Water level response to hydropower development in the upper Mekong River

Environmental changes and their transboundary influences on the Mekong watercourse system have been an international research focus in recent years, but the opinions and results related to the impacts of upper Mekong River dams are quite different. In this paper, based on the records of water levels from 1960 to 2003 at three mainstream sites in the upper Mekong River, a quantitative examination has been undertaken into characteristics of the mainstream water-level process at multiple timescales and its response to cascade development. The major results are: i) Annual mean, wet period mean, and the mean water levels during the period between March and April (PBMA period) exhibit a significant increasing trend at Jiuzhou and Yunjinghong sites, which are influenced by large-scale factors such as climate change and solar activity. ii) The interdecadal and interannual variations of annual mean, annual maximum, and wet period mean water levels at three sites show similar features during the dam construction period. iii) The interdecadal variations of PBMA period water level show a gradual increase at Gajiu and Yunjinghong sites but a falling trend at Jiuzhou; these trends confirm that there is some regulation on the flow in the dry season caused by the two existing dams. iv) The downstream effects of the present dams on water levels are very limited at the annual mean and wet season mean levels, not apparent at the monthly and yearly timescales, and relatively significant at daily and hourly timescales.     

Anaerobic degradation behavior of nonylphenol polyethoxylates in sludge

Anaerobic biodegradation behavior of nonylphenol polyethoxylates (NPEOs) was investigated. Results showed that terminal electron acceptors, organic matters, initial concentration, and temperature had great influence on the anaerobic biodegradation of NPEOs. Anaerobic biodegradation of NPEOs could be enhanced by adding sulfate or nitrate while this process could be inhibited by adding organic matters. The maximum removal rate increased 1.24 microM d(-1) for each ten micromoles increase in initial concentration. The decrease in temperature caused a sharp decrease in the removal efficiency of NPEOs. The temperature coefficient (PHI) for the anaerobic biodegradation of NPEOs was 0.01 degrees C(-1). Nonylphenol (NP), the typical intermediate of NPEOs, could inhibit the anaerobic biodegradation of NPEOs only at high concentration. However, these environmental factors had no effect on the anaerobic biodegradation pathway of NPEOs. The accumulation of NP and short-chain NPEOs during NPEO biodegradation led to a significant increase in the estrogenic activity during the biodegradation period.     

Enhancement of solubilization and acidification of waste activated sludge by pretreatment

The effects of various pretreatment methods, including thermo-acid, thermo-alkaline, ultrasonic-alkaline and ultrasonic-acid, on solubilization and subsequent acidification efficiency of waste activated sludge (WAS) were investigated. The results showed that both thermo-alkaline and ultrasonic-alkaline significantly improved the solubilization of WAS at a high concentration (7.4% of total solids). Solubilization of volatile solids (VS) and crude protein was 60.2-61.6% and 66.8-67.5%, respectively. Thermo-alkaline or ultrasonic-alkaline pretreatment also enhanced the efficiency of subsequent WAS acidification. Experimental results showed that they had similar effects on the acidification of WAS. The conversion ratio from VS to total volatile fatty acids (TVFAs) was 0.230 in the case of the ultrasonic-alkaline pretreatment. Through this pretreatment, the level of TVFAs was 68% more than the untreated WAS after 252 h of fermentation. The mechanism of TVFAs production under different pretreatment methods was further investigated and the results indicated that soluble protein was the main substrate for TVFAs production from the WAS after the thermo-alkaline or ultrasonic-alkaline pretreatment.     

