Total mercury and methylmercury concentrations over a gradient of contamination in earthworms living in rice paddy soil

Abstract

Mercury (Hg) deposited from emissions or from local contamination, can have serious health effects on humans and wildlife. Traditionally, Hg has been seen as a threat to aquatic wildlife, because of its conversion in suboxic conditions into bioavailable methylmercury (MeHg), but it can also threaten contaminated terrestrial ecosystems. In Asia, rice paddies in particular may be sensitive ecosystems. Earthworms are soil-dwelling organisms that have been used as indicators of Hg bioavailability; however, the MeHg concentrations they accumulate in rice paddy environments are not well known. Earthworm and soil samples were collected from rice paddies at progressive distances from abandoned mercury mines in Guizhou, China, and at control sites without a history of Hg mining. Total Hg (THg) and MeHg concentrations declined in soil and earthworms as distance increased from the mines, but the percentage of THg that was MeHg, and the bioaccumulation factors in earthworms, increased over this gradient. This escalation in methylation and the incursion of MeHg into earthworms may be influenced by more acidic soil conditions and higher organic content further from the mines. In areas where the source of Hg is deposition, especially in water-logged and acidic rice paddy soil, earthworms may biomagnify MeHg more than was previously reported. It is emphasized that rice paddy environments affected by acidifying deposition may be widely dispersed throughout Asia. Environ Toxicol Chem 2017;36:1202-1210. © 2016 SETAC.

Concentration of Mercury in the Livers of Small Terrestrial Rodents from Rural Areas in Poland

“…The deposition of Hg may lead to contamination of both aquatic and terrestrial ecosystems [1], and inorganic Hg may be converted by microbial communities into more toxic methylmercury [7], which can be accumulated in the trophic chain [8]. Different organisms have been used as bioindicators of Hg pollution in terrestrial ecosystems, including invertebrates [9,10,11,12], birds [13,14,15], bats [16], shrews [17,18,19], moles [19], foxes [20], and mustelids [21,22]. Rodents are also considered good bioindicators of environmental pollution due to their widespread occurrence, high reproductive rate and abundance, short lifespan, and good availability [23,24].…”