How will the rates of mercury in rice change in the future?
We examined a high emission scenario, which assumes no new policies to control mercury emissions by 2050, and a low emission scenario, where China uses less coal and coal-fired power plants have advanced mercury emission controls. Median Chinese rice methylmercury concentrations increased by 13 percent in the high scenario and decreased by 18 percent under the low scenario. Regions where rice methylmercury declined the most under strict policy controls were in central China, where rice production is high and rice is an important source of methylmercury exposure.
Managing mercury concentrations in rice thus requires an integrated approach, addressing both deposition and soil and water contamination. Understanding local conditions is also important: Other environmental factors not captured by our model, such as soil acidity, can also influence methylmercury production and accumulation to rice.
Different rice production strategies can also help – for example, alternating wetting and drying cycles in rice cultivation can reduce water consumption and methane emissions as well as rice methylmercury concentrations.
Our scenarios likely underestimate the potential health benefits of Minamata Convention controls in China, which is a party to the Convention. We include in our scenarios only changes in air emissions from power generation, while the Convention controls emissions from other sectors, bans mercury mining and addresses contaminated sites and land and water releases.
Reducing mercury could also be beneficial for other rice-producing countries, but at present, there are few data available outside China. However, our research suggests that the problem of mercury is not just a fish story – and that policy efforts can indeed make a difference.
Commentary by Noelle Eckley Selin and Sae Yun Kwon, an Associate Professor of Data, Systems, and Society and Atmospheric Chemistry and an Assistant Professor at the Division of Environmental Science & Engineering at Massachusetts Institute of Technology and Pohang University of Science and Technology, respectively. They are also contributors at The Conversation, an independent source of news and views from the academic and research community. Follow Noelle Eckley Selin on Twitter @noelleselin.
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