Hg Concentration Range Research Articles

Assessment of mercury and selenium concentrations in captive bottlenose dolphin's (Tursiops truncatus) diet fish, blood, and tissue

Concentrations of total mercury (Hg) and selenium (Se) were determined in diet fish and whole blood and tissue samples from seven bottlenose dolphins (Tursiops truncatus) housed at the National Aquarium Baltimore (NAB). In addition, concentrations of monomethylmercury (CH3Hg+) were determined in diet fish and dolphins' tissue samples. The data were compared with the values found in wild populations to better understand how the dietary Hg and Se uptake rates affect the Hg and Se levels in dolphins. The diet fish total Hg concentrations ranged between 14 and 47ngg−1 and were markedly lower than for similar fish found in Florida, South Carolina, and other aquaria. CH3Hg+ accounted for 85 to 91% of the total Hg found in diet fish. The diet fish Se concentrations ranged between 270 and 800ngg−1, indicating excess molar concentrations of Se over Hg. The Hg concentration range in the blood of NAB dolphins was 27–117ngg−1 and the concentrations were about one order of magnitude and several factors lower than the concentrations found in the blood of wild bottlenose dolphins in Florida and in South Carolina, respectively. The total Hg and CH3Hg+ in tissue samples were also significantly lower than the reported values obtained from wild populations of bottlenose dolphins. The differences in the Hg concentrations in the dolphins' blood may be due to the different levels of Hg atmospheric deposition in the area where the dolphins' diet fish were found. The Se concentration range in the blood of NAB dolphins was 221–297ngg−1 which was two factors lower than the values found in wild populations. The lower Hg levels, as well as higher Se:Hg molar ratios in the blood of NAB dolphins, suggest that NAB dolphins may be less susceptible to the potential neurotoxicity from the CH3Hg+ in their blood.

Mercury contamination and accumulation in sediments of the East China Sea

Mercury (Hg) concentrations in sediment samples collected from the inner and middle shelves of the East China Sea (ECS) were analyzed to evaluate Hg contamination levels and to calculate Hg sedimentation rates and total accumulation in the ECS. The range of Hg concentrations in surface sediments of the inner shelf was 26.5-47.6 ng/g, and that for the middle shelf was 4.1-13.9 ng/g. Hg concentrations correlated well with organic carbon contents but varied inversely with sediment grain size. Enrichment factors indicated that the whole inner shelf and a small portion of the middle shelf were slightly contaminated by Hg. Hg accumulation rates in the ECS ranged between 0.42-48.7 ng/(cm 2·yr), with higher values observed in the inner shelf. Total Hg accumulation in the calculated area (accounting for 80% of the ECS continental shelf area) ranged from 25 to 30 tons/yr; approximately 51% and 17% of the accumulated Hg mass was deposited in the Yangtze estuarine zone and the inner shelf, respectively.

Influence of mercury on chlorophyll content in winter wheat and mercury bioaccumulation

Mercury (Hg) is one of the major pollutants in soils because of the annual import of toxic Hg into the agricultural lands. The aims of the present studies are to investigate the effect of Hg on chlorophyll content in winter wheat var. jinan No. 17. Moreover, calcium (Ca) levels and bioaccumulation of Hg in wheat leaves were studied with the technique of inductively coupled plasma sector field mass spectrometer (ICP-SF-MS). The study conducted a range of Hg concentrations from 0~500 mg Hg/kg in the dry weight soil. The soil was artificially contaminated with Hg as follows: 0, 100, 200, and 500 mg Hg/kg as HgCl<SUB>2</SUB>. At early stages of the wheat growth, both low and high concentration of Hg stimulates chlorophyll content, but inhibits chlorophyll content at later stages of the wheat growth. Furthermore, the concentrations of Ca and Hg in wheat leaves increased with the increasing concentration of Hg<SUP> </SUP>on the thirty-fourth day with the technique of ICP-SF-MS. The results indicate that Hg can accelerate the absorption of Ca in winter wheat and Hg stress may affect Ca levels in wheat leaves.

