Spatial patterns of atmospheric deposition of nitrogen and sulfur using ion-exchange resin collectors in Rocky Mountain National Park, USA

Abstract

h i g h l i g h t sDeposition of NO 3 À and DIN were positively related to elevation.Summer DIN deposition was 25e50% greater on the east side of the park than on the west. A high-resolution geospatial model of summer DIN deposition was created for the park. Emissions sources and climate patterns affect spatial patterns in N and S deposition. Seasonal patterns in NO 3 À isotopes may reflect variations in emissions sources. a b s t r a c tLakes and streams in Class 1 wilderness areas in the western United States (U.S.) are at risk from atmospheric deposition of nitrogen (N) and sulfur (S), and protection of these resources is mandated under the Federal Clean Air Act and amendments. Assessment of critical loads, which are the maximum exposure to pollution an area can receive without adverse effects on sensitive ecosystems, requires accurate deposition estimates. However, deposition is difficult and expensive to measure in high-elevation wilderness, and spatial patterns in N and S deposition in these areas remain poorly quantified. In this study, ion-exchange resin (IER) collectors were used to measure dissolved inorganic N (DIN) and S deposition during June 2006eSeptember 2007 at approximately 20 alpine/subalpine sites spanning the Continental Divide in Rocky Mountain National Park. Results indicated good agreement between deposition estimated from IER collectors and commonly used wet þ dry methods during summer, but poor agreement during winter. Snowpack sampling was found to be a more accurate way of quantifying DIN and S deposition during winter. Summer DIN deposition was significantly greater on the east side of the park than on the west side (25e50%; p 0.03), consistent with transport of pollutants to the park from urban and agricultural areas to the east. Sources of atmospheric nitrate (NO 3 À ) were examined using N isotopes. The average d 15 N of NO 3 À from IER collectors was 3.5‰ higher during winter than during summer (p < 0.001), indicating a seasonal shift in the relative importance of regional NO x sources, such as coal combustion and vehicular sources of atmospheric NO 3 À . There were no significant differences in d 15 N of NO 3 À between east and west sides of the park during summer or winter (p ¼ 0.83), indicating that the two areas may have similar sources of atmospheric NO 3 À . Results from this study indicate that a combination of IER collectors and snowpack sampling can be used to characterize spatial variability in DIN and S deposition in high-elevation wilderness areas. These data can improve our ability to model critical loads by filling gaps in geographic coverage of deposition monitoring/modeling programs and thus may enable policy makers to better protect sensitive natural resources in Class 1 Wilderness areas.Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/3.0/).

Atmospheric deposition of inorganic nitrogen in Spanish forests of Quercus ilex measured with ion-exchange resins and conventional collectors

“…When excluding the most influencing NH 4 -N values on Pearson's r, this metric became lower ( 0.70), while better results were found for RMSE (0.29), and MFB showed and overall overestimation of NH 4 -N bulk deposition (27%). Other authors have reported similar overestimations of bulk deposition of NH 4 -N when using IECs compared to CBCs (Clow et al, 2015;Fenn and Poth, 2004;Hansen, 2012;Langlois et al, 2003). There are three main processes that could account for the discrepancy between methods: release of NH 4 þ from the amine groups of the IER, and nitrification or volatilization losses of NH 3 in the liquid samples of the CBCs (Fenn and Poth, 2004).…”

“…But the need to expand monitoring networks has impelled the use of less expensive methods, easy to operate, and without requiring frequent visits to the field (Clow et al, 2015;Erisman et al, 2005). The common alternative is using open samplers (bulk deposition collectors), which have no provision to exclude dry deposition during rainless periods.…”

Export flux of unprocessed atmospheric nitrate from temperate forested catchments: A possible new index for nitrogen saturation

“…The volume of each sample was determined using plastic cylinders in the field, and portions of each sample were brought to the 10 laboratory for further analysis. Please note that the dry deposition flux, especially for gaseous HNO 3 , is underestimated in the NO 3 − atm deposition flux determined through this method (Aikawa et al, 2003), while the deposition flux of NO 3 − atm could be overestimated due to the progress of nitrification in sample bottles during storage in the field until recovery (Clow et al, 2015).…”

“…The areal bulk deposition flux of NO 3 As presented in section 2.4, the deposition flux could be either underestimated, due to insufficient inclusion of the dry deposition flux (Aikawa et al, 2003) or overestimated, due to the progress of nitrification in sample bottles during storage in the field until recovery (Clow et al, 2015). As a 15 result, we use the bulk deposition flux determined in this study (45.6 mmol m -2 yr -1 ) as the areal total (wet + dry) deposition flux of NO 3 − atm (D atm ) at the KJ site by allowing error range of 20% in the discussions in this study.…”

Atmospheric concentration and deposition of reactive nitrogen in Spanish forests of Quercus ilex

“…Measurements of bulk deposition of N using the IEC method showed a good agreement CBCs (Clow, et al, 2015;Fenn and Poth, 2004;Hansen, 2012;Langlois et. al., 2003).…”