Long-range Transport Of Hg Research Articles

Bog and lake sediment archives reveal a lagged response of subarctic lakes to diminishing atmospheric Hg and Pb deposition

We used a flux deconstruction approach on peat and sediment archives of four bogs and five lakes from two subarctic taiga ecoregions of the Northwest Territories (Canada) to distinguish the atmospheric and catchment-based responses to changing metal pollution emissions over the last 2000 years. Bogs tracked the atmospheric signal, whereas lake sediments provided a mixed atmospheric and catchment-based response. Anthropogenic mercury (Hg) and lead (Pb) contamination was identified in lake sediment and bog records from the mid-1800s onward and increased rapidly after ca. 1900. Long-range transport of Hg and Pb was likely the dominant source of the post-1900 enrichment in lake sediments, with minor contributions from local mining, mostly between 1950 and 1970. Bogs and sediment records of small lakes on the Taiga Plains showed that atmospheric deposition peaked in the late 1990s for Pb and in the 1970s for Hg. In contrast, the Pb and Hg accumulation rates in Taiga Shield lakes have continued to increase since the peak atmospheric deposition period due to on-going catchment transport, and may reflect recent climate change favoring late-fall and early-winter precipitation as rain rather than snow. The divergent trends in metal accumulation rates between ecoregions and environmental archives demonstrate that interactions of climate and catchment characteristics will be key to future contamination trajectories for subarctic lakes following reductions of anthropogenic metal emissions in North America.

Elemental mercury in the marine boundary layer of North America: Temporal and spatial patterns

Gaseous elemental mercury (Hg0) comprises the majority of atmospheric mercury (Hg) and results in long-range transport of Hg. Secondary emissions from the marine surface mixed layer result in spatial and temporal Hg0 variability, which subsequently determine marine pools of divalent mercury (HgII) available for methylation. We measured atmospheric Hg0 concentrations in the marine boundary layer (MBL) around North America in regions of the Atlantic, Pacific, and Arctic Oceans (6.7°–77.3° N, 52.3°–150.0° W). Observed spatial Hg0 distributions across these regions match patterns revealed from current published biogeochemical models. These models have supported marine processes as the major factors controlling MBL Hg0. We observe differences in variability between ocean basins. Asian emissions appear to be well-mixed in the Eastern Pacific MBL, with stable measurements across a 3200 km transect in the North Pacific. Hg0 concentrations decrease but remain relatively stable in tropical regions of the Pacific and Atlantic. In contrast, we measured several 100–200 km regions of elevated Hg0 above North Atlantic surface waters. Repeated offshore sampling of Arctic Hg0 reveals strong seasonal trends that are similar to those collected at coastal long-term Arctic monitoring stations. These similarities suggest marine processes control seasonal Arctic trends, which are linked to sea ice formation and melt. Together our observations are consistent with marine controls on MBL Hg0 concentrations although further study is needed to fully distinguish between marine and atmospheric controls.

Atmospheric mercury deposition and its contribution of the regional atmospheric transport to mercury pollution at a national forest nature reserve, southwest China.

Atmospheric mercury deposition by wet and dry processes contributes to the transformation of mercury from atmosphere to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to subtropical forests were identified in this study. Throughfall and open field precipitation samples were collected in 2012 and 2013 using precipitation collectors from forest sites located across Mt. Jinyun in southwest China. Samples were collected approximately every 2 weeks and analyzed for total (THg) and methyl mercury (MeHg). Forest canopy was the primary factor on THg and MeHg deposition. Simultaneously, continuous measurements of atmospheric gaseous elemental mercury (GEM) were carried out from March 2012 to February 2013 at the summit of Mt. Jinyun. Atmospheric GEM concentrations averaged 3.8 ± 1.5 ng m(-3), which was elevated compared with global background values. Sources identification indicated that both regional industrial emissions and long-range transport of Hg from central, northeast, and southwest China were corresponded to the elevated GEM levels. Precipitation deposition fluxes of THg and MeHg in Mt. Jinyun were slightly higher than those reported in Europe and North America, whereas total fluxes of MeHg and THg under forest canopy on Mt. Jiuyun were 3 and 2.9 times of the fluxes of THg in wet deposition in the open. Highly elevated litterfall deposition fluxes suggest that even in remote forest areas of China, deposition of atmospheric Hg(0) via uptake by vegetation leaf may be a major pathway for the deposition of atmospheric Hg. The result illustrates that areas with greater atmospheric pollution can be expected to have greater fluxes of Hg to soils via throughfall and litterfall.

