首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m2. The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m2/yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m3 with highest concentrations during the winter months.  相似文献   

2.
Ambient concentrations and dry deposition fluxes of Hg in the gas and particle phase to Lakes St. Clair, Erie and Huron were estimated with a hybrid receptor-deposition model (HRD). The ambient gas and particulate phase Hg concentrations were predicted to vary by a factor of 12 to 18 during the transport of air masses traversing the lakes. The ensemble average deposition fluxes of fine particle Hg ranged from 7 pg/m2-h to 15.3 pg/m2-h over Lake St. Clair, 0.5 to 4.2 pg/m2-h over Lake Huron and 5.1 to 20.6 pg/m2-h over Lake Erie. The deposition flux of coarse particle Hg was in the range of 50 to 84 pg/m2-h over Lake St. Clair, 4.7 to 24.2 pg/m2-h over Lake Huron and 5.1 to 20.6 pg/m2-h over Lake Erie. Gaseous Hg volatilized at a rate of 0.21 to 0.52 ng/m2-h from Lake Huron and 0.13 to 0.36 from Lake Erie. Gas phase Hg was deposited at a rate of 5.9 ng/m2-h and/or volatilized at a rate of 0.5 ng/m2-h from Lake St. Clair depending upon the location of the sampling site used in the HRD model. The effect of meteorological conditions, particle size distributions and type and location of the sampling sites played an important role in the transfer of atmospheric Hg to and/or from the lakes.  相似文献   

3.
To assess the sources, transport and deposition of atmospheric mercury (Hg) in Michigan, a multi-site network was implemented in which Hg concentrations in event precipitation and ambient samples (vapor and participate phases) were determined. Results from the analysis of 2 years of event precipitation samples for Hg are reported here. The volume-weighted average Hg concentration in precipitation was 7.9, 10.8 and 10.2 ng/L for the Pellston, South Haven and Dexter sites, respectively. Yearly wet deposition of Hg for 1992–93 and 1993–94 was 5.8 and 5.5 μg/m2 at Pellston, 9.5 and 12.7 μg/m2 at South Haven and 8.7 and 9.1 μg/m at Dexter. A spatial gradient in both the Hg concentration and wet deposition was observed. Northern Michigan received almost half the deposition of Hg recorded at the southern Michigan sites. The concentration of Hg in precipitation exhibited a strong seasonal behavior with low values of 1.0 to 2.0 ng/L in winter and maximum values greater than 40 ng/L in summer. The spring, summer and autumn precipitation accounted for 89 to 91% of the total yearly Hg deposition. Mixed-layer back trajectories were calculated for each precipitation event to investigate the meteorological history and transport from potential Hg source regions. Elevated Hg concentrations were observed with air mass transport from the west, southwest, south, and southeast. At each of the sites precipitation events for which the Hg concentration was in the 90th and 10th percentile were-analyzed for trace elements by ICP-MS to investigate source impacts.  相似文献   

4.
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   

5.
Measurements of Total Gaseous Mercury (TGM) in the atmosphere are being conducted as part of the Florida Atmospheric Mercury Study (FAMS). FAMS is a multi-year study focusing on the atmospheric transport and deposition of Hg and other trace metals at several locations in central and south Florida. A major component of this study, which this paper addresses, involves determining regional TGM concentrations and seasonal variability patterns at the various collection sites. Occasional problems were encountered in the collection efficiency of TGM on Au. The reason for this interference was not identified, but it was dramatically reduced by heating the collection columns to 80 °C. Atmospheric Hg samples are currently being collected using Au-coated silica sand traps from atop 48 ft. aluminum sampling towers using an unattended and automated sampling and data recording system. We currently have approximately a two year record of TGM, beginning in the summer of 1992, for the Lake Barco Site, located in central Florida approximately 30 miles east of Gainesville, FL. The records at the south Florida sites are shorter, ranging from one month at Andytown to 16 months at both Fort Myers and Fakahatchee Strand. Average TGM concentrations (ng/m3) for 3 to 6 day integrated samples at the various sites are: Lake Barco, 1.59±0.58 (n=78); Fort Myers, 1.59±0.40 (n=42), Fakahatchee Strand, 1.42±0.41 (n=30); Tamiami Trail 1.46±0.80 (n=27); Everglades National Park 3.11±1.52 (n=13); and Andy Town, 1.78±0.62 (n=3). The mean Hg concentration for all the sites is 1.64±0.76 ng/m3 (n=191).  相似文献   

