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1.
Mercury is emitted from soil and water surfaces, but few actual direct flux measurements have been reported. During June, 1994 we performed the first micrometeorological measurements of Hg vapor fluxes over a boreal forest lake. Using highly precise methods with multiple replicate samplers, we measured concentration gradients of Hg vapor, CO2 and H2O over the lake surface. Mercury was readily emitted from the lake surface, and we found no evidence of Hg dry deposition to the lake. Emission rates over the lake averaged 8.5 ng m2 h?1, and appeared to be weakly influenced by water temperature and solar radiation. These fluxes were somewhat higher than those previously measured using surface chambers at this site.  相似文献   

2.
利用动力学通量箱与高时间分辨率测汞仪联用技术对贵阳市市区及其郊区4个点的土壤大气界面间的汞交换通量进行了测定,用小型多功能气象仪记录了采样期间的气象参数。结果显示:4个采样点的大气汞含量都明显高于全球背景值(1.5~2.0 ng m-3),显示出贵阳市市区及郊区都遭受了不同程度的大气汞污染。土壤大气界面间的汞交换通量与光照强度具有显著的相关关系,与土壤温度也有很好的相关性。  相似文献   

3.
Rencz  A. N.  O'Driscoll  N. J.  Hall  G. E. M.  Peron  T.  Telmer  K.  Burgess  N. M. 《Water, air, and soil pollution》2003,143(1-4):271-288
This study investigates the ranges and spatial variation ofmercury in various media in the wetland ecosystems ofKejimkujik Park, Nova Scotia. Mercury concentrations infive-year-old yellow perch (age based on regression analysesof existing data) ranged from 0.12–0.72 μgg-1(wet weight basis) in 24 lakes. Mercury concentrations inred maple ranged from 5 to 41 ng g-1 and levels inwhite pine ranged from 5 to 58 ng g-1, dry weight.Concentrations of total mercury were found to besignificantly higher in epiphytic lichens (maximum of 660 ngg-1) and in feather mosses (maximum of 395 ng g-1)compared to vascular species. The soil Ah horizon exhibitsthe highest concentrations for both mercury and gold, withmaximum values of 466 and 42.8 ng g-1 respectively;whereas the C-horizon appears to host the most Zn (maximum209.9 μg g-1). Lake water pH and dissolved organic carbon (DOC) were thevariables most highly correlated with mercury in lake watersand yellow perch. No correlations were observed betweenmercury in terrestrial components and mercury in yellowperch; however, mercury in yellow perch was correlated withP in leaf tissues of both red maple and white pine. Theimportance of understanding linkages between terrestrial andaquatic ecosystems is emphasized through this study.  相似文献   

4.
The goal of this study was to investigate net mercury flux associated with seedlings of two species (Populus tremuloides and Pinus ponderosa) grown in three soil exposure concentrations (0.010 ± 0.001, 6.15 ± 0.86, and 25.56 ± 2.10 µg Hg g-1) and to determine if mercury flux from vegetation was directly correlated with mercury concentration in the soil. Net mercury flux was measured using a gas exchange system. Mercury emission from foliage was not influenced by mercury concentration in the soil. Experiments were also done to assess the significance of mercury emission from vegetation relative to that occurring from associated soils. Mean soil mercury emissions were 1 to 3 orders of magnitude higher than that from plants grown in similar soil mercury concentrations. Light and the addition of water were found to significantly increase mercury emission from soils, and the magnitude of the flux response to watering was correlated with soil mercury concentration.  相似文献   

5.
We measured carbon dioxide (CO2) fluxes across air?Cwater interface with floating chambers in Lake Medo (a small, shallow lake in peatland) on the eastern Tibetan Plateau in the warm season of 2009. During the study period, mean CO2 fluxes was 488.63?±?1,036.17?mg?CO2?m?2?h?1. The flux rate was high compared to those of lakes in other regions, and represented a ??hotspot?? of CO2 evasion. Temporal variation of CO2 flux was significant, with the peak value in the beginning and lowest point in the end of warm season. High concentration of dissolved organic carbon (DOC) in lake water (WDOC) was found to highly correlated to CO2 flux (R?=?0.47, P?<?0.01, n?=?54). Besides, fluorescence index of WDOC showed its terrestrial origin character. In accordance with lakes in northern and boreal regions, terrestrial DOC concentration in water column was the most important regulator of CO2 flux from this lake. We suggest that large area of peatlands in catchments support high concentration of DOC in this lake, and consequently high CO2 evasion.  相似文献   

6.
Purpose

Select South Dakota, USA water bodies, including both natural lakes and man-made impoundments, were sampled and analyzed to assess mercury (Hg) dynamics and historical patterns of total Hg deposition.