Mercury wet deposition in rural Korea: concentrations and fluxes

The characteristics of Hg wet deposition were investigated in a rural area of Korea from August 2006 to July 2008. The volume weighted mean (VWM) Hg(T) concentration and cumulative Hg(T) flux were 8.8 ng L(-1) and 9.4 μg m(-2) per year, respectively. The VWM Hg(T) concentration varied seasonally, similar to the seasonal pattern in atmospheric Hg(p) concentration. The enhancement of both VWM Hg(T) and atmospheric Hg(p) concentrations in spring and winter was likely caused by the long-range transport of Hg from China. Monthly VWM Hg(T) and atmospheric Hg(p) concentrations were well correlated (R(2) = 0.36); however, there was no correlation between VWM Hg(T) and RGM (reactive gaseous mercury) concentrations, suggesting that Hg(p) was responsible for the majority of the Hg in wet deposition at this site. The VWM Hg(T) concentration in snow was statistically higher than in rain. In addition, the atmospheric Hg(p) concentration appeared to be elevated for snow events as well. This suggests that both elevated Hg(p) concentrations and the enhanced scavenging efficiency of snow for Hg(p) were responsible for the elevated VWM Hg(T) concentrations measured during snow events.

Atmospheric gaseous elemental mercury (GEM) concentrations and mercury depositions at a high-altitude mountain peak in south China

Abstract. China is regarded as the largest contributor of mercury (Hg) to the global atmospheric Hg budget. However, concentration levels and depositions of atmospheric Hg in China are poorly known. Continuous measurements of atmospheric gaseous elemental mercury (GEM) were carried out from May 2008 to May 2009 at the summit of Mt. Leigong in south China. Simultaneously, deposition fluxes of THg and MeHg in precipitation, throughfall and litterfall were also studied. Atmospheric GEM concentrations averaged 2.80±1.51 ng m−3, which was highly elevated compared to global background values but much lower than semi-rural and industrial/urban areas in China. Sources identification indicates that both regional industrial emissions and long range transport of Hg from central, south and southwest China were corresponded to the elevated GEM level. Seasonal and diurnal variations of GEM were observed, which reflected variations in source intensity, deposition processes and meteorological factors. Precipitation and throughfall deposition fluxes of THg and MeHg in Mt. Leigong were comparable or lower compared to those reported in Europe and North America, whereas litterfall deposition fluxes of THg and MeHg were higher compared to Europe and North America. This highlights the importance of vegetation to Hg atmospheric cycling. In th remote forest ecosystem of China, deposition of GEM via uptake of foliage followed by litterfall was very important for the depletion of atmospheric Hg. Elevated GEM level in ambient air may accelerate the foliar uptake of Hg through air which may partly explain the elevated litterfall deposition fluxes of Hg observed in Mt. Leigong.

장기간 관측을 통한 황사 현상이 수은의 분포에 미치는 영향 고찰

To evaluate the possibly potent role of Asian Dust (AD) on the long range transport of Hg, statistical analyses were carried out using the hourly concentration data of gaseous elemental mercury (Hg) along with relevant environmental parameters. For the purpose of this study, Hg data were collected from Yang-Jae monitoring station in Seoul, Korea during Sept. 1997 to June 2002. During the study period, Hg concentrations in non-AD period ranged from with a mean , while those in AD period from with a mean . The air quality during AD were typically deteriorated by enhanced PM10 mass concentration (by times) compared to non-AD period, however comparison of the Hg concentration data indicates that they are not critically distinguished between events of AD and non-AD, except for the high minimum level of Hg during AD. The results of correlation and factor analysis also indicated somewhat complex patterns; in the case of AD events, Hg and were assorted concurrently into a same factor. Evidence collected from this study thus suggests that long-range transport of Hg, if occurring, is unlikely to raise statistically Hg concentration levels such as seen during AD event. However, in nighttime of winter season, Hg concentrations are higher during AD (along with PM10 levels) than non-AD period. Although such observations suggest the effect of long range transport on the enhancement of Hg concentrations, more deliberate analysis may be required to track down the effect of such mechanism in relation with various factors including the air mass transport route.