Mercury levels in Oryza sativa cultivated in Philippine small-scale mining villages

Abstract

Soil physico-chemical parameters and total mercury concentrations were measured in soil and rice plant samples collected over a cropping period grown in areas near mine tailings ponds in two Philippine small-scale mining (SSM) communities. Step-wise regression analysis relating environmental parameters to Hg uptake showed that pH has a highly significant effect on Hg content in the samples (p < 0.001) while temperature, contrary to previous studies, had no significant effect. The mean total Hg concentrations appeared to be significantly lower in rice plant parts sampled in control sites than in the contaminated sites in both SSM communities: 0.020 and 2.832 mg/kg, respectively in Aroroy, Masbate and 0.004 and 0.016 mg/kg, respectively in Fidelisan, Sagada. Harvested rice grains from the Masbate sampling sites further revealed total Hg concentration at 0.1331 mg/kg, exceeding the maximum permissible limit of 0.02 mg/kg Hg contamination. The study shows that Hg use in SSM activities and the cumulative effects of prolonged exposure to the metal through regular consumption of the village-cultivated rice may put the local residents at risk of health problems related to mercury.

Keywords:

• Heavy metals
• mercury
• mining effluent
• contamination