Leaching behavior of heavy metals from municipal solid waste incineration bottom ash and its geochemical modeling

With the increase in the number of municipal solid waste incineration (MSWI) plants constructed in China recently, great attention has been paid to the heavy metal leaching toxicity of MSWI residues. In this study, the effects of various parameters, including extractant, leaching time, liquid-to-solid ratio, leachate pH, and heavy metal content, on the release properties of Cd, Cr, Cu, Ni, Pb, and Zn from MSWI bottom ash were investigated. Partial least-squares analysis was employed to highlight the interrelationships between the factors and response variables. Both experimental research and geochemical modeling using Visual MINTEQ software were conducted to study the pH-dependent leaching behavior of these metals in fresh and weathered bottom ash, considering precipitation/dissolution and surface complexation reactions (adsorption by hydrous ferric oxide and amorphous aluminum oxide/hydroxide). The results showed that leachate pH was the predominant factor influencing heavy metal leachability. The leaching of Cu, Pb, and Zn was mainly controlled by precipitation/dissolution reactions, whereas surface complexation had some effect on the leaching of Cr, Cd, and Ni for certain pH ranges. The modeling results aggreed well with the experimental results. Part of this work was presented at the Fourth International Conference on Combustion, Incineration/Pyrolysis and Emission Control (i-CIPEC)     

上海地区农业气象灾害监测警示系统的研究

上海地区农业气象灾害监不系统是以实时气象数据为基础,根据农业气象灾害指标进行了评判分析,反映了农业气象灾害,接着,基于Activex的Web/GIS平台展示灾害的分布,并通过Internet网络,提供了多用户服务。     

Molecular detection of three gastroenteritis viruses in urban surface waters in Beijing and correlation with levels of fecal indicator bacteria

To assess the presence of three gastroenteritis viruses responsible for human acute gastroenteritis in surface water, a 1-year study was carried out in the city of Beijing, China. A total of 108 urban surface water samples were collected from nine collection sites which were defined with a global positioning system in rivers or lakes from September 2006 to August 2007. The water samples were subjected to virus concentration using an HA electronegative filter, followed by polymerase chain reaction (PCR) for rotavirus (RV) astrovirus (AV), and norovirus (NV). It showed that the number of viruses detected in water samples from different sites was variable, totaling 63 virus strains, with rotavirus (48.1%) verified as the most prevalent detected, followed by astrovirus (AV, 5.6%), and norovirus (NV, 4.6%). RV was also quantified by real-time PCR and the concentration of RV ranged from 0 to 18.27 genome copies·L(-1). And the distributions of RV in surface water were abundant in cold weather (from September to February) while less prevailing in warm weather (from March to August). The high detection rate of RV we encountered in this study provided convincing evidence that RV circulated at a certain frequency in the Beijing population. There was no statistically significant correlation between RV levels and both fecal coliform (R (2)?=?0.02) and Enterococcus faecalis (R (2)?=?0.02) densities. Our study suggests prolonged virus persistence in aquatic environments and emphasizes the enteric virus group as the most reliable for environmental monitoring.     

Chemical forms and ecological risk of arsenic in the sediment of the Daliao River System in China

The chemical forms and ecological risk of As were characterized in the sediment of the Daliao River System (DRS), which has been affected by long-term intensive industrial, urban, and agricultural activities. Twenty-seven samples of surface sediment were collected and analyzed for total As content and that of its chemical forms. The results indicated that the average total As content in the sediment was 9.83 mg kg^− 1 but that the levels ranged from 1.57 to 83.09 mg kg^− 1. At the sites near cities, mining sites, and the estuary of the DRS, it is likely that adverse effects on aquatic organisms occur, due to As levels in the sediment that are often higher than the threshold effect level and occasionally higher than the probable effect level. A selectively sequential extraction indicated that the majority of As in the sediment was bound to Fe oxides (62.1%), with moderate proportions of residual As (19.8%), specifically adsorbed As (17.9%), and a low proportion of non-specifically adsorbed As (1.1%). In addition, the content of Fe in the sediment was positively and significantly correlated with the contents of amorphous and crystalline Fe oxide-bound As, confirming the crucial role of Fe oxides in immobilizing high amounts of As in superficial environments. The average molar ratio of As to Fe was 1.18 × 10^− 4 in the surface sediment of the DRS, similar to that of natural Fe oxides, but much lower than that of synthesized Schwertmannite. Therefore, the release of As under reduced and low pH conditions can cause serious problems for water resources and for living organisms.     

