Effect of land use on chloride leaching from a large heterogeneous central European catchment during 1900–2010

Jiří Kopáček1, Josef Hejzlar1, Jiří Porcal1, Maximilian Posch2
1 Biology Centre AS CR, Institute of Hydrobiology, České Budějovice, Czech Republic
2 Coordination Centre for Effects, RIVM, Bilthoven, The Netherlands

O 1.6 in Long term trends in the functioning of ecosystems

14.07.2014, 15:35-15:55, H18

Using data on long-term monitoring of water quality, mass budgets, and empirical models, we quantified chloride (Cl) leaching from major diffuse and point sources in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900–2010), with the major aim to evaluate the influence of historical changes in land use and management practice on Cl leaching from agricultural land. The Cl input to farmland in synthetic fertilizers, livestock feed, and atmospheric deposition tripled in the 1950s–1980s (from 23 to 64 kg/ha/yr on average), and then abruptly decreased to ca 14 kg/ha/yr during 1990–2010. The proportion of drained agricultural land rapidly increased from 4% in the 1950s to its maximum of 43% in the 1990s. The Cl leaching from agricultural land did not exhibit a simple dose-response function. Agricultural soils retained on average ca 16 kg/ha/yr of Cl during 1959–1985, when the most important changes in land use and management practice occurred, and finally became a net Cl source of ca 11 kg/ha/yr on average during 1986–2010, when Cl input to soils declined and drainage of new land ceased. Our data suggest that the temporal changes in the Cl storage in agricultural land are associated with changes in Cl concentrations in both permanent soil water and soils. Physicochemical conditions in freshly drained soils (i.e., mainly elevated aeration and high concentrations of organic matter (SOM)) and high Cl inputs probably resulted in higher Cl immobilization in soils by adsorption and formation of organic chlorine (Cl-org) than was the Cl production from desorption and Cl-org mineralization. In contrast, Cl desorption and Cl-org mineralization have exceeded the Cl retention during the consecutive period of low Cl inputs and decreasing SOM concentrations in agricultural soils. Our study implies that changes in land use and agricultural management can significantly affect dose-response function even in Cl, which is traditionally considered as a conservative ion.

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Letzte Änderung 05.02.2014