[Groundwater organic pollution source identification technology system research and application].

Groundwater organic pollutions are found in large amount of locations, and the pollutions are widely spread once onset; which is hard to identify and control. The key process to control and govern groundwater pollution is how to control the sources of pollution and reduce the danger to groundwater. This paper introduced typical contaminated sites as an example; then carried out the source identification studies and established groundwater organic pollution source identification system, finally applied the system to the identification of typical contaminated sites. First, grasp the basis of the contaminated sites of geological and hydrogeological conditions; determine the contaminated sites characteristics of pollutants as carbon tetrachloride, from the large numbers of groundwater analysis and test data; then find the solute transport model of contaminated sites and compound-specific isotope techniques. At last, through groundwater solute transport model and compound-specific isotope technology, determine the distribution of the typical site of organic sources of pollution and pollution status; invest identified potential sources of pollution and sample the soil to analysis. It turns out that the results of two identified historical pollution sources and pollutant concentration distribution are reliable. The results provided the basis for treatment of groundwater pollution.

[In situ experimental research on natural attenuation of oil pollutants in a gas station].

The natural attenuation rules of oil pollutants are investigated by carrying out a field experiment in a gas station in Beijing, using a set of soil gas sampling and monitoring device designed independently. The samples of soil gas were collected in the field and tested to examine the content of O2, CO2 and VOCs in the unsaturated zone. The results show that after 381 days' natural attenuation, the concentration of the contaminants at the polluted point deceased by 99.2%, while the ratio of BTEX to TVOC decreased from 17.0% to 12.1%. Moreover, the content of O2 decreased while that of CO2 grew as the soil depth increases at G3 point. Further theoretical analysis indicated that: (1) The test results of first-step experiment show that there was a certain level of contamination in G3 area. And after 381 days' natural attenuation, the content of the BTEX at G3 point fell below the environmental standard level, which means the control measures could be removed. (2) The origin of the contamination was proved as short-term sources, and no long-term sources of leakage existed. (3) An effective removal of contaminants in the soil was found under the influence of the natural attenuation. This method could be applied in long-term monitoring for similar contaminated sites. (4) The test of O2and CO2 contents was proved to be an effective approach to determine if the aerobic degradation happens.

[Research of the natural attenuation capacity of oil pollutants based on in-situ experiment].

Based on the results of the in-situ experiment carried out in a Beijing gas station, the ways of natural attenuation were evaluated as both aerobic and anaerobic biodegradation via oxygen and carbon equilibrium calculation. And the research got the rates of the natural attenuation and half-life of the oil pollutants byusing the first-order decay model. Based on the analysis, the capability of monitored natural attenuation and the environmental quality were evaluated. The results show that the actual oxygen consumption of contaminated site is less than that needed theoretically in aerobic degradation of all pollutants, while the amount of CO2 detected is far less than that in the aerobic degradation by theoretical formation. And the half-life of petroleum contaminants in contaminated site is about 50 days. The analysis indicated that: (1) The ways of natural attenuation were proved as both aerobic and anaerobic biodegradation; (2) The contamination of the BTEX tested by the fist-step experiment fell below the environmental standard level after about 250 days' natural attenuation, which means the environmental risk in this gas station had been eliminated and the control measures could be removed.

[Physicochemical properties of Guanting Reservoir sediment and its land application].

Surface sediment of Guanting Reservoir was dredged up and dewatered in field, and pollutant and physicochemical characterizations were mensurated. The stabilization and agricultural land use of the sediment was also studied in the field. Results showed that the sediments have a higher clay content, bulk density (1.89 g x cm(-3)) and lower porosity (23.8%), higher deoxidize material and available nitrogen, phosphorus concentration. Heavy metal and organochlorinated pesticides concentration was lower than the class II of national standard for soil. Stabilized the sediment with sand soil and straw could improve the physical property and decrease the concentration of deoxidize material and available nitrogen, phosphorus. Stabilized sediment could be a suitable medium for alfalfa, tree and corn growth and used for agricultural land.

[Performance of treatment wetland systems for surface water quality improvement].

Intercropped with Phragmites communis and Typha angustifolia, subsurface flow constructed wetland systems (CWs) with the surface area of 3 x 20m x 2m were established beside Guanting Reservoir, an important source water base of Beijing. The treatment performance of the systems with different season were studied, the impacts of influent concentration, hydraulic loading rate and water temperature on contaminations removal were analyzed. The result showed that the subsurface flow CWs had the better decontamination effect to micro-pollution surface water. The relationship between the concentrations of CODMn and NH4+ -N in inflow and outflow followed the linear equation. The removal rates of total nitrogen (TN) and total phosphorus (TP) in the systems were 20%-60% and 30%-45%, respectively. The removal rates of contaminations were reduced with the decrease of water temperature and the increase of hydraulic loading rate, the removal rates of CODMn, N4+ -N and TN showed the positive correlation with their inflow concentration, but the removal rate of TP showed the negative correlation with its inflow concentration. Operation and management considerations of the subsurface flow CWs in winter were investigated in this study.