Background wet deposition of mercury in Great Britain

Precipitation samples have been collected on a monthly basis from a network of 10 sites in Great Britain (GB) in order to estimate background mercury (Hg) deposition in the rural environment. Collection started in February 2005 and results presented here cover the period up to June 2009. The annual volume-weighted mean (AVWM) Hg concentrations range from 1.0 ng L(-1) at Cockley Beck in the Lake District in 2006 to 8.8 ng L(-1) at Heigham Holmes on the Norfolk Coast England in 2008. The largest validated solution concentrations were 33.7 ng L(-1) Hg measured at Cockley Beck in May 2008. The large difference in rainfall amount between sites means that the remote site at Cockley Beck has both the lowest long-term AVWM concentration (1.6 ng L(-1)) and the greatest annual flux is greatest at 43 mg ha(-1) yr(-1). Predicted deposition tends to be much greater in western Britain where the greater rainfall occurs. Because some observations are very close to the analytical detection limit (1.0 ng L(-1)), rigorous cleaning procedures, the use of replicate samplers to monitor contamination, and the inclusion of 'bottle blanks' are required to obtain valid measurements of Hg in the bulk deposition. Deposition in rural sites is equivalent to about 10% of the estimated magnitude of known emissions in GB.

Wetland influences on mercury transport and bioaccumulation in South Carolina

There are three distinct geological provinces in South Carolina (SC), with the blue ridge/piedmont regions in the west/central portion of the state and the coastal plain region in the central/eastern region of the state. Samples were collected along this gradient to identify potential factors contributing to the concentrations of total Hg and total organic carbon (TOC) throughout the state. Overall, there is a gradient across the state, with water column concentrations of total Hg (9–53 pM) and TOC (80–2721 μM) increasing as one moves from the blue ridge/piedmont region to the coastal floodplain region. Total Hg at all sites in SC is significantly ( R 2 = 0.78; P < 0.001) correlated with TOC in the water samples. This correlation explains 78% of the variance in the data and suggests that mercury is associated with organic matter in water bodies throughout the state. A study of mercury speciation within the coastal plain Waccamaw River indicates that concentrations of total Hg range from 10–68 pM and methyl Hg concentrations range from 1–7 pM. Watershed transport efficiencies for coastal floodplain rivers sampled in this study range from 32–72% for total Hg and 78–477% for methyl Hg. The coastal plain sites are located in watersheds that contain a significantly ( P < 0.001) higher percentage of wetlands (16.3 ± 5%) than the blue ridge/piedmont region (1.14 ± 1.6%), suggesting that drainage through wetlands contributes to the increased concentrations of TOC and total Hg found in SC coastal plain rivers. There is a significant correlation between mean fish Hg concentrations in largemouth bass from each watershed and percent wetland area in each watershed ( R 2 = 0.66; P = 0.003). This correlation explains 66% of the variance in the data and suggests that increasing percentages of wetland area contribute to fish Hg concentrations in SC coastal plain rivers.

Anthropogenic impact of mercury accumulation in fish from the Rio Madeira and Rio Negro rivers (Amazonia)

Fish is an important concentrator of mono-methyl mercury and the main route to human contamination. We compared fish Hg bioaccumulation (within similar weight ranges) in two Amazonian river habitats during high-water seasons. The Rio Madeira has been greatly impacted by agriculture, alluvial gold extraction, and a hydroelectric reservoir, whereas the Rio Negro is much less affected by these human activities. The species at the top of the food web, Hoplias malabaricus (piscivorous; 80-668 ng Hg/g) and Cichla spp. (piscivorous; 42-747 ng Hg/g) showed the highest range of Hg concentrations. Nonpiscivorous species with comparable weight range, such as Potamorhina latior (detritivorous; 20-157 ng Hg/g) and Myleus torquatus (herbivorous; 2-182 ng Hg/g), had lower Hg concentrations. Triportheus elongatus (omnivorous; 5-350 ng Hg/g), with the lowest weight range, also showed a low range of Hg concentrations. Despite the Rio Madeira's higher sediment load as well as environmental impacts (deforestation, agriculture, hydroelectric reservoir, and alluvial gold mining) on natural Hg release, fish Hg bioaccumulation was no different between the two river habitats for nonpiscivorous species. In this small observational study only the species at the top of the food web (M. torquatus, Cichla spp, T. elongatus) showed higher mean Hg concentrations in the Rio Madeira than the dominantly wilderness habitat of the Rio Negro.

