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101.
Michel Robert L. Turk John T. Campbell Donald H. Mast M. A. 《Water, Air, & Soil Pollution: Focus》2002,2(2):5-18
Measurements of the cosmogenically-produced 35S, a radioisotope of sulphur (t1/2 = 87 days), are reported for the Ned Wilson Lake watershed in Colorado. The watershed contains two small lakes and a flowing spring presumed to be representative of local ground water. The watershed is located in the Flattops Wilderness Area and the waters in the system have low alkalinity, making them sensitive to increases in acid and sulphate deposition. Time series of 35S measurements were made during the summers of 1995 and 1996 (July–September) at all three sites. The system is dominated by melting snow and an initial concentration of 16–20 mBq L-1 was estimated for snowmelt based on a series of snow samples collected in the Rocky Mountains. The two lakes had large initial 35S concentrations in July, indicating that a large fraction of the lake water and sulphate was introduced by meltwater from that year's snowpack. In 1995 and 1996, 35S concentrations decreased more rapidly than could be accounted for by decay, indicating that other processes were affecting 35S concentrations. The most likely explanation is that exchange with sediments or the biota was removing 35S from the lake and replacing it with older sulphate devoid of 35S. In September of 1995 and 1996, 35S concentrations increased, suggesting that atmospheric deposition is important in the sulphate flux of these lakes in late summer. Sulphur-35 concentrations in the spring water were highly variable but never higher than 3.6 mBq L-1 and averaged 2 mBq L-1. Using a simple mixing model, it was estimated that 75% of the spring water was derived from precipitation of previous years. 相似文献
102.
Development of Stream Water Chemistry during Spring Melt in a Northern Hardwood Forest 总被引:1,自引:0,他引:1
Semkin R. G. Hazlett P. W. Beall F. D. Jeffries D. S. 《Water, Air, & Soil Pollution: Focus》2002,2(1):37-61
The role of snowmelt and subsurface hydrology in determiningthe chemistry of a small headwater stream in the TurkeyLakes Watershed (TLW) was evaluated for the spring meltperiods 1992 to 1996. Spring runoff is the dominanthydrological event at the TLW each year. Processesoccurring within the snowpack during snowmelt wereprincipally responsible for the above-ground changes inchemical fluxes relative to bulk deposition (the effect ofwinter throughfall was minimal). Large changes in chemicalfluxes occurred below ground. Organic matter decomposition,weathering, nitrification, and element cycling are some ofthe more important below-ground processes that operateduring the snow accumulation and ablation season and controlthe composition of the water ultimately appearing in thestream. Maximum stream discharge was accompanied byelevated concentrations of H+, NO3
-, K+,NH4
+, DOC, Al and Mn, but reduced levels ofCa2+, Mg2+, SO4
2- and SiO2. Theconcentration-discharge relationships were consistent withwater movement through and above the forest floor duringpeak discharge, a flowpath facilitated by rapid infiltrationof meltwater and the existence of a relatively impermeablelayer in the mineral soil creating a perched water table. Averaged over the five periods of snow accumulation andablation, it was estimated that pre-melt stream flow, andwater routed through the forest floor and through the uppermineral soil contributed 9, 28 and 63%, respectively, ofthe discharge measured at the outlet of the catchment. Theforest floor contribution would be greater at peak dischargeand at higher elevations. An end-member mixing modelestimated concentrations of SO4
2-, NO3
-,Cl-, Ca2+, Mg2+, Na+ and Al that werecomparable to average values measured in the stream. Othervariables (NH4
+, H+, K+ and DOC) wereover-estimated implying retention mechanisms operatingoutside the model assumptions. 相似文献
103.
Rose N. L. Shilland E. Yang H. Berg T. Camarero L. Harriman R. Koinig K. Lien L. Nickus U. Stuchlík E. Thies H. Ventura M. 《Water, Air, & Soil Pollution: Focus》2002,2(2):251-260
Spheroidal carbonaceous particles(SCPs) are produced only from high temperaturecombustion of fossil-fuels. In mountain lakesystems, they provide an unambiguous indicator ofatmospheric deposition. In order to comparedepositional fluxes of SCPs between mountainareas experiencing various pollutant regimes,intensive bulk deposition sampling was undertakenat five sites across Europe. Catchment soil coresand lake sediment cores were also taken at eachsite to compare SCP storage over the post-industrial period. Atmospheric, sediment and soilSCP data showed similar patterns. Highestcontamination was found in Scotland, Slovakia andSpain with the Austrian site intermediate and themid-Norwegian site least contaminated. A highproportion of accumulated SCPs were found to bestored in catchment soils at each site.Therefore, a significant increase in soilerosion, possibly as a result of future climatechange, could lead to the input of largequantities of catchment stored SCPs and, byimplication, other atmospherically depositedcontaminants to the lake ecosystem. 相似文献
104.