6.
Samples for measurements of total gaseous mercury (Hg) in air have been collected since 1980 in south-western part of Scandinavia. A collection program for precipitation samples used to determine changes in depositional fluxes of total Hg has been in operation since 1987. A comparison of today's total gaseous Hg levels in air and the total Hg concentrations in precipitation with the ones found earlier, shows a clear decrease with time. At the Swedish west-coast, yearly average air concentrations and median levels of 3.3 and 3.1 (1980–1984), 3.2 and 2.8 (1985–1989), and 2.7 and 2.6 ng Hg/m3 (1990–1992), respectively, were found. Increased average and median winter concentrations were always found, with levels at 3.7 and 3.4, 3.7 and 3.3, and 3.0 and 2.7 ng Hg/m3 for the respective time period. Higher winter values were expected due to increased anthropogenic emissions and changes in the mixing height of the atmosphere. The corresponding total wet deposition rates decreased from 27 (1987–1989) to 10 μg Hg/m2 yr. (1990–1992). A finding of special interest was the decreased number of episodic events of high total gaseous Hg levels in air, from 1990 and further on. In addition, the frequency distribution of the concentrations of Hg in air seems to be different for these years compared to the other two time periods. A frequency distribution of air concentrations of Hg more resembling a normal distribution was found for the years 1990 to 1992. The decrease of the atmospheric burden of total gaseous Hg and deposition of total Hg are most probably connected to lower emissions in source areas on the European continent. It seems logical to state that the problem of high Hg depositional fluxes to Scandinavia, is best solved by abatement strategies on the regional scale.  相似文献   

7.
A seasonal variation of both particle and gaseous Hg concentrations in the atmosphere is present in south-western Sweden. An average gaseous Hg level of 3.7 ng m?3 is found in winter, compared to 2.8 ng m?3 in summer. A weak decreasing south-north gradient for gaseous Hg in air over the Nordic countries is also present, with yearly average values from 3.2 to 2.8 ng m?3. A gradient for particulate Hg is less clear. An air parcel trajectory sector classification of gaseous Hg levels in air, and to some extent the particulate associated Hg, clearly demonstrates the increased concentrations in the southern sectors, especially in south-western Sweden where the gaseous Hg increase is about I ng m?3. These observations are consistent with an influence from the European continent. The average concentrations of Hg in precipitation at the various stations show a pronounced decreasing south-north gradient. A major portion of the total Hg present in precipitation is associated with particles. For the southern stations, a strong correlation between Hg and sulfate, or pH, is present suggesting a connection between Hg in precipitation and anthropogenic activities.  相似文献   

8.
The primary goal of the Florida Atmospheric Mercury Study (FAMS) is to quantify the seasonal and geographical variability in the atmospheric deposition of Hg and other trace elements in central and south Florida. Precipitation, aerosol, and gaseous Hg samples have been collected at seven sites in Florida for periods ranging from 3 to 24 months. The summertime wet season in south Florida accounts for 80 to 90% of the annual rainfall Hg deposition. Depositional rates in south Florida are 30 to 50% higher than those from central Florida. Particle phase measurements range from 2 to 18 pg/m3Hg at all sites. Measurements of monomethylmercury in precipitation range from <0.005 to 0.020 ng/L.  相似文献   

