh water algae bloom. The different predicted abilities of the two methods in Liuhai lakes were compared. A principle analysis method was first used to select the input variables of the models to avoid the phenomenon of collinearity in the data. The results showed that the input variables for the artificial neural networks were T, TP, transparency（SD）, DO, chlorophyll-a （Chl-a）,pH and the output variable was Chl-a. A three layer Levenberg-Marguardt feed forward leaming algorithm in ANN was used to model the eutrophication process of Liuhai lakes. 20 nodes in hidden layer and 1 node of output for the ANN model had been optimized by trial and error method. A sensitivity analysis of the input variables was performed to evaluate their relative significance in determining the predicted values. The correlation coefficient between predicted value and observed value in all data and in test data were 0.717 and 0.816 respectively in the artificial neural networks. The stepwise regression method was used to simulate the linear relation between Chl-a and temperature, of which the correlation coefficient was 0.213. By comparing the results of the two models, it was found that neural network models were able to simulate non-linear behavior in the water eutrophication process of Liuhai lakes reasonably and could successfully estimate some extreme values from calibration and test data sets.

A Bayesian method for comprehensive water quality evaluation of the Danjiangkou Reservoir water source area, for the middle route of the South-to-North Water Diversion Project in China

The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators （dissolved oxygen, permanganate index, ammonia nitrogen, total nitrogen, and total phosphorus）, were measured at three monitoring sites （the Danjiangkou Reservoir dam, the Hejiawan and the Jiangbei bridge）, to investigate changing trends, and spatiotemporal characteristics of water quality in the Danjiangkou Reservoir area from January 2006 to May 2012. We then applied a Bayesian statistical method to evaluate the water quality comprehensively. The normal distribution sampling method was used to calculate likelihood, and the entropy weight method was used to determine indicator weights for variables of interest in to the study. The results indicated that concentrations of all five indicators increased during the last six years. In addition, the water quality in the reservoir was worse during the wet season （from May to October）, than during the dry season （from November to April of the next year）. Overall, the probability of the water＇s belonging to quality category of type lI, according to environmental quality standards for surface water in China, was 27.7%-33.7%, larger than that of its belonging to the other four water quality types. The increasing concentrations of nutrients could result in eutrophication of the Danjiangkou Reser- voir. This method reduced the subjectivity that is commonly associated with determining indicator weights and artificial classifications, achieving more reliable results. These results indicate that it is important for the interbasin water diversion project to implement integrated water quality management in the Danjiangkou Reservoir area.

Variations in concentrations and bioavailability of heavy metals in rivers caused by water conservancy projects： Insights from water regulation of the Xiaolangdi Reservoir in the Yellow River

Water regulation of the Xiaolangdi Reservoir of the Yellow River was chosen as a case to investigate variations in concentrations and bioavailability of heavy metals caused by water conservancy projects in rivers. Water and suspended sediment（SPS） samples were collected at downstream sampling sites along the river during this period. Concentrations and speciation of Zn, Cr, Cu, Ni, and Pb in water and SPS samples were analyzed, and their bioaccumulation was studied with Daphnia magna. This study indicated that the exchangeable and carbonatebound fractions of heavy metals in SPS decreased along the studied stretch, and the dissolved heavy metal concentrations increased along the river with 1.6–15 folds. This is because sediment resuspension increased along the river during water regulation, giving rise to the increase of heavy metal release from SPS. The dissolved Zn, Cu, Ni, and Pb concentrations were significantly positively correlated with SPS concentrations, and their increase along the river was greater than Cr. The body burdens of heavy metals in D. magna exposed into samples collected from the reservoir outlet were 1.3–3.0 times lower than those from downstream stations, suggesting that the heavy metal bioavailability increased during water regulation.This should be considered in the reservoir operation.

