Acid atmospheric deposition in a forested mountain catchment

Abstract

(2) Acid atmospheric deposition is harmful to both forest and aquatic ecosystems. In mountain catchments, acidification also leads to difficulties in water resource management. In 2010-2012, acid atmospheric deposition was analysed in a small forest catchment located in the upper plain of the Jizera Mountains (Czech Republic). Patch observations included monitoring of the canopy interception in two mature stands of Norway spruce (Picea abies) at elevations of 745 and 975 metres a.s.l., and twelve passive fog collectors situated along an elevation gradient between 862 and 994 metres a.s.l. In the studied area, fog (and low cloud) precipitation starts to affect the interception loss of the spruce canopy at elevations above 700 metres. However, fog drip was found to also rise with the canopy area. At the catchment scale, methods of spatial interpolation (ArcGIS 10.2) were used to approximate the aerial atmospheric deposition of water and acidic substances (sulphate, nitrate and ammonia). In the watersheds of two adjacent drinking water reservoirs, Josefův Důl and Souš, the mean annual fog drip from the canopy was between 88 and 106 mm (i.e., 7-8% of the mean annual gross precipitation, or 10-12% of the mean annual runoff). Simultaneously, this load also deposited 658 kg km -2 of sulphur and 216 kg km -2 of nitrogen (i.e., 55% and 48% of the "open field" bulk amounts). Therefore, in headwater catchments stressed by acidification, the additional precipitation (measured under the canopy) can increase the water yield, but can also contribute to a decline in water quality, particularly in environments of low buffering capacity.

Environmental Role of Snowmelt in Headwaters Affected by Atmospheric Acid Deposition

“…Sample bottles there were protected against direct rainfall access by a wide-brimmed cover that overlapped the fog collector at an angle of 34 • . The throughfall observation method was used to detect fog drip in the mature spruce stand at 3 different elevations [37,38]. Ten 200 cm 2 storage gauges were randomly adjusted under the canopy on plots of 30 × 30 m (substituted by snow lysimeters in winter periods) while stem flow in spruce stands was considered negligible according to [38,39].…”

“…where I is the canopy interception (mm), P is the open field (gross) precipitation (mm), and P t is throughfall under the canopy (mm). Seasonal atmospheric loads of studied acidifying chemicals (SO 4 2− , NO 3 − , and NH 4 + ) by fog drip were estimated by Equation ( 6) [37]:…”

“…Annual values of the open field load of sulphur and nitrogen registered at Jizerka in the years 1982-2021 are presented in Figure 9. In the Jizerka experimental catchment, fog drip is significantly rising with the number of foggy days, elevation, and the canopy density [37]. Generally, in the upper part of the Jizera Mountains, the number of winter foggy days exceeds the summer foggy days by 60% [27].…”

“…For the respected canopy classes (Figure 8), the fog drip coefficient Fc (Equation 7) was found to decrease from Fc = 1 (mature spruce forests with the horizontal canopy density CD > 0.8) to values Fc = 0.33 (middle age stands with CD > 0.3) and Fc = 0.18 (young stands with a dominant herbaceous layer by CD < 0.3). Seasonal coefficients b and b0 (Equation ( 3)) of the deposited fog water and acidic ions (SO4 2− , NO3 − and NH4 + ) in summer In the Jizerka experimental catchment, fog drip is significantly rising with the number of foggy days, elevation, and the canopy density [37]. Generally, in the upper part of the Jizera Mountains, the number of winter foggy days exceeds the summer foggy days by 60% [27].…”

Ambient Air Quality in the Czech Republic: Past and Present

“…Similarly as in other regions of Europe and US [194,195], it was demonstrated that in the CR, by not considering (1) deposition path via fog and (2) unmeasured constituents of dry deposition, such as NH 3 and HNO 3 (g), the total sulphur and nitrogen depositions are likely to be underestimated substantially [196,197]. Although the chemistry of fog is regularly observed at only a few sites in the CR, and information on fog chemistry is scarce [198,199], it is widely recognised that fog in the CR is enriched as compared to rain, particularly in SO 4 2-and NO 3 - [103,104,200]. Moreover, the hydrological input of fog, namely in forested mountain areas, in the CR above 800 m above sea level might not be negligible [201].…”