Baseline values of Cadmium and Zinc in three land uses in a selected mapping unit of the dry zone of Sri Lanka

Abstract

Anthropogenic activities change the natural concentrations of soil trace metals in different land uses with varying magnitudes. Establishment of baseline concentration of metals is important in assessing human impact on metal concentrations in soils over time. A study was conducted to compare Cd and Zn concentrations in different land uses (lowland, upland and non-agricultural) to investigate relationships of Cd and Zn with soil properties and to establish geochemical baseline concentrations of the two metals for three land uses of Madawachchiya – Ranorawa – Elayapattuwam – Hurathgama - Nawagattegama soil association of the Dry Zone of Sri Lanka. Soils were analyzed for organic carbon (OC), clay, pH, electrical conductivity (EC), and HNO3 acid-soluble Cd and Zn. Land use had a significant effect (p<0.05) on Cd and Zn contents in soils studied. Accordingly, Cd content of non-agricultural soils was significantly lower than that of both lowland and upland soils. The Zn content of upland soils was significantly higher than that of lowland and non- agricultural soils. A significant correlation between Cd and Zn in the non-agricultural soils indicated a possible common source of origin for Cd and Zn, whereas poor correlations in upland and lowland soils indicated multiple sources of origin. The influence of OC, clay % and EC on metal contents of soils was visible in different land uses. For lowland, upland and non-agricultural soils, the upper baseline limits for Cd were 1.43, 1.47, 0.44 mg/kg, respectively, and for Zn were 39, 55 and 38 mg/kg in, respectively. The results revealed that Cd has not reached the contaminated level in the land uses studied, while Zn contamination was evident in some samples of lowland and upland land uses.Tropical Agricultural Research Vol. 25 (1): 84-95 (2013)

Keywords

• alfisols, low land, non-agricultural soils, soil properties, up land