Cong-Guo Tang

Tissue S/N ratios and stable isotopes (δ34S and δ15N) of epilithic mosses (Haplocladium microphyllum) for showing air pollution in urban cities in Southern China

In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO(4)(2-)/NH(4)(+) ratios, each people SO(2) emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal delta(34)S and NH(4)(+)-N wet deposition, respectively, indicating that local coal and animal NH(3) are the major atmospheric S and N sources.

Indicating atmospheric sulfur by means of S-isotope in leaves of the plane, osmanthus and camphor trees.

Foliar δ(34)S values of three soil-growing plant species (Platanus Orientalis L., Osmanthus fragrans L. and Cinnamomum camphora) have been analyzed to indicate atmospheric sulfur. The foliar δ(34)S values of the three plant species averaged -3.11±1.94‰, similar to those of both soil sulfur (-3.73±1.04‰) and rainwater sulfate (-3.07±2.74‰). This may indicate that little isotopic fractionation had taken place in the process of sulfur uptake by root or leaves. The δ(34)S values changed little in the transition from mature leaves to old/senescing leaves for both the plane tree and the osmanthus tree, suggestive of little isotope effect during sulfur redistribution in plant tissues. Significantly linear correlation between δ(34)S values of leaves and rainwater sulfate for the plane and osmanthus trees allowed the tracing of temporal variations of atmospheric sulfur by means of foliar sulfur isotope, while foliage δ(34)S values of the camphor is not an effective indicator of atmospheric sulfur.

Surface Water Hydrologic Simulation of Qingshuijiang Watershed Based on SRTM DEM

The Digital Elevation Model (DEM) derived from NASAs Shuttle Radar Topography Mission is the most accurate nearglobal elevation model that is publicly available. The characteristics, advantages, and disadvantages of Shuttle Radar Topography Mission (SRTM) data sets were reviewed and discussed briefly. In order to verify the effect of applying SRTM data sets in surface water hydrologic simulation, a tool set named Arc Hydro Tools that is utilized to extract watershed characteristics was introduced, developed as an ArcGIS interface. The Qingshuijiang watershed in Guizhou Province, Southwest China, was taken as a case study. Using the tool set, the river network and subwatersheds of main tributaries were delineated from CGIAR- CSI SRTM 90 m DEM. By comparing the river network delineated from CGIAR-CSI SRTM 90 m DEM with the actual river network and comparing areas of the subwatersheds delineated from CGIAR-CSI SRTM 90 m DEM with the actual areas of the subwatersheds, it can be concluded that the delineated river network is generally in accord with the actual river network, as well as the areas of the delineated subwatersheds. The CGIAR-CSI SRTM 90 m DEM will promote the use of geospatial science and applications for digital topography analysis, especially for surface water hydrologic simulation.

Simulation of runoff based on digital Wujiang watershed

Nonpoint source pollutants are mainly carried over land and into stream networks by surface runoff, and how to simulate surface runoff is the key to determining the loads of nonpoint source pollutants. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use of the watershed. Five subwatersheds that can represent the whole watershed are chosen and their average annual precipitation, average annual surface runoff and percent land use are calculated respectively in the grid model of Wujiang River watershed based on climatic and hydrological data from 1965 to 2000 and land use data of 2000. The surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and percent land use. Thus the rainfall-runoff model for each land use type is built respectively. When calibrating these models, the result shows that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.