Mercury Loading Research Articles

The dry-deposition of speciated mercury to the Florida Everglades: Measurements and modeling

The Florida Everglades Dry-Deposition Study (FEDDS) was designed to test the viability of using new and existing measurement techniques in the estimation of the dry-depositional loading of speciated mercury (elemental gaseous, reactive gaseous and particulate) to a mixed sawgrass (Cladium jamaicense) and cattail (Typha domingensis) stand within the Florida Everglades. Measurement intensives were performed during 24 February–04 March 1999 and 05–21 June 2000, which corresponded to the climatological dry and wet seasons in South Florida, respectively. During these intensives, direct measurements of mercury dry-deposition were made using a newly developed surrogate water surface technique. These direct measurements were compared with modeled estimates of mercury dry-deposition to the site that were obtained through the use of an inferential or “bigleaf” model that was modified for use with speciated mercury. On-site measurements of ambient speciated mercury concentrations and numerous micrometeorological variables were used as input to the model. The average mercury dry-deposition measured during the 1999 FEDDS measurement intensive was 13.3±4.0 ng m −2 day −1, while the modeled deposition for this period was 3.4±2.3 ng m −2 day −1. The average mercury dry-deposition measured during the 2000 FEDDS measurement intensive was lower, 5.9±2.8 ng m −2 day −1, while the average modeled deposition for this period was 1.8±0.6 ng m −2 day −1. A least-squares linear regression suggests that the model was able to explain 74% and 73% of the variability in the datasets for the 1999 and 2000 FEDDS intensives, respectively. While reported reductions in total mercury emissions across South Florida between study periods could explain the reductions in both the measured and predicted mercury dry-deposition estimates, the increased presence of cumulus convection during the summer-intensive could have also resulted in a removal of reactive and particulate mercury species within the atmosphere of South Florida.

Environmental and human exposure assessment monitoring of communities near an abandoned mercury mine in the Philippines: A toxic legacy

Abandoned mines are an important global concern and continue to pose real or potential threats to human safety and health including environmental damage/s. Very few countries had government mine regulation and reclamation policies until the latter part of the century where legal, financial and technical procedures were required for existing mining operations. Major reasons for mine closure may be mainly due to poor economies of the commodity making mining unprofitable, technical difficulties and national security. If the mine is abandoned, more often than not it is the government that shoulders the burden of clean-up, monitoring and remediation. The topic of abandoned mines is complex because of the associated financial and legal liability implications. Abandoned mercury mines have been identified as one of the major concerns because of their significant long-term environmental problems. Primary mercury production is still ongoing in Spain, Kyrgzystan, China, Algeria, Russia and Slovakia while world production declined substantially in the late 1980s. In the Philippines, the mercury mine located southeast of Manila was in operation from 1955 to 1976, before ceasing operation because of the decline in world market price for the commodity. During this time, annual production of mercury was estimated to be about 140,000 kg of mercury yearly. Approximately 2,000,000 t of mine-waste calcines (retorted ore) were produced during mining and roughly 1,000,000 t of these calcines were dumped into nearby Honda Bay to construct a jetty to facilitate mine operations where about 2000 people reside in the nearby three barangays. In October, 1994 the Department of Health received a request from the Provincial Health Office for technical assistance relative to the investigation of increasing complaints of unusual symptoms (e.g. miscarriages, tooth loss, muscle weakness, paralysis, anemia, tremors, etc.) among residents of three barangays. Initial health reports revealed significant elevation of blood mercury levels exceeding the then recommended exposure level of 20 ppb in 12 out of the 43 (27.9%) residents examined. The majority of the volunteers were former mine workers. In this study the abnormal findings included gingivitis, mercury lines, gum bleeding and pterydium. The most common neurologic complaints were numbness, weakness, tremors and incoordination. Anemia and elevated liver function tests were also seen in a majority of those examined. The assessment also revealed a probable association between blood mercury level and eosinophilia. The same association was also seen between high mercury levels and the presence of tremors and working in the mercury mine. To date, there are very limited environmental and health studies on the impact of both total and methylmercury that have been undertaken in the Philippines. Thus, this area of study was selected primarily because of its importance as an emerging issue in the country, especially regarding the combined effects of total and methylmercury low-dose and continuous uptake from environmental sources. At present the effects of total mercury exposure combined with MeHg consumption remain an important issue, especially those of low-dose and continuous uptake. Results of the study showed that four (4) species of fish, namely ibis, tabas, lapu-lapu and torsillo, had exceeded the recommended total mercury and methylmercury levels in fish (NV>0.5 ug/g f.w., NV>0.3 ug/g f.w., respectively). Saging and kanuping also exceeded the permissible levels for methylmercury. Total and methylmercury in canned fish, and total mercury in rice, ambient air and drinking water were within the recommended levels, however, additional mercury load from these sources may contribute to the over-all body burden of mercury among residents in the area. Surface water quality at the mining area, Honda Bay and during some monitoring periods at Palawan Bay exceeded total mercury standards (NV>0.002 ng/mL). Soil samples in two sites, namely Tagburos and Honda Bay, exceeded the EPA Region 9 Primary Remediation Goal recommended values for total mercury for residential purposes (NV>23 mg/kg). The hand to mouth activity among infants and children is another significant route for mercury exposure. Statistically significant results were obtained for infants when comparing the results after one year of monitoring for methylmercury levels in hair for both exposed and control sub-groups. Likewise, comparing the initial and final hair methylmercury levels among pregnant women/mothers in the exposed group showed statistically significant ( p<0.05) results. Comparing the exposed and control sub-groups’ mercury hair levels per sub-group showed statistically significant results among the following: (a) initial and final total mercury hair levels among children, (b) initial and final methylmercury hair levels among children, (c) final total mercury hair levels among pregnant women, (d) initial and final total mercury hair levels among mothers, and (e) initial and final methyl hair levels among mothers.

