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81.
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
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84.
亚铵法制浆造纸厂中段废水处理技术分析研究 总被引:1,自引:0,他引:1
通过对采用两级气浮做预处理 ,生物硫化床串联接触氧化做深度处理的治理技术的分析研究 ,结合废水处理工程实例 ,说明了用两级串联气浮 +硫化床 +接触氧化工艺处理造纸中段水技术切实可靠 ,该治理工艺对处理亚铵法麦草制浆造纸中段废水有较强的针对性和可行性。 相似文献
85.
Wong MY Sauser KR Chung KT Wong TY Liu JK 《Environmental monitoring and assessment》2001,67(3):361-378
The green alga Selenastrum capricornutum expresses a uniqueascorbate peroxidase, that responds to copper and lead. Attemptswere made to test if this peroxidase could be used to monitor thelevels of copper and lead in natural waters. When S.capricornutum was exposed to a stormwater sample, the specificactivity of the peroxidase in the cell extract was commensuratewith the combined copper and lead contents in the sample. Theperoxidase responses were also correlated with the 96 hr biomasstoxicity assay of S. capricornutum. However, unlike thebiomass toxicity assay, the peroxidase activity was not affectedby the anions in the samples. The use of this peroxidase can beused as a marker for testing heavy metal toxicity in the water. 相似文献
86.
This study determined the spatial distribution of soiland of sediment-associated lead in Iqaluit, Nunavut.Samples were collected from the following areas:outside the built-up area of the town to reflectbackground concentrations; known or potential pointsources of lead, such as the Upper Base, the SylviaGrinnell Dump and the Metal Dump (North 40); andresidential and commercial areas of Iqaluit and Apex,a satellite community. In the laboratory, the <63 m sample fraction was analyzed for total lead andbioavailable lead, estimated by non-residual acidextractable lead content. The research findings revealthat elevated levels of bioavailable lead are presentin the study area. Total lead concentrations generallydo not exceed environmental guidelines. However, leadconcentrations in the Sylvia Grinnell Dump, and Apexand Iqaluit grid areas exceed health-based guidelines.The research concludes that there is not a serioushealth hazard posed by lead levels in the soil andsediment in the study area. However, severalenvironmental (elevated lead levels, bioavailableforms of lead and bare soil surfaces) and behaviouralfactors (vigorous and unsupervised play outside) maycreate a risk of lead exposure. 相似文献
87.
活性炭法测量室内空气中氡浓度的影响因素研究 总被引:1,自引:0,他引:1
探讨了各种因素对活性炭法测量室内空气中氡浓度的影响,并提出既能保证检测质量,又能符合工程检测需要、提高检测效率的检测条件范围。 相似文献
88.
Kimpo metropolitan landfill has received various kinds of wastessince January 1992. The leachate level was measured to be 10.3 m in May 1995 and the level increased to 12.2 m in August 1996. Therefore, to prove the reason for the increasing leachate level, we calibrated hydraulic conductivity of each waste andintermediate layer using the HELP (Hydrologic Evaluation ofLandfill Performance) model. The leachate generation data measured from February 1993 to October 1995 was used in the model calibration. As a result of a model calibration, we obtained anaverage infiltration ratio and used this in analysis of the total water balance to predict elevation of leachate level. Main causes of the elevation of the leachate level were the high water content of the waste and the degradation of the leachate-drainage system caused by the subsidence of a naturalbarrier layer. 相似文献
89.
During the summers of 1991–1994, the Environmental Monitoringand Assessment Program (EMAP) sampled 344 lakes throughout thenortheastern United States using a proportional stratified sampling design based on lake size. Approximately one-quarter ofthe 344 lakes were sampled each year (4 years) for totalphosphorus to determine the proportion (and associated95% confidence intervals) of the northeast lake population 1ha (11,076 ± 1,699 lakes) that was in oligotrophic,mesotrophic, eutrophic, or heupereutropic (4 classes) conditionaccording to the total phosphorus criteria of the North AmericaLake Manegement Society. Estimates for the second, third, andfourth yr were developed as cumulative of the previous yrsamples and the current yr samples for the northeast as a wholeand for each of its three ecoregions (4 regions). New confidence intervals were computed for each cumulative yrcondition estimate. This produced a total (4 years × 4classes × 4 regions) of 64 cumulative yr tropic conditionestimates. Confidence intervals for 21% of these estimates didnot shorten with increased sample size. This phenomena raisedquestions about the accuracy of estimates based on cumulativesampling procedures. We explain why and how the phenomenon comesabout with both straight random and proportional randomsampling. Further, we present an example of the effects thisphenomenon has on lake tropic state condition estimates in thenortheastern United States. 相似文献
90.
为修复灌区内土壤有机氯农药污染,降低六氯环己烷对土壤环境的危害,对内蒙古某灌域表层土壤进行采样,利用气相色谱测定50个土壤样品中六氯环己烷及其异构体的含量,并利用ArcGIS空间分析技术确定表层土壤中六氯环己烷的分布状况。样本中六氯环己烷的检出率为96%,各样本中六氯环己烷的浓度范围为未检出~23.0 ng/g,平均浓度为4.4 ng/g。4种异构体含量平均值顺序为γ-六氯环己烷>δ-六氯环己烷>β-六氯环己烷>α-六氯环己烷。灌域东北部和西南部残留浓度较高,并由这2个方向向中部地区逐渐递减,表层土壤中的六氯环己烷分布受土壤黏粒量、不同种植种类和灌溉水源的影响较大。虽受人类耕作的影响,但表层土壤中的六氯环己烷污染水平相对较低。 相似文献