A digital image analysis procedure for mercury quantification based on the analysis of the color developed in a spot-test derived reaction using a commercial scanner is described. The color intensity is related to the concentration in the original sample. Digital image analysis of the developed color was used to establish a quantitative relationship between the color components and the mercury concentration. Different color separation models were compared and their sensitivity to the variation of the mercury concentration was evaluated. The Hue-Lightness-Saturation (HLS) model provided the best results, showing a linear relationship between the Hue value and the mercury concentration. The procedure was used for the analysis of interlaboratorial fish samples and good concordance between found and reported values was found. The detection limits were estimated from the confidence bands of the analytical curves. For a calibration interval of 100 to 600 ng, a detection limit of 0.007 µg g-1 (wet weight) was found.
The paper assesses methyl and total mercury concentrations in three mollusc species (Perna perna - common mussel, Crassostrea rhizophorae - mangrove oyster, Anomalocardia brasiliana - clam) from two estuaries in Rio de Janeiro State, both impacted by organic matter and heavy metals. Mussels showed higher capacity to accumulate mercury compared to the other mollusc species (oyster, clam). A significant difference was observed between mercury concentration in the female mussel organisms and in males (81 ± 1 µg kg-1 dry wt. and 70 ± 5 µg kg-1 dry wt. respectively) with similar total shell length. No significant difference was observed among the % MeHg in the female (64%) and male (63%) mussel organisms. Even though the feeding habits of the molluscs are similar; mussels presented higher mercury and methylmercury concentrations in their soft tissues (76 ± 7 µg kg-1 dry wt. and 48 ± 5 µg kg-1 dry wt.) than oysters (19 ± 4 µg kg-1 dry wt. and 6 ± 1 µg kg-1 dry wt.). This is possible related to their capacity to select particle size and the composition of the ingested food they assimilate, and also reflects the greater ability of mussels to concentrate and excrete methylmercury and also to reflect their environmental conditions.
Total (HgT), reactive (HgR) and organic (HgORG) mercury species have been quantified in non-filtered waters collected from the Negro River Basin, Amazon (from January/2002 through January/2004), in both black and white water bodies. Black waters presented the highest HgT, HgORG and HgR concentration (29.1 ng L-1, 1.63 ng L-1 and 3.9 ng L-1, respectively), while, white waters presented the lowest HgT, HgORG and HgR concentration (8.8 ng L-1, 0.49 ng L-1 and 1.2 ng L-1, respectively). An inverse correlation between HgT and the water level over the basin was obtained, although the HgORG concentration has increased in the first rainy months and then decreased as the water level rose. Total mercury in surface sediments (0-10 cm) ranged from 70 to 271 mg kg-1 being the methylmercury 0.47-1.79 % of this stock.The results indicate that HgR and the labile dissolved organic matter were introduced into the aquatic environment during the flooding season, especially in the earlier stages, thus contributing to mercury methylation.
Nano-Ag particles loaded on TiO2 (Ag-TiO2) were used as catalyst for the UV-induced cold vapour generation with formic acid coupled to atomic absorption for determination of total mercury in analytical samples. The reducing activity of Ag-TiO2 was compared with two semiconductor catalysts: unmodified TiO2 and ZnO. The effect of catalyst type, its concentration in the analyzed sample, sample pH, formic acid concentration and ultraviolet irradiation time have been investigated. In the presence of formic acid, most effective in the reduction of mercury was Ag-TiO2. Under the optimized experimental conditions recovery of mercury in four reference materials containing 0.20-1.99 µg g-1 Hg was 95-99% of certificate values. The relative standard deviation for samples was equal to or better than 11%. Certified reference materials (corresponding to biological and environmental samples) analysis using the Ag-TiO2-UV-CVGAAS method revealed that it is promising for mercury determination in analytical samples at ultratrace level.
High mercury concentrations in different environmental matrices in the Amazon have been attributed to mining activities. However, high concentrations of mercury are also present in the soil and water in places like in the middle of the Negro River Basin, which is far away from any anthropogenic emission sources. The Amazon region is characterized by two different regional seasons, with well-defined flood and low water periods. The objective of this work was to investigate the seasonal influences of the interaction between mercury and aquatic humic substances (AHS), which are the main agents of the natural organic complexation capacity. The results of the multivariate statistical analysis of the data showed that the humic substances had different structural characteristics, depending on each season. The ability of humic substances to form complexes with Hg(II) is not directly related to their carbon content, but to the nature and availability of the functional groups present in its structure. The functional groups are carboxylic and aromatic directly related to the higher complexation capacity of AHS by mercury ions.
