Expanding Our Knowledge of Wet and Total Deposition through Resin Technology: Possibilities for Extending the NADP Network
H.A. Ewing
Program in Environmental Studies,
Bates College,
Lewiston, ME, USA
The NADP and CASTNET are critical national networks for monitoring trends in deposition and its spatial variation across the country. However, the density of both networks is insufficient to fully characterize wet, dry, and total deposition across landscapes, especially in areas with complex patterns of topography or land cover. We describe here what is known about the utility of resin technology and the steps needed to make resins a viable part of an extended national monitoring network. Our laboratory experiments loading anion, cation, and mixed resins have shown that resins can effectively capture—and then be extracted to measure—atmospheric loads of the anions NO3-, Cl-, SO42-, and Br-. Cation recovery in the laboratory has been less effective, particularly for the divalent cations Ca2+ and Mg2+ and in experiments with small loadings. Field studies have used resins in dense networks both in the open and under canopies to provide time-integrated measures of both wet and total deposition of several ionic species, demonstrating the potential of resins to extend monitoring of deposition spatially. We propose a design for further laboratory- and field-based testing of resin technology necessary for implementation in a national network such as NADP. Such work would include tests of resin efficiency, the suitability of different extractant solutions, resin stability during storage (pre- and post-deployment), resin response to freezing and drying, and comparisons of resin collections to aqueous field loads. With further testing, resin technology could effectively extend the wet-deposition—and eventually also the total-deposition—networks through their time-integrated measure of atmospheric ion deposition to complex terrain. We also highlight the ways in which multiple kinds of institutions—including undergraduate institutions, established analytical labs, and the NADP lab at the Illinois State Water Survey—can play a role in the development of this technology.