Atmospheric deposition of phosphorus and nitrogen in Central Alberta with emphasis on Narrow Lake

Abstract

Average rates of atmospheric deposition of total phosphorus (TP) and total nitrogen (TN) to Narrow Lake, located on sedimentary bedrock in the boreal forest of central Alberta, were 20 and 424 mg m z yr-l, respectively, between 1983-1986. There were no significant differences (P > 0.05) in deposition rates between sites on Narrow Lake, on the lake shore, and on land 18 km away. Deposition of TP, but not TN, followed a distinct pattern during the open-water season; TP was highest just after ice-off (May) and decreased throughout the remainder of the open-water season. Deposition during the winter accounted for only 4 and 12% of the annual TP and TN loads, respectively. Dry fallout contributed 50 and 33% of atmospheric deposition of TP and TN, respectively. In both dry and wet fallout, dissolved P (< 0.45 lam) and organic N were the predominant fractions of TP and TN, respectively. During July 1986, unusually heavy rainfalls caused an increase in TP, but not TN, concentrations in the epilimnion of Narrow Lake. Wet fallout accounted for only 9% of the observed increase of epilimnetic TP; the rest was from surface runoff from the drainage basin. The design of sampling programs to measure atmospheric deposition of nutrients to lakes is discussed.

Measuring and Calculating Current Atmospheric Phosphorous and Nitrogen Loadings to Utah Lake Using Field Samples and Geostatistical Analysis

“…These seasonal trends agree with many other studies which found that deposition increased in early summer and decreased over the remainder of the summer [32][33][34]. In a review of studies on TP deposition from long-range transport, deposition rates showed a wide range.…”

“…NADP-reported rates ranged from 2.14 to 8.42 mg m −2 year −1 [24] while our measured rates ranged from 0.04 to 24.82 mg m −2 year −1 . Our measured values appear to be reasonable when compared to other studies [31,33], again with the higher values used for the upper bound being attributed to local sources.…”

Measuring atmospheric nutrient deposition to inland waters: Evaluation of direct methods

“…The atmospheric input of N can be especially significant to aquatic ecosystems (Shaw et al 1989;Hu et al 1998;Larsen et al 2001) and humans have approximately doubled the rate of N input into terrestrial cycles (Galloway et al 1995;Vitousek et al 1997). Several reports suggest that P deposition should be included more frequently in atmospheric deposition studies (Gomolka 1975;Cole et al1990;Jassby et al 1994;Ahn and James 2001).…”

“…Two studies have shown that measured deposition rates decreased as collectors were moved from shore to open water (Gomolka 1975;Cole et al 1990) whereas another showed no significant difference between deposition rates measured onshore and offshore (Shaw et al 1989). Another study has shown that measured rates of phosphorus deposition are lower and less variable when automated samplers are placed 15 m from the ground (Pollman et al 2002).…”

“…Several studies have found significant differences in dry deposition rates between wet and dry surfaces (Gomolka 1975;Cole et al 1990;Jassby et al 1994). Because many studies of atmospheric deposition examine nutrient deposition to water bodies (Gomolka 1975;Shaw et al 1989;Cole et al 1990;Jassby et al 1994;Hu et al 1998;Tamatamah et al 2005), the relative retention efficiency of wet surfaces and dry buckets is an important assumption. These methodological problems have led some to calculate deposition indirectly by measuring aeolian particle concentrations using filter packs and modeling deposition rates.…”