Materials and methods

Sediment cores were collected from seven South Dakota lakes. Mercury concentrations and flux profiles were determined using lead (210Pb) dating and sedimentation rates.

Results and discussion

Most upper lake sediments contained variable heavy metal concentrations, but became more consistent with depth and age. Five of the seven lakes exhibited Hg accumulation fluxes that peaked between 1920 and 1960, while the remaining two lakes exhibited recent (1995–2009) Hg flux spikes. Historical sediment accumulation rates and Hg flux profiles demonstrate similar peak and stabilized values. Mercury in the sampled South Dakota lakes appears to emanate from watershed transport due to erosion from agricultural land use common to the Northern Great Plains.

Conclusions

For sampled South Dakota lakes, watershed inputs are more significant sources of Hg than atmospheric deposition.

  相似文献   

7.
Fluxes of mercury from a waste repository and from an agricultural field amended with sewage sludge were measured. The measurements were performed by utilising a Relaxed Eddy Accumulation (REA) system synchronously coupled to automated mercury cold vapour atomic fluorescence analysers (CVAFA). The waste repository was severely contaminated and fluxes of between 0.16μg m?2 h?1 and 29μg m?2 h?1 could be measured. Fluxes at the slightly contaminated agricultural field measured between 8 ng m?2 h?1 and 1.9μg m?2 h?1. The results showed that the REA-CVAFA system could be used for measurements above both severely-and slightly contaminated soils. The measurements at the chlor-alkali plant showed that temperature was the most important parameter controlling the release of mercury at this site. At the agricultural field, the measurements indicated that both solar radiation and temperature may have influenced the emissions. Most of the mercury added to the field was lost to the atmosphere during the summer season.  相似文献   

8.
We determined mercury in fish (perch Perca fluviatilis) from 26 Russian lakes in three regions over four years. The lakes ranged in size from 2 to 395,000 ha, in pH from 4.5 to 10.0, and in color from 3 to 190 hazen. Sixteen lakes were drainage lakes, with permanent outlets, and 10 were seepage lakes, with no permanent inlets or outlets. The lakes were generally located in forested regions with little or no human habitation in the watershed. The three regions were geologically distinct: Precambrian Shield granitic bedrock covered with thin soil; Triassic bedrock covered with thick glacial tills; and Triassic bedrock covered with thin sediments. At each lake water samples were collected and analyzed for pH, add neutralizing capacity (ANC), major cations, and anions. Dissolved mercury species were estimated with a thermodynamic equilibrium model (MINTEQA2). Mercury content of dorsal muscle varied from 0.04 to 1.0 g/g wet weight, and was linearly related to calculated HgCH3Cl (r20.68, p<0.001). lake=">3Cl, in turn, was related to lake pH (r2=0.86, p<0.001). stepwise=" multiple=" regression=" selected=" lake=">3Cl and color as the factors most highly related to fish mercury content, with the model accounting for 75% of the variation.  相似文献   

9.
Distribution and sources of total mercury were evaluated in sixty lakes in Nova Scotia and Newfoundland. The concentration of total mercury in the lake water samples was similar to those observed in other natural water systems. Mercury concentration in the lakes correlated positively with aluminum, total organic carbon, color, iron, and total nitrogens and inversely with pH and sulfate. The lake water quality parameters were placed in three distinct groups using principal component and cluster analyses. The chemical constituents in the groups were identified as being associated with lake watershed geology, atmospheric washouts of long range transported acidic pollutants and dust particles, and a marine source. Stepwise multiple regression applied to the variables in the same principal component and strongly correlating with mercury identified total organic carbon, total nitrogen, pH, aluminum and iron as the best predictors for total mercury concentrations in the study lakes.  相似文献   

