排序方式: 共有9条查询结果,搜索用时 31 毫秒
1
1.
2.
Long-term (1860–2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty
in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish
IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass
balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated
base cation (BC) release rates (weathering) varied in a relatively narrow range of 47–62 or 42–47 meq m−2 year−1, depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or
introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted
changes in acid neutralizing capacity (ΔANC ca. 10–41 μeq l−1) and pH (ca. ΔpH = 0.1–0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent
on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants,
temporal changes in soil element pools, and fluxes of Al between compartments. 相似文献
3.
中国南方生态系统的酸沉降临界负荷 总被引:17,自引:0,他引:17
将中国南方生态系统的酸沉降敏感性等级与用MAGIC模型在对应样点计算的临界负荷值相结合,对中国南方生态系统的酸沉降临界负荷进行了研究,并编制了1°×1°经纬度网格的临界负荷图.研究结果表明,中国南方生态系统硫沉降临界负荷大多在2.3~5.2gm2a之间,在地域分布上由东南向西北逐渐增大,其中临界负荷小于3.0g/m2a的极敏感地区为浙江南部、广东与福建交界地区、贵州西南部和广西中部. 相似文献
4.
Reduction of sulphur deposition causesrecovery of acidified surface waters. Processes in thecatchment delay recovery. The acidification model MAGICwas applied to the Vikedal and Tovdal rivers in southernNorway. Response in water chemsitry is delayed by 10–20 yr. The delay is due to release of old sulphate atVikedal and cation exchange at Tovdal. Assuming that theGothenburg protocol is fully implemented by the year2010, much of the predicted increase of ANC will occur inthe next 10 yr with a levelling off by about 2040. Ifnitrogen leaching increases in the future, however,recovery of ANC will not be as rapid, nor as complete.Critical load for acidity calculated by steady-statemodels is confirmed by the MAGIC predictions. Futurerequirement for mitigation measures such as liming willdecrease in the future as acid deposition decreases. Bythe year 2046 the liming requirement will be reduced byabout 45% at Vikedal and 65% at Tovdal. One of the mainpurposes of the Norwegian national monitoring programmeis to provide documentation of changes in environmentalquality due to long-range transported air pollutants.Modelling applications such as this clearly show that thedata fill this purpose. 相似文献
5.
This paper describes an application of the long termdynamic model, MAGIC, on a monthly timestep, enablingincorporation of the seasonal dynamics associated with abroad understanding of the ecosystem N cycle. The modelhas been applied to the Dargall Lane catchment in theGalloway region of Scotland where marked seasonal Ndynamics are apparent. Mean monthly proportions ofrainfall, runoff, deposition fluxes and net retention ofN are utilised to drive the model on a monthly timestep.Calibration of the model has successfully reproduced thepresent day observed seasonal variation in streamNO3 and ANC. Prediction of recovery at the siteunder the second sulphur protocol indicates that,although mean annual ANC increases, mean monthly ANC doesnot rise above zero for all months of the year until2010. 相似文献
6.
7.
IntroductionThemodelofacidificationofgroundwaterincatchment(MAGIC)isoneofthemostwidelyusedmodelsworldwideforpredictingcatchmentacidificationandisstillunderfurtherupgrading(Cosby,1985;Hinderer,1995;Cosby,1995).Themodel,however,isinherentlyassociatedwithnumericali… 相似文献
8.
酸沉降临界负荷计算模式的修正 总被引:2,自引:0,他引:2
酸沉降临界负荷是酸沉降水平的函数,不同酸沉降水平下,矿物风化速率有数量级差别,在因此,酸沉降临界负荷的计算应先使用判别方程计算平衡PH值,然后确定采用何种方法计算,在欧洲可以直接采用动态模式计算临界负荷,是因为其酸沉水平能满足判别方程成立,但在中国大多数情况下不成立。 相似文献
9.
Ian?F.?Dennis Thomas?A.?ClairEmail author Bernard?J.?Cosby 《Environmental Modeling and Assessment》2005,10(4):303-314
Accurate predictions of acid precipitation effects on water resources are important in order to allow a better understanding
of various pollution control strategy outcomes. Dynamic geochemical models have been developed to address this need, but have
to be tested under a variety of environmental conditions to provide confidence in their predictions. The most commonly used
aquatic acidification model in North America and Europe is the model of acidification of groundwater in catchments (MAGIC).
Though extensively used, MAGIC has never been tested in catchments with extremely low ionic strength water and high in natural
organic acids (NOAs) from wetlands, two conditions which are common in large parts of Canada. We calibrated the model for
two catchments located in Nova Scotia, Canada, which had some of the most dilute freshwaters reported in the literature and
very high NOA. We also evaluated the variability inherent in calibration data sets by using five separate data sets collected
over a 15-year period at the same sites. We show good model simulations for the main cations and anions in catchment waters.
However, modeling pH is more difficult in the highly organic waters and requires modification to the acid dissociation constants.
Calculated acid neutralization capacity can also be more difficult to model due to the low ion content making small errors
more important. In theory, multiple calibrations of a model at a same site should produce identical hindcasts and predictions.
In reality, the multiple calibrations produced a series of similar, but not identical outcomes which give a probable range
of past values and future outcomes. We feel that this practical approach to validation is a useful addition to the arsenal
of model testing tools. 相似文献
1