title: Sulphate leaching from diffuse agricultural and forest sources in a large central European catchment during 1900-2010.
abstract: Using dynamic, mass budget, and empirical models, we quantified sulphate-sulphur (SO4-S) leaching from soils in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900-2010). SO4-S inputs to soils with synthetic fertilisers and atmospheric deposition increased in the 1950s-1980s, then rapidly decreased (~80%), and remained low since the middle 1990s. The proportion of drained agricultural land rapidly increased from 4 to 43% between the 1950s and 1990s; then the draining ability of the system slowly decreased due to its ageing. Sulphate concentrations in the Vltava exhibited similar trends as the external SO4-S inputs, suggesting that they could be explained by changes in atmospheric and fertiliser S inputs. The available data and modelling, however, showed that (i) internal SO4-S sources (mineralization of soil organic S in the drained agricultural land), (ii) a hysteresis in SO4-S leaching from forest soils (a net S retention at the high S inputs and then a net release at the lowered inputs), and (iii) hydrology must be taken into account. An empirical model was then employed, based on parameters representing hydrology (discharge), external SO4-S sources (inputs by synthetic fertilisers and atmospheric deposition), and internal SO4-S sources (mineralization related to soil drainage). The model explained 84% of the observed variability in annual SO4-S concentrations in the Vltava river during 1900-2010 and showed that forest soils were a net sink (105 kg ha(-1)) while agricultural land was a net source (55 kg ha(-1)) of SO4-S during 1960-2010. In the late 1980s, forest soils changed from a sink to a source of S, and the present release of SO4-S accumulated in forest soils thus delays recovery of surface waters from acidification, while S losses from agricultural soils increase the risk of future S deficiency in S-demanding crops.
authors.affiliation: Biology Centre AS CR, Institute of Hydrobiology, Na Sádkách 7, 37005 České Budějovice, Czech Republic. Electronic address: jkopacek@hbu.cas.cz.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kopáček
authors.affiliation: Biology Centre AS CR, Institute of Hydrobiology, Na Sádkách 7, 37005 České Budějovice, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Hejzlar
authors.affiliation: Biology Centre AS CR, Institute of Hydrobiology, Na Sádkách 7, 37005 České Budějovice, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Porcal
authors.affiliation: Coordination Centre for Effects, RIVM, P.O. Box 1, NL-3720 BA Bilthoven, The Netherlands.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Posch
mesh_terms: D000383:Agriculture; D018153:Czech Republic; D004784:Environmental Monitoring; D008956:Models, Chemical; D045483:Rivers / Q000737:chemistry; D013431:Sulfates / Q000032:analysis*; D014197:Trees; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D013431:Sulfates; D014874:Water Pollutants, Chemical
keywords: Diffuse sources; Modelling; Sulphate leaching; Sulphur mineralization