9.
Mercury uses in human endeavors will lead to a general, though variable, volatilization of Hg. Current estimates for anthropogenic interferences range from about 50 to 75% of the total annual Hg emissions to the atmosphere. Recent modeling suggests that the present atmospheric Hg burden has increased by a factor of 3 during the last 100 years with a current rate of increase of about 0.6% yr?1 (ca. 0.01ng m?3yr?1). This impact, which is significant, can be examined and assessed empirically. To date, however, atmospheric Hg programs have not employed an experimental design sufficient to account for short time scale atmospheric Hg variations of natural and anthropogenic origin, and to resolve the long term temporal pattern. I am proposing an international research program, AMNET, or Atmospheric Hg Network, to address the important question, “Is Hg increasing in the atmosphere?” AMNET would examine temporal and spatial variations in atmospheric Hg and assess the influence of natural and anthropogenic sources on the global atmospheric Hg cycle. This program requires international support and cooperation. The experimental design of AMNET would follow the successful Atmospheric Lifetime Experiment Program (ALE), which examined the contemporary temporal changes in the atmospheric concentrations of the freons, methyl chloroform, carbon tetrachloride, and nitrous oxide. Following the ALE design, AMNET sampling stations would be maintained in both hemispheres and at sites free from strong local pollution sources of Hg (e.g., remote islands). Measurements would be made for a period of three to five years. The precision and accuracy of the Hg0 determinations must be ≥ 1%. The accurate resolution of the variability and secular trends in the atmospheric Hg burden can provide: (1) a direct quantitative assessment of the scale to which anthropogenic processes are affecting the natural biogeochemical cycling of Hg; (2) an essential refinement and constraint currently lacking in mass balance models; (3) an enhanced knowledge of the behavior of Hg in the atmosphere, and (4) an accurate data base required for global circulation atmospheric chemical Hg models.  相似文献   

10.
An intensive multi-site pilot study of atmospheric Hg was conducted in Broward County, Florida in August and September of 1993. Broward County, which contains the city of Fort Lauderdale, is located in southeastern Florida. The county borders the Florida Everglades on the west and the Atlantic Ocean on the east. A network of four sampling sites was set up for 20 days throughout Broward County to measure Hg in both the vapor phase and the particle phase as well as Hg in precipitation. The mean concentrations of total vapor phase Hg measured at two inland sites were found to be significantly higher (3.3 and 2.8 ng/m3) than that measured at a site located on the Atlantic shore (1.8 ng/m3). The mean concentrations of particle phase Hg collected at the two inland sites (51 and 49 pg/m3) were found to be 50% greater than that measured at the coastal site (34 pg/m3). In addition, event precipitation samples were collected at four sampling sites over the 20 day study period and were analyzed for both reactive and total Hg. The mean concentration of total Hg in the precipitation samples was found to be 44 ng/L, with a range of 14 to 130 ng/L. It was determined that further meteorological analysis and a more complete characterization of the aerosol and precipitation composition are needed to identify the probable source(s) contributing to the increased deposition of Hg.  相似文献   

11.
The Hg accumulation in sedimentary environments of a mangrove ecosystem in Sepetiba Bay, SE Brazil, was investigated. These environments include sediments of a mangrove forest, the main tidal creek that drains the forest, and the bare seaward-edge mud flat adjacent to forest and tidal creek. Maximum Hg concentration peaks in sediments from the mud flat (184 ng g-1), tidal creek (98 ng g-1), and mangrove forest (60 ng g-1) correspond to enrichment factors of 6.1, 3.3, and 2.0 above the estimated average background level, respectively. Average inventories of Hg excess (background-corrected) concentrations were substantiallydifferent between environments, decreasing from mud flat sediments (5.2 mg m-2) to creek sediments (3.3 mg m-2)to mangrove forest sediments (0.9 mg m-2). Mercury concentration profiles indicated a consistently higher accumulation of Hg in surface layers of mud flat and tidal creeksediments, whereas mangrove forest sediments showed a higher Hgaccumulation in root-rich subsurface layers, in agreement with an enrichment of Fe and organic matter contents. While Hg distribution in mud flat and tidal creek sediments appears to belargely affected by contamination, its distribution in mangrove forest substrate appears to be greatly affected by root-sedimentinteractions. Mercury levels in the study site were comparable tothose observed in coastal sediments under moderate Hg contamination at local and regional scales. Results indicate thatsedimentary environments surrounding the mangrove forest retain most of the anthropogenic Hg reaching the ecosystem. Since tidal waters have been previously demonstrated as the main source of metals to the site, it is suggested that the Hg retention in mudflat sediments precede and may avoid a higher Hg accumulation inlandward environments.  相似文献   

