Spatial characteristics of soil enzyme activities and microbial community structure under different land uses in Chongming Island, China: geostatistical modelling and PCR-RAPD method.

Information about soil enzyme activity and soil DNA as indicators of how land use affects soil quality remains unknown for alluvial island. The purpose of this study was to investigate the effects of land use on enzyme activities and soil gene diversity in the Chongming Island, Shanghai, China, with the aim of providing further knowledge about the problems related to soil quality and its evolving spatial characteristic on the Chongming Island. The results indicate that land use causes an important change of organic matter, with either causing a small decrease or an increase in the absolute enzyme activity. With increased management intensity, there is an increase in the number of soils with high organic matter content and a decrease in the soils with low organic matter content. The effect on enzyme activity varies depending on the type of land use or management and the type of enzyme. The orders of the number of gene polymorphic bands under different land uses were as follows: agriculture soil>commercial soil>industrial soil>wetland. The complexities of the behaviors of the soil enzymes indicate that genetic analysis and biomarkers in conjunction with geostatistics method will be a powerful and accurate indicator to evaluate soil quality under land use.

[Output characteristics of non-point nitrogen from a typical village region in Yangtze Delta under an individual rainfall event].

In order to provide a scientific foundation for controlling non-point source pollution, we studied on output characteristics of non-point nitrogen under different land uses in a typical agricultural village in the Yangtze River Delta. The various species of nitrogen and output load under a typical individual rainfall runoff event were investigated. The results indicated that the event mean concentrations (EMC) of total nitrogen (TN) in monitoring sites ranged from 20.01 mg/L to 22.83 mg/L, and the main form was dissolved nitrogen (DN) in TN. The main form of the lost nitrogen in the studied area was DN which was mainly composed by dissolved organic nitrogen (DON). Coupled with the characteristics of nitrogen concentration and runoff, two peaks of non-point nitrogen output could be found, and appeared 4-55 min before the runoff peaks. The concentrations of TN, DN, and nitrate (NO3(-) -N) decreased with the rainfall time increasing. Nitrogen load was influenced by its concentration and runoff, and showed the same output characteristics of nitrogen concentration with a gentle variation. Form the cumulative load curve of nitrogen in a typical rainfall event, first-flush effect could be found for each nitrogen species in rural runoff.