Algal blooms usually occur in semi-closed water bodies such as lakes or estuaries; however, it has occurred frequently in the mid-downstream of the Han River (MSHR) in China since the 1990s. We made a comparative analysis of the hydrological conditions and identified the hydrological condition thresholds that induce algal blooms. From the hydrodynamic point of view, the changes and characteristics of the hydrological conditions in the MSHR were analyzed. Furthermore, the influence on the risk of algal blooms under different design water transfer schemes for the middle route of the South-to-North Water Diversion Project (SNWDP) was studied. The results indicated that (1) the flow in the MSHR less than 900 m3/s and water level in the Yangtze River higher than 14 m provided a suitable hydrological environment for diatoms multiply. (2) The flow of the MSHR showed a downtrend, while the water level of the Yangtze River showed an uptrend. There were variations in hydrological processes. Through specific IHA index analysis, the fact of flow reduction in the MSHR was demonstrated, and further indicated that algal bloom outbreak was in low flow period. (3) The water transfer in the middle route of SNWDP affected the risk probability of algal blooms. The more the amount of water transfer, the greater the risk probability of algal blooms. It was the Water Diversion Project from Yangtze River to Han River (WDPYHR) that replenished flow of the MSHR and was conducive to the prevention and control of algal bloom risk.
Environmental Economics and Policy Studies - The objectives of this study are to investigate Chinese hog farmers’ minimum willingness-to-accept (WTA) subsidies for complying pro-environmental... 相似文献
Biodegradation mechanisms and microbial functional diversity during coupled p-nitrophenol (PNP) and p-aminophenol (PAP) degradation were studied in a bioelectrochemical system. PNP in the biocathode and PAP in the bioanode were almost completely removed within 28hr and 68hr respectively. The degradation followed the steps including hydrating hydroxyalkylation, dehydrogenating carbonylation, and hydrolating ring cleavage, etc. Metagemomic analysis based on the KEGG and eggNOG database annotations revealed the microbial composition and functional genes/enzymes related to phenol degradation in the system. The predominant bacteria genera were Lautropia, Pandoraea, Thiobacillus, Ignavibacterium, Truepera and Hyphomicrobium. The recognized biodegradation genes/enzymes related to pollutant degradation were as follows: pmo, hbd, & ppo for phenol degradation, nzba, amie, & badh for aromatic degradation, and CYP & p450 for xenobiotics degradation, etc. The co-occurrence of ARGs (antibiotic resistant genes), such as adeF, MexJ, ErmF, PDC-93 and Escherichia_coli_mdfA, etc., were annotated in CARD database during the biodegradation process. The Proteobacteria & Actinobacteria phylum was the primary host of both the biodegradation genes & ARGs in this system. The microbial functional diversity ensured the effective biodegradation of the phenol pollutants in the bioelectrochemical system. 相似文献
Sorption of U(VI) onto TiO2 as functions of pH, ionic strength, contact time, soil humic acid (SHA), solid-to-liquid ratio and temperature was studied under ambient conditions using batch and spectroscopic approaches. The sorption of U(VI) on TiO2 was significantly dependent on pH and ionic strength. The presence of SHA slightly enhanced the sorption of U(VI) on TiO2 below pH 4.0, while it inhibited U(VI) sorption in the higher pH range. U(VI) sorption on TiO2 was favored at high temperatures, and the sorption process was estimated to be endothermic and spontaneous. Reduction of U(VI) to lower valent species was confirmed by X-ray photo-electron spectroscopy analysis. It is very interesting to find that U(VI) sorption on TiO2 was promoted in solutions with higher back-ground electrolyte concentrations. In the presence of U(VI), higher back-ground electrolyte made more TiO2 particles aggregate through (001) facets, leading more (101) facets to be exposed. Therefore, the reduction of U(VI) was enhanced by the exposed (101) facets and more U(VI) removal was observed. 相似文献
Efficient use of phosphorus (P) for producing food, preventing water pollution, and managing a dwindling rock P reserve are major challenges for China. We analyzed P stocks and flows in the Chinese food chain to identify where P use efficiency can be improved, where P leaks to the environment, and the research, technologies, and policies needed to improve P use. We found a high degree of inefficiency; of 6652 Gg P entering the food chain, only 1102 Gg P (18%) exit as food for humans. The greatest inefficiencies were a large build-up of soil P (3670 Gg P yr; 52% of P inputs) and high P losses to the environment from animal production (1582 Gg P yr; 60% of excreted P). Improving P use in China must focus on national-scale nutrient management strategies, better animal nutrition, and adoption of technologies and policies to reduce P discharges from the animal sector and recycle P as manures in agriculture. 相似文献