Trends In Mercury Concentrations Research Articles

Mercury in tree rings close to emission sources in Austria.

Mercury in wood is an important pool of this heavy metal in forest ecosystems because of its relatively high proportion in the biomass compared to other pools. This paper describes the successful application of a modified methodology for stem disk sampling based on wood particles from stem disks from Donawitz (Styria, Austria; pig iron production), from Brixlegg (Tyrol; former copper and silver mining, copper ore processing and copper recycling), and from Gmunden (Upper Austria; cement production). The maximum mercury concentration in the stem disks from Donawitz (Hinterberg: 20.5ppb, St. Peter: 9.3ppb) was recorded in the early 1970s. Several maxima were obtained from the stem disks from Brixlegg: the first was in 1813 (149.9ppb), potentially even earlier, a second (37.6ppb) in the late nineteenth century until the late 1920s, and a third local maximum in the 1970s (9.1ppb), followed by a tendency to decline until the present. A stem disk from Gmunden in Upper Austria showed values of mercury concentrations indicating no increases compared to literature about background sites (≤ 3.2ppb). This method revealed trends in mercury concentrations in tree rings originating from several different mercury emission sources in Austria coinciding with information about industrial history (where available) together with a justifiable effort. We therefore recommend it for further investigations on mercury concentrations in tree rings and their changes over time.

Trends in mercury concentrations and methylation in Minamata Bay, Japan, between 2014 and 2018

Methylmercury concentrations in Minamata Bay are high, but the cause is unclear. We conducted a basic study on the behavior of methylmercury in Minamata Bay seawater; the findings suggest that mercury methylation may occur throughout the year in Minamata Bay. Seawater temperature, salinity, and concentrations of dissolved organic carbon were the environmental factors that affected methylation, and the degree of methylation was closely related to bacterial community structure. The concentration of methylmercury in suspended particulate matter was highest 10 m below the surface and decreased with greater depths. We did not observe a correlation between methylmercury concentrations in suspended particulate matter and concentrations of dissolved methylmercury.

Spatial patterns and temporal trends in mercury concentrations in common loons (Gavia immer) from 1998 to 2016 in New York's Adirondack Park: has this top predator benefitted from mercury emission controls?

Mercury (Hg), a neurotoxic pollutant, can be transported long distances through the atmosphere and deposited in remote areas, threatening aquatic wildlife through methylation and bioaccumulation. Over the last two decades, air quality management has resulted in decreases in Hg emissions from waste incinerators and coal-fired power plants across North America. The common loon (Gavia immer) is an apex predator of the aquatic food web. Long-term monitoring of Hg in loons can help track biological recovery in response to the declines in atmospheric Hg that have been documented in the northeastern USA. To assess spatial patterns and temporal trends in Hg exposure of the common loon in the Adirondack Park of New York State, we analyzed Hg concentrations in loon blood and egg samples from 116 lakes between 1998 and 2016. We found spatially variable Hg concentrations in adult loon blood and feathers across the Park. Loon Hg concentrations (converted to female loon units) increased 5.7% yr-1 from 1998 to 2010 (p = 0.04), and then stabilized at 1.70 mg kg-1 from 2010 to 2016 (p = 0.91), based on 760 observations. Concentrations of Hg in juvenile loons also increased in the early part of the record, stabilizing 2 years before Hg concentrations stabilized in adults. For 52 individual lakes with samples from at least 4 different years, loon Hg increased in 34 lakes and decreased in 18 lakes. Overall, we found a delayed recovery of Hg concentrations in loons, despite recent declines in atmospheric Hg.