Analysis of Mercury in Sequential Micrometer Segments of Single Hair Strands of Fish-Eaters

Although it has been established that mercury (Hg) can be detected in single hair strands using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), calibration remains a challenge due to the lack of well-characterized matrix-matched standards. We concurrently evaluated two strategies for quantifying Hg signals in single hair strands using LA-ICP-MS. The main objective was to obtain time-resolved Hg concentrations in single hair strands of fish-eaters that would correspond to the changes of their body burden over time. Experiments were conducted using hair samples collected from 10 individuals. The first experiment involved the construction of a calibration curve with four powdered hair standard reference materials (SRMs) with a range of Hg concentrations (0.573-23.2 mg/kg). An internal standard, sulfur, as 34S, was applied to correct for ablation efficiency for both the hair strands and the SRMs. Results showed a linear relationship (R2 = 0.899) between the ratio of 202Hg to 34S obtained by LA-ICP-MS and the certified total Hg concentration in the SRMs. Using this calibration curve, average Hg concentrations of 10 shots within a 1-cm segment of a hair strand were calculated and then compared to the total Hg concentrations in the matched 1-cm segment as measured by cold vapor atomic absorption spectrometry (CV-AAS). A significant difference (p < 0.05) was observed. The difference could be attributed to the highly variable ablation/sampling process caused by the use of the laser on the hair powder SRM pellets and the difference in the physical properties of the SRMs. An alternative approach was adopted to quantify consecutive 202Hg to 34S ratios by calibrating the signals against the average Hg concentration of the matched hair segment as measured by CV-AAS. Consecutive daily Hg deposition in single hairs of fish eaters was determined. Results showed that apparent daily changes in Hg concentrations within a hair segment that corresponds to 1 month of hair growth. In addition, a significant decreasing or increasing time-trend was observed. The difference between the minimum and maximum Hg concentration within each individual corresponded to a change of 26-40%. Our results showed that LA-ICP-MS can be used to reconstruct time-resolved Hg exposure in micrometer segments of a single hair strand.

Field tests for a regional mercury deposition network—sampling design and preliminary test results

A number of actions have been undertaken within the National Atmospheric Deposition Program (NADP) to implement a regional mercury deposition network. This paper describes a field test designed to evaluate a collector design and protocol for implementation within a new Hg network. The collector chosen for evaluation is a “dual-orifice” collector, designed to sample precipitation for mercury and other metals simultaneously. The method chosen for Hg analysis was cold vapour atomic fluorescence spectroscopy (CVAFS). The weekly precipitation Hg concentrations range between 4.29 and 17.88 ng ℓ −1, with a volume-weighted mean of 10 ng ℓ −1 comparable to those reported in other ongoing studies in North America and Europe. Calculated deposition flux ranges from 43 to 358 ng m −2 week −1, with a mean of 186 ng m −2 week −1.

Determination of total mercury in scalp hair of humans by gold amalgamation cold vapour atomic absorption spectrometry

Cold vapour atomic absorption spectrometry (CVAAS) with a laboratory-built system using a Au–Pt grid for mercury amalgamation, was applied in the determination of total mercury (Hg-T) in human scalp hair. Two sample dissolution procedures by HNO3 digestion were tested and compared: in a poly(tetrafluoroethylene)(PTFE) bomb for 1.5 h at 110 °C (procedure 1), and in sealed Pyrex ampoules for 24 h at 50 ± 10 °C (procedure 2). After optimization of the aeration gas flow rate (100 ml min–1), de-amalgamation temperature(700 °C) and releasing time (19 s), the analytical methodology was characterized and validated. The linear working range extended from 0.5 to 12.5ng, and the characteristic mass was 0.29 ng of Hg (mass of analyte giving an absorbance of 0.0044). The repeatibility of measurements (within-day variation), expressed as percent relative standard deviation (RSD%) was 5.5% at 1.25 ng of Hg (n=8) and 3.7% at 12.5 ng (n=14), and the mean reproducibility (between-day variation), estimated from calibration curves on different days, was 6.4 ± 1.1%(n=5). The absolute detection limit (3 ×σb) was 0.13 ng of Hg and the limit of quantitation (10 ×σb) was 0.43 ng of Hg (≈ 0.11 mg kg–1 in hair). Analytical precision (8.4 ± 4.0% RSD) and accuracy (4.7 ± 2.5% mean relative error) were satisfactory for ppm and sub-ppm levels of Hg-T in several biological and environmental certified and standard reference materials (CRMs and SRMs) including hair. Procedure 2 was selected as it is much simpler, requires inexpensive reagents and is more amenable for routine application. Mean recovery of Hg-T in hair spiked with Hg standard solutions was 105% in the range 0.83–1.27 mg kg–1. In addition, two human head hair samples were assayed as prospective laboratory control materials. Thus, sub-sample homogeneity, analytical intra-laboratory variability and external quality control were assessed to confirm the methodology in use. Between-day variation in hair analysis for Hg-T conducted on pooled scalp hair over a period of 5 months was 4.8% RSD (1.10 ± 0.053 mg kg–1 for the 95% confidence interval; n=16). Instrumental neutron activation analysis used as an independent method, showed significant correlation in results with CVAAS, both in several biological and environmental SRMs and CRMs and in human hair samples of pregnant and nursing women (Hg concentration range =0.1–6.9 mg kg–1; n=21; r2=0.880, p < 0.0001).