Mercury is one of the most toxic metals present in the environment. Adsorption has been proposed among the technologies for mercury abatement. Activated carbons are universal adsorbents which have been found to be a very effective alternative for mercury removal from water. The effectiveness with which a contaminant is adsorbed by the solid surface depends, among other factors, on the charge of the chemical species in which the contaminant is in solution and on the net charge of the adsorbent surface which depend on the pH of the adsorption system. In this work, activated carbon from carbonized eucalyptus wood was used as adsorbent. Two sulphurization treatments by impregnation with sulphuric acid and with carbon disulphide, have been carried out to improve the adsorption capacity for mercury entrapment. Batch adsorption tests at different temperatures and pH of the solution were carried out. The influence of the textural properties, surface chemistry and operation conditions on the adsorption capacity, is discussed.
A simple and easy new technique for volatilized mercury determination in biological systems was developed. This technique is fast and sensitive and can overcome the problems that arise due to the extremely low readings during the measurements and reproducibility in biological material (bacteria). It measures directly the volatilized metallic mercury of bacteria by means of a chemical adsorbent in a coupled mini-system, as a modified technique for mercury in air analysis. It is potentially of interest to the bioremediation and bacterial mercury resistance communities
Mercury is the only element capable to biomagnificate along the food chain, and carnivorous fish tend to accumulate high concentrations of this element. Total mercury in muscle tissue of Carcharhinus signatus sampled along the western equatorial Atlantic Ocean was measured by atomic emission spectrophotometry with ICP/AES. The average total mercury concentrations were consistently greater than the maximum limit for human consumption established by the Brazilian Health Ministry for carnivorous fishes (1000 µg. kg-1 w.w.). Therefore, an average consumption of 0.1 kg/day of C. signatus would result in an average daily ingestion of 174.2 µg of Hg, more than five times the 30 µg/day intake established by the World Health Organization. In the range of lengths studied, body length could not be used as an indicator of the Hg contamination degree for C. signatus. Also, sex cannot be considered a determining factor in the total mercury accumulation in C. signatus.
A hydride-generation atomic absorption spectroscopy (AAS) method was developed for the analysis of total Hg in liquid matrices of mercury-rich plants and mine tailings samples. The detection limit for this method was as low as 11.4 ng/mL. The reproducibility of the mercury signals (in terms of relative standard deviation) was 4.6%. Accuracy of the method was verified by analyses of deionised water samples spiked with HgCl2 and HgNO3. Recovery values for total mercury ranged from 88.5 to 94.3% for both mercury species added. An external certified laboratory validated the analytical method with a maximum discrepancy of 15 %. Optimal analytical response of the equipment for Hg analysis of plant samples was achieved when the sample volume added to the reaction vessel was 0.25 mL.
Observed wet deposition fluxes of mercury in the United States show a maximum in the Southeast, and a consistent seasonal variation (maximum in summer, minimum in winter) that increases in amplitude from north to south. We simulate these patterns successfully with a global 3-D chemical transport model (GEOS-Chem) including our best estimates of sources and processes. We attribute the high wet deposition over the Southeast in summer to scavenging of upper-altitude Hg(II) by deep convection. Seasonal variation at higher latitudes is attributed to a combination of enhanced summertime oxidation of Hg(0) and inefficient scavenging of Hg(II) by snow. Scavenging of Hg(II) from above the boundary layer contributes over half of wet deposition to the US in the model. Even within the boundary layer, we find that most of Hg(II) originates from the global mercury pool. Wet deposition in the model accounts for only 30% of total mercury deposition in the US, the remainder being from dry deposition, including 42% from Hg(0) uptake. North American anthropogenic emissions contribute 20% of total mercury deposition in the US (up to 50% in the industrial Midwest and Northeast).; Earth and Planetary Sciences; Engineering and Applied Sciences
The distribution of mercury in sediments
of the Patos Lagoon estuary and nearby
coastal marine deposits has been investigated for the period 1998???2008. Polluted urban soils and coastal reclamation fills are the principal sources of high mercury concentrations for shallow estuarine
sediments. The shallow sediments that form
near the urban area enter the navigation canal and are transported into the ocean. The mercury concentration in sediments of the navigation canal has considerably increased since 2004, due to intense reconstruction activity in the urban area. Periodic dredging of the canal strengthens the preconditions for coastal marine sediment contamination by mercury. However, this does not occur because the resuspended dredged sediments are significantly diluted by natural suspended particulate matter.
