干旱区生态环境知识资源中心

Spatial distribution of heavy metals can be used for planning, risk assessment, and decision making in the environmental management of a region. In this context, the present research has three specific objectives: to characterize spatial distribution of heavy metals in a saline environment, to determine the relationship between some of soil properties and heavy metal distributions, and to assess the controlling factors for the spatial variability of heavy metals prior to reclamation and intensive irrigated agricultural activities. The field was 2650 ha, and divided into square sub-blocks, with 400 m spacing in x and y directions, for sampling procedure. One hundred fifty one soil samples were collected from 0-30 cm of soil surface. Heavy metal (nickel (Ni), cadmium (Cd), lead (Pb), cobalt (Co) and chromium (Cr)) concentrations of soils along with some of physical and chemical characteristics were determined. Geostatistical techniques were employed to determine the spatial variability of heavy metals. Topsoil salinity was highly variable at short distances and terrain attributes were the most influential factors. Mean concentrations of metals were lower than that of allowable level in European Union. The nugget variance to sill ratio ranged from 0.2 for Cr to 28.02% for Cd suggesting strong to moderate spatial dependency that might be attributed to the effect of intrinsic factors (such as parent material) in the distribution of metals. Low levels of heavy metals in this arid region indicate that the main factor in distribution of metals was lithology, and contributions from agricultural activities and atmospheric deposition are negligible at the moment. However, the levels of metals need to be monitored with the introduction of fertilizers, pesticides and other agricultural inputs to the region.