Research progress in cold region wetlands, China

China has some of the most abundant wetland resources in the world. Cold region wetlands cover more than 60% of the total natural wetlands in China and play an indispensable role in global climate regulation, water holding, uptake and emission of greenhouse gases, and biodiversity conservation. Because cold region wetlands are sensitive to climatic and environmental changes, it is important for ecological conservation and environmental management to summarize and analyze current research progress on these specific ecosystems. This paper reviews the focus of present studies on the typical cold region wetlands in the northeast region and the Qinghai-Tibet Plateau of China from several aspects as follows： types and distribution, responses of permafrost to climatic changes, uptake and emission of greenhouse gas, eco-hydrological processes, and vegetation succession. Our conclusions are： global wanning has a long-term and serious impact on cold region permafrost; emission of greenhouse gases has great temporal and spatial heterogeneity; and hygrophytes in the cold region wetlands have been generally replaced by xerophytes, although it is still unclear whether the vegetation diversity index has increased or decreased. Based on this review, some key topics for future study are recommended as follows： （1） the response of degeneration of cold region permafrost at various spatial and temporal scales; （2） prediction of wetland degeneration tendency by coupling weather, soil, and hydrological models; （3） evaluation of carbon storage; （4） the actual response mechanisms of greenhouse gases to climatic changes; and （5） development of water requirement calculation methods tailored to the unique ecosystems of cold region wetlands.

Sequence of the main geochemical controls on the Cu and Zn fractions in the Yangtze River estuarine sediments

Metal speciation can provide sufficient infor- mation for environmental and geochemical researches. In this study, based on the speciation determination of Cu and Zn in the Yangtze Estuary sediments, roles of eight geochemical controls （i.e., total organic carbon （TOC）, clay, Fe/Mn in five chemical fractions and salinity） are fully investigated and sequenced with correlation analysis （CA） and principal components analysis （PCA）. Results show that TOC, clay and Fe/Mn oxides are key geochemical factors affecting the chemical speciation distributions of Cu and Zn in sediments, while the role of salinity appears to be more indirect effect. The influencing sequence generally follows the order： TOC 〉 clay 〉 Mn oxides 〉 Fe oxides 〉 salinity. Among the different fractions of Fe/Mn oxides, residual and total Fe content, and exchangeable and carbonate Mn exert the greatest influences, while exchangeable Fe and residual Mn show the poorest influences.

Enhanced flushing of polychlorinated biphenyls contaminated sands using surfactant foam: Effect of partition coefficient and sweep efficiency

Foam flushing is an in situ soil remediation technology based on the traditional surfactant flushing method. The contribution of mobility control to contaminant removal by foam is helpful for improving this technology. Foam flushing of polychlorinated biphenyl （PCB）- contaminated unconsolidated media was performed to evaluate the effect of the partition coefficient （PC） and sweep efficiency （SE） on PCB removal. Column flushing with surfactant solution and foam with different types and concentrations of surfactant was carried out for PCB removal. Two types of quartz sand were investigated to evaluate the Jamin effect on the SE value of the washing agent. The results demonstrate that a small PC value and large SE value are necessary to achieve high PCB removal for foam flushing. Compared with solution flushing, the introduction of foam can effectively control the mobility of the washing agent. Similar to solution flushing, solubilization is a key factor which dominates the removal of PCBs in foam flushing, In addition, the SE value and PCB removal by foam flushing is less affected by particle size. Therefore, foam flushing was proved to be more effective in porous media with low hydraulic conductivity and high porosity. An integrated flushing with water, surfactant solution and foam was performed and the results prove that this technology successfully combines the advantages of solution solubilization and mobility control by foam, and thus further increases the remediation efficiency of PCBs to 94.7% for coarse sand.

土地覆盖与气候变化对黄河源区径流的影响(英文)

After dividing the source regions of the Yellow River into 38 sub-basins, the paper made use of the SWAT model to simulate streamflow with validation and calibration of the observed yearly and monthly runoff data from the Tangnag hydrological station, and simulation results are satisfactory. Five land-cover scenario models and 24 sets of temperature and precipitation combinations were established to simulate annual runoff and runoff depth under different scenarios. The simulation shows that with the increasing of vegetation coverage annual runoff increases and evapotranspiration decreases in the basin. When temperature decreases by 2oC and precipitation increases by 20%, catchment runoff will increase by 39.69%, which is the largest situation among all scenarios.