Assessment of Soil Arsenic, Chromium, Mercury, and Lead at an Agricultural Landscape Scale

Abstract

Knowledge of arsenic and heavy metal concentrations and distributions is essential in the design of environmental regulatory strategies. The present study was undertaken as a preliminary survey on soil contamination in a representative agricultural area of southwestern China. The objectives were: (1) to characterize the variability of As, Cr, Hg, and Pb; (2) to assess the effect of land use (vegetable land and paddy fields) on these elements; and (3) to identify their natural or artificial origins. Samples from 119 sites were collected and analyzed in 2006. Land use map units were delineated at a scale of 1:2000 from field survey. Analysis of variance, correlation analysis, factor analysis, and a geographic information system were adopted to investigate the spatial distributions and sources of the elements. The average concentrations of the elements were 6.26 mg As kg⁻¹, 52.90 mg Cr kg⁻¹, 0.066 mg Hg kg⁻¹, and 33.13 mg Pb kg⁻¹. Mean contents of Hg and Pb were markedly higher than their background levels indicating the risk of mercury and lead pollution (p < 0.05). Mean concentration of Pb was significantly higher in paddy fields than vegetable land (p < 0.05). The variability of Cr was associated with topography, while Hg was controlled by human activities and atmospheric deposition. The high heterogeneities of As and Pb were mainly ascribed to land use and the consequent agricultural management practices. The results of the study will assist planners and policymakers in developing effective policies to protect soils from long-term arsenic and heavy metal accumulation.

Keywords:

• Land use
• multivariate analysis
• spatial variability
• geostatistics
• effects
• topography

Acknowledgements

This work was supported by the National Key Technology R&D Program (2008BADA4B10), Natural Science Foundation Project of CQ CSTC (2010BB1008), Scientific Research Foundation for the Returned Overseas Chinese Scholars (2010-1174), State Education Ministry and Southwest University Science and Technology Innovation Fund for graduate students (KY2009021).