排序方式： 共有11条查询结果，搜索用时 15 毫秒
1.
M. Alisa Mast Donald H. Campbell David P. Krabbenhoft Howard E. Taylor 《Water, air, and soil pollution》2005,164(1-4):21-42
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
2.
3.
4.
Abbott Michael L. Susong David D. Krabbenhoft David P. Rood Arthur S. 《Water, air, and soil pollution》2002,139(1-4):95-114
Mercury (total and methyl) was evaluated in snow samples collected near a major mercury emission source on the Idaho National Engineering and Environmental Laboratory (INEEL) insoutheastern Idaho and 160 km downwind in Teton Range in westernWyoming. The sampling was done to assess near-field (<12 km)deposition rates around the source, compare them to those measured in a relatively remote, pristine downwind location, andto use the measurements to develop improved, site-specific modelinput parameters for precipitation scavenging coefficient and thefraction of Hg emissions deposited locally. Measured snow waterconcentrations (ng L-1) were converted to deposition (ugm-2) using the sample location snow water equivalent. Thedeposition was then compared to that predicted using the ISC3 airdispersion/deposition model which was run with a range ofparticle and vapor scavenging coefficient input values. Acceptedmodel statistical performance measures (fractional bias andnormalized mean square error) were calculated for the differentmodeling runs, and the best model performance was selected. Measured concentrations close to the source (average = 5.3 ngL-1) were about twice those measured in the Teton Range(average = 2.7 ng L-1) which were within the expected rangeof values for remote background areas. For most of the samplinglocations, the ISC3 model predicted within a factor of two of theobserved deposition. The best modeling performance was obtainedusing a scavenging coefficient value for 0.25 μm diameterparticulate and the assumption that all of the mercury isreactive Hg(II) and subject to local deposition. A 0.1 μm particle assumption provided conservative overprediction of thedata, while a vapor assumption resulted in highly variable predictions. Partitioning a fraction of the Hg emissions to elemental Hg(0) (a U.S. EPA default assumption for combustion facility risk assessments) would have underpredicted the observed fallout. 相似文献
5.
Brigham M. E. Krabbenhoft D. P. Olson M. L. DeWild J. F. 《Water, air, and soil pollution》2002,138(1-4):61-78
We studied methylmercury (MeHg) and totalmercury (HgT) in impounded and natural surface waters innorthwestern Minnesota, in settings ranging from agriculturalto undeveloped. In a recently constructed (1995) permanent-pool impoundment, MeHg levels typically increased from inflowto outflow during 1997; this trend broke down from late 1998 toearly 1999. MeHg levels in the outflow reached seasonal maximain mid-summer (maximum of 1.0 ng L-1 in July 1997) andlate-winter (maximum of 6.6 ng L-1 in February 1999), andare comparable to high levels observed in new hydroelectricreservoirs in Canada. Spring and autumn MeHg levels weretypically about 0.1–0.2 ng L-1. Overall, MeHg levels inboth the inflow (a ditch that drains peatlands) and outflowwere significantly higher than in three nearby referencenatural lakes. Eleven older permanent-pool impoundments andsix natural lakes in northwestern Minnesota were sampled fivetimes. The impoundments typically had higher MeHg levels(0.071–8.36 ng L-1) than natural lakes. Five of six lakesMeHg levels typical of uncontaminated lakes (0.014–1.04 ngL-1) with highest levels in late winter, whereas ahypereutrophic lake had high levels (0.37–3.67 ng L-1)with highest levels in mid-summer. Seven temporary-poolimpoundments were sampled during summer high-flow events. Temporary-pool impoundments that retained water for about 10–15days after innundation yielded pronounced increases in MeHgfrom inflow to outflow, in one case reaching 4.6 ng L-1,which was about 2 ng L-1 greater than the mean inflowconcentration during the runoff event. 相似文献
6.
David P. Krabbenhoft Janina M. Benoit Christopher L. Babiarz James P. Hurley Anders W. Andren 《Water, air, and soil pollution》1995,80(1-4):425-433
Although there have been recent significant gains in our understanding of mercury (Hg) cycling in aquatic environments, few studies have addressed Hg cycling on a watershed scale. In particular, attention to Hg species transfer between watershed components (upland soils, groundwater, wetlands, streams, and lakes) has been lacking. This study describes spatial and temporal distributions of total Hg and MeHg among watershed components of the Allequash Creek watershed (northern Wisconsin, USA). Substantial increases in total Hg and MeHg were observed as groundwater discharged through peat to form springs that flow into the stream, or rivulets that drain across the surface of the wetland. This increase was concomitant with increases in DOC. During fall, when the Allequash Creek wetland released a substantial amount of DOC to the stream, a 2–3 fold increase in total Hg concentrations was observed along the entire length of the stream. Methylmercury, however, did not show a similar response. Substantial variability was observed in total Hg (0.9 to 6.3) and MeHg (<0.02 to 0.33) concentrations during synoptic surveys of the entire creek. For the Allequash Creek watershed, the contributing groundwater basin is about 50% larger than the topographic drainage basin. Total Hg concentrations in groundwater, the area of the groundwater basin, and annual stream flow data give a watershed-yield rate of 1.2 mg/km2/d, which equates to a retention rate of 96%. The calculated MeHg yield rate for the wetland area is 0.6 to 1.5 mg/km2/d, a value that is 3–6 fold greater than the atmospheric deposition rate. 相似文献
7.
