Givelet Nicolas, Roos-Barraclough Fiona, Shotyk William
Institute of Geological Sciences, University of Berne, Baltzerstrasse 1-3, CH-3012 Berne, Switzerland.
J Environ Monit. 2003 Dec;5(6):935-49. doi: 10.1039/b307140e.
Peat cores from three bogs in southern Ontario provide a complete, quantitative record of net rates of atmospheric Hg accumulation since pre-industrial times. For comparison with modern values, a peat core extending back 8000 years was used to quantify the natural variations in Hg fluxes for this region, and their dependence on climatic change and land use history. The net mercury accumulation rates were separated into "natural" and "excess" components by comparing the Hg/Br ratios of modern samples with the long-term, pre-anthropogenic average Hg/Br. The average background mercury accumulation rate during the pre-anthropogenic period (from 5700 years BC to 1470 AD) was 1.4 +/- 1.0 microg m(-2) per year (n = 197). The beginning of Hg contamination from anthropogenic sources dates from AD 1475 at the Luther Bog, corresponding to biomass burning for agricultural activities by Native North Americans. During the late 17th and 18th centuries, deposition of anthropogenic Hg was at least equal to that of Hg from natural sources. Anthropogenic inputs of Hg to the bogs have dominated continuously since the beginning of the 19th century. The maximum Hg accumulation rates decrease in the order Sifton Bog, in the City of London, Ontario (141 microg Hg m(-2) per year), Luther Bog in an agricultural region (89 microg Hg m(-2) per year), and Spruce Bog which is in a comparatively remote, forested region (54 microg Hg m(-2) per year). Accurate age dating of recent peat samples using the bomb pulse curve of 14C shows that the maximum rate of atmospheric Hg accumulation occurred during AD 1956 and 1959 at all sites. In these (modern) samples, the Hg concentration profiles resemble those of Pb, an element which is known to be immobile in peat bogs. The correlation between these two metals, together with sulfur, suggests that the predominant anthropogenic source of Hg (and Pb) was coal burning. While Hg accumulation rates have gone into strong decline since the late 1950's, Hg deposition rates today still exceed the average natural background values by 7 to 13 times.
安大略省南部三个沼泽地的泥炭芯提供了自工业化前时代以来大气汞积累净速率的完整定量记录。为了与现代值进行比较，一个可追溯到8000年前的泥炭芯被用于量化该地区汞通量的自然变化，以及它们对气候变化和土地利用历史的依赖性。通过将现代样本的汞/溴比率与长期的、人为活动前的平均汞/溴比率进行比较，将汞的净积累速率分为“自然”和“过量”两部分。人为活动前时期（公元前5700年至公元1470年）的平均背景汞积累速率为每年1.4±1.0微克/平方米（n = 197）。来自人为源的汞污染始于公元1475年的卢瑟沼泽，这与北美原住民为农业活动进行的生物质燃烧相对应。在17世纪末和18世纪，人为汞的沉积至少与自然源汞的沉积相当。自19世纪初以来，人为向沼泽地输入汞一直占据主导地位。汞积累速率最大值按以下顺序递减：安大略省伦敦市的西夫顿沼泽（每年141微克汞/平方米）、农业地区的卢瑟沼泽（每年89微克汞/平方米）以及相对偏远的森林地区的云杉沼泽（每年54微克汞/平方米）。利用14C的核弹脉冲曲线对近期泥炭样本进行精确测年表明，所有地点大气汞积累的最大速率都出现在公元1956年和1959年。在这些（现代）样本中，汞浓度剖面与铅相似，铅是一种已知在泥炭沼泽中不易移动的元素。这两种金属以及硫之间的相关性表明，汞（和铅）的主要人为来源是煤炭燃烧。尽管自20世纪50年代末以来汞积累速率大幅下降，但如今汞的沉积速率仍比自然背景平均值高出7至13倍。
