Modeling the effect of liming on calcium concentration in Swedish lakes.
To abate the severe acidification of Swedish lakes are about 7% directly limed (AL-lakes). These are important to include when assessing acidification. Consequently, we need to estimate their chemical status as if they were not lime-affected. We hypothesize that there is a spatial dependence for calcium (Ca) and magnesium (Mg) concentrations. Spatial variation is determined using variograms. We study lakes within two 150 * 150 km quadrates (EMEP150-grid) in the middle and southern parts of Sweden. We model Ca in AL-lakes using the Ca and Mg concentrations in nearby, unaffected lakes (UL-lakes). The mean Ca/Mg for the three or seven closest UL-lakes is used. We assume that Ca/Mg is constant for UL-lakes and that Mg unaltered by liming. For UL-lakes, Ca and Mg are spatially dependent. For AL-lakes, there is a spatial dependence for Mg, but, as anticipated, not for Ca. The modeled Ca for UL-lakes show a good correspondence with measured Ca; r2 > 0.6; slopes close to 1 and intercepts almost 0. Using three or seven nearby lakes when modeling Ca give similar results. Modeled Ca was higher than measured Ca for 36% (three closest lakes) and 38% (seven closest) of the modeled AL-lakes in the middle part of Sweden. The corresponding results for the southern part were 10% and 9%, respectively. This model is an acceptable estimator of Ca in limed lakes and for estimating critical loads and acidification status on an EMEP-scale.
Göransson
Elisabet
E
Department of Environmental Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Bringmark
Ewa
E
Rapp
Lars
L
Wilander
Anders
A
D002118:Calcium / Q000032:analysis*; D017610:Calcium Compounds / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000032:analysis*; D008274:Magnesium / Q000032:analysis; D010087:Oxides / Q000737:chemistry*; D013548:Sweden; D014873:Water Pollutants / Q000032:analysis
D017610:Calcium Compounds; D010087:Oxides; D014873:Water Pollutants; C016538:lime; D008274:Magnesium; D002118:Calcium