[Scenario analysis of integrated model of nutrients in the Miyun Reservoir and its watershed].

Supported by the integrated model of nutrients for the Miyun Reservoir in part I, effects of different control measures were studied on the water quality of the reservoir. Four scenarios were assumed and analyzed. Results of the base case scenario showed that TN concentration of the Miyun Reservoir had highly exceeded the environmental quality standard for surface water, and TP was relatively better. Furthermore, there were many regions that chlorophyll-a concentration exceeded 10 microg/L in the reservoir, and centralized in the reservoir area of Chaohe River. Scenario 1, 2 and 3 investigated effects of different pollution control measures on the water quality of the reservoir. Results showed that the control of nutrient input loads could improve the water quality greatly, especially control of TP loadings would limit algae growth effectively, and regions that chlorophyll-a concentration exceeded 10 microg/L even disappeared. The results indicated that some control measures, such as changing farming style, part treatment on stockbreeding pollution and reducing point source pollutant loadings were very effective and essential to decrease the eutrophic level of the reservoir.

[Integrated model of nutrients for the Miyun Reservoir and its watershed].

In recent years, the Miyun Reservoir faces severe problems of water quality and quantity due to continuous drought. In order to simulate and predict the eutrophic status of the Miyun Reservoir and its watershed, an integrated model was developed based on GIS and RS technology, which was composed of non-point source (NPS) simulation model, aquatic ecological-hydrodynamic model, and river water quality model. Ecological-hydrodynamic model was developed through coupling water quality analysis simulation program (WASP) with environmental fluid dynamics Code (EFDC). SWAT was selected as NPS simulation model, which could also perform water quality simulation in the river. Then the integrated model was calibrated using Markov Chain Monte Carlo method and verified using observed data. Results indicated that observed water quality data laid around the mode curves of simulation distribution, and which also dropped into the confidence interval on 80 percent credibility of water quality simulation distribution. In conclusion, the results show that the integrated model can meet the need of application.

[Study on spatial site selection assessment of urban medical waste treatment facility].

Based on the principle of regional differentiation and gravity model, this paper proposes a GIS-based urban medical waste treatment facility spatial site selection assessment method. And the method is implemented by use of the third generation GIS database model, Geodatabase. Taking a city in Pearl River Delta as a case, based on its 46 basic units, two scenarios for medical waste central treatment are designed and analyzed by means of scenario analysis (SA) and then the better scenario is recommended. The assessment result of traditional cost model shows the same conclusion. Further spatial analysis shows that the distribution of medical waste quantity and density are both related to the better scenario spatially.

[Markov Chain Monte Carlo scheme for parameter uncertainty analysis in water quality model].

Parameter identification plays an important role in environmental model application. Markov Chain Monte Carlo method was introduced to estimate parameter uncertainty, since usual Bayes discrete methods were not applicable to produce posterior distribution of complicated environmental model due to the limit of computation. In order to study the performance and efficiency of MCMC, two case studies were used. Results indicate that, either sampling performance or sampling efficiency, MCMC method both has its special advantages in producing posterior distribution. Moreover, results of Gelman convergence diagnostics indicate that sampling sequence can converge to a stationary distribution. A key finding was that the MCMC scheme presented herein provided a powerful means of parameter identification and uncertainty analysis.

Risk forecasting and evaluating model of environmental pollution accident.

Environmental risk (ER) factors come from ER source and they are controlled by the primary control mechanism (PCM) of environmental risk, due to the self failures or the effects of external environment risk trigger mechanism, the PCM could not work regularly any more, then, the ER factors will release environmental space, and an ER field is formed up. The forming of ER field does not mean that any environmental pollution accident (EPA) will break out; only the ER receptors are exposed in the ER field and damaged seriously, the potential ER really turns into an actual EPA. Researching on the general laws of evolving from environmental risk to EPA, this paper bring forwards a relevant concept model of risk forecasting and evaluating of EPA. This model provides some scientific methods for risk evaluation, prevention and emergency response of EPA. This model not only enriches and develops the theory system of environment safety and emergency response, but also acts as an instruction for public safety, enterprise' s safety management and emergency response of the accident.

[Parameter optimization of water quality model: implementation of genetic algorithm and its control parameters analysis].

Parameter identification plays an important role in environmental model application. As a commonly used global optimization method, genetic algorithm (GA) has very simple structure, the key related to whether a practical issue can be solved using GA or not is algorithm design and selection of the control parameters. Based on the feature of parameter optimization of water quality model, orthogonal test method was proposed for reviewing effects of different control parameters of GA on the performance of water quality parameter optimization. The results indicate that orthogonal method could identify key factors, and also provide possible optimized experiment plan. It is concluded that GA can be applied to the research on parameter identification of complicated water quality model.

[GIS and scenario analysis aid to water pollution control planning of river basin].

The forward and backward algorithms for watershed water pollution control planning were summarized in this paper as well as their advantages and shortages. The spatial databases of water environmental function region, pollution sources, monitoring sections and sewer outlets were built with ARCGIS8.1 as the platform in the case study of Ganjiang valley, Jiangxi province. Based on the principles of the forward algorithm, four scenarios were designed for the watershed pollution control. Under these scenarios, ten sets of planning schemes were generated to implement cascade pollution source control. The investment costs of sewage treatment for these schemes were estimated by means of a series of cost-effective functions; with pollution source prediction, the water quality was modeled with CSTR model for each planning scheme. The modeled results of different planning schemes were visualized through GIS to aid decision-making. With the results of investment cost and water quality attainment as decision-making accords and based on the analysis of the economic endurable capacity for water pollution control in Ganjiang river basin, two optimized schemes were proposed. The research shows that GIS technology and scenario analysis can provide a good guidance to the synthesis, integrity and sustainability aspects for river basin water quality planning.

[Regular pattern of non-point source pollutants losses in Luxi watershed].

The losses of non-point pollutant combined with natural rainfall events were monitored at outlets of Luxi watershed and several field plots with different land use. The paper probes characteristics of the sediment and chemical losses during a single rainfall-runoff process. The impact of preceding precipitation is also discussed. The results of field experiments show that the concentration of SS in runoff dropped off obviously with the increase of antecedent rainfall. The observed data were 265.6, 145.8, 124.2mg/L respectively with precipitation of 15, 115, 161 mm in preceding 5 days. Compared to the losses of SS, nutrients and COD were not changed greatly by the preceding rainfalls. The fluctuations of pollutant concentration were less than 15%. The results from plots suggested that land use play an important role in pollutant losses. The following is the list ordered according to concentration of pollutant in runoff, from the highest to the lowest: Dry land,residential area, grassland, woodland and paddy land. Vegetation cover is effective on the reduction of soil erosion and sediment loss. About 80% SS could be cut down when the coverage changed from 50% to 90%. Losses of TN were mainly determined by the TN concentration in soil. The ratios of TN concentration in runoff to that in soil were 2.75%, 2.79%, 2.42 % respectively for the land use of dry land, grassland and woodland. Augment of vegetation overage contributed to increment of N losses,including NO3- -N and NH+ -N.