12.
In the Pocone district, Brazil, Hg distribution was studied in a small watershed which drains tailings from a 10 yr old gold mining operation. Heavy regional rains are responsible for continuous weathering, thereby making it possible to transport Hg into the ecologically important Pantanal area. Mercury concentrations in creek sediments range from < 0.02 to 0.18 mg. kg?1. The highest concentrations occur close to the tailings deposit. Mercury concentrations in the water were always below the detection limit of the analytical method used (<0.04 µg. L?1). Suspended matter samples collected before, during and after a storm, showed a Hg peak value of 0.61 mg kg?1. about 30 min after the event. Dissolved Hg concentration still fell below the detection limit. Among the biota, molluscs accumulated moderately high concentrations of Hg, while macrophytes and fish did not. Mercury concentrations in molluscs were dependent on size, with larger animals presenting higher Hg concentration. We conclude that Hg present in the tailings shows low mobility and that its eventual transport into the drainage system is dependent on the erosion of fine material from the wastes during rains, resulting in a restricted contamination of the area and low Hg concentration in the biota.  相似文献   

13.
Mercury concentrations and depositions for northeastern Minnesota were measured in precipitation to investigate depositional trends, relationships with major cations and anions, and possible source emission regions. Results for 1987–1990 showed that environmentally significant amounts of Hg are present in precipitation and air and are subsequently deposited to remote lake watersheds. Volume-weighted concentrations of total Hg in precipitation averaged about 18 ng Hg L−1 with calculated annual depositions near 15 μg Hg m−2. Mercury concentrations in precipitation are positively correlated with the major ions, conductivity, and pH, and are negatively correlated with precipitation volume. The best predictor equation from stepwise regression has an r2 of 0.65 with Mg and chloride concentrations as predictor variables. From measurements of Hg in rain concentrations as a function of time within events, scavenging ratios for “washable” Hg were calculated to be 140 ± 80 (mass based at a 1 mm hr −1 precipitation rate). Up to about 10% of the total Hg in air is subject to washout by precipitation for a given event. Air parcel back-trajectories indicate that possible source regions within 72-hr travel time were located mostly to the south, southeast, and southwest, up to 2500 km distance away but local sources may also be important.  相似文献   

14.
Mercury (Hg) transport was studied in a river in Kobbefjord, near Nuuk in West Greenland, during the 2009 and 2010 summer periods. The river drains an area of 32?km2, and the Kobbefjord area is considered representative to low-Arctic West Greenland. The river water origins from both precipitation and melting of small glaciers and annual water discharges for 2009 and 2010 were estimated to be 29 and 26 million?m3, respectively. Mean Hg concentrations (±SD) were 0.46?±?0.17 and 0.26?±?0.17?ng?L?1 for 2009 and 2010. The annual Hg transport was estimated to 14 and 6.4?g, corresponding to a transport rate of 0.45 and 0.20?g Hg km?2?year?1 from the river basin. The highest Hg concentrations (up to 1.0?ng?L?1) and discharges were measured in spring 2009 along with melting of extensive amounts of snow deposited during the 2008?C2009 winter period. In contrast, the following 2009?C2010 winter period was relatively dry with less snowfall. This indicates that a major fraction of the Hg in this area is likely to come from Hg deposited along with winter precipitation (as wet deposition) released upon snowmelt. Also, the results show that while Hg concentrations were low in Kobbefjord River compared to other sub-Arctic/Arctic rivers, the annual Hg transport rates from the basin area were within the range reported for other sub-Arctic/Arctic areas.  相似文献   

