Oiffer Lindsay, Siciliano Steven D
Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan S7N 5A8, Canada.
Sci Total Environ. 2009 Feb 15;407(5):1691-700. doi: 10.1016/j.scitotenv.2008.10.025. Epub 2008 Dec 11.
Mercury has been found in polar bears and other top predators in the Arctic at concentrations that pose a risk to the indigenous population, however, the means by which this occurs is uncertain. There has been extensive research on the atmospheric cycling of mercury but little is known about mercury cycling in Arctic terrestrial ecosystems. The objective of this study was to determine whether wet sedge meadow soils within the Truelove Lowlands, Devon Island, NT, Canada (75 degrees 33'N, 84 degrees 40'N) were acting as sources or sinks for methylmercury (MeHg). Over the course of an Arctic summer, MeHg concentrations and other biophysical characteristics were measured at four wet sedge meadows over a 19 day study period that commenced approximately 1 month after snowmelt. Soil MeHg concentrations declined during the study period, indicating a net loss of MeHg over the summer. The dominant ligand in solution appeared to be dissolved organic matter, little sulfide was detected, and it would seem that most of the mercury was unavailable for methylation during the summer sampling period. In soil microcosms, spiked with 5.0 nmol g(-1) (1 microg g(-1)) HgCl2, the soil did methylate mercury suggesting that there is the potential for mercury methylation. We also noted significant spatial variability in MeHg concentrations between catenas that could not be explained by other biophysical parameters, which are known to affect methylation. Given our data and previous geochemical data collected from suprapermafrost groundwater during snowmelt, it seems likely that methylation may occur during the spring melt period in the arctic. Furthermore the geochemical variability of the melt water may lead to the spatial variability observed in MeHg concentrations in this study.
在北极熊和北极其他顶级掠食者体内发现了汞，其浓度对当地居民构成风险，然而，汞的这种存在方式尚不确定。人们对汞的大气循环进行了广泛研究，但对北极陆地生态系统中的汞循环却知之甚少。本研究的目的是确定加拿大努纳武特地区德文岛特鲁洛夫低地（北纬75°33′，西经84°40′）的湿苔草草甸土壤是甲基汞（MeHg）的源还是汇。在北极夏季期间，于融雪后约1个月开始的19天研究期内，对四个湿苔草草甸的甲基汞浓度和其他生物物理特征进行了测量。研究期间土壤甲基汞浓度下降，表明夏季甲基汞出现净损失。溶液中的主要配体似乎是溶解有机物，几乎未检测到硫化物；在夏季采样期，大部分汞似乎无法进行甲基化。在添加了5.0 nmol g⁻¹（1 μg g⁻¹）HgCl₂的土壤微观世界中，土壤确实使汞发生了甲基化，这表明存在汞甲基化的潜力。我们还注意到不同链状地貌之间甲基汞浓度存在显著的空间变异性，这无法用已知会影响甲基化的其他生物物理参数来解释。根据我们的数据以及之前在融雪期间从永冻层上覆地下水收集的地球化学数据，北极地区春季融雪期似乎可能发生甲基化。此外，融水的地球化学变异性可能导致了本研究中观察到的甲基汞浓度的空间变异性。
