Ecological risk assessment of water environment for Luanhe River Basin based on relative risk model.

The relative risk model (RRM) was applied in regional ecological risk assessments successfully. In this study, the RRM was developed through increasing the data of risk source and introducing the source-stressor-habitat exposure filter (SSH), the endpoint-habitat exposure filter (EH) and the stressor-endpoint effect filter (SE) to reflect the meaning of exposure and effect more explicit. Water environment which include water quality, water quantity and aquatic ecosystems was selected as the ecological risk assessment endpoints. The Luanhe River Basin located in the North China was selected as model case. The results showed that there were three low risk regions, one medium risk region and two high risk regions in the Luanhe River Basin. The results also indicated habitat destruction was the largest stressor with the risk scores as high as 11.87 for the Luanhe water environment, the second was oxygen consuming organic pollutants (9.28) and the third was nutrients (7.78). So these three stressors were the main influencing factors of the ecological pressure in the study area. Furthermore, animal husbandry was the biggest source with the risk scores as high as 20.38, the second was domestic sewage (14.00), and the third was polluting industry (9.96). For habitats, waters and farmland were enduring the bigger pressure and should be taken considerable attention. Water deterioration and ecological service values damaged were facing the biggest risk pressure, and secondly was biodiversity decreased and landscape fragmentation.