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31.
J. Shubzda S. E. Lindberg C. T. Garten S. C. Nodvin 《Water, air, and soil pollution》1995,85(4):2265-2270
From 1986–1989, a team of scientists measured atmospheric concentrations and fluxes in precipitation and throughfall, and modeled dry and cloudwater deposition in a spruce-fir forest of the Great Smoky Mountains National Park which is located in the Southern Appalachian Region of the United States. The work was part of the Integrated Forest Study (IFS) conducted at 12 forests in N. America and Europe. The spruce-fir forest at 1740 m consistently received the highest total deposition rates (~2200, 1200, and 700 eq ha?1 yr?1 for SO4 2?, NO3 ?, and NH4 +). During the summers of 1989 and 1990 we used multiple samplers to measure hydrologie, SO4 2?, and NO3 ? fluxes in rain and throughfall events beneath spruce forests above (1940 m) and below (1720 m) cloud base. Throughfall was used to estimate total deposition using relationships determined during the IFS. Although the SO4 2? fluxes increased with elevation by a factor of ~2 due to higher cloudwater interception at 1940 m, the NO3 ? fluxes decreased with elevation by ~30%. To investigate further, we began year round measurements of fluxes of all major ions in throughfall below spruce-fir forests at 1740 m and at 1920 m in 1993–1994. The fluxes of most ions showed a 10–50% increase with elevation due to the ~70 cm yr?1 cloudwater input at 1920 m. However, total inorganic nitrogen exhibited a 40% lower flux in throughfall at 1920 m than at 1740 m suggesting either higher dry deposition to trees at 1740 m or much higher canopy uptake of nitrogen by trees at 1920 m. Differential canopy absorption of N by trees at different elevations would have significant consequences for the use of throughfall N fluxes to estimate deposition. We used artificial trees to understand the foliar interactions of N. 相似文献
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An intensive 1-month investigation of trace metal deposition and throughfall at a mountain spruce forest 总被引:1,自引:0,他引:1
During July 1986, atmospheric concentrations and deposition rates of Ph, Cd, Zn, and Mn were measured at a spruce forest in the Great Smoky Mountains National Park, and meteorological data were recorded. Precipitation, cloud water impaction, and dry deposition were quantified. Average total fluxes of 12, 1.0, 53, and 40 µg m?2 d?1 for Pb, Cd, Zn, and Mn, respectively, were measured; dry deposition constituted 46, 32, 62 and 66% of each of the totals. Cloud impaction (unusually low for this particular month) was measurable but not quantitatively important. Dry deposited Pb and Zn were washed from the canopy by subsequent rainfall — revealing greater throughfall fluxes associated with increasing antecedent dry period durations. Cadmium and Mn did not, however, show this relationship. Measurements revealed little interaction of Cd with the forest canopy, while considerable net leaching of Mn was evident (as had been expected). The canopy behaviors of both Pb (i.e., leaching) and Zn (i.e., uptake) were contrary to expectations. 相似文献
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In an effort to establish reliable methodologies for measuring fluxes of mercury (Hg) across the soil-air interface, we have developed a field flux chamber built with FEP Teflon. To evaluate our field flux chamber system, a series of laboratory and field tests were performed. The observations of relatively low chamber blanks and low blank-to-sample ratios for the FEP Teflon chamber suggest its potential in Hg flux investigations. Despite its potential, Hg exchange rate measurements using the field flux chamber method must be made with great caution since it can be subject to contamination problems associated with the selection of chamber materials. 相似文献
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A field study was conducted in June of 1998 to characterize the dynamics of dissolved gaseous mercury (DGM) in the TahquamenonRiver watershed and nearshore waters of Whitefish Bay in the Upper Michigan Peninsula. We found that over a transect acrossthe watershed, DGM levels increased generally from a creek (mean = ~12 pg L-1), passing through the watershed, to the nearshore surface waters of the bay (mean = ~29 pg L-1). DGM levels in nearshore surface waters of the bayranged from ~15 to ~50 pg L-1 and peaked generally around noontime, exhibiting diurnal trends. A significant DGM decline from ~32 pg L-1 in the early morning to ~15 pg L-1 during the day was observed in these surface waters following passage of a coldfront, probably caused by wind-induced mixing and decrease insolar radiation associated with the frontal passage. 相似文献
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D Garaleviciene H Pettersson G Augonyte K Elwinger J E Lindberg 《Archives of Animal Nutrition》2001,55(1):25-42
Moulded and mycotoxin containing barley was incorporated into the diets for laying hens to study the effects on performance and health. Health indicators were different blood plasma parameters and liver vitamin A and E levels. A total of 30 hens were fed 3 diets, one supplemented with 30% of toxin-free and two with differently moulded barley from 1997 and 1998 for 7 weeks. The moulded diets contained low to moderate concentrations of ochratoxin A, zearalenone, deoxynivalenol and nivalenol. Inclusion of mouldy barley in the diets had an adverse effect on feed intake, feed conversion, digestibility of nutrients, egg production and egg quality. Plasma alkaline phosphatase was increased and certain biochemical blood parameters (bilirubin, uric acid, chlorine, protein, albumin, vitamin A) were also higher or changed compared to control. The ochratoxin A contamination although relatively low could have contributed to some of these effects as well as reduced intake of feed. The higher mould contamination and an unidentified cell-toxic constituent in the diet containing barley from 1998 can probably also explain the more marked effects from this diet. 相似文献
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M L Bruss Y Gr?hn E M Huffman L A Lindberg 《American journal of veterinary research》1986,47(2):336-341
Sodium propionate (3 mmol/kg) was injected IV into 8 nonlactating dairy cows before and after 6 days (144 hours) of fasting. During fasting, long-chain fatty acids in plasma increased from 0.30 +/- 0.05 (SE) mM to 1.09 +/- 0.15 mM (P less than 0.05). Liver fat increased from 0.5 +/- 0.3% to 9.3 +/- 1.7% (P less than 0.05). Half-life of injected sodium propionate increased significantly (P less than 0.05) from 7.6 +/- 0.5 minutes to 10.1 +/- 1.0 minutes during fasting. Sulfobromophthalein half-life did not change significantly (3.8 +/- 0.79 minutes to 5.3 +/- 1.3 minutes). Increases in plasma glucose concentrations after propionate loading were significantly less during fasting than during feeding. Thus, the change in glucose concentration served as an indicator of hepatic conversion of propionate to glucose. Increases in glucose concentration of less than 2 mM at 30 minutes after propionate loading indicated that liver function was altered in nonlactating dairy cows. 相似文献
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