The mass balance of mercury in the springtime arctic environment

The load of mercury in the Arctic environment is to a large extent controlled by atmospheric mercury depletion events. At Barrow, Alaska, these depletion events have been linked with the near‐surface air formation of reactive gaseous mercury (Hg(II)) (RGM), to a much lesser extent in a particulate‐bound form, and the accumulation of total mercury in the snow pack (&gt;100 ng/L in late Spring). This transport of Hg from atmospheric conversion, to deposition, to bio‐available forms is likely to be the predominant pathway for mercury into Arctic biota. For the first time we combine flux rate measurements, atmospheric chemistry measurements, and air mass trajectories to give a comprehensive two‐week window into the springtime dynamics and mass balance of Arctic mercury. We have conducted polar‐sunrise to snowmelt mercury monitoring at Barrow from 1998 to 2004, and the time period March 25th–April 7th (Julian days 84–97), 2003 appears typical for this time of year. A clear link was observed between air of marine origin, the build‐up of BrO together with removal of gaseous elemental mercury (GEM)), and the formation of RGM. This provides the most direct evidence so far for Br and Hg chemistry as the direct source of RGM. The fluxes of RGM and GEM were determined and the net flux calculated.

Managing mercury in the great lakes: An analytical review of abatement policies

Mercury, a toxic metal known to have several deleterious affects on human health, has been one of the principal contaminants of concern in the Great Lakes basin. There are numerous anthropogenic sources of mercury to the Great Lakes area. Combustion of coal, smelting of nonferrous metals, and incineration of municipal and medical waste are major sources of mercury emissions in the region. In addition to North American anthropogenic emissions, global atmospheric emissions also significantly contribute to the deposition of mercury in the Great Lakes basin. Both the USA and Canada have agreed to reduce human exposure to mercury in the Great Lakes basin and have significantly curtailed mercury load to this region through individual and joint efforts. However, many important mercury sources, such as coal-fired power plants, still exist in the vicinity of the Great Lakes. More serious actions to drastically reduce mercury sources by employing alternative energy sources, restricting mercury trade and banning various mercury containing consumer products, such as dental amalgam are as essential as cleaning up the historical deposits of mercury in the basin. A strong political will and mass momentum are crucial for efficient mercury management. International cooperation is equally important. In the present paper, we have analyzed existing policies in respective jurisdictions to reduce mercury concentration in the Great Lakes environment. A brief review of the sources, occurrence in the Great Lakes, and the health effects of mercury is also included.