Occurrence and characterization of selected organochlorine contaminants in outdoor dust collected from Xinxiang,a fast developing city in North China

As facile “environmental media”, the outdoor dust may reflect the changes of contaminants in environment more promptly. In the present study, selected organochlorine contaminants (OCs) include hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), hexachlorobenzene (HCB), and pentachlorobenzene (PeCB) were detected in 20 outdoor dust samples collected from Xinxiang City. The concentrations of ΣHCHs, ΣDDTs, HCB, and PeCB in dust were in the range of 0.18–5.05 ng/g dry weight, 0.44–13.50 ng/g dry weight, 0.13–51.61 ng/g dry weight and ND-0.74 ng/g dry weight, respectively. Long-range transport, historical use, and recent impact of impure pesticides might be the main sources of OCs in the outdoor dust. The results of this study indicated that impure pesticide application maybe an important source of DDTs and HCB in the environment.     

Simulation of soil loss processes based on rainfall runoff and the time factor of governance in the Jialing River Watershed,China

Jialing River is the largest tributary in the catchment area of Three Gorges Reservoir, and it is also one of the important areas of sediment yield in the upper reaches of the Yangtze River. In recent years, significant changes of water and sediment characteristics have taken place. The "Long Control" Project implemented since 1989 had greatly changed the surface appearance of the Jialing River Watershed (JRW), and it had made the environments of the watershed sediment yield and sediment transport change significantly. In this research, the Revised Universal Soil Loss Equation was selected and used to predict the annual average amount of soil erosion for the special water and sediment environments in the JRW after the implementation of the "Long Control" Project, and then the rainfall–runoff modulus and the time factor of governance were both considered as dynamic factors, the dynamic sediment transport model was built for soil erosion monitoring and forecasting based on the average sediment yield model. According to the dynamic model, the spatial and temporal distribution of soil erosion amount and sediment transport amount of the JRW from 1990 to 2007 was simulated using geographic information system (GIS) technology and space-grid algorithm. Simulation results showed that the average relative error of sediment transport was less than 10% except for the extreme hydrological year. The relationship between water and sediment from 1990 to 2007 showed that sediment interception effects of the soil and water conservation projects were obvious: the annual average sediment discharge reduced from 145.3 to 35 million tons, the decrement of sediment amount was about 111 million tons, and decreasing amplitude was 76%; the sediment concentration was also decreased from 2.01 to 0.578 kg/m³. These data are of great significance for the prediction and estimation of the future changing trends of sediment storage in the Three Gorges Reservoir and the particulate non-point source pollution load carried by sediment transport from watershed surface.     

Baseline values for metals in soils on Fildes Peninsula, King George Island, Antarctica: the extent of anthropogenic pollution

Metal contents (Al, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Ti, and Zn) have been measured in 30 surface soils on Fildes Peninsula, King George Island, Antarctica, yielding values (in milligrams kilogram(-1)) of 41.57-80.65 (Zn), 2.76-60.52 (Pb), 0.04-0.34 (Cd), 7.18-25.03 (Ni), 43,255-70,534 (Fe), 449-1,401 (Mn), 17.10-64.90 (Cr), 1,440-25,684 (Mg), 10,941-49,354 (Ca), 51.10-176.50 (Cu), 4,388-12,707 (Ti), 28,038-83,849 (Al), and for Hg (in nanograms gram(-1)) 0.01-0.06. Relative cumulative frequency analysis was used to determine the baseline values for the 13 metals. Compared with adjacent areas in Antarctica, Mg and Ni are significantly lower, but Cu is significantly higher than that of McMurdo Station. Enrichment factor analysis and the geo-accumulation index method were applied in order to determine the extent of anthropogenic contamination, and both show that Pb, Cd, and Hg have been significantly increased by human activities. Principal component analysis was used to identify the sources of metals in these soil samples.