Fluxes, pools, and turnover of mercury in Swedish forest lakes

In boreal forest lakes, high Hg concentrations in fish are common, even in remote areas. Data from recent Swedish surveys were synthesized to assess sources, sinks, fluxes and turnover rates of Hg in headwater lakes of different type, to determine and quantify controlling factors and their relative influence, and to discuss implications for the contamination of fish and potential remedial actions. In humic lakes, annual input of Hg is dominated by the transport from forest soils, whereas in clearwater lakes, direct deposition on the lake surface is often more important. Direct deposition is more likely to dominate during the growing season when the water discharge in forest streams is low. Sedimentation of Hg is largely controlled by the water residence time and is related to water quality. In clearwater lakes, most of the Hg load is deposited in the sediment, which is in contrast to humic lakes, and which partly explains the susceptibility of headwater lakes to atmospheric Hg pollution. The fish community contains about half or more of the methylmercury pool in the water column, and internal recycling in the food web may be important. However, only a minor fraction of the total annual Hg load to lakes is channeled through the fish community. As this allows large variations in the ecological fractionation and bioavailability of Hg, differences in Hg fluxes can only partly explain the wide range of Hg concentrations found in fish from different lakes. The annual Hg load to headwater lakes exceeds the total Hg pool in the water column by a factor of up to 20. Single remedial measures aiming at the removal of Hg from the water column are therefore likely to have little success. Local actions should aim primarily at reducing the bioavailability of the Hg entering the lakes and need to be repeated continuously.

Soil mercury study of thermal areas, Rincón de la Vieja Volcano, Costa Rica

Numerous thermal areas are found on the southwest flank of the active volcano Rincón de la Vieja, Costa Rica. These are part of a larger band of thermal areas that parallels the volcanic front for about 25 km. A total of 318 soil Hg samples were collected on the southwest flank of the volcano, predominantly at the Las Pailas hot springs. Soil Hg concentrations range from 6 to 180,000 ppb and can be divided into three populations with threshold values of 47 and 190 ppb. Aureole Hg values are widely distributed; anomalous soil Hg concentrations were found at four locations. Two-dimensional Fourier analysis of smoothed Hg values from the Las Pailas thermal area reveals a N70W trending lineament of high Hg concentration. This lineament is thought to indicate the presence of a fault along which upwelling of geothermal fluids is enhanced. The orientationof this fault coincides with the orientation of volcano alignments and structural features identified elsewhere in the region.

Uptake of mercury by exhausted coffee grounds

Abstract In view of using low cost material for the removal of mercury from wastewaters, Exhausted Coffee Grounds (ECG), appropriately pretreated with NaOH 0.5 M, have been tested as a possible scavenger from 10 mgl‐1 Hg solutions characterized by ionic strength 0.1 M NaNO3 or 0,1 M NaCl, in the range of pH 3–11. The Hg uptake can be expressed in terms of a Lang‐muir relationship over the Hg concentration range 0.05–50 mgl‐1 in both pH value 3 and 11, respectively, the evaluated capacity being of the order of 80 mg/g, which is 10 times higher than that of the activated carbon. Sorption occurred also in presence of chlorides provided that the pH was adjusted to the range 10–11. Results of experiments performed on columns containing 2 g of ECG, while confirming the order of magnitude of the capacity value evaluated with batch experiments, showed an efficiency of Hg removal of about 99.9% for solutions at pH=3 and 99% for solutions at pH 11 after treatment of 540 and 160 bedvolumes, respectively. A recovery of 70% of mercury uptaken at pH 11 was possible by elution with 16 bed volumes of HC1 1 M; the same volume of HC1 1 M allows 85% of the mercury sorbed at pH=3 to be recovered.