Spatial trends and pollution assessment for mercury in the surface soils of the Nansi Lake catchment, China.

Surface soil samples collected from Nansi Lake catchment were analyzed for mercury (Hg) to determine its spatial trends and environmental impacts. Results showed that the average soil Hg contents were 0.043 mg kg-1. A positive correlation was shown between TOC and soil Hg contents. The main type of soil with higher TOC contents and lower pH values showed higher soil Hg contents. Soil TOC contents and CV values were both higher in the eastern catchment. The eastern part of the catchment, where the industry is developed, had relatively high soil Hg contents and a banding distribution of high Hg contents was corresponded with the southwest-northeast economic belt. Urban soils had higher Hg contents than rural soils. The urbanization pattern that soil Hg contents presented a decreasing trend from city center to suburb was shown clearly especially in the three cities. Soil Hg contents in Jining City showed a good consistency with the urban land expansion. The spatial trends of soil Hg contents in the catchment indicated that the type and the intensity of human activities have a strong influence on the distribution of Hg in soils. Calculated risk indices showed that the western part of the catchment presented moderately polluted condition and the eastern part of the catchment showed moderate to strong pollution level. The area with high ecological risk appeared mainly along the economic belt.

[Residues and Spatial Distribution Characteristics of Organochlorine Pesticides DDTs in Soil of Linyi City, Shandong Province].

Surface soil samples were collected every 36 km2 from Linyi City to study the residues, composition and origin, influencing factors, spatial distribution and environment quality characteristics of soil DDTs. Measurements were taken for DDTs, OrgC, N, etc. for all samples. The results indicated that the detectable rate of DDTs was 71. 75%, and the mean content of DDTs was 0. 035 µg.g-1. p,p'-DDT and p,p'-DDE were the predominant contaminant compounds, with mean concentrations of 0.033 µg.g-1 and 0.010 µg.g-1, and accounted for 60. 99% and 34. 62% of the detectable samples, respectively. The degradation rate of DDTs suggested that 58% surface soils were recently inputted, these newly inputted locations were especially distributed in the middle to south of the study area, meanwhile, p,p'-DDD/p,p'-DDE revealed that the degradation of DDTs was mainly under oxidizing condition, and o,p'-DDT/p,p'-DDT illustrated that 71. 37% DDTs in soils of the study area were concerned with technical DDTs sources. Besides, the correlation, analysis showed that the external factors affecting the distribution of DDTs included OrgC, N, C and pH etc. and the higher the p, p'-DDT proportion of DDTs, the greater the effect. The distribution of DDTs had an obvious point source characteristic, and significant concentration centers were located nearby the cities and counties, typically, the DDTs concentrations of middle to southern area were much higher. However, DDTs environmental quality assessment suggested that the pollution level was relatively low, and the soil was mainly classified into grade I or II, which accounted for 78. 95% and 21. 05% of the whole study area, respectively.

[Pollution Status and Migration of Mercury in the Sediments of Nansi Lake in Shandong Province].

The content of mercury and fractions were determined, in order to discuss the pollution situation and migration ability of mercury in inflow rivers and surface sediments of Nansi Lake. The average content of mercury in the sediments of the Nansi Lake was 0.046 mg · kg(-1), significantly higher than the environmental background values, which showed that Nansi Lake suffered from mercury pollution. Mercury in sediments existed mainly in the residual fraction, accounting for 65. 15%. The proportion of non-residual fractions was relatively small, in the order of organic bound fraction (30.61%), extractable fraction (2.93%), and Fe/Mn oxide (1.31%). The spatial change of non-residual fractions was that Weishan Lake and Nanyang Lake had higher non-residual mercury content than Zhaoyang Lake and Dushan Lake, and the non-residual mercury had a certain potential ecological harm on Weishan Lake and Nanyang Lake. From the horizontal view, the mercury content in the surface sediments of Nansi Lake had visible difference and the pollution degree was different among sub-lakes, so horizontal migration of mercury was obvious. Vertically, the mercury content showed a trend of increasing from the bottom to the top in core sediments, which might be associated with social and economic conditions in different periods.