Mercury accumulation in surface sediments of salt marshes of the Bay of Fundy

Mercury contamination in Canada's Bay of Fundy is a priority concern because of elevated levels observed in fish, birds and wildlife. Salt marshes constitute an important part of the Bay's coastline and are potential stores of mercury for the region. We measured the amount of mercury accumulated over a 5-yr period from 1997 to 2002 in surface sediments of seven salt marshes along the New Brunswick coast of the Bay. The seven study sites extended from outer to inner Bay, spanning a gradient in tidal range (6–12 m) and sediment characteristics such as %LOI (4–29%) and sediment deposition rate (0.27–1.76 cm yr −1). In each study site, mercury was measured in low and high marsh areas. Sediment mercury concentrations ranged from 7 to 79 ng g −1 and loading rates ranged from 0.1 to 1.1 mg m −2. Total estimated 5-yr storage of mercury in salt marsh sediments of the Bay is 854 ± 465 kg. We also compared sediment mercury loading to atmospheric inputs measured at a deposition monitoring station operating in New Brunswick from 1997 to 2002 and found that direct atmospheric deposition appears to be a minor input of mercury to these sediments. We are unaware of documentation of mercury loading in salt marshes on a bay-wide scale and over a constrained (5-yr) time period elsewhere.

Fatigue properties of type 316LN stainless steel in air and mercury

An extensive fatigue testing program on 316LN stainless steel was recently carried out to support the design of the mercury target container for the spallation neutron source (SNS) that is currently under construction at the Oak Ridge National Laboratory in the United States. The major objective was to determine the effects of mercury on fatigue behavior. The S– N fatigue behavior of 316LN stainless steel is characterized by a family of bilinear fatigue curves which are dependent on frequency, environment, mean stress and cold work. Generally, fatigue life increases with decreasing stress and levels off in the high cycle region to an endurance limit below which the material will not fail. For fully reversed loading as well as tensile mean stress loading conditions mercury had no effect on endurance limit. However, at higher stresses a synergistic relationship between mercury and cyclic loading frequency was observed at low frequencies. As expected, fatigue life decreased with decreasing frequency, but the response was more pronounced in mercury compared with air. As a result of liquid metal embrittlement (LME), fracture surfaces of specimens tested in mercury showed widespread brittle intergranular cracking as opposed to typical transgranular cracking for specimens tested in air. For fully reversed loading (zero mean stress) the effect of mercury disappeared as frequency increased to 10 Hz. For mean stress conditions with R-ratios of 0.1 and 0.3, LME was still evident at 10 Hz, but at 700 Hz the effect of mercury had disappeared ( R = 0.1). Further, for higher R-ratios (0.5 and 0.75) fatigue curves for 10 Hz showed no environmental effect. Finally, cold working (20%) increased tensile strength and hardness, and improved fatigue resistance. Fatigue behavior at 10 and 700 Hz was similar and no environmental effect was observed.

Increased Ethyl Mercury Load in Protein A Immunoadsorption

Immunoadsorption is an adsorption technique for extracorporeal removal of circulating autoantibodies in autoimmune diseases. To prevent microbial growth during storage, the protein A columns are primed with thiomersal, which contains toxic ethyl mercury, which may be released during the procedure and potentially begin to accumulate and become toxic. To reduce the thiomersal-related mercury release during immunoadsorption treatment, we introduced a modified rinsing solution containing N-acetylcysteine, which is an avid mercury scavenger. Thirteen patients received 17 protein A immunoadsorption treatments and their venous blood samples were collected immediately before and after each session. The total blood mercury levels were measured by atomic absorption spectrometry, and the ethyl mercury levels by atomic fluorescence spectrometry. Following the manufacturer's recommendations, we used 600 mg of N-acetylcysteine to rinse the mercury from protein-loaded columns before each immunoadsorption treatment. After immunoadsorption, the ethyl mercury levels increased from 0.148 +/- 0.402 ng/g to 2.026 +/- 1.944 ng/g (P < 0.001), and the total blood mercury levels increased from 2.447 +/- 3.065 ng/g to 20.437 +/- 28.603 ng/g (P = 0.02). The post-treatment values of total blood mercury exceeded the upper safety level of 5 ng/g in all 17 immunoadsorption treatments, but no patient developed clinical signs of mercury toxicity. The results of our study showed an increase in total blood mercury and ethyl mercury levels during the immunoadsorption treatments, suggesting mercury release from thiomersal-primed columns despite the addition of N-acetylcysteine to the rinsing solution.