10.
Results from surveys of low-ANC lakes (high elevation, and seepage lakes), and of surface waters in dystrophic, acidic bogs, indicate that acidic precipitation and organic acidity are each generally necessary, but not solely sufficient, for chronically acidic status in Maine lakes. Acidic, low DOC (ANC < 0; DOC < 5 mg L-1) lakes of all hydrologic types are acidic due largely to acidic deposition; high DOC (DOC > 30 mg L-1) acidic seepage lakes are acidic due largely to organic acidity, and high DOC drainage lakes are acidic due to a combination of both factors. No low DOC drainage lakes are known with pH less than about 5.0, suggesting that organic acidity is necessary to depress lake pH values to below 5 in Maine at current deposition loadings,The dominant anion of low DOC, acidic waters is sulfate. Acidic waters with intermediate concentrations of DOC (5 to 30 mg L-1), may be dominated by S04 and/or organic acidity. Seepage-input lakes were the only group to include both organically-dominated (37% of the acidic lakes) and S04-dominated members (63% of the acidic lakes). High DOC systems are typically low pH bogs, and are all organic acid-dominated.  相似文献   

11.
Yearling yellow perch were collected from sixteen Muskoka-Haliburton lakes to determine interrelationships between water quality, Hg residues in fish and fish condition. The lakes studied were Precambrian shield lakes with a pH range of 5.6 to 7.3 and total inflection point alkalinities of 0.4 to 16.0 mg L?1. Mercury residues in yellow perch ranged from 31 to 233 ng g?1 and were inversely correlated (p < 0.001; r = 0.84) with lakewater pH. Stepwise linear regression analyses selected lakewater pH as the only significant parameter associated with Hg accumulations. Alkalinities, sulphate, Ca and dissolved organic carbon (DOC) were not selected as significant. Likewise, lakewater pH and Hg residues in yellow perch were inversely (p < 0.001) correlated with fish condition. Lakewater pH, accounted for 74% and Hg in fish a further 11% of the variability in fish condition. Terrestrial drainage size/lake volume ratios were also correlated (p < 0.05; r = 0.78) with Hg accumulations in perch from a subset of nine headwater lakes. No temporal trends in Hg residues were evident in yellow perch over a 9 yr interval (1978–1987).  相似文献   

12.
Red soils, one of the typical agricultural soils in subtropical China, play important roles in the global carbon budget due to their large potential to sequester C and replenish atmospheric C through soil CO2 flux. Soil CO2 emission was measured using a closed chamber method to quantify year-round soil flux and to determine the contribution of soil temperature, dissolved organic carbon (DOC) and soil moisture content to soil CO2 flux. Soil flux was determined every 10 d during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil (the Chinese Academy of Sciences). In addition, diurnal flux measurements for 24 hr were made on August 5 and November 5, 1999 during this experiment. The average soil fluxes from 2 hr measurements between 9:00 and 11:00 can be regarded as the representative of daily averages. Soil CO2 fluxes were generally higher in summer and autumn than in winter and spring, averaged 7.16 and 0.86 g CO2 m-2 d-1 for the former and latter two seasons, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The annual soil CO2 flux was estimated as 1.65 kg CO2 m-2 yr-1. Regressed separately, the reasons for soil flux variability were 86.6% from soil temperature, 58.8% from DOC, and 26.3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained 85.2% of the flux variance, but only soil temperature was the dominant factor affectingsoil flux, with significant partial correlation coefficient (r2 = 0.804, p ≤ 0.05), through stepwise regression analysis. Based on the exponential equation using soil temperature, the predicted fluxes were calculated and were essentially equal to the measured ones throughout the experiment. No significant difference was detected between the predicted average and the measured one. The exponential relationship describing the response of soil CO2 flux to the changes in soil temperature should accurately predict soil CO2 flux from red soils in subtropical China.  相似文献   

13.
Soil respiration and methane flux from adjacent forest, grassland, and cornfield were measured by using the closed chamber method from June to November, 1999 in Shizunai, Hokkaido, Japan, where the soil was an Aquic Humic Udivitrands derived from volcanic ash. The forest soil absorbed methane, at arate ranging from -0.12 to -0.02 mg C m-2 h-1, while the grassland soil emitted methane, at a rate ranging from undetectable levels to 0.18 mg C m-2 h-1. In the cornfield soil methane flux ranged from -0.01 to 0.04 mg C m-2 h-1. The soil respiration rate varied from 3 to 230 mg C m-2 h-1, 27 to 372 mg C m-2 h-1, and 29 to 156 mg C m-2 h-1 for the cornfield, grassland, and forest soils, respectively. Linear regression analysis demonstrated that the methane flux rate was positively correlated with the soil water-filled pore space (WFPS), and negatively correlated with the relative gas diffusion coefficient (D/D o) and air-filled pore space (AFPS). Soil respiration rates were positively correlated with the soil temperature at all the sites. The Q 10 value was 4.8, 3.3, and 1.9 for the cornfield, grassland, and forest soils, respectively.  相似文献   

