Passive monitoring techniques for evaluating atmospheric ozone and nitrogen exposure and deposition to California ecosystems

Abstract

Measuring the exposure of ecosystems to ecologically relevant pollutants is needed for evaluating ecosystem effects and to identify regions and resources at risk. In California, ozone (O₃) and nitrogen (N) pollutants are of greatest concern for ecological effects. "Passive" monitoring methods have been developed to obtain spatially extensive measurements of atmospheric pollutant concentrations and deposition flux inputs of N and other nutrient ions in California ecosystems. Two general types of passive samplers have been used: (1) passive samplers for determining time-averaged concentrations of gaseous pollutants in the atmosphere and (2) ion exchange resin (IER) collectors for measuring ionic deposition inputs. Common pollutants measured with passive samplers include nitrogen dioxide, nitric oxide, nitric acid vapor, ammonia, and O₃. Common ions measured with IER deposition samplers include nitrate, ammonium, sulfate, phosphate, chloride, calcium, magnesium, potassium, and sodium. Laboratory and field methods, and the principles of use and appropriate applications for these atmospheric and deposition samplers, are described. Data from monitoring networks using these techniques help identify areas at risk and provide the foundation for describing pollution impacts to sensitive resources. In this report, several alternative approaches for estimating N deposition are also considered as a guide for selecting appropriate techniques in ecosystemeffects studies in California and elsewhere. We emphasized that measurements of N deposition in precipitation (wet deposition) alone are highly inadequate for characterizing deposition inputs under the climatic conditions of California and much of the arid West. Dry deposition of N must also be accounted for by using methods such as those described herein.

Citation

Fenn, Mark E.; Bytnerowicz, Andrzej; Schilling, Susan L. 2018. Passive monitoring techniques for evaluating atmospheric ozone and nitrogen exposure and deposition to California ecosystems. Gen. Tech. Rep. PSW-GTR-257. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 129 p.