Climate warming is having a myriad of effects on our environment, one of which is the degradation of permafrost, underlying approximately 50% of Canada. Permafrost degradation is altering the boreal forest landscape in unpredictable ways, including hydrological changes such as lake expansion and/or drainage. One example from the Seward Peninsula in Alaska is the alteration of aquatic habitats through expansion of floating vegetation mats (FVMs) on lake margins as a result of permafrost subsidence. An emerging concern is the transport of terrestrial mercury into water bodies as permafrost thaws, posing a risk of exposure to native communities in this region. FVMs have been observed on lakes in the southern Northwest Territories (NWT), however it is poorly understood whether these are a long-standing feature of these lakes or have developed recently and are expanding. Therefore, paleolimnology can be used to indirectly infer past environmental conditions in this region, including possible changes in lake habitat from FVMs. Diatoms, a widely used group of paleolimnological indicators, were used as a biological proxy to track changes in the development and expansion of a FVM on a lake (KAK-1) in the Great Slave region, NWT, and to determine if changes coincide with increased mercury accumulation in the lake sediments. These results are compared to a lake that does not currently contain a FVM (TAH-7) in order to control for aquatic changes resulting from a warmer climate. Both lakes record divergent environmental trajectories...
A probabilistic risk assessment model using GOLDSIM software was developed to evaluate the uncertainty of selected hydrological and soil parameters on mercury releases from a mercury containment system, which will be constructed within the Environmental Management Waste Management Facility in the Bear Creek Valley at the Oak Ridge Reservation in Tennessee. The main objective was to determine the concentrations and risk of exceeding the drinking water standard of mercury in a selected receptor well. A series of simulations were then conducted for various design periods, with emphasis on 10,000 years to determine those concentrations and risks. Experimental data for selected parameters such as dry bulk density, partition coefficient, and porosity and infiltration rate were represented by Probability Density Functions in support of Monte Carlo analyses. A sensitivity analysis showed that concentrations and risk are, for instance, most sensitive to porosity in the unsaturated zone. The simulations suggest that all herein estimates of concentrations and risks of mercury in drinking water should be well below established limits.
An integrated flow and transport model using MIKE SHE/MIKE 11 software was developed to predict the flow and transport of mercury, Hg(II), under varying environmental conditions. The model analyzed the impact of remediation scenarios within the East Fork Poplar Creek watershed of the Oak Ridge Reservation with respect to downstream concentration of mercury. The numerical simulations included the entire hydrological cycle: flow in rivers, overland flow, groundwater flow in the saturated and unsaturated zones, and evapotranspiration and precipitation time series. Stochastic parameters and hydrologic conditions over a five year period of historical hydrological data were used to analyze the hydrological cycle and to determine the prevailing mercury transport mechanism within the watershed. Simulations of remediation scenarios revealed that reduction of the highly contaminated point sources, rather than general remediation of the contaminant plume, has a more direct impact on downstream mercury concentrations.
There is scarce information on the possible
effects of chronic exposure to mercury on skeletal
muscle. Dental personnel are frequently exposed to
inhalation of metallic mercury vapours. The skeletal
muscle of five technicians and one dentist (females, age
36-55) was studied. All of them presented symptoms of
chronic mercury poisoning. Needle biopsy was taken
from the quadriceps femoris muscle and samples were
prepared for light microscope histochemistry and for
transmission electron microscopy. Selective atrophy of
type IIB muscle fibres was found in patients, and in one
of them there was fibre grouping. Most of the muscles
showed increased fibre area per capillary. Atrophy was
confirmed by the ultrastructural study, demonstrating
increase of intermyofibrillar spaces, loss of myofibrils or
complete disappearance in some fibres, and sarcolemmal
folding. Splitting of the fibres was also found. Some
capillaries were altered, showing endothelial infoldings
into the lumen, thickened basement membrane and
partial or total occlusion. The alterations found in
muscle may be secondary to nerve damage, to ischemia
caused by capillary lesion andlor to a direct effect of
mercury on muscle fibre proteins.
Mercury (Hg) is classified as a pollutant of primary importance because of its
high degree of toxicity, persistence and bioaccumulative properties, especially
in the aquatic environment. It is released from natural and anthropogenic
sources, and once in the environment, the inorganic Hg can be converted in to
organic Hg (Methylmercury – MeHg) through bacterial processes.