Mercury Binding Sites in Thiol-Functionalized Mesostructured Silica

Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO(2))(1)(-)(x)()(LSiO(1.5))(x)(), where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50-1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg-O bonds and can rule out oxygen coordination of the mercury at greater than the 10% level. The relative intensities of the PDF peaks corresponding to Hg-S and Hg-Hg atomic pairs indicate that the mercury centers cluster on the functionalized surfaces by virtue of thiolate bridging, regardless of the overall mercury loading. However, the Raman results indicate that the complexation of mercury centers by thiolate depends on the mercury loading. At low mercury loadings (Hg/S < or = 0.5), the dominant species is an electrically neutral complex in which mercury most likely is tetrahedrally coordinated to bridging thiolate ligands, as in Hg(SBu(t))(2). At higher loadings (Hg/S 1.0-1.3), mercury complex cations predominate, as evidenced by the presence of charge-balancing anions (nitrate) on the surface. This cationic form of bound mercury is assigned a linear coordination to two bridging thiolate ligands.

An assessment of anthropogenic source impacts on mercury cycling in the Willamette Basin, Oregon, USA

In Oregon's Willamette River Basin (Basin), methylmercury levels in fish triggered health advisories and required development of a mercury Total Maximum Daily Load (TMDL) for the Willamette River. A seasonally-responsive dynamic systems model is used to identify the principal sources of natural and anthropogenic mercury, the relative contributions of these sources to the river, the impact of hypothetical reductions in specific natural and anthropogenic sources on mercury levels in surface water, sediment, and fish tissue, and the degree to which any such changes would be clearly discernible to environmental managers and Basin stakeholders. Two scenarios are modeled: “PRES”, which considered all currently known natural and anthropogenic mercury sources and “LEEM”, which (hypothetically) eliminated all local, but not global, anthropogenic sources and greatly lowered native soil erosion rates. Elimination of local air emissions reduces runoff of air-deposited mercury by ≈34% and advection from the Basin by ≈12%, while lowering erosion rates reduces particulate runoff by ≈57%, deposition from the water column to surficial sediment by ≈33%, and fluvial load by ≈24%; for a net reduction of 25.6% in the total mercury load to the river. Such hypothetical reductions bring methylmercury concentrations in predatory fish to levels that would allow restoration of fish consumption as a beneficial use. However, several factors, primarily technical feasibility and global sources, may impede attempts to attain this beneficial use. Actualizing the hypothetical 100% elimination of local anthropogenic sources and a > 50% reduction in erosion could pose significant technical challenges. Because local anthropogenic emissions make relatively smaller contributions to the Basin than do persistent global sources (sources over which there is little, if any, possibility of local control), localized environmental management actions alone may not be adequate to address mercury impacts within the Basin.

Adsorption of Aqueous Mercury(II) on Propylthiol-Functionalized Mesoporous Silica Obtained by Cocondensation

Adsorption of inorganic mercury(II) from an aqueous solution on mercaptopropyl-functionalized SBA-15 mesoporous silicas has been investigated. Adsorbents were prepared by the cocondensation method using tetraethoxysilane and different quantities of (mercaptopropyl)trimethoxysilane. Pluronic P123 was employed as a structure-directing agent. Mercury adsorption isotherms at 20 °C are reported for every synthesized material. The maximum mercury loading has been obtained from Langmuir fitting. Stoichiometric ratios of 1:1 S−Hg have been observed in all cases. Adsorbents were extremely efficient in removing inorganic mercury from an aqueous solution with a maximum in mercury loading of ca. 2.9 mmol of Hg g-1 for the material with the higher organic content. The effect of the pH on mercury adsorption has been studied. The efficiency of the adsorbents has been found to remain almost constant from neutral pH up to 3 M nitric acid concentration.

