Investigation of biogeochemical controls on the formation, uptake and accumulation of methylmercury in rice paddies in the vicinity of a coal-fired power plant and a municipal solid waste incinerator in Taiwan

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題名:	Investigation of biogeochemical controls on the formation, uptake and accumulation of methylmercury in rice paddies in the vicinity of a coal-fired power plant and a municipal solid waste incinerator in Taiwan
作者:	林居慶;Su, Yen-Bin;Chang, Wei-Chun;Hsi, Hsing-Cheng;Lin, Chu-Ching
貢獻者:	工學院環境工程研究所
關鍵詞:	active transport;agricultural soils;bioavailability;Biogeochemistry;Biological Availability;chemical speciation;Coal;ecosystems;Environmental Monitoring;exudation;flooded conditions;Food Chain;Food Contamination;food webs;genes;growing season;Humans;hydroponics;hypoxia;Incineration;laboratory experimentation;ligands;mercury;Mercury - analysis;methylation;Methylmercury;methylmercury compounds;Methylmercury Compounds - analysis;Methylmercury Compounds - chemistry;microorganisms;municipal solid waste;nutrient solutions;Oryza - chemistry;Oryza - microbiology;paddies;Paddy soil;paddy soils;Plant Roots - metabolism;Power Plants;Rhizosphere;Rice;Root uptake;roots;seasonal variation;Soil - chemistry;Soil Microbiology;Soil Pollutants - analysis;soil pore water;soil sampling;Solid Waste;Taiwan;toxicity;Waste Management;Water - metabolism
日期:	2016-07-01
上傳時間:	2026-04-23 15:04:26 (UTC+8)
出版者:	Elsevier Ltd.;England: Elsevier Ltd
摘要:	摘要： Recent studies have shown that rice consumption is another critical route of human exposure to methylmercury (MeHg), the most toxic and accumulative form of mercury (Hg) in the food web. Yet, the mechanisms that underlie the production and accumulation of MeHg in the paddy ecosystem are still poorly understood. In 2013 and 2014, we conducted field campaigns and laboratory experiments over a rice growing season to examine Hg and MeHg cycling, as well as associated biogeochemistry in a suite of paddies close to a municipal solid waste incinerator and a coal-fired power plant station in Taiwan. Concentrations of total Hg and MeHg in paddy soil and rice grain at both sites were low and found not to exceed the control standards for farmland soil and edible rice in Taiwan. However, seasonal variations of MeHg concentrations observed in pore water samples indicate that the in situ bioavailability of inorganic Hg and activity of Hg-methylating microbes in the rhizosphere increased from the early-season and peaked at the mid-season, presumably due to the anoxia created under flooded conditions and root exudation of organic compounds. The presence of Hg-methylators was also confirmed by the hgcA gene detected in all root soil samples. Subsequent methylation tests performed by incubating the root soil with inorganic Hg and an inhibitor or stimulant specific for certain microbes further revealed that sulfate-reducers might have been the principal Hg-methylting guild at the study sites. Interestingly, results of hydroponic experiments conducted by cultivating rice in a defined nutrient solution amended with fixed MeHg and varying levels of MeHg-binding ligands suggested that chemical speciation in soil pore water may play a key role in controlling MeHg accumulation in rice, and both passive and active transport pathways seem to take place in the uptake of MeHg in rice roots. •Field campaigns at paddies over a rice-growing season were conducted.•High Hg-methylation potential occurred at the rice mid-growing season.•Detection of hgcA in all soil samples confirmed the prevalence of Hg-methylators.•Sulfate-reducers might have been the principal Hg-methylators at the study sites.•Pore-water chemical speciation controls the uptake of methylmercury in rice roots. 其他題名： Chemosphere 出版者： England: Elsevier Ltd 出版日期： 2016-07 出處： Chemosphere (Oxford), 2016-07, Vol.154, p.375-384 版權： 2016 Elsevier Ltd 版權： Copyright © 2016 Elsevier Ltd. All rights reserved. 識別號： ISSN: 0045-6535 識別號： ISSN: 1879-1298 識別號： EISSN: 1879-1298 識別號： DOI: 10.1016/j.chemosphere.2016.03.087 識別號： PMID: 27070857
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