Date of Award

Spring 2012

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Arts

First Advisor

Bill McDowell

Abstract

In this study, I compare the chemical composition of throughfall in deciduous and coniferous forest stands to the chemistry of wet deposition. The study was conducted at Thompson Farm, Durham NH, which is owned and managed by the University of New Hampshire. Thompson Farm (43.11N, 70.95W) is at an altitude of 23 m and about 24 km from the Gulf of Maine. Throughfall samples were obtained from two forest stands using wet-dry Aerochem Metrics 301 collectors and rainfall samples were collected in a wet-only precipitation collector (N-CON Atmospheric Deposition Samples Model 00-120) from 14 April 2009 to 14 November 2009.The amount of throughfall at the two sites was similar, and less than rainfall during the study period.

A total of 35 sets of rainwater and throughfall chemistry were collected and analyzed for pH, electrical conductivity, specific conductance and major ions; SO42--, NO3-, Cl-, Ca2+, Na+, Mg2+, K+ and NH4+ as well as dissolved organic carbon and nitrogen. The chemical concentration of rainfall and throughfall were analyzed in conjunction with meteorological variables to evaluate the nature of temporal and monthly variations.

The pH of individual rainfall and throughfall fluctuated widely, ranging from 3.5 to 7.9 in rainfall (TF2), 3.7 to 6.2 in coniferous throughfall (TFC), and 4.2 to 6.9 in deiciduous throughfall (TFD), indicating high variability in the acid sources and in neutralization processes. The mean concentrations of NO3- and non-sea salt SO42-- were 14.45 and 11.08 mueql--1 (TF2), 16.8 and 18.28 mueql--1 (TFC), and 13.6 and 18.03 mueql --1 (TFD), respectively. Dominant ionic species in TF2, TFC and TFD were: CI-- > Na+ > NH4 +-N>NO3-- > SO42-- > Ca2+ >K+> Mg2+ > PO 43---P, Cl-- > Ca2+> K+> Na+> Mg2+> SO4 2-- > NO3-- > NH4 +-N > PO43---P and K+> Mg2+>Ca2+ > Cl-->Na +> SO42-- > NO3-- PO43---P > NH4+ -N, respectively.

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