Amalgam: Eine Risikobewertung unter Berücksichtigung der neuen Literatur bis 2005

Amalgam, which has been in use in dentistry for 150 years, consists of 50 % elemental mercury and a mixture of silver, tin, copper and zinc. Minute amounts of mercury vapour are released continuously from amalgam. Amalgam contributes substantially to human mercury load. Mercury accumulates in some organs, particularly in the brain, where it can bind to protein more tightly than other heavy metals (e. g. lead, cadmium). Therefore, the elimination half time is assumed to be up to 1 - 18 years in the brain and bones. Mercury is assumed to be one of the most toxic non-radioactive elements. There are pointers to show that mercury vapour is more neurotoxic than methyl-mercury in fish. Review of recent literature suggests that mercury from dental amalgam may lead to nephrotoxicity, neurobehavioural changes, autoimmunity, oxidative stress, autism, skin and mucosa alterations or non-specific symptoms and complaints. The development of Alzheimer's disease or multiple sclerosis has also been linked to low-dose mercury exposure. There may be individual genetical or acquired susceptibilities for negative effects from dental amalgam. Mercury levels in the blood, urine or other biomarkers do not reflect the mercury load in critical organs. Some studies regarding dental amalgam reveal substantial methodical flaws. Removal of dental amalgam leads to permanent improvement of various chronic complaints in a relevant number of patients in various trials. Summing up, available data suggests that dental amalgam is an unsuitable material for medical, occupational and ecological reasons.

30 Increased Mercury Load in Protein A Immunoadsorption

Background Immunoadsorption is an adsorption technique for extracorporeal removal of circulating autoantibodies in autoimmune diseases such as myasthenia gravis and Guillain‐Barré syndrome. To prevent microbial growth during storage, the protein A columns are primed with thiomersal containing toxic ethylmercury which could be released during the immunoadsorption treatment and potentially result in its accumulation and toxicity. To reduce a thiomersal‐related mercury release during immunoadsorption treatment we introduced a modified rinsing solution containing N‐acetylcysteine which is an avid mercury scavenger.Methods Thirteen patients were treated by 17 protein A immunoadsorption treatments and venous blood samples were collected immediately before and after each session. Whole blood mercury levels were measured by atomic absorption spectroscopy and ethylmercury levels by atomic fluorescent spectroscopy. According to the manufacturer's recommendations we used 600 mg of N‐acetylcysteine to rinse the mercury from protein‐loaded columns before each immunoadsorption treatment.Results Following protein A immunoadsorption ethylmercury levels increased from 0.148 ± 0.402 ng/g to 2.026 ± 1.944 ng/g (P &lt; 0.001) and whole blood mercury increased from 2.447 ± 3.065 ng/g to 20.437 ± 28.603 ng/g (P = 0.02). Post‐treatment values of whole blood mercury exceeded upper safety level of 5 ng/g in all 17 immunoadsorption treatments but no patient developed clinical signs of mercury toxicity.In one patient immunoadsorption treatment was repeated within 7 days and the results of serial determinations of blood mercury levels are shown in Table A30. Ethylmercury Whole blood mercury (ng/g) (ng/g) Before IA After IA Before IA After IA Day 0 0.13 ± 0.03 1.35 ± 0.12 0.49 ± 0.06 76.8 ± 5.6 Day 1 0.17 ± 0.00 0.10 ± 0.02 8.14 ± 1.24 19.4 ± 0.6 Day 2 0.05 ± 0.00 0.09 ± 0.00 9.57 ± 0.80 11.8 ± 0.9 Day 3 0.03 ± 0.00 0.08 ± 0.01 6.96 ± 0.09 8.52 ± 0.39 Day 7 1.69 ± 0.00 4.23 ± 0.12 5.54 ± 0.32 9.04 ± 0.48 Data are presented as means ± standard deviation. IA, immunoadsorption. Conclusions The results of our study showed that whole blood mercury and ethylmercury levels were increased during the immunoadsorption treatments, suggesting mercury release from thiomersal‐primed columns even with addition of N‐acetylcysteine to the rinsing solution. Mercury release was more pronounced at the beginning of serial immunoadsorption treatments which indicates that mercury exposure might depend on the storage time of protein A columns containing thiomersal priming solution.

