Sulphate leaching from diffuse agricultural and forest sources in a large central European catchment during 1900–2010 Jiří Kopáček a, ⁎, Josef Hejzlar a , Petr Porcal a , Maximilian Posch b a Biology Centre AS CR, Institute of Hydrobiology, Na Sádkách 7, 37005 České Budějovice, Czech Republic b Coordination Centre for Effects, RIVM, P.O. Box 1, NL-3720 BA Bilthoven, The Netherlands HIGHLIGHTS • Study is based on 50-year monitoring of SO 4 –S export from the upper Vltava catchment. • SO 4 –S export primarily reflects hydrology and S inputs in fertilisers and deposition. • But, mineralization and desorption contribute to SO 4 –S leaching from soils. • Leaching of accumulated SO 4 –S delays recovery of surface waters from acidification. • S losses from farmland increase a risk of S deficiency for S-demanding crops. abstract article info Article history: Received 30 July 2013 Received in revised form 6 October 2013 Accepted 7 October 2013 Available online xxxx Editor: Christian EW Steinberg Keywords: Modelling Sulphate leaching Sulphur mineralization Diffuse sources Using dynamic, mass budget, and empirical models, we quantified sulphate–sulphur (SO 4 –S) leaching from soils in a large central European catchment (upper Vltava river, Czech Republic) over a 110-year period (1900–2010). SO 4 –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 SO 4 –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 SO 4 –S sources (mineralization of soil organic S in the drained agricultural land), (ii) a hysteresis in SO 4 –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 SO 4 –S sources (inputs by synthetic fertilisers and atmospheric deposition), and internal SO 4 –S sources (mineralization related to soil drainage). The model explained 84% of the observed variability in annual SO 4 –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 SO 4 –S during 1960–2010. In the late 1980s, forest soils changed from a sink to a source of S, and the present release of SO 4 –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. © 2013 Published by Elsevier B.V. 1. Introduction Since the mid-1900s, when anthropogenic acidification was rec- ognized as a wide-spread phenomenon in many parts of Europe and North America, great progress has been made in the documentation, understanding, and modelling of sulphur (S) deposition effects on terrestrial and aquatic ecosystems (e.g. Psenner and Catalan, 1994; Norton and Veselý, 2004). Long-range atmospheric transport of S has contributed to the acidification of sensitive areas and resulted in elevated sulphate–sulphur (SO 4 –S) concentrations in receiving fresh waters. In contrast to unmanaged (forest and alpine) areas, where atmospheric deposition represents the major S input, agricultural land has also received SO 4 –S as a part of S-bearing synthetic fertilisers such as ammonium sulphate, potassium sulphate, superphosphate and complex fertilisers since the early 20 th century (Eriksen, 2009). Sulphur is not only an acidifying pollutant, but also an essential nutrient required for plant growth, and plays an important role in many plant processes such as synthesis of essential amino acids, chlorophyll, and fixation of nitrogen (N) by leguminous plants (Blair, 2002; Eriksen, 2009). Consequently, significant reductions in S emissions since the 1980s (Smith et al., 2011), decreasing concentrations of Science of the Total Environment 470–471 (2014) 543–550 ⁎ Corresponding author. Tel.: +420 38 7775878; fax: +420 385 310 248. E-mail address: jkopacek@hbu.cas.cz (J. Kopáček). 0048-9697/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.scitotenv.2013.10.013 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv