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Sulphate, Nitrogen and Base Cation Budgets at 21 Forested Catchments in Canada, the United States and Europe 总被引:1,自引:0,他引:1
Watmough SA Aherne J Alewell C Arp P Bailey S Clair T Dillon P Duchesne L Eimers C Fernandez I Foster N Larssen T Miller E Mitchell M Page S 《Environmental monitoring and assessment》2005,109(1-3):1-36
To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s
average) for sulphate (SO4), inorganic nitrogen (NO3-N; NH4-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada,
the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more
than 9 years of data were available (14 regions, 17 sites). Annual average SO4 deposition during the 1990s ranged between 7.3 and 28.4 kg ha−1 per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha−1 per year, of which 41–67% was nitrate (NO3-N). Over the period of record, SO4 concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO4 in runoff decreased at 14/17 catchments. In contrast, NO3-N concentrations in deposition decreased in only 1/14 regions, while NH4-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff
decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH4-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments
and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations
in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively,
which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at
18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31–100%; median 94%)
was retained in the catchments, although there was a tendency for greater NO3-N leaching at sites receiving higher (<7 kg ha-1 per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at
all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for
18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively.
Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses
at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty
associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium
ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions
in SO4 and H+ deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of
Ca and Mg of primary concern.
The U.S. Government's right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.
The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright. 相似文献
2.
Shaun A. Watmough Julian Aherne M. Catherine Eimers Peter J. Dillon 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):301-306
In response to reduced sulphur emissions, there has been a large decrease in sulphate (; −0.97 μeq l−1 year−1) and hydrogen (−1.18 μeq l−1 year−1) ion concentration in bulk precipitation between 1980 and 2000 at Plastic Lake in central Ontario. The benefit of this large
reduction in deposition on stream water chemistry was assessed using the gauged outflow from a conifer-forested catchment (PC1; 23.3 ha),
which is influenced by a small wetland located immediately upstream of the outflow. Sulphate concentrations declined, but
not significantly due to large inter-annual variation in concentration. Between 1980 and 2000, there were significant increases in dissolved organic carbon, ammonium and potassium
concentration likely reflecting increased mineralisation in the wetland. Calcium concentrations in PC1 decreased during the
two decade period (−2.24 μeq l−1 year−1), as a consequence there was no improvement in stream pH and the Ca:Al ratio in PC1 continued to decline. A similar response
was noted in an upland-draining sub-catchment of PC1-08 that has been monitored since 1987. Despite large reductions in deposition and almost complete retention of nitrogen in soil, there has been no improvement (in terms of pH) in stream water
at PC1 due to a combination of soil acidification and climatic (droughts, increased mineralisation) perturbations. 相似文献
3.
Eimers MC Watmough SA Buttle JM Dillon PJ 《Environmental monitoring and assessment》2007,127(1-3):399-407
Increased sulphate (SO4) export from wetlands following summer droughts in central Ontario, Canada has been associated with the delayed chemical
recovery of downstream surface waters following decreased sulphur (S) emissions. Prolonged summer droughts result in a decrease
or cessation of stream flow, declines in wetland water table level and oxidation of reduced S compounds to SO4, which is subsequently flushed into drainage streams when stream flow resumes. Sulphate input-output budget calculations
(1983–1995 and 1999–2001) at a conifer Sphagnum swamp in the Plastic Lake catchment, indicate that SO4 is retained in most years but is exported on a net basis following particularly severe summer droughts that result in the
cessation of stream flow for more than 54 days (95% CI: 41–72 days). Hindcast calculations using long-term (1916–2000) stream
discharge records from a nearby station indicate that while droughts occurred frequently in south-central Ontario over the
past 85 years, sufficiently dry conditions to cause net SO4 export occurred in only18 of the past 85 years, and indicate a cumulative positive SO4 balance for the swamp (i.e. net SO4 retention). Furthermore, the S pool at the Plastic Lake swamp has been estimated to be ∼1500 kg S/ha in the upper 40 cm peat
layer, which is large compared to the amount of net SO4 export that occurs even in years with particularly dry summers (e.g. −43 kg S/ha in 1987/88). Together, these data suggest
that the wetland S pool at Plastic Lake has not been depleted by previous droughts and will continue to sustain episodic drought-related
SO4 export for the foreseeable future. 相似文献
4.