15.
Research on mercury (Hg) distribution and speciation was carried out in Lake Baikal, a large, strong-oligotrophic freshwater reservoir in Siberia, Russia, during June 1992 and march 1993. In summer, total Hg in the water column ranged from 0.14 to 0.77 ng Hg/L, with the highest concentrations observed in the central basin of the lake in surface water samples. Labile inorganic Hg was found to be 7 to 20 % of the total Hg content. Highest total Hg concentrations were found in river waters: up to 2 ng Hg/L. Labile methylmercury (MeHg) concentrations ranged from 2 to 38 pg Hg/L in the water column, with the higher concentrations in the central part of the lake, and showing a slight increase in near bottom waters. Labile MeHg makes up 1 to 15 % of the total Hg content in the water column, with larger fractions in deep waters. The slight increase of the MeHg gradient with depth corresponds with the O2 minimum region. Highest MeHg concentrations were observed in river waters (up to 145 pg Hg/L) and in some bays of the lake (up to 160 pg Hg/L). In these high temperature- and phytoplankton-rich water masses, the MeHg-fraction increased up to 35 % of total Hg. Labile MeHg concentrations in water samples taken in winter in the southern basin (under the ice cover), showed slightly higher concentrations than in summer, possibly due to an early spring bloom. In rainwater, total Hg ranged from 3 to 20 ng Hg/L and MeHg from 0.1 to 0.25 ng Hg/L. In snow, a large fraction of total Hg is bound to particulate matter; concentrations of total Hg ranged from 8 to 60 ng Hg/L and labile MeHg from 0.1 to 0.25 ng Hg/L. Atmospheric Hg was found to be 0.73 to 2.31 ng/m3 as gaseous Hg and 0.005 to 0.02 ng/m3 in its particulate form. Spatial distribution patterns of atmospheric Hg show slightly higher concentrations over the central part of the lake and the Selenga river delta. In winter, atmospheric Hg values (measured in the southern region), ranged from 1.2 to 6.1 ng/m3 as total gaseous Hg and 0.02 to 0.09 ng/m3 as total particulate Hg, and are higher than in summer, probably influenced by coal burning and traffic by the local population. MeHg contents in fish ranged from 20 ng Hg/g dry weight in small Cottocomephorus to 300 ng Hg/g dry weight in pike and trout species, which were caught in organic-rich waters.  相似文献   

16.
Mercury (Hg) was measured in stream water and precipitation in the Loch Vale watershed in Rocky Mountain National Park, Colorado, during 2001–2002 to investigate processes controlling Hg transport in high-elevation ecosystems. Total Hg concentrations in precipitation ranged from 2.6 to 36.2 ng/L and showed a strong seasonal pattern with concentrations that were 3 to 4 times higher during summer months. Annual bulk deposition of Hg was 8.3 to 12.4 μ g/m2 and was similar to deposition rates in the Midwestern and Northeastern U.S. Total Hg concentrations in streams ranged from 0.8 to 13.5 ng/L and were highest in mid-May on the rising limb of the snowmelt hydrograph. Stream-water Hg was positively correlated with dissolved organic carbon suggesting organically complexed Hg was flushed into streams from near-surface soil horizons during the early stages of snowmelt. Methylmercury (MeHg) in stream water peaked at 0.048 ng/L just prior to peak snowmelt but was at or below detection (< 0.040 ng/L) for the remainder of the snowmelt season. Annual export of total Hg in Loch Vale streams ranged from 1.2 to 2.3 μ g/m2, which was less than 20% of wet deposition, indicating the terrestrial environment is a net sink of atmospheric Hg. Concentrations of MeHg in stream water and corresponding watershed fluxes were low, indicating low methylation rates or high demethylation rates or both.  相似文献   

