Distribution characteristics of total mercury and methylmercury in the topsoil and dust of Xiamen, China

The levels and distribution of mercury （Hg） species, including total mercury （THg） and methylmercury （MeHg） in the topsoil and dust collected from twenty sampling stations located in different land function areas of Xiamen, China, were investigated. The THg concentrations in topsoil ranged from 0.071 to 1.2 mg/kg, and in dust ranged from of 0.034 to 1.4 mg/kg. For stations where the THg of dust was less than 0.31 mg/kg, THg concentrations in the topsoil were significantly correlated to those in the corresponding dust （r = 0.597, n = 16, P = 0.014）. The MeHg concentrations in topsoil were varied between 0.14 and 5.7 μg/kg. The ratios of MeHg/THg in the topsoil ranged from 0.069% to 0.74%. The range of MeHg concentration in the dust were 0.092-2.3 μg/kg. The ratios of MeHg/THg in the dust were at the same level as those in the topsoil. The MeHg concentrations in both topsoil and dust were linked to corresponding THg concentrations and soil organic matter. Neither THg nor MeHg concentration in the topsoil and dust was obviously linked to the land function.

Determination and assessment of total mercury levels in local, frozen and canned fish in Lebanon

Fish is an important constituent of the Lebanese diet.However,very little attention in our area is given to bring awareness regarding the effect of the toxicity of mercury （Hg） mainly through fish consumption.This study aimed to report analytical data on total mercury levels in several fish species for the first time in thirty years and to also made individuals aware of the presence and danger from exposure to mercury through fish consumption.Fish samples were selected from local Lebanese markets and fisheries and included 94 samples of which were fresh,frozen,processed,and canned fish.All values were reported as microgram of mercury per gram of fish based on wet weight.The level of mercury ranged from 0.0190 to 0.5700 μg/g in fresh samples,0.0059 to 0.0665 μg/g in frozen samples,and 0.0305 to 0.1190 μg/g in canned samples.The data clearly showed that higher levels of mercury were detected in local fresh fish as opposed to other types thus placing consumers at higher risk from mercury exposure.Moreover,the data revealed that Mallifa （yellowstripe barracuda/Sphyraena chrysotaenia）,Sargous （white seabream/Diplodus sargus）,Ghobbos （bogue/Boops boops）,and shrimp （Penaeus sp.） were among the types containing the highest amounts of mercury.On the other hand,processed fish such as fish fillet,fish burger,small shrimp and crab are found to contain lower levels of mercury and are associated with lower exposure risks to mercury.Lebanese population should therefore,be aware to consume limited amounts of fresh local fish to minimize exposure to mercury.

Impacts of Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau

Air pollutants can be transported to the pristine regions such as the Tibetan Plateau,by monsoon and stratospheric intrusion.The Tibetan Plateau region has limited local anthropogenic emissions,while this region is influenced strongly by transport of heavy emissions mainly from South Asia.We conducted a comprehensive study on various air pollutants (PM_(2.5),total gaseous mercury,and surface ozone) at Nam Co Station in the inland Tibetan Plateau.Monthly mean PM_(2.5)concentration at Nam Co peaked in April before monsoon season,and decreased during the whole monsoon season (June–September).Monthly mean total gaseous mercury concentrations at Nam Co peaked in July and were in high levels during monsoon season.The Indian summer monsoon acted as a facilitator for transporting gaseous pollutants (total gaseous mercury) but a suppressor for particulate pollutants (PM_(2.5)) during the monsoon season.Different from both PM_(2.5)and total gaseous mercury variabilities,surface ozone concentrations at Nam Co are primarily attributed to stratospheric intrusion of ozone and peaked in May.The effects of the Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau are complex and require further studies.

Mercury levels and estimated total daily intakes for children and adults from an electronic waste recycling area in Taizhou, China: Key role of rice and fish consumption

In order to assess the potential health risks of Hg pollution, total mercury（T–Hg） and methyl mercury（Me Hg） concentrations were determined in air, dust, surface soil, crops, poultry,fish and human hair samples from an electronic waste（e-waste） recycling area in Taizhou,China. High concentrations of T–Hg and Me Hg were found in these multiple matrices, and the mean concentration was 30.7 ng/m3 of T–Hg for atmosphere samples, 3.1 μg/g of T–Hg for soil, 37.6 μg/g of T–Hg for dust, 20.3 ng/g of Me Hg for rice and 178.1 ng/g of Me Hg for fish,suggesting that the e-waste recycling facility was a significant source of Hg. The inorganic Hg（I–Hg） levels（0.84 μg/g） in hair samples of e-waste workers were much higher than that in the reference samples. Pearson＇s correlation coefficients showed that strong positive correlations（p 〈 0.01） between hair I–Hg and time staying in industrial area（r = 0.81） and between Me Hg and fish consumption frequency（r = 0.91）, imply that workers were mainly exposed to Hg vapor through long-time inhalation of contaminated air and dust, while other population mainly exposed to Me Hg through high-frequency fish consumption. The estimated daily intakes of Hg showed that dietary intake was the major Hg exposure source,and Hg intakes from rice and fish were significantly higher than from any other foods. The estimated total daily intakes（TDIs） of Me Hg for both children（696.8 ng/（kg·day）） and adults（381.3 ng/（kg·day）） greatly exceeded the dietary reference dose（Rf D） of 230 ng/（kg·day）,implying greater health risk for humans from Hg exposures around e-waste recycling facilities.