P. F. Schuster J. B. Shanley M. Marvin-Dipasquale M. M. Reddy G. R. Aiken D. A. Roth H. E. Taylor D. P. Krabbenhoft J. F. DeWild 《Water, air, and soil pollution》2008,187(1-4):89-108
Mercury and organic carbon concentrations vary dynamically in streamwater at the Sleepers River Research Watershed in Vermont, USA. Total mercury (THg) concentrations ranged from 0.53 to 93.8 ng/L during a 3-year period of study. The highest mercury (Hg) concentrations occurred slightly before peak flows and were associated with the highest organic carbon (OC) concentrations. Dissolved Hg (DHg) was the dominant form in the upland catchments; particulate Hg (PHg) dominated in the lowland catchments. The concentration of hydrophobic acid (HPOA), the major component of dissolved organic carbon (DOC), explained 41–98% of the variability of DHg concentration while DOC flux explained 68–85% of the variability in DHg flux, indicating both quality and quantity of the DOC substantially influenced the transport and fate of DHg. Particulate organic carbon (POC) concentrations explained 50% of the PHg variability, indicating that POC is an important transport mechanism for PHg. Despite available sources of DHg and wetlands in the upland catchments, dissolved methylmercury (DmeHg) concentrations in streamwaters were below detection limit (0.04 ng/L). PHg and particulate methylmercury (PmeHg) had a strong positive correlation (r 2?=?0.84, p?<?0.0001), suggesting a common source; likely in-stream or near-stream POC eroded or re-suspended during spring snowmelt and summer storms. Ratios of PmeHg to THg were low and fairly constant despite an apparent higher methylmercury (meHg) production potential in the summer. Methylmercury production in soils and stream sediments was below detection during snowmelt in April and highest in stream sediments (compared to forest and wetland soils) sampled in July. Using the watershed approach, the correlation of the percent of wetland cover to TmeHg concentrations in streamwater indicates that poorly drained wetland soils are a source of meHg and the relatively high concentrations found in stream surface sediments in July indicate these zones are a meHg sink. 相似文献
8.
Stephen R. Hinkle Kenneth E. Bencala Dennis A. Wentz David P. Krabbenhoft 《Water, air, and soil pollution》2014,225(1):1-17
The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r 2?=?0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems. 相似文献
9.
10.
Kirk W. Olson Trevor J. Krabbenhoft Thomas R. Hrabik Bud Mendsaikhan Olaf P. Jensen 《Ecology of Freshwater Fish》2019,28(3):411-423
Resource polymorphism is a widespread phenomenon in post‐glacial fishes where multiple morphotypes of a species occur sympatrically and exhibit distinct resource use. Availability of open niches and high levels of within and among species competition are thought to drive differences in morphology and may provide insights into early stages of speciation. Hovsgol grayling (Thymallus nigrescens) are endemic to Lake Hovsgol, a lake colonised by fish following the Pleistocene, and are threatened with habitat loss due to climate change and illegal harvest. Previous analysis of Hovsgol grayling diet inferred through C and N stable isotopes suggested the presence of littoral and pelagic foraging groups. We hypothesised that morphology of the two foraging groups would reflect predictions of functional morphology, indicating the presence of resource polymorphism. To test this hypothesis, we evaluated evidence from C and N stable isotopes, stomach contents, fish ages, capture location and morphology. Two foraging groups of Hovsgol grayling were identified through stomach content and C and N stable isotope analysis. Individuals with greater zooplankton consumption were more frequently captured in the pelagic zone, exhibited higher gill raker counts, larger orbit (eye) sizes, longer paired fins, narrower head width, larger maxilla and smaller size at age than the group with greater reliance on benthic invertebrate prey. These differences were generally consistent with those described in other fish species exhibiting littoral–pelagic resource polymorphism. Our study provides the first example of littoral–pelagic resource polymorphism in the salmonid subfamily Thymallinae and highlights the potential influence of competition on fish evolution. 相似文献