Trends in the Water Chemistry of High Altitude Lakes in Europe 总被引:2,自引:0,他引:2
Mosello R. Lami A. Marchetto A. Rogora M. Wathne B. Lien L. Catalan J. Camarero L. Ventura M. Psenner R. Koinig K. Thies H. Sommaruga-Wögrath S. Nickus U. Tait D. Thaler B. Barbieri A. Harriman R. 《Water, Air, & Soil Pollution: Focus》2002,2(2):75-89
Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984–1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions. 相似文献
105.
The size and isotopic behavior of sulfur pools in210Pb-dated peat cores were investigated to obtain aninsight into retention mechanisms of pollutant S in twomountain-top peatlands of the Northern Czech Republic, CentralEurope. The bogs were situated 40 km apart in an area whichbetween the years 1985 and 1995 received as much as 130 kg Sha-1 yr-1 from the atmosphere. Vertical peataccretion was faster at Pod Jelení horou (JH) than atVelký moál (VM). Organic carbon-bonded S was themost abundant sulfur pool, constituting 77 and 65 wt. % at JHand VM, respectively. At JH both the S concentration maximumand the highest annual S deposition rate were displaceddownward by more than 20 years (from 1987 to the 1960s)indicating that the buried S is vertically mobile. At VM the Sconcentration was the highest in the topmost 2-cm section eventhough atmospheric S deposition peaked in 1987. Differentmechanisms of S isotope redistribution prevailed in thetopmost peat layers at JH, where a negative 34Sshift occurred, and at VM, where a positive 34Sshift occurred. Bacterial sulfate reduction was responsiblefor the negative 34S shift at JH. One possibleexplanation of the positive 34S shift at VM isrelease of 32S-enriched products of mineralization duringpeat diagenesis. There was a strong positive correlationbetween the abundance of total and pyrite S along the profiles.The presence of pyrite S at VM (526 ± 60 ppm) suggestedthat even at VM bacterial sulfate reduction occurred. Ananaerobic incubation of JH peat indicated sulfate reductionrate of 600 nmol g-1 day-1. The turnover times forinorganic S pools were shorter than for the organic S pools.Cumulative S contents in the Czech peat bogs were found to besignificantly lower than in similar sites in the NortheasternU.S., even though the atmospheric S inputs were more thanthree times higher at the Czech sites. Possible causes of suchdiscrepancy are discussed. 相似文献
106.
Watershed scale assessment of nitrogen and phosphorus loadings in the Indian River Lagoon basin,Florida 总被引:3,自引:0,他引:3
There is a growing evidence that the ecological and biological integrity of the lagoon has declined during the last 50 years, probably due to the decline in water quality. Establishment of a watershed scale seagrass-based nutrient load assessment is the major aim of water quality management in the Indian River Lagoon (IRL). Best estimate loadings incorporate wet and dry deposition, surface water, groundwater, sediment nutrient flux, and point source effluent discharge data. On the average, the IRL is receiving annual external loadings of 832, 645 and 94,476kg of total nitrogen (TN) and total phosphorus (TP), respectively, from stormwater discharges and agricultural runoff. The average internal cycling of TN and TP from sediment deposits in the IRL was about 42,640kg TN and 1050kg TPyr(-1). Indirect evidence suggests that atmospheric deposition has played a role in the ongoing nutrient enrichment in the IRL. The estimated total atmospheric deposition of TN and TP was about 32,940 and 824kgyr(-1), while groundwater contribution was about 84,920 and 24,275kgyr(-1), respectively, to the surface waters of the IRL. The estimated annual contribution of point effluent discharge was about 60,408kg TN and 7248kg TP. In total, the IRL basin is receiving an annual loading of about 1,053,553kg TN and 127,873kg TP. With these results, it is clear that the current rate of nutrient loadings is causing a shift in the primary producers of the IRL from macrophyte to phytoplankton- or algal-based system. The goal is to reverse that shift, to attain and maintain a macrophyte-based estuarine system in the IRL. 相似文献
107.
