The chemical stability of heavy metals in a natural water system

A comprehensive investigation of heavy metal pollutants in Xiangjiang river was accomplished to evaluate their chemical stability through three different ways: (1) Chemical speciation by direct measurements; (2) Chemical equilibrium model simulation; (3) Sediment extraction experiments. All the results demonstrated that the directly bioavailable fraction was in a very limited amount. The metal bound to organic ligands, adsorbed particles and precipitated species presented a buffer for solution species. The majority of metals occured in the residues as solid particulates. It was inferred that the heavy metal pollutants in this aquatic system exhibited a high chemical stability. The critical limits of discharging load and pH values were suggested.     

A study on the hydraulics of waste stabilization pond

In this study, tracer tests and organic removal tests were conducted on three different ponds in the purpose of evaluating the influence of the flow velocity and dispersion on the hydraulic efficiency of the pond. The authors have compared the hydraulic flow patterns among ponds with different configurations. Experimental and theoretical analyses were performed. This study indicated that the flow characteristics of square ponds are different from that of baffled ponds; the flow velocity and dispersion are equally important factors which affect the pond hydraulics; the number of inserting baffles can be optimized; and the hydraulic efficiency of multistage ponds is superior to that of baffled ponds.     

粮食安全与耕地的关系

粮食安全是关系到长治久安，社会稳定的大事，而耕地是粮食生产的主要载体。在广东省目前耕地面积不断减少，并且耕地质量面临下降的情况下，各级政府有责任采取各项措施，加大对耕地质量改良的投入。只有提高了耕地质量，才能确保广东省的粮食安全。     

广东耕地地力调查与质量评价试点工作的成果及其应用展望

根据农业部的布置，广东省选择佛山市高明区开展耕地地力调查与质量评价试点工作。查清了高明区耕地等级及其分布、土壤肥力状况、土壤及水源受污染的背景，建立了高明区耕地质量管理信息系统，为高明区土壤合理利用和改良、作物布局调整、肥料合理生产和正确施用、土地有偿使用、无公害优质农产品生产等提供了指导，也为今后全省各地开展该项工作提供了参考。     

控释肥料推广施用的意义与措施

讨论了控释肥料推广施用的意义，总结了广东省控释肥料试验示范的效果，并对今后推广施用控释肥料提出了若干意见和建议。     

Coping with the environmental effects of point-source discharges

Current methods for assessing the environmental impact of point source discharges in the United States are reviewed. The emphasis of many assessments of damage from pollution is shifting from chemical or technological standards to biological standards, i.e., the protection of biological integrity in the receiving system. The importance of integrating information from chemical measurements, toxicity tests, and field surveys in impact assessment is re-emphasized. Ways in which environmental professionals can improve methods for assessing damage from pollution and its control are discussed.     

Estimation of greenhouse gas emissions in China and the abatement measures

The major emission sources of carbon dioxide, methane, nitrous oxide and CFCs in China have been identified, and the emission trends has been estimated. Besides fossil fuel combustion, human respiration and biomass burning are important sources. Some feasible abatement measures on energy conservation, afforestation and biomass recycling have been discussed.     

Effect of atmospheric aerosols on UV-B radiation reaching the ground

Solar ultraviolet radiation reaching the ground can be reduced due to light scattering of atmospheric aerosols. Aerosol pollution has led to the decrease in biological active UV-B radiation by about 45% and 10% in city and rural areas, respectively. In populated areas, effect of aerosol scattering on UV-B radiation may offset the increased amount of UV-B caused by ozone depletion, but in clean areas such as two poles, ozone depletion may have great damage effects on ecosystems.     

Research on organic matters in the drinking water of Kaschin-Beck disease area

Organic matters in drinking water of Kaschin-Beck disease areas were extracted. Then analyses and characterization were performed by means of multiply chemical and physical methods. The results did not show the obvious difference in the frame structure of humic substances and the structure of rmcromolecular compounds in the drinking water of disease and non-disease areas, but the difference in the contents of some micromolecular compounds and radicals. The investigation also includes the preliminary research on the photoreaction of drinking water from disease and non-disease areas and the accumulation of natural organic matter in the bone of tested animals.     

Determination of atmospheric concentrations of halocarbons in Beijing area

Gas chromatography with ambient temperature injection and frozen-trapped techniques was used to determine the atmospheric concentrations of halocarbons over Beijing. Halogenated compounds such as CFC-11, CFC-12, CHCl_3, CCl_4, CH_3CCl_3, CHCl =CCl_2, and CCl_2=CCl_2 were measured and their concentrations are 109±8, 234±13, 47±22, 97±24, 88±29, 11±1 and 17±3 (pptv), respectively.