Mercury Accumulation in Commercial Varieties of Oryza sativa L. Cultivated in Soils of La Mojana Region, Colombia.

Germán Enamorado-Montes,Iván Urango-Cardenas,Brayan Reino-Causil,Siday Marrugo-Madrid,José Marrugo-Negrete

doi:10.3390/toxics9110304

Abstract

The Hg accumulation in different commercial varieties of Oryza sativa L. was evaluated in the region of La Mojana, Colombia, where rice cultivation has become the staple food of the population living in this area. The varieties studied were Fedearroz-473 (FA473), Fedearroz-2000 (FA2000), and Fedearroz-Mocari (FAM). Soil spiked at different Hg levels was evaluated, (130, 800, and 1500 µg kg−1) using a 32 factorial design that consisted of 3 (rice varieties) × 3 (Hg contents). The biomass, 1000-grain weight, and the accumulation of Hg in the roots, grains, and husks were determined. The highest biomass was found in the FA473 (308.76 ± 108.26 g), and the lowest was found in FAM (144.04 ± 26.45 g) in the 1500 µg kg−1 Hg soil in both cases. The weight per 1000-grains decreased significantly in the soil containing 800 µg of Hg kg−1. Hg accumulation in the organs of the evaluated varieties was higher in the roots, followed by in the husks and grains. The Hg in the rice grains of the evaluated varieties presented levels close to the permissible limit of the Chinese standard (20 μg Hg kg−1) in the evaluated soils and were only exceeded by FA473. Although in natural soil concentrations, the non-cancer health risk (HQ) from rice consumption was lower for FA473 and FAM; Hg enrichment in the soil of La Mojana region may endanger the health of future populations due to their high consumption of rice.

Highlights

Mercury (Hg) is one of the most highly studied pollutants because of its impacts on human health and ecosystems worldwide
All of the treatments in the present study presented Hg concentrations in the rice grain that were below those reported by Zhu et al [42], who found Hg levels in the grain between 52.0 and 623.2 μg kg−1 in an experiment developed in China with 38 rice varieties grown in a soil with 4. 72 mg kg−1 of Hg; in that same experiment, the 38 rice varieties grown in soils with 0.47 mg kg−1 of Hg accumulated between 1.1 and 59.0 μg kg−1 of Hg in the grain, which are values that are within the range of those observed in the present study
Three varieties of Oryza sativa L. were established, developed, and harvested in mercury-contaminated soils, which proved to be tolerant to the levels studied without visible phytotoxic damage

Summary

Introduction

Mercury (Hg) is one of the most highly studied pollutants because of its impacts on human health and ecosystems worldwide. In terms of sources of Hg contamination, gold mining is the most significant [2]. A study on Hg in the trophic chain of Colombia has revealed important findings regarding the use of Hg during gold exploitation in different regions of this country [3], confirming what was previously disclosed by other authors, who reported that Colombia is one of the regions with the highest incidence of this dangerous metal in the world [4]. Its ecosystems have suffered environmental contamination by toxic metals associated with surrounding mining activities, especially gold mining, which involves the use of Hg to recover this precious metal [3]. The first two rivers are known as important sites for gold production [3]

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