Climate control on sulphate and nitrate concentrations in alpine streams of Northern Italy along a nitrogen saturation gradient

Abstract

Abstract. The role of meteorology, hydrology and atmospheric deposition on the temporal pattern of SO 4 and NO 3 concentrations was investigated for three streams draining alpine catchments in Northern Italy.The study sites lie on a gradient of atmospheric fluxes of SO 4 and NO 3 (from about 50 to 80 meq m −2 y −1 , and from 40 to 90 meq m −2 y −1 , respectively). As a consequence of the increasing N input, the three catchments are also representative of aggrading levels of N saturation. Different methods of statistical analysis were applied to monthly data for the period 1997-2005 to identify which variables (temperature, precipitation, hydrology, SO 4 and NO 3 deposition) were the main predictors of water chemistry and its change in time. Hydrological changes and snow cover proved to be the main confounding factors in the response to atmospheric deposition in the River Masino catchment. Its particular characteristics (small catchment area, rapid flushing during runoff and thin soil cover) meant that this site responded without a significant delay to SO 4 deposition decrease. It also showed a clear seasonal pattern of NO 3 concentration, in response to hydrology and biological uptake in the growing season.The selected driving variables failed to model the water chemistry at the other study sites. Nevertheless, temperature, especially extreme values, turned out to be important in both SO 4 and NO 3 export from the catchments. This result might be largely explained by the effect of warm periods on temperature-dependent processes such as mineralization, nitrification and S desorption.Our findings suggest that surface waters in the alpine area will be extremely sensitive to a climate warming scenario: higher temperatures and increasing frequency of drought could exacerbate the effects of high chronic N deposition.Correspondence to: M. Rogora

On the tracks of Nitrogen deposition effects on temperate forests at their southern European range – an observational study from Italy

“…Nitrogen release from forest soil (a symptom of soil N saturation, e.g. Dise & Wright, 1995) was already detected in previous studies carried out at some of our plots (Mosello et al, 2002;Rogora et al, 2008). A year-round release of NO 3 -from the watersheds of five of the plots considered in this paper, and high level of N saturation according to the Stoddard & Traaen (1995) criteria were reported for the plot PIE1.…”

Catchment features controlling nitrogen dynamics in running waters above the tree line (central Italian Alps)

“…The fluxes reported for European Alpine sites at elevation above 2000 m a.s.l. are between 0.5-3 kg N ha −1 yr −1 , but at lower altitude sites these rates greatly increase (Hiltbrunner et al, 2005;Rogora et al, 2008).…”

Spatiotemporal Variability in Microbiological Water Quality of the Białka River and Its Relation to the Selected Physicochemical Parameters of Water

“…In April, there is a sharp decline in the water conductivity, which is related to the dilution with low-mineralized water from melting snow cover. As for nutrients (NH 4 + and NO 3 − ) in all sampling sites, it was confirmed that the highest concentrations occur in the beginning of snowmelt period (March, April), when the nitrogen compounds are leached out of the snow cover and soil (Rogora et al 2008;Holko et al 2006). On the other hand, during the growing period (June-September), the concentrations of these ions decrease, which is associated with assimilating them by plants (Campbell et al 2000;Clark et al 2004).…”