Impacts of acid deposition on contaminant mobility and biogeochemical processing in peri-urban
soils
There is a considerable body of literature on the effects of atmospheric deposition on ecosystem structure
and function, primarily in non-urban systems. A smaller portion of this literature focuses on the effects of
atmospheric deposition on biogeochemical dynamics in urban and peri-urban ecosystems. The bulk of
this literature describes the composition of atmospheric deposition in urban environments (e.g. Gatz 1991,
Treloar 1993, Bricker and Rice 1993, Lee 1993, Sansui et al. 1996, He at al. 2002, Kulshrestha et al.
2003) and the direct impacts of this deposition on receiving water quality (e.g.; Groffman and Jaworski
1991) and on urban infrastructures (e.g.; May and Klessig 199)0). A separate and growing body of
literature suggests that urban development alters both the nature and composition of urban soils (Pouyat et
al. 1995, Freedman et al. 1996, Carreiro et al. 1999, Weathers et al. 2001, Baxter et al. 2002, Brack 2002,
Pouyat et al. 2002). This is clearly the case in contaminated sites. But even in developed areas that
would not normally be thought of as contaminated, pollutants accumulate. Interactions between
atmospheric deposition and soil processes in peri-urban environments that are characteristic of ‘urban
sprawl’ in the northeast are not well known. We hypothesize that atmospheric deposition on peri- urban
soils mobilizes important contaminants, such as heavy metals and that, in turn, these contaminants and
the atmospheric deposition itself interfere with key soil biogeochemical processes; in particular,
respiration, mineralization, and nitrification. If true, this hypothesis has important implications for the
extension of results from studies proposed elsewhere in this workplan which focus on deposition-induced
stress in forests, including urban forests.
Proposed research: To address this hypothesis, we propose three linked sub-studies
Study 5a. Soil characteristics as a function of development intensity: Previous research suggests that
substantial differences in soil properties occur along undeveloped to urbanized gradients (Pouyat et al.
1995, Freidman et al. 1996, Carreiro et al. 1999, Weathers et al. 2001, Baxter et al. 2002, Brack 2002,
Pouyat et al. 2002). Urban sprawl in the Burlington-Chittenden County area in Vermont is widely
recognized as a pressing problem and the development patterns that have evolved here are representative
of those seen elsewhere in the formerly undeveloped, but urbanizing fringes of the northeast. For this
reason, we propose to use the greater Burlington-Chittenden County as our study area. The purpose of
this sub-study is to establish that identifiable differences do exist among sites that differ as a function of
development intensity.
Study 5b. Soil leachate characteristics as a function of development intensity: The same soil samples
from study 5a will be used for studies 5b and 5c. The objective of this study is not focused on
measurement of in situ rates. Rather, we wish to develop simple and reliable comparative indicators of
the influences of development intensity on key soil characteristics and processes.
Study 5c. Soil biogeochemical processes as a function of development intensity: The purpose of this
objective is to examine whether selected biogeochemical processes (respiration, mineralization,
nitrification) are affected by acid rain on soils contaminated as a consequence of urban development.