Zhao Chuanyan

Spatial Distribution of Selected trace Metals in Urban Soils of Lanzhou City, Gansu Province, Northwestern of China

Contamination of urban ecosystems with trace elements has become an important topic of investigation. A preliminary survey was conducted in Lanzhou city with an approximately 1.8 million inhabitants and a surface area of 1663 km. A total of 56 surface soil samples (0~15 cm) had been collected in the urban area according to the city planning districts, and each sample site was located by GPS, and the digestion soil total contents of copper, zinc, and lead had been determined using AAS with a graphite furnace. Results show that: 1the means of metal Zn and Pb were about 1.5 and 1.8 times more than the soil background contents, respectively; and contents of both metals showed wide ranges (Pb 7.6-96 mg/kg DW, Zn 33.9-282 mg/kg DW); 2Concentrations of selected metals Cu, Zn and Pb in most sites, 56% for Cu, 84% for Zn and 63% for Pb of total sample number, respectively; and3From maps made by means of GIS with kriging-interpolated method, it can be discovered that the heavy polluted soils were in the proximity of the motorway and streets with high traffic flows, especial near city crossroad or service station, and in sites of industrial region corresponding with areas of oil refineries where combustible deposit occurred. So, the following conclusion can be drawn that the urban soils studied has been affected by human activity resulted in a high accumulation of selected trace metals, and the topsoil metal contents clearly revealed an anthropogenic origin of contamination. Keywords-Urban soils of Lanzhou; Heavy metals Cu, Zn and Pb; Pollution; Spatial distribution

Monitoring Glacier Changes of Recent 50 Years in the Upper Reaches of Heihe River Basin Based on Remotely-Sensed Data

The upper reach of the Heihe River Basin was selected as the study area. The distribution data of glaciers in the study area has been automatically derived from topographic maps made in 1960 and from Landsat TM images in 1990, 2000 and 2010 by object-oriented image interpretation method combined with expert knowledge rules. Spatial-temporal variations of glaciers were analyzed with GIS technology. Results show that glaciers have shrunk significantly by 138.90 km2 during the period from 1960 to 2010. Compared with the data of 1960, 35.6% of glaciers have been retreating and the calculated average rate of glaciers retreating is 2.78 km2 every year since 1960. The glacial retreating has been most significant if the glaciers have lower-elevation ablation areas and low-elevation accumulation areas. The temperature rising is the key factor of glacier retreating.

Effects of agro-activities on the soil organic carbon and soil properties in the middle reaches of Heihe river, Northwestern China

Knowledge about changes of SOC and other properties under influence of human activities in arid zone is very important for local cropland persistent management. In our study, SOC and selected soil properties had been investigated in the Linze country located in Hexi corridor, northern west China. The GIS tool was used to explain the causes resulted in SOC spatial distribution. The results indicated that the highest levels of SOC, humic acid, and fulvic acid presented in early cultivated plots, then in lately reclaimed cropland, and the lowest in desert soil. The remarkable increasing of soil CEC and clay content can been seen in arable land in contrast to desert land. Our findings may suggest that agricultural practices, such as irrigation, use of manure and fertilizer, return of crop residues, etc. protect SOC from loss and improve the soil fertility in arid area studied.

Comparison of Present and Potential Spatial Distribution of Vegetation in the Groundwater-Fluctuating Belt in the Lower Reaches of Heihe-River Northwestern China

The present and potential spatial distributions of vegetation were estimated respectively by remote sensing data and a logarithmic normal distribution model in the lower reaches of Heihe River, northwestern China. The results show: (1) the comparability of the potential and present spatial distribution of Populus euphratica is 66.3% and Tamarix ramossima is 74.7%; (2) the higher comparability of the potential and present spatial distribution indicates that the groundwater level is the decisive factor in the changes of spatial distribution of Populus euphratica and Tamarix ramossima in the study area. The difference is obvious between the potential and present spatial distribution of Populus euphratica and Tamarix ramossima in the distribution region of hardy salt layer. This study is an important reference for analyzing the relationships between vegetation distribution and groundwater level.

Relationship between vegetation distribution and groundwater level in the lower reaches of Heihe River basin, China

The relationship between vegetation coverage and groundwater level was built in the study area according to investigation data. The spatial and temporal variation of groundwater levels was simulated by FEFLOW from 1980 to 2010. Temporal-spatial distribution of Potential vegetation in the study area was estimated using the relationship combining with spatial distribution of groundwater level. The results of coverage estimated were validated by Landsat TM data.