Heavy Metal Pollution and Ecological Risk Assessment of Cultivated Land Soil in the Farming Areas of Coastal China:A Case Study of Donghai County,Jiangsu Province

Classical statistics,Inverse Distance Weighted and Hakasnson potential ecological index were used to study the distribution characteristics of 8 kinds of heavy metals( Cr,Ni,Cu,Zn,As,Cd,Pb and Hg) as well as their potential ecological risks in the topsoil( 0-20 cm) of cultivated land in Donghai County,a typical agricultural area along the Southeast Coast of China.The results showed that the average content of heavy metals in the cultivated soil of Donghai County was not over the risk screening values set in the Environmental Quality Standard for Soils.However,it was worth noting that in some of the sampling points,the content of Cr exceeded the risk screening value,and the standard exceeding points accounted for 24.74% of the total.In addition,the average content of Cr,Ni,As,Cd,Pb and Hg exceeded the soil background values of Jiangsu Province,and values for Cd,Cr and Pb were more than 1.5 times of the soil background value of Jiangsu Province.The heavy metals were at the medium integrated potential ecological risk level,and the potential ecological risk indices were high in the east and low in the west,and distributed in interlaced island shape.The potential ecological risk indices of the plains in the east were higher than those of the central gentle slope area and the western hillock area.The potential ecological risk was at a high level in Niushan Town which was situated the county center and in some regions with high urbanization levels.

The Spatio-temporal Evolution and Effect Factors of Cultivated Land Fragmentation in Jiangsu,China

Based on the land use change data obtained from the interpretation of remote sensing images in 1985, 1995, 2005 and 2008, the research applied principal component analysis, Markov chain and ESDA method, and took cultivated land patch as the basic unit of landscape. A comprehensive measure of the fragmentation of cultivated land was made in Jiangsu counties and its temporal and spatial evolution characteristics and driving process from the perspective of landscape ecology were discussed. The results are as follows:(1)The overall fragmentation of cultivated land in Jiangsu Province presents that the eastern coastal areas are low, the interior of the west is high, the fragmentation of northern and southern Jiangsu is high, while the fragmentation of mid-Jiangsu is low.(2)The degree of fragmentation of cultivated land in most area of southern Jiangsu and midJiangsu showed an upward trend, while the fragmentation of cultivated land in northern Jiangsu showed a downward trend from 1985 to 2008. The degree of agglomeration of cultivated land is weakened continuously, the area of high value agglomeration is decreasing and the trend of "polarization" is weakening.(3) Topographic condition is the decisive factor for the formation of the difference pattern. The change of rural residential land, cultivated land and the scale of urban land use plays a role on the cultivated land fragmentation index, among them, the change of rural residential land scale has the most significant effect on cultivated land fragmentation.