Effect of Mercury Column on the Microdynamics of the Piezo-Driven Pipettes

This study is on an interesting phenomenon concerning cellular microinjection procedures which are used for various biomedical applications, and in particular intracytoplasmic sperm injection. Recent years have brought considerable practical improvements in these operations. One of them suggests aspirating a very small quantity of mercury in the injection pipettes prior to piercing into cells. This process is proven to enhance the rate of success considerably. We present a unique study in determining the influence of mercury on the microdynamics of the pipette. The effort contains both numerical simulations and corresponding experimental verification. Ultimately we offer two critical results: (1) The mercury column increases the mass loading and expectedly decreases the natural frequencies of the pipette and (2) The lateral oscillations, which play a destructive role in piercing, are subdued in amplitude due to the mass loading of mercury. Simulation results are presented, which are also verified experimentally using high-speed digital imaging. As a consequence of these findings we also propose some alternative design directions for future microinjection devices.

Calculating Mercury Loading to The Tidal Hudson River, New York, Using Rating Curve and Surrogate Methodologies

Total mercury (THg) load in rivers is often calculated from a site-specific “rating-curve” based on the relation between THg concentration and river discharge along with a continuous record of river discharge. However, there is no physical explanation as to why river discharge should consistently predict THg or any other suspended analyte. THg loads calculated by the rating-curve method were compared with those calculated by a “continuous surrogate concentration” (CSC) method in which a relation between THg concentration and suspended-sediment concentration (SSC) is constructed; THg loads then can be calculated from the continuous record of SSC and river discharge.

Atmospheric vapour phase and particulate phase mercury in a coastal desert climate

Vapour (T-Hg(v)) and particulate (T-Hg(p)) mercury were measured in the lower atmosphere at a ground station in Kuwait Bay. The concentration of T-Hg(v) varied from 0-86 ng m(-3) with a mean of 3.8 +/- 5.5 ng m(-3)(n= 13 326). About 40% of the measured T-Hg(v) values over Kuwait Bay are higher than the global range (1-3 ng m(-3)). Car exhausts contributed to the increase of T-Hg(v) during the rush hours. However the contribution of T-Hg(v) from air crossing Kuwait Bay exceeds that T-Hg(v) produced by traffic probably because of the effects of the substantial load of industrially-derived mercury in the sediments of this shallow region. Thermal inversions have a major impact on the levels during the evening hours. The concentration of T-Hg(p) varied from 0.00-0.22 ng m(-3) with a mean of 0.03 +/- 0.03 ng m(-3)(n= 175). The T-Hg(p)/T-Hg(v)% ratio varied from 0-11.1 (n= 171) with a mean of 1.0 +/- 1.5%. Meteorological parameters influence the T-Hg(v) and T-Hg(p) concentrations with dust storms having a major impact on T-Hg(p) concentrations.

A comparison of total mercury and methylmercury export from various Minnesota watersheds

Methylmercury (MeHg) bioaccumulates in aquatic food webs and can pose health risks to animals at higher trophic levels. Characterization of MeHg production in and export from watersheds can help clarify exposure scenarios for aquatic life downstream. A number of studies have demonstrated that anoxic conditions in the saturated soils of wetlands can promote the production of MeHg, and these wetlands may be major sources of MeHg to connected water bodies. Here, we report in-stream loadings of total mercury (THg) and MeHg for five rivers in Minnesota (USA). The watersheds of these rivers differ widely in the proportion of land area made up by wetlands and in other land use, drainage, and soil characteristics. Export of THg from these rivers varied widely, with much higher loadings and annual average concentrations of THg in streams of the Minnesota River basin compared to streams in the headwater Mississippi River basin. In contrast and despite the apparent differences in the makeup of these watersheds, yields and annual average concentrations of MeHg were remarkably similar for the rivers studied here. Differences in land use/land cover, drainage, soils, and other characteristics of these watersheds influence the export of both THg and MeHg in these rivers, but overall MeHg yields vary less than THg yields.

