Exploration of Amendments and Agronomic Measures on the Remediation of Methylmercury-Polluted Rice in a Mercury Mining Area

Abstract

An in situ pot method was conducted using 2-year experiments to address the issue of methylmercury (MeHg) pollution in a paddy field ecosystem that was influenced by mercury (Hg) mining activities. The reduction effect of adopted amendments and agronomic measures on MeHg-polluted rice was investigated, and positive results had been achieved in our experiments. In the first-year experiment, the reductions of 27.86–71.61 and 29.48–64.96 % (with the averages of 51.55 and 49.41 %) for rice MeHg under high and low pollution levels were observed, respectively. In our second year experiment, all selected amendments and agronomic measures still showed a stable and significant reduction effect as we found in the first year (p < 0.05), with a reduction rate ranging from 42.21 to 75.25 %. Overall, significant reduction effect was validated through the use of calcium magnesium phosphate fertilizer, farmyard manure, activated clay, ground phosphate rock, and maifanite in the 2-year experiments. Among those five treatments, activated clay showed the most stable performance, followed by ground phosphate rock and then calcium magnesium phosphate fertilizer. Moreover, the changes of irrigation water sources and fertilizer patterns had great impact on the enrichment ability of MeHg in rice. Finally, our studies also showed that the pros and cons of reduction effect by amendments or agronomic measures based on the pollutant patterns: MeHg concentrations in rice were generally reduced to a greater degree than total Hg (THg).