MeHg tends to bioaccumulate and biomagnify through the food web,
representing a serious risk to human health. Due to the health risks of
excessive Hg exposure, international agencies such as the USEPA (United
States Environmental Protection Agency) have established safety levels
(reference doses (RfD)) of daily exposure, being the Hg concentration present
in human hair used to estimate MeHg exposure. Fish is an important
component of a healthy diet for the human population and the fish consumption
is expected to be relatively stable in the next two decades; however, fish is also
considered a major source of MeHg exposure to human population.
The key question of the present study was evaluating the Hg bioaccumulation
in humans based in fish consumption. Specific tasks were delineated: (i)
evaluatue the human exposure to Hg via fish consumption using a food
Environmental conditions can lead to mercury accumulations in fish that are highly variability among spatially close lakes in Ontario, Canada. Mercury methylation caused by sulfate reduction can influence total mercury concentrations in fish (THgfish). Kahshe and Mountain lakes were chosen to assess temporal trends of THgfish and using paleolimnological tools described the lake environment in terms of total mercury (THgsed), total sulfur (TSsed), chromium-reducible sulfur (CRSsed), and chrysophyte-inferred lake-water pH (CI-pH).
THgfish were standardized by length (LS-THgfish) to identify trends and make comparisons with archived fish from the Royal Ontario Museum. In Kahshe Lake, LS-THgfish for 30-cm smallmouth bass and 40-cm walleye displayed peak concentrations in the early 1980s (0.74 +/- 0.17 µg/g d.w; n=41 and 1.40 +/- 0.42 µg/g d.w; n=16, respectively) with clear declines starting in 1999 (0.33 µg/g d.w +/- 0.13, n=12). At Mountain Lake, LS-THgfish in smallmouth bass (0.31 – 0.45 µg/g) and walleye (0.30 – 0.49 µg/g) were low and stable through the period of observation. Peak concentrations at Kahshe Lake were over 300% higher than the 1926 archival sample (0.22 µg/g d.w, 22.1 cm total length), while the 1948 Mountain Lake sample (0.28 µg/g...
The mercury bioaccumulation and population
dynamics of the mysid Mesopodopsis slabberi was assessed
along a mercury gradient in Ria de Aveiro (Portugal).
M. slabberi is one of the most important mysid species in
European temperate coastal shallow waters playing a key
ecological role. Nevertheless, no references were found
concerning the possible consequences of the Hg on the
trophodynamics of these coastal ecosystems. M. slabberi
showed a clear bioaccumulation along the Hg gradient and
through life, with mature females reaching the highest
concentrations. In terms of population structure, higher
densities and biomasses of M. slabberi were assessed in the
most contaminated areas contrarily to the least polluted
areas. Despite the mercury accumulation in its tissues no
strong negative effects on the structure and population
dynamics of the species were observed. However, mysids
might be important in the transfer of metals from the
sediments and zooplankton to higher trophic levels such as
fishes, most of them with commercial interest.; This work was supported by FCT (Fundac¸a˜o
para a Cieˆncia e Tecnologia) through a project n. FCOMP-01-0124-
FEDER-010598 (MERCOAST, Refa. FCT PTDC/MAR/101906/
2008) and by POPH and QREN—Promotion of scientific job funded
by European social fund and national funds of MEC.
The Goiana River Estuary (7º30'S 34º47'W) is a typical estuary of the semi-arid tropical regions. This estuary shelters a rich fauna of fish, crustaceans and mollusks which play an important role in the life of traditional populations. It is also the main recipient of the effluents from the sugarcane agro-industry and sewage from settlements and villages. Trichiurus lepturus (n = 104), from the Goiana Estuary were examined for total mercury contents during ten months (2005 to 2007) spaning two dry seasons and part of a rainy season. The studied individuals showed weight (W) (204.1±97.9 g) and total length (TL) (63.1±10.1 cm, range 29.5-89.0 cm) with a significant (p<0.05) correlation. Correlation between TL and Hg-T (r = 0.37286) and between W and Hg-T (r = 0.38212) were positive and significant (p<0.05). Two-way ANOVA (n = 81) showed that TL and W had significant difference (p<0.05) among seasons. The Hg-T showed differences in relation to the factor season (p<0.05). The correlation between Hg-T and rainfall showed a negative and significant relation (r = -0.56; p<0.05). Rainfall strongly influenced the bioacumulation of mercury in this species. Dryer months showed relatively higher mercury concentrations than the end of the rainy season. Less rainfall...