Tailings fans and valley‐spur cutoffs created by hydraulic mining

AbstractSand and gravel tailings from nineteenth century open‐pit hydraulic gold mines formed large alluvial fans at tributary confluences in the northwestern Sierra Nevada, California. In the Bear River watershed, several of these fans were so large that they blocked main channels for decades. Some channels not only aggraded deeply, but also moved laterally and cut across the inner bends of valley spurs. Now locked in bedrock channels, these valley‐spur cutoffs impose local controls on geomorphic, hydraulic, and sedimentary processes. One cutoff has incised 25 m into bedrock over the past century (25 cm a−1) with rapid initial incision rates of up to 50 cm a−1 (1884–1890). Recognition of spur cutoffs in the geological record may help to identify large landslides and provide an analogue for a type of natural earthfill dam spillway not prone to catastrophic failures. Tailing fans, valley‐spur cutoffs, and the sediment they trap are described from contemporary accounts and recent field conditions in the Bear River watershed. These anthropogenic changes represent a major shift in the watershed from supply‐limited to transport‐limited sediment budgets and a change in geomorphic processes away from long‐term drainage evolution dominated by ingrown meanders. The large volumes of mining sediment stored in these landforms will be slowly released over the next millennium and could be significant to contemporary ecological and public health issues due to recent findings of high mercury loadings associated with hydraulic mines. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Speciation and bioavailability of mercury in well-mixed estuarine sediments

Despite regulations controlling anthropogenic mercury sources in North America, high levels of mercury in coastal fish and shellfish are an ongoing problem in Maritime Canada and the Northeastern United States. This study presents sediment core data from a macrotidal estuary located at the mouth of the Bay of Fundy showing stratigraphic profiles of total and methylmercury concentrations and potential methylation rates measured using stable mercury isotopes. The results show that in contrast to the expected methylmercury profile typically observed in unmixed sediments, methylmercury production occurs throughout the estimated 15-cm-thick active surface layer of these well-mixed sediments. The resulting large reservoir of methylmercury in these sediments helps to explain why mercury concentrations in organisms in this system remain high despite emissions reductions. Current management policies should take into account the expected delay in the response time of well-mixed estuarine systems to declines in mercury loading, considering the greater reservoir of historic mercury available in these sediments that can potentially be converted to methylmercury and biomagnify in coastal food chains.

Mercury and methylmercury concentrations and loads in the Cache Creek watershed, California

Concentrations and loads of total mercury and methylmercury were measured in streams draining abandoned mercury mines and in the proximity of geothermal discharge in the Cache Creek watershed of California during a 17-month period from January 2000 through May 2001. Rainfall and runoff were lower than long-term averages during the study period. The greatest loading of mercury and methylmercury from upstream sources to downstream receiving waters, such as San Francisco Bay, generally occurred during or after winter rainfall events. During the study period, loads of mercury and methylmercury from geothermal sources tended to be greater than those from abandoned mining areas, a pattern attributable to the lack of large precipitation events capable of mobilizing significant amounts of either mercury-laden sediment or dissolved mercury and methylmercury from mine waste. Streambed sediments of Cache Creek are a significant source of mercury and methylmercury to downstream receiving bodies of water. Much of the mercury in these sediments is the result of deposition over the last 100–150 years by either storm-water runoff, from abandoned mines, or continuous discharges from geothermal areas. Several geochemical constituents were useful as natural tracers for mining and geothermal areas, including the aqueous concentrations of boron, chloride, lithium and sulfate, and the stable isotopes of hydrogen and oxygen in water. Stable isotopes of water in areas draining geothermal discharges showed a distinct trend toward enrichment of 18O compared with meteoric waters, whereas much of the runoff from abandoned mines indicated a stable isotopic pattern more consistent with local meteoric water.

The Tail Feathers of Osprey Nestlings (Pandion haliaetus L.) as Indicators of Change in Mercury Load in the Environment of Southern Sweden (1969–1998): Case Study with a Note on the Simultaneous Intake of Selenium

The tail feathers of 104 osprey nestlings (Pandion haliaetus) from Lake Asnen, southern Sweden, were analyzed for total mercury and selenium content. Concentrations of mercury in feathers from the western part of the lake fell during the period 1969-1998, when pollution from industrial mercury had decreased and a paper mill upstream of the lake was closed down in 1979. Nestlings from the eastern part of the lake had initially lower levels of mercury, predominantly from atmospheric fallout. The levels did not decrease during the period. The reason for the differences seems to be the limited water flow between the western and the eastern part of the lake. The selenium concentrations were constant over time and approximately the same in both parts of the lake. The total-Hg/Se ratio in the western part of the lake was 2.94, which is somewhat higher than the 1:1 molar ratio constant (2.54). This indicates that the bioaccumulated quantity of selenium which is thought to be protective for the organisms against the toxic effects of mercury, is somewhat insufficient to bind all body mercury.