Mercury in an ultraoligotrophic North Patagonian Andean lake (Argentina): Concentration patterns in different components of the water column

The deep, ultraoligotrophic piedmont lakes of Northern Patagonia （Argentina） are located in pristine and barely impacted areas, along a wide latitudinal range. Several studies have reported moderate to high total mercury （Hg） concentrations and contrasting methylmercury （CH3Hg＋） production in different lake compartments. Sources of Hg for western Patagonian terrestrial and aquatic ecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along with contribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial （between lake branches）, and vertical （between water column strata） heterogeneity in the total Hg concentrations found in the pelagic zone of Lake Moreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg＋ in autumn with a decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10–53 μm; which dominated within the euphotic （epilimnetic） zone of the lake due to the high densities attained by two species of the dinoflagellate Gymnodinium. The 53–200 μm planktonic size fraction （comprising rotifers, ciliates and immature stages of crustaceans） and the 200 μm fraction （calanoid copepods and cladocerans） were found to bear strikingly lower total Hg concentrations, suggesting that the magnification of Hg at the planktonic consumer level is negligible.

Trophic transfer of mercury and methylmercury in an aquatic ecosystem impacted by municipal sewage effluents in Beijing, China

Gaobeidian Lake, located in Beijing, China, serves as a recipient lake for efluents from a large municipal sewage treatment plant （MSTP）. In order to evaluate the effects of discharging MSTP efluent on the mercury contamination of the local aquatic ecosystem, sediment cores, water, plankton, fish, and turtle samples were collected from Gaobeidian Lake for mercury speciation analysis. High concentrations of total mercury （T-Hg） were detected in sediment cores （5.24–17.0 μg/g dry weight （dw）, average： 10.1 μg/g）. The ratio of methylmercury （MeHg） to T-Hg was less than 0.3% in sediments and ranged from 35% to 76% in biota samples. The highest level of T-Hg and MeHg were found in aquatic bryophyte and crucian carp （3673 and 437 ng/g dw, respectively）. The relative contents of MeHg were significantly correlated with trophic levels （R2 = 0.5506, p 0.001）, which confirmed that MeHg can be bio-transferred and biomagnified via food chain in this aquatic ecosystem.

Atmospheric mercury over the marine boundary layer observed during the third China Arctic Research Expedition

TGM measurements on board ships have proved to provide valuable complementary information to measurements by a ground based monitoring network.During the third China Arctic Research Expedition （from July 11 to September 24,2008）,TGM concentrations over the marine boundary layer along the cruise path were in-situ measured using an automatic mercury vapor analyzer.Here we firstly reported the results in Japan Sea,North Western Pacific Ocean and Bering Sea,where there are rare reports.The value ranged between 0.30 and 6.02 ng/m 3 with an average of （1.52 ± 0.68） ng/m 3 ,being slightly lower than the background value of Northern Hemisphere （1.7 ng/m 3 ）.Notably TGM showed considerably spatial and temporal variation.Geographically,the average value of TGM in Bering Sea was higher than those observed in Japan Sea and North Western Pacific Ocean.In the north of Japan Sea TGM levels were found to be lower than 0.5 ng/m 3 during forward cruise and displayed obviously diurnal cycle,indicating potential oxidation of gaseous mercury in the atmosphere.The pronounced episode was recorded as well.Enhanced levels of TGM were observed in the coastal regions of southern Japan Sea during backward cruise due primarily to air masses transported from the adjacent mainland reflecting the contribution from anthropogenic sources.When ship returned back and passed through Kamchatka Peninsula TGM increased by the potential contamination from volcano emissions.

Vertical distribution characteristics of soil mercury and its formation mechanism in permafrost regions:A case study of the Qinghai-Tibetan Plateau

Continuing permafrost degradation is increasing the risk of mercury(Hg) exposure in the permafrost regions on the Qinghai-Tibetan Plateau(QTP),but related studies are still limited,especially the ones on the detailed Hg migration processes in permafrost.The vertical distribution characteristics of soil Hg were investigated in three ecosystems in the Beiluhe area on the QTP,and its influencing factors and formation mechanism were investigated.The results indicate that the total soil mercury(THg)concentration in the Beiluhe area remains at an extremely low level(6.33±2.45 ng/g).In the vertical profile,the THg concentration of the shallow soil layer(0-50 cm)(5.96±2.22 ng/g)is significantly lower than that of the deep layer(50-400 cm)(7.44±2.71 ng/g)(p<0.05).Within the upper 50 cm,the THg concentration decreases with soil depth,and the peak THg concentration occurs at 100-300 cm on the entire profile.Although the THg concentration is slightly affected by the organic matter in the shallow soil layer,in general,the soil parent material is the dominant factor affecting the THg concentration.Intense weathering results in a low THg concentration in the shallow soil layer because the soil Hg is carried downward with the soil moisture.To a certain depth,the impermeable frozen soil layer intercepts the flow of the soil Hg,and it forms a Hg enrichment layer.This paper presents the distinctive pattern of the soil Hg distribution in the permafrost regions of the QTP.