Trends in Cloud and Rain Water Chemistry from 1984-2007 on Mount Washington, NH (1,534 M)

Georgia L. D. Murray1, Kenneth Kimball1, L. Bruce Hill2, Chris Eagar3, Jane Hislop3 and Kathleen Weathers4

The Appalachian Mountain Club (AMC), with cooperation from the US National Forest and Institute of Ecosystem Studies, has sampled June – August montane rain and cloud events on Mt. Washington, NH since 1984. The Lakes of the Clouds (LOC) sampling site is located at 1,540 m asl, 1.6 km SW of the summit of Mount Washington, NH (44° 16’N, 71° 18’W, 1,914 m ASL), and adjacent to two designated Class I areas (Great Gulf and Presidential Dry River Wildernesses). The AMC/WPI cloud water collector used excludes rain from the cloud water sampled. Rain water was collected with an open funnel. Rain and cloud samples were analyzed in the field and lab for pH. Major cation and anions were analyzed for a subset of samples from 1984-1989, no analysis from 1990-1994, and for all samples from 1995-2007. Cloud volume data are insufficient across the historical dataset to volume weight cloud chemistry values; volume weighting rain water chemistry is possible. Some data gaps exist across the temporal record due to staffing and/or funding restrictions.

An initial comparison of non-volume weighted cloud and rain water event sample concentrations for pre (H ion: 1984-1994, sulfate ion: 1984-1989) and post (1995-2004) full implementation of the 1990 Clean Air Act Amendments (CAAA) show significantly lower hydrogen ion concentrations for the later time period (non-parametric Mann Whitney U tests p<0.001). Pre and post CAAA trends in cloud and rain water sulfate concentrations were weaker (p= 0.08 and >0.1 respectively). The absence of sulfate samples from 1990-1994 may contribute to the lack of significant differences in pre- and post CAAA implementation. We will present an update of this analysis through 2007 and include wet and dry chemistry reported from the nearby (55 km SW from LOC) but much lower (250m asl) USFS Hubbard Brook Experimental Forest’s NADP and CASTNET sampling site, understanding that we used event samples while NADP and CASTNET used weekly samples. In addition, we will present comparisons of concurrent rain and cloud water sample chemistry, relationships of hydrogen ion with major anion concentrations in rain and cloud water, and the relationship of cloud hydrogen ion concentration with sampling period average wind speed and temperature.

1 Appalachian Mountain Club, Research Department, Route 16 Gorham, NH 03581, USA 603-466-2721 or
2 Clean Air Task Force, 18 Tremont Street, Suite 530 Boston, MA 02108, USA
3 USFS Northern Research Station, 271 Mast Road, Durham, NH 03824
4 Cary Institute of Ecosystem Studies, P.O. Box AB, Millbrook NY 12545-0129, USA