14.
Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the O f(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the O f(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter.  相似文献   

15.
Lake Velenje is located in one of the most polluted regions ofSlovenia, the ?alek Valley. The major source of pollution is the coal-fired thermal power plant in ?o?tanj (?TPP). In the past, dumping of coal ash directly into Lake Velenje and drainage water from the ash disposal site resulted in unique chemical characteristics of the lake water, such as very high pH (10–12) and high concentrations of heavy metals. The introduction of a closed cycle ash transport system in 1995resulted in a very fast recovery of the lake water quality. The aim of our study was to establish the sources, fate and distribution of mercury in Lake Velenje. In order to establishrecent sources of mercury, total mercury and methylmercury concentrations were measured in various environmental samples(lake inflows, outflow, rainwater, sediments, etc.). Total mercury and methylmercury concentrations were measured at thesurface and at different depths to establish mercury cycling, its transport and chemical transformations in the lake. Generalwater quality parameters (such as pH, Eh, O2, temperature,TDS, conductivity) were also determined. The results show that the major sources of mercury in Lake Velenje are lake inflows and wet deposition. Total mercury andmethylmercury concentrations in the water column are very low (total mercury: 0.2–2.7 ng L-1; methylmercury: 20–86 pg L-1) and can be compared to other non-contaminated freshwater lakes. These results suggest that the major form of mercury emitted from thermal power plant stacks is volatile Hg0, whichhas no or very little influence on the nearby surroundings, but rather is subject to long-range atmospheric transport.  相似文献   

16.
A number of recent studies have documented elevated concentrations of mercury (Hg) in fish caught in remote lakes and a pattern of increased concentrations of Hg in fish tissue with decreasing water column pH. Because of the potential linkage between fish Hg and surface water acidification, factors regulating water column concentrations and bioavailability of Hg were investigated in Adirondack lakes through a field study and application of the Mercury Cycling Model (MCM). Concentrations of total Hg and total MeHg were highly variable, with concentrations of total MeHg about 10% of total Hg in lakes which did not show anoxic conditions. In lakes exhibiting anoxic conditions in the hypolimnion during summer stratification, concentrations of total MeHg were elevated. Concentrations of total Hg and total MeHg increased with decreasing pH in remote Adirondack lakes. However, more importantly, concentrations of total Hg and total MeHg increased with increasing concentrations of dissolved organic carbon (DOC) and percent near-shore wetlands in the drainage basin. Mercury concentrations in muscle tissue of yellow perch from Adirondack lakes were elevated above the U.S. FDA action level (1 μg/g Hg) in 7% of the fish sampled or in one or more individual fish from 9 of the 16 lakes sampled. Fish Hg concentrations generally increased with increasing fish length, weight and age. Patterns of increasing Hg concentration with age likely reflect shifts in prey of yellow perch and the bioconcentration of Hg along the food chain. For age 3 to 5 perch, concentrations of Hg increased with increasing concentrations of DOC and percent near-shore wetlands in the drainage basin. However, for a lake with very high DOC concentrations, fish concentrations of Hg declined. Calculations with the MCM also show that concentrations of Hg species increase with increasing DOC due to complexation reactions. Increases in DOC result in increasing concentrations of Hg in biota but decreases in the bioconcentration factor of Hg in fish tissue. This research suggests that DOC is important in the transport of Hg to lake systems. High concentrations of DOC may complex MeHg, diminishing its bioavailability. At high concentrations of monomeric Al, the complexation of MeHg with DOC apparently decreases, enhancing the bioavailability of MeHg.  相似文献   

