Nitrogen Cycling And Correlative Microorganism Tracing And Impacting In Karst Groundwater System, Qingmu Guan, Chongqing

Karst groundwater pollution in China has been so serious that the usable quantities of groundwater resources are very little. Thus, protection of karst groundwater resources couldn't be delayed any more. In the karst area, groundwater is an important water resource of local people life and agriculture, but nitrogen pollution caused by fertilization is very common. Therefore, reducing nitrogen pollution in karst groundwater is very important to ensure the people's livelihood, and social harmony and stability. The situation of "3-N" pollution and nitrogen cycling process in soil and groundwater were reported a lot, but most of them were focus on non-karst area and few studies with regard to karst area have been documented.The contaminations transferring has its unique characters for the special hydrogeology background in karst area. In the transferring processes, contaminations couldn't be absorbed or degraded, which will transfer to a place far away in short time after they leaching into ground river and discharging to non-karst area. Thus the accumulation of nitrogen pollution isn't of great notability in soil and groundwater in karst area, but the occurrence of nitrogen pollution may be even worse. In this paper, a case of a typical karst valley in Qingmu Guan, Chongqing, has been employed to investigate the nitrogen transferring and transforming processes in soil and groundwater, and give some suggestion for nitrogen management in management of rocky desertification and protection of groundwater and drinking water sources.Soil elements and microorganisms have been measured in ten kinds of soil samples within different land use, and also principal factor analysis was used to conclude the main affecting factor of soil nitrogen cycling. Two of the ten soil samples, representation of typical land uses, were specially sampled to analyze the characteristics of nitrogen transferring and transforming in vertical been concluded. First, in the rainy season, protection zones and adaptations in land use practices around the swallow holes and sinking streams, and within their hydrologic catchments, need special attention and must help to reduce microbiological contaminations of spring. Second, in the dry season, protection zones and adaptations in land use practices should be better attention in the whole watershed, which including control the use of pesticides and fertilizers and sewage irrigation. Third. if possible, using soil situ ecological repairing to degrade contaminations and reduce contaminations transferring to underground flows.Generally, the nitrogen cycling in karst area is different from that in non-karst area, and need to pay more attention. In the future, some researches should be done in different karst system to find out the nitrogen cycling mechanisms in different hydrogeology background. Numerical simulation model about nitrogen cycling in karst area should be established to help reduce the ground water nitrogen pollution in rocky desertification management projects. Otherwise, the preliminary study of soil microorganism tracer test shows the character of soil microorganism community is useful in groundwater tracer test, but it needs more research in detail, such as the detail of microorganism community composition and characteristic in different soil, which more advanced technology should participates.