An assessment of temporal trends in mercury concentrations in fish

The importance of fish consumption as the primary pathway of human exposure to mercury and the establishment of fish consumption advisories to protect human health have led to large fish tissue monitoring programs worldwide. Data on fish tissue mercury concentrations collected by state, tribal, and provincial governments via contaminant monitoring programs have been compiled into large data bases by the U.S. Environmental Protection Agency's Great Lakes National Monitoring Program Office (GLNPO), the Ontario Ministry of the Environment's Fish Contaminants Monitoring and Surveillance Program (FMSP), and many others. These data have been used by a wide range of governmental and academic investigators worldwide to examine long-term and recent trends in fish tissue mercury concentrations. The largest component of the trend literature is for North American freshwater species important in recreational fisheries. This review of temporal trends in fish tissue mercury concentrations focused on published results from freshwater fisheries of North America as well as marine fisheries worldwide. Trends in fish tissue mercury concentrations in North American lakes with marked overall decreases were reported over the period 1972-2016. These trends are consistent with reported mercury emission declines as well as trends in wet deposition across the U.S. and Canada. More recently, a leveling-off in the rate of decreases or increases in fish tissue mercury concentrations has been reported. Increased emissions of mercury from global sources beginning between 1990 and 1995, despite a decrease in North American emissions, have been advanced as an explanation for the observed changes in fish tissue trends. In addition to increased atmospheric deposition, the other factors identified to explain the observed mercury increases in the affected fish species include a systematic shift in the food-web structure with the introduction of non-native species, creating a new or expanding role for sediments as a net source for mercury. The influences of climate change have also been identified as contributing factors, including considerations such as increases in temperature (resulting in metabolic changes and higher uptake rates of methylmercury), increased rainfall intensity and runoff (hydrologic export of organic matter carrying HgII from watersheds to surface water), and water level fluctuations that alter either the methylation of mercury or the mobilization of monomethylmercury. The primary source of mercury exposure in the human diet in North America is from the commercial fish and seafood market which is dominated (>90%) by marine species. However, very little information is available on mercury trends in marine fisheries. Most of the data used in the published marine trend studies are assembled from earlier reports. The data collection efforts are generally intermittent, and the spatial and fish-size distribution of the target species vary widely. As a result, convincing evidence for the existence of fish tissue mercury trends in marine fish is generally lacking. However, there is some evidence from sampling of large, long-lived commercially-important fish showing both lower mercury concentrations in the North Atlantic in response to reduced anthropogenic mercury emission rates in North America and increases in fish tissue mercury concentrations over time in the North Pacific in response to increased mercury loading.

Temporal trends in mercury concentrations in raptor flight feathers stored in an environmental specimen bank in Galicia (NW Spain) between 2000 and 2013.

Temporal trends in Hg concentrations were investigated in primary flight feathers from 319 specimens of three birds of prey: P7 in the northern goshawk (Accipiter gentilis), P6 in the common buzzard (Buteo buteo) and P5 in the tawny owl (Strix aluco). The samples were stored in a regional environmental specimen bank and belonged to specimens which died between 2000 and 2013 in Galicia (NW Spain). We would expect to see a decline in Hg concentrations across the study period, as data of atmospheric emissions show a gradual reduction of this pollutant in Europe in the last two decades. The study did not reveal any temporal pattern in Hg concentrations of feathers in any of the three species for the study period, may be due to the persistence of Hg in the environment, but showed a low level of contamination by this metal in the study area. In addition, the results show high intra-specific, as well as, inter-annual and inter-specific variability in data, mainly attributed to the level of exposure of the raptors to this pollutant and to the biomagnification process of Hg through food chains. These findings indicate that the high variability can be a limiting factor in the use of raptors for biomonitoring temporal patterns of Hg, but nevertheless, the technique provides qualitative information about the amount of Hg that reach the top of the terrestrial food chains.

Study of temporal trends in mercury concentrations in the primary flight feathers of Strix aluco

Temporal trends in Hg concentrations were determined in the primary flight feathers of 146 specimens of Strix aluco which had died in various Wildlife Recovery Centres in Galicia (NW Spain) between 1997 and 2014. The aim of the study was to determine whether standardization of a primary flight feather (or feathers) in this species is essential for identifying temporal trends in Hg concentrations. For this purpose, we had to first standardize the feather(s) analyzed to enable comparison of the levels of Hg detected in different feathers. The results show a high degree of both inter and intra-individual variability but despite that, it was possible to identify P5 as the most representative feather taking into account the amount of metal excreted in each feather and the intra-individual variability: its median was 133ng, which represents 15% (from 7% to 15%) of the total Hg present in all the primary feathers. However, this “standard feather” did not reveal any temporal trend in Hg concentrations for the study period. This lack of trend was found irrespective of the feather considered and it is expected that detection of any existing trend would also not depend on the feather considered. We conclude that use of any particular feather is not essential for identifying temporal trends in Hg concentrations, because the pattern will be identified regardless of the feather selected.