17.
A pot experiment with 38 commonly cultivated rice cultivars from the Yangtze River Delta was conducted in a greenhouse to study the effect of mercury (Hg) contamination of a paddy soil (4.7 mg Hg [kg soil]–1) on crop growth and Hg accumulation in the grains. Mercury contamination differentially affected growth, grain yield, and Hg accumulation in brown rice of the tested cultivars. The average Hg concentration in the grains was significantly higher (p < 0.01) when plants were grown in the Hg‐contaminated compared to the control soil. Averaged over cultivars, the Hg concentration in brown rice exceeded the maximum permissible limit of 20 μg Hg kg–1. Increasing Hg concentrations were associated with grain‐yield declines up to 70%. This yield decline was mainly due to a reduction in the number of panicles. Japonica cultivars tended to be generally less affected by Hg than indica cultivars. The two japonica cultivars Jiahua and Chunjiang 026 showed both low Hg concentrations and no Hg‐induced grain‐yield reduction. These cultivars may be preferred candidates for cultivation in Hg‐contaminated soils or for studies on possible Hg‐exclusion mechanisms.  相似文献   

18.
The distribution of mercury species was determined in soil from a site with Hg contamination. Mercury contamination was primarily confined to the top 40 cm of soil, and the concentration of total Hg ranged from 0.5 to 3000 µg Hg g?1. Of total Hg present, we determined that 91% was inorganic, 0.01% organic (as methyl Hg), and 6% elemental Hg. Furthermore, of total inorganic Hg present, 85% was in the insoluble mercuric sulfide form. Thus, of total Hg present in soil at this contaminated site, 91% was in the relatively insoluble HgS and Hg0 forms.  相似文献   

19.
A seasonal variation of both particle and gaseous Hg concentrations in the atmosphere is present in south-western Sweden. An average gaseous Hg level of 3.7 ng m−3 is found in winter, compared to 2.8 ng m−3 in summer. A weak decreasing south-north gradient for gaseous Hg in air over the Nordic countries is also present, with yearly average values from 3.2 to 2.8 ng m−3. A gradient for particulate Hg is less clear. An air parcel trajectory sector classification of gaseous Hg levels in air, and to some extent the particulate associated Hg, clearly demonstrates the increased concentrations in the southern sectors, especially in south-western Sweden where the gaseous Hg increase is about I ng m−3. These observations are consistent with an influence from the European continent. The average concentrations of Hg in precipitation at the various stations show a pronounced decreasing south-north gradient. A major portion of the total Hg present in precipitation is associated with particles. For the southern stations, a strong correlation between Hg and sulfate, or pH, is present suggesting a connection between Hg in precipitation and anthropogenic activities.  相似文献   

20.
The importance of participate mercury (Hg(p)) in the transport, chemistry and deposition of this toxic metal has long been underestimated and largely ignored. While it was once believed to constitute a small percentage of total atmospheric mercury, Hg(p) may contribute a significant portion of the deposition of this metal to adjacent natural waters. Recent measurements of Hg(p) in several urban/industrial areas have documented that Hg can be associated with large particles (>2.5 μm) and in concentrations similar to those of the vapor phase Hg (ng/m3). As part of ongoing effort to diagnose the sources, transport and deposition of Hg to the Great Lakes and other Great Waters, the University of Michigan Air Quality Laboratory (UMAQL) has investigated the physical and chemical properties of particulate-phase Hg in both urban and rural locations. It appears that particulate Hg may be the one of the most difficult of the Hg measurements to perform, and perhaps the one of the most important for deposition and source apportionment studies. Particulate Hg concentrations measured in rural areas of the Great Lakes Region and Vermont ranged from 1 to 86 pg/m3 whereas Hg(p) levels in urban/industrialized areas were in the range 15 pg/m3 to 1.2 ng/m3.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号