Clow David W. Striegl Robert G. Nanus Leora Mast M. Alisa Campbell Donald H. Krabbenhoft David P. 《Water, Air, & Soil Pollution: Focus》2002,2(2):139-164
A chemical survey of 69 high-altitude lakes in seven national parks in the western United States was conducted during the fallof 1999; the lakes were previously sampled during the fall of 1985, as part of the Western Lake Survey. Lakes in parks in the Sierra/southern Cascades (Lassen Volcanic, Yosemite, Sequoia/Kings Canyon National Parks) and in the southern RockyMountains (Rocky Mountain National Park) were very dilute; medianspecific conductance ranged from 4.4 to 12.2 S cm-1 andmedian alkalinity concentrations ranged from 32.2 to 72.9 eqL-1. Specific conductances and alkalinity concentrations were substantially higher in lakes in the central and northernRocky Mountains parks (Grand Teton, Yellowstone, and GlacierNational Parks), probably due to the prevalence of more reactivebedrock types. Regional patterns in lake concentrations of NO3 and SO4 were similar to regional patterns in NO3 and SO4 concentrations in precipitation, suggestingthat the lakes are showing a response to atmospheric deposition.Concentrations of NO3 were particularly high in Rocky Mountain National Park, where some ecosystems appear to be undergoing nitrogen saturation. 相似文献
108.
Regular additions of NH4NO3 (35–140 kg N ha−1 yr−1) and (NH4)2SO4 (140 kg N ha−1 yr−1) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the
indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure
and composition of this calcareous bryophyte community. The lowest NH4NO3 additions of 35 kg N ha−1 yr−1 produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH4NO3 application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH4NO3 and (NH4)2SO4 additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH4NO3 deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of
>1 pH unit, between the NH4NO3 and (NH4)2SO4 treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of
35 kg N ha−1 yr−1 or less. These effects are of particular concern for rare or endangered species of low frequency. 相似文献
109.
Mary Beth Adams James N. Kochenderfer Pamela J. Edwards 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):267-273
In 1989, a watershed acidification experiment was begun on the Fernow Experimental Forest in West Virginia, USA. Ammonium
sulfate fertilizer (35.5 kg N ha−1 yr−1and 40.5 kg S ha−1 yr−1) was applied to a forested watershed (WS3) that supported a 20-year-old stand of eastern deciduous hardwoods. Additions of
N and S are approximately twice the ambient deposition of nitrogen and sulfur in the adjacent mature forested watershed (WS4),
that serves as the reference watershed for this study. Acidification of stream water and soil solution was documented, although
the response was delayed, and acidification processes appeared to be driven by nitrate rather than sulfate. As a result of
the acidification treatment, nitrate solution concentrations increased below all soil layers, whereas sulfate was retained
by all soil layers after only a few years of the fertilization treatments, perhaps due to adsorption induced from decreasing
sulfate deposition. Based on soil solution monitoring, depletion of calcium and magnesium was observed, first from the upper
soil horizons and later from the lower soil horizons. Increased base cation concentrations in stream water also were documented
and linked closely with high solution levels of nitrate. Significant changes in soil chemical properties were not detected
after 12 years of treatment, however. 相似文献
110.
J. R. Williams 《Journal of the American Water Resources Association》1975,11(5):965-974
ABSTRACT: A sediment routing technique was developed to route sediment yield from small watersheds through streams and valleys to the outlet of large watersheds. The technique is based on the modified universal sol loss equation and a first order decay function of travel time and particle size. Deposition is dependent upon settling velocities of sediment particles, travel time, and the amount of sediment in suspension. Sediment routing increases sediment yield prediction accuracy and allows determination of subwatershed contributions to the total sediment yield. Also, the locations and amounts of floodplain scour and deposition can be predicted. Another advantage of sediment routing is that measured sediment yield data are not required. The procedure performed satisfactorily in test routings on two Texas blackland watersheds Sediment routing will be useful in flood control evaluation, reservoir and channel design, water quality calculations, environmental impact assessment, and land-use planning. 相似文献