Differential trends in mercury concentrations in double-crested cormorant populations of the Canadian Prairies

Mercury and selenium concentrations were measured in double-crested cormorants (Phalacrocorax auritus), piscivorous fish, and common prey items in five lakes in two ecoregions in Saskatchewan, Canada. Hg and Se concentrations in cormorants were within the natural ranges of birds living in un-impacted sites. Site explained a significant proportion of the variation in total Hg (THg) and methylmercury (MeHg) concentrations in both cormorant breast muscle and livers. Birds nesting on more northern lakes in the Boreal Plain ecoregion (THg range0.11-1.06 and 0.26-9.27μgg(-1) wet weight, for breast and liver respectively) had lower THg concentrations compared to those from lakes in the Prairie ecoregion (THg range0.60-4.26μgg(-1) ww and 1.59-25.11μgg(-1), for breast and liver respectively). Concentrations of MeHg in livers was also lower in birds from northern sites (0.06-1.15μgg(-1) ww) compared to those from prairie sites (0.22-4.06μgg(-1) ww). We documented a wide range of %MeHg in livers (4.5-52%), indicative of detoxifying MeHg via demethylation to inorganic Hg. Our data suggest that the threshold value where demethylation rates increase substantially appears to be ~10μgg(-1) ww MeHg, similar to thresholds in other wildlife. Molar ratios of Hg:Se suggests that some birds from highly saline Reed Lake in the prairie region had insufficient Se available to bind to Hg, thereby removing Se binding as a mitigative strategy for high Hg levels for these birds.

Kinetic Study of Mercury Adsorption on Activated Carbon in Simulated Flue Gas

Two types of activated carbon for the removal of element mercury in simulated flue gas were studied in the paper. Mercury adsorption process on fixed bed reactor has been researched. The conclusions are as follows: The trend of mercury concentration first decreased and then increased over time; as for two types of activated carbon, the adsorption corresponds to pseudo-first-order equation and pseudo-second-order equation respectively. Because of the high correlation coefficient, the pseudo-second-order equation will correspond to actual adsorption process.

Mercury in Perch (Perca fluviatilis) from Sweden and Finland

High mercury concentrations in freshwater fish from the Nordic region have been of concern for a long time. Ongoing monitoring of key ecological species occurs in these countries to follow the situation. Here, we investigated spatial and temporal trends in mercury concentrations in European perch (Perca fluviatilis) within the Swedish and Finnish aquatic environments, collated from national monitoring programmes collected between 1974 and 2005 (n = 5,172). Data were length and weight adjusted to remove perch size as a confounding factor. Temporal trend analyses and t tests comparing pre- and post-1996 mercury concentrations for each country (1974–1995; 1996–2005; perch adjusted to 200 g/25 cm), showed a significant decrease in mercury concentration in perch from Sweden (p < 0.001) and a possible increase in mercury concentration in perch from Finland (p < 0.001). No statistically significant geographical trends were seen. Average mercury concentrations exceeded both the current environmental quality standard (EQS) of 20 ng/g wet weight (ww) and a discussed EQS for the Nordic region of 200–250 ng/g ww. Despite large reductions in mercury use and production in these countries, concentrations in perch continue to be higher here than in other European areas, posing a continued environmental risk.

Investigations of mercury concentrations in walleye and other fish in the Athabasca River ecosystem with increasing oil sands developments

Recent studies have reported an increasing trend of mercury concentrations in walleye (Sander vitreus) from the Athabasca River, north eastern Alberta (Canada); these studies were based on three years of comparison and attributed the mercury increase to expanding oil sands developments in the region. In order to conduct a more comprehensive analysis of mercury trends in fish, we compiled an extensive database for walleye, lake whitefish (Coregonus clupeaformis), northern pike (Esox lucius) and lake trout (Salvelinus namaycush) using all available data obtained from provincial, federal, and industry-funded monitoring and other programs. Evidence for increasing trends in mercury concentrations were examined for each species by location and year also considering fish weight and length. In the immediate oil sands area of the Athabasca River, mercury concentrations decreased (p < 0.001) in walleye and lake whitefish over 1984-2011. In western Lake Athabasca and its delta, mercury concentrations decreased (p < 0.0001) in northern pike (1981-2009) although no trend was evident for walleye (1981-2005) and lake trout (1978-2009). Mercury concentrations in lake trout from Namur Lake, a small lake west of the oil sands area, were higher in 2007 than 2000 (p < 0.0001); it is difficult to ascribe this increase to an oil sands impact because similar increases in mercury concentrations have been observed in lake trout from similar sized lakes in the Northwest Territories. While mercury emissions rates have increased with oil sands development and the landscape become more disturbed, mercury concentrations remained low in water and sediments in the Athabasca River and its tributaries and similar to concentrations observed outside the development areas and in earlier decades. Our fish database was assembled from a series of studies that differed in study purpose, design, and analytical methods. Future monitoring programs investigating mercury trends in fish should be more rigorous in their design.