17.
自然源汞释放对全球大气汞的贡献和循环具有重要影响,地表过程释汞是大气汞重要的自然源,土壤空气汞浓度与大气汞浓度差决定着土壤/大气汞的交换通量。基于目前测定土壤空气中汞浓度的缺点,建立了一种新的测定土壤空气汞浓度的方法。本研究在南京六合循环农业生态区采集了水稻土壤剖面空气,并对样品总汞浓度进行了分析。利用本实验装置,真空泵在低流量下连续抽取土壤剖面空气并预富集于金管上,并结合冷原子荧光法(CVAFS)测定。实验结果显示方法检出限为0.023 ng m-3,水稻土壤空气汞浓度变化范围在6.0~18.9 ng m-3。平行实验装置在同时测定实验室大气和农田土壤空气汞浓度时,相对标准偏差(RSD)均小于15%,同时对比实验证明没有采集土壤表层大气。实验装置简单,野外操作方便,能准确和精确的测定水分不饱和土壤空气中汞浓度。  相似文献   

18.
The atmospheric emission of mercury (Hg) from a contaminatedwetlands system was studied in the floodplains along the riverElbe (Northern Germany). Results suggest that wetlands can beimportant transformation and phase transfer regions, linking theterrestrial, aquatic and atmospheric compartments of regionalbiogeochemical Hg cycles. Fluxes determined by flux chambermeasurements averaged 43 ± 5 ng m-2 h-1. Additionally,soil gas probe sampling was introduced to determine mercuryconcentrations in soil air. This technique shows some promise fordetecting and confining mercury contamination in soils. We alsopropose that measurements of total gaseous mercury (TGM) in soilair and the near-surface atmosphere, in combination with simplesoil physical parameters, may be suitable for calculatingsemiquantitative estimates of Hg evaporation from contaminatedsoils, based on laminar diffusion considerations. The results arecompared to other Hg flux measurements, and the advantages anddisadvantages of different approaches to quantify Hg emissionsfrom soils are discussed, especially with regard to possiblesystematic bias.  相似文献   

19.
To date there have only been a few studies that measured mercury emissions from background substrate worldwide, and only a small amount of mercury flux data, from background substrate, exists for the Western United States. Because of this, the database of mercury emissions from background units < 0.1 mg kg-1 mercury) is incomplete. This study focused on the collection of in-situ mercury flux data from representative lithologic units in Nevada. Measured mercury fluxes from substrate with background mercury concentration throughout Nevada were low (mean 2.0 ± 4.1 ng m-2 hr-1), and ranged from –3.7 to 9.3 ng m-2 hr-1. The mean measured mercury flux is slightly higher than those measured from background substrate from various locations throughout the world. The mean mercury flux from in-situ mercury measurements from substrate located near altered geologic units across Nevada was 15.5 ± 24.2 ng m-2 hr-1. These mercury fluxes are higher than the values applied in published global models for naturally enriched geologic units.  相似文献   

20.
The processes affecting the concentrations of total mercury (total Hg) and methylmercury (MeHg) in a freshwater system comprising two connected reservoirs in southwest Tasmania were investigated. Surface concentrations of total mercury (total Hg)were temporally and spatially uniform in both Lake Gordon (2.3±0.4 ng L-1, n = 27) and Lake Pedder (2.3±0.3 ng L-1, n = 11). The surface concentrations of MeHg in Lake Gordon (0.35±0.39 ng L-1, n = 25) were more variable than total Hg and MeHg typically comprised 10–20% of total Hg. The relatively high amount of total mercury present as MeHg in Lake Gordon was attributed to the high proportion of wetlandsin the upper catchment (50% of total area) and in-lake contributions (ca. 40% of total MeHg). Despite the close proximity of the two lakes, MeHg concentrations in Lake Pedder were consistently lower than in Lake Gordon. This phenomenon canbe explained in part by the greater contribution of direct rainfall to Lake Pedder leading to the dilution of MeHg. Water column MeHg concentrations were higher in warmer months in bothlakes, reflecting increased net methylation of inorganic mercury.Unlike previous studies of seasonally anoxic lakes, depth profiles of total mercury and MeHg in Lake Gordon were uniform and were not affected by water column stratification occurringin the summer months, and oxygen depletion with depth. This suggests that redox cycling and accumulation of MeHg in the hypolimnion following seasonally-induced anoxia is not a significant part of the mercury cycle in Lake Gordon. The primary location of MeHg production within the lake's water column is not conspicuous. Mercury speciation measurements made above and below the lake system over a period of 19 months indicates that after 20 yr of impoundment, the reservoirs are not significantly affecting MeHg concentrations in the downstreamriverine environment.  相似文献   

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