Content area
Full Text
Environ Monit Assess (2009) 153:435448 DOI 10.1007/s10661-008-0369-4
Does road salting induce or ameliorate DOC mobilisation from roadside soils to surface waters in the long term?
Sophie M. Green Robert Machin Malcolm S. Cresser
Received: 16 August 2007 / Accepted: 5 May 2008 / Published online: 20 June 2008 Springer Science + Business Media B.V. 2008
Abstract Soils down slope of roads have been affected over decades by road salting in the UK uplands. Salt additions to fresh soil facilitate dispersal of organic matter so there is a potential risk of release of DON and DOC to nearby rivers where these run parallel to roads. Over time, however, salting enhances soil pH of naturally acid soils, and thus organic matter degradation through to CO2, thereby, lowering soil organic matter content. In addition any relatively labile organic matter may have already been dispersed. Thus, it is hypothesised that enhanced DOC mobilisation should only be a potential problem if soils not previously exposed to salt become heavily exposed in the future. This paper combines data from eld observations and laboratory simulations to elucidate mechanisms controlling organic matter mobilisation processes to determine what controls spatial and temporal trends in DOC concentrations in soil solutions down slope of roads. Organic matter solubilisation is dependent on the degree of road salt exposure soils have had. The laboratory experiment provided evidence that there are two competing effects upon which solubilisation is dependent (a) pH suppression and
S. M. Green (B) R. Machin M. S. Cresser
Environment Department, University of York, Heslington, York Y010 5DD, UKe-mail: [email protected]
(b) sodium dispersion. Other organic matter solubility models, if correct, link quite well with the authors when its gone, its gone hypothesis.
Keywords Road salt Sodium chloride
DOC concentration Upland river
Introduction
Green et al. (2008) examined the long-term implications of road salting to the nitrogen cycle. They emphasised its impacts on the fates of low-level inputs of ammonium-N and on the mobilization of nitrate-N from roadside soils to streams, and showed a reduction in soil organic-N pools. The use of road salt disrupted the relative contributions of ammonium-N and nitrate-N to total mineral N, and substantially altered mineralisation and nitrication rates due to a road salt-induced pH shift close to the highway. They did not...