Mercury levels and trends (1993–2009) in bream ( Abramis brama L.) and zebra mussels ( Dreissena polymorpha) from German surface waters

Mercury concentrations have been analysed in bream ( Abramis brama L.) and zebra mussels ( Dreissena polymorpha) collected at 17 freshwater sites in Germany from 1993–2009 and 1994–2009, respectively, within the German Environmental Specimen programme. Mercury concentrations in bream ranged from 21 to 881 ng g −1 wet weight with lowest concentrations found at the reference site Lake Belau and highest in fish from the river Elbe and its tributaries. Statistical analysis revealed site-specific differences and significant decreasing temporal trends in mercury concentrations at most of the sampling sites. The decrease in mercury levels in bream was most pronounced in fish from the river Elbe and its tributary Mulde, while in fish from the river Saale mercury levels increased. Temporal trends seem to level off in recent years. Mercury concentrations in zebra mussels were much lower than those in bream according to their lower trophic position and varied by one order of magnitude from 4.1 to 42 ng g −1 wet weight (33–336 ng g −1 dry weight). For zebra mussels, trend analyses were performed for seven sampling sites at the rivers Saar and Elbe of which three showed significant downward trends. There was a significant correlation of the geometric mean concentrations in bream and zebra mussel over the entire study period at each sampling site (Pearson’s correlation coefficient = 0.892, p = 0.00002). A comparison of the concentrations in bream with the environmental quality standard (EQS) of 20 ng g −1 wet weight set for mercury in biota by the EU showed that not a single result was in compliance with this limit value, not even those from the reference site. Current mercury levels in bream from German rivers exceed the EQS by a factor 4.5–20. Thus, piscivorous top predators are still at risk of secondary poisoning by mercury exposure via the food chain. It was suggested focusing monitoring of mercury in forage fish (trophic level 3 or 4) for compliance checking with the EQS for biota and considering the age dependency of mercury concentrations in fish in the monitoring strategy.

Bi-phasic trends in mercury concentrations in blood of Wisconsin common loons during 1992–2010

We assessed the ecological risk of mercury (Hg) in aquatic systems by monitoring common loon (Gavia immer) population dynamics and blood Hg concentrations. We report temporal trends in blood Hg concentrations based on 334 samples collected from adults recaptured in subsequent years (resampled 2-9 times) and from 421 blood samples of chicks collected at lakes resampled 2-8 times 1992-2010. Temporal trends were identified with generalized additive mixed effects models and mixed effects models to account for the potential lack of independence among observations from the same loon or same lake. Trend analyses indicated that Hg concentrations in the blood of Wisconsin loons declined over the period 1992-2000, and increased during 2002-2010, but not to the level observed in the early 1990s. The best fitting linear mixed effects model included separate trends for the two time periods. The estimated trend in Hg concentration among the adult loon population during 1992-2000 was -2.6% per year, and the estimated trend during 2002-2010 was +1.8% per year; chick blood Hg concentrations decreased -6.5% per year during 1992-2000, but increased 1.8% per year during 2002-2010. This bi-phasic pattern is similar to trends observed for concentrations of methylmercury and SO(4) in lake water of an intensely studied seepage lake (Little Rock Lake, Vilas County) within our study area. A cause-effect relationship between these independent trends is hypothesized.

Spatial patterns and temporal trends in mercury concentrations, precipitation depths, and mercury wet deposition in the North American Great Lakes region, 2002–2008

Annual and weekly mercury (Hg) concentrations, precipitation depths, and Hg wet deposition in the Great Lakes region were analyzed by using data from 5 monitoring networks in the USA and Canada for a 2002–2008 study period. High-resolution maps of calculated annual data, 7-year mean data, and net interannual change for the study period were prepared to assess spatial patterns. Areas with 7-year mean annual Hg concentrations higher than the 12 ng per liter water-quality criterion were mapped in 4 states. Temporal trends in measured weekly data were determined statistically. Monitoring sites with significant 7-year trends in weekly Hg wet deposition were spatially separated and were not sites with trends in weekly Hg concentration. During 2002–2008, Hg wet deposition was found to be unchanged in the Great Lakes region and its subregions. Any small decreases in Hg concentration apparently were offset by increases in precipitation.