An assessment of the nutrient status of sugar maple in Ontario: indications of phosphorus limitation 总被引:1,自引:0,他引:1
Soil acidification, caused by elevated anthropogenic deposition, has led to concerns over nutrient imbalances in Ontario's sugar maple (Acer saccharum Marsh.) forests. In this study, soil chemistry, foliar chemistry, crown condition, and tree growth were measured at 36 sugar maple stands that included acidic (pH?4.4), moderately acidic (4.4?≤?pH?5.4), and non-acidic (pH?≥?5.4) soil groups. Acidic sites had significantly lower foliar P, Ca, and Mg concentrations, and the Diagnosis and Recommendation Integrated System indicated that P, rather than Ca or Mg, was the most limiting nutrient. This is in spite of widespread reports of net Ca losses from acidified soils. Mass balance studies in the region indicate that in acidic forest soils, P input from deposition is greater than stream export. Low foliar P is therefore most likely due to low P availability to trees resulting from accumulation in organic matter/biomass and/or adsorption to Fe and Al hydroxides which are more prevalent in acidic soils. Despite differences in foliar nutrition, there were no significant differences in crown condition or tree growth across the study region, suggesting that low P availability is not yet having a widespread detrimental effect on tree health. 相似文献
5.
Partitioning and bioaccumulation of cadmium in artificial sediment systems: application of a stable isotope tracer technique 总被引:2,自引:0,他引:2
The utility of stable isotope tracers for investigating the relationship between cadmium (Cd) partitioning in artificial sediment-water systems and Cd accumulation in a benthic detritivore (Asellus racovitzai, Isopoda) was explored. In the laboratory, Cd isotopes were applied to synthetic sediment and isotope concentrations were measured in sediment, overlying water and exposed asellids over a 10-day period. Isotope ratios measured in sediment and water were compared to ratios measured in asellids to determine whether Cd partitioning could predict metal bioaccumulation. Two different parameters which might affect Cd partitioning between the sediment and overlying water compartments were investigated: the chemical form in which Cd was added to systems, and the organic matter content of the sediment. To test the effect of chemical form on Cd partitioning, three isotopes of cadmium were individually applied to formulated sediment in varying combinations of 113Cd(NO3)2, 112Cd-humic acid (HA) 114CdSO4. The results demonstrated that chemical form did not influence partitioning, as the Cd isotope that was applied to sediment in the nitrate form exhibited similar partitioning between sediment and overlying water as the isotope that was applied in the sulfate or HA form. However, Cd isotope concentrations in overlying water were strongly related to the pattern of isotope accumulation in asellids suggesting that overlying water concentrations determined Cd bioaccumulation. In contrast, when the organic matter content of sediment was increased through the addition of Sphagnum peat moss, total Cd concentrations in overlying water and tissue were low, and there was no relationship between Cd-isotope concentrations in tissue and water. These results indicate that Cd accumulation occurred primarily from water, and factors that increase metal partitioning to sediment, such as increased sediment organic matter content, decrease Cd accumulation in asellids. The stable isotope tracer method described herein appears to be a useful technique for investigating the relationship between metal partitioning and bioaccumulation in simple sediment systems, but could also be extended to more complex systems, and used with different metals that have multiple stable isotopes. 相似文献
6.
A stable isotope tracer technique was used to evaluate the relative importance of particulates and water as respective sources of cadmium (Cd) uptake in the freshwater isopod Asellus racovitzai (Isopoda, Crustacea). 113Cd(NO3)2 was applied to the sediment at a nominal concentration of 20.0 ng g-1, and 114Cd(NO3)2 was added to the overlying water (nominal concentration of 4.4 ng g-1), in the same test systems. Asellids added were either free-ranging on the sediment surface, where they were exposed to both particulate and water sources of Cd, or were enclosed in dialysis 'tubes', 10 cm above the sediment surface, and were therefore exposed to Cd in water only. By analysis of both isotopes, uptake vectors could be determined simultaneously. After 7 days of exposure, average 114Cd concentrations in 'free' asellids were 15.6 +/- 2.0 micrograms/g, compared with 10.4 +/- 1.8 micrograms/g in 'tube'-held asellids (P < 0.05), i.e. at least 60% of accumulated 114Cd was from water. Furthermore, water-spiked 114Cd was accumulated in asellids to tissue concentrations that were more than four-times greater than sediment-spiked 113Cd. When the sediment organic content was increased (20% peat moss), total Cd concentrations in both overlying water and asellids were significantly lower (P < 0.01), compared with the mineral sediment treatments, and Cd accumulation in tube and free asellids was similar. This study shows that water is an important vector of Cd accumulation in A. racovitzai, and factors that lower Cd concentrations in solution (such as increased organic content of sediment), decrease Cd bioaccumulation. 相似文献
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