Trends in Mercury Concentrations in New York State Fish

Atmospheric emissions of mercury in the US are being reduced, but worldwide mercury emissions remain high. Mercury is also being removed from many consumer items. Changes over time in mercury concentrations in fish remain important to resource managers and the general public. There is hope that mercury concentrations in fish will decline, and the number of fish consumption advisories due to mercury will decrease. We compared mercury concentrations in yellow perch (Perca flavescens) from a group of Adirondack lakes with data collected 12-17 years earlier and found variable responses among lakes. We observed an average decline of 14% in yellow perch mercury concentrations over the past 15 years.

Trend Reversal of Mercury Concentrations in Piscivorous Fish from Minnesota Lakes: 1982−2006

The trend of mercury concentrations in standardized length northern pike (NP55) and walleye (WE40) was evaluated for a 25-year period, 1982-2006, based on a data set of 1707 cases from 845 lakes throughout Minnesota. Two lines of evidence--changes within individual lakes and regression analyses for all lakes together--indicate a downward trend before the mid-1990s and an upward trend thereafter. Within lakes,the evidence is based on the difference between two years of data at least 5 years apart. Before 1995, 64% decreased and 31% increased; after 1995,35% decreased and 60% increased. Three regression models-linear, quadratic, and two-segment linear piecewise-were evaluated for best fit using the Akaike Information Criteria (AIC). The two-segment linear piecewise regression model, with a breakpoint of 1992, was the best fit, while the quadratic model, with an inflection point of 1995, also had substantial support. The linear model was not supported (deltaAIC > 10). Based on least-squares linear regressions applied separately to 1982-1992 and 1992-2006, mercury concentrations in NP55 and WE40 decreased 4.6 +/- 1.3% (95% CI) per year from 1982 to 1992 and increased 1.4 +/- 0.8% per year from 1992 to 2006.

Temporal and geographic trends in mercury concentrations in muscle tissue in five species of hudson river, USA, fish

AbstractWe analyzed a New York (USA) state database of mercury concentrations in muscle tissue for five species of fish (striped bass, yellow perch, largemouth bass, smallmouth bass, and carp) over a range of locations in the Hudson River (USA) between 1970 and 2004. We used regression models to discern temporal and geographic change in the fish while controlling for a positive correlation between mercury concentration and body mass. Mercury concentrations significantly increased in fish from New York Harbor waters to the mid‐Hudson River. Striped bass and yellow perch showed a shallower increase in mercury concentration with river mile than did carp, largemouth bass, and smallmouth bass. Mercury concentrations declined over the 34‐year period. These results imply that a geographically restricted source of mercury may be spread throughout the watershed by toxin‐laden dispersing species. The increase of mercury toward the north may relate to a point source in the mid‐Hudson River, or it may indicate mercury released from the Adirondack watershed. The decline of mercury over three decades corresponds to a reduction of various inputs in the region. The temporal and geographic pattern of mercury in sediments corresponds to the geographic trend of mercury in fish.

Temporal and Geographic Trends in Mercury Concentrations in Muscle Tissue in Five Species of Hudson River, USA, Fishes

We analyzed a New York (USA) state database of mercury concentrations in muscle tissue for five species of fish (striped bass, yellow perch, largemouth bass, smallmouth bass, and carp) over a range of locations in the Hudson River (USA) between 1970 and 2004. We used regression models to discern temporal and geographic change in the fish while controlling for a positive correlation between mercury concentration and body mass. Mercury concentrations significantly increased in fish from New York Harbor waters to the mid-Hudson River. Striped bass and yellow perch showed a shallower increase in mercury concentration with river mile than did carp, largemouth bass, and smallmouth bass. Mercury concentrations declined over the 34-year period. These results imply that a geographically restricted source of mercury may be spread throughout the watershed by toxin-laden dispersing species. The increase of mercury toward the north may relate to a point source in the mid-Hudson River, or it may indicate mercury released from the Adirondack watershed. The decline of mercury over three decades corresponds to a reduction of various inputs in the region. The temporal and geographic pattern of mercury in sediments corresponds to the geographic trend of mercury in fish.

Temporal trends of mercury in marine biota of west and northwest Greenland

Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77° N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69° N) during the last decade. Stable-nitrogen (δ 15N) and carbon (δ 13C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on δ 15N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994–2004. However, during the last part of the period (1999–2004) the [Hg] increased significantly. Including tissue δ 15N values as a covariate had a marked effect on these results. The annual changes in δ 15N-adjusted [Hg] was estimated to −5.0% for the whole period and 2.2% during the last 5 years compared to −1.3% and 12.4%, respectively, for the non-adjusted [Hg].