Since 1978, the National Atmospheric Deposition Program (NADP) has tracked the status and changes in the many different chemical compounds within precipitation across the continent. The NADP monitors the removal of pollutants from the atmosphere; but more importantly, it monitors the addition of chemical compounds into the Biosphere and ecosystems of North America.
Our primary charge has been to provide data for the determination of both spatial and temporal trends in chemical species and mercury wet-deposition fluxes for North America. And over the 30 years of monitoring, we have shown the value of consistent monitoring techniques, high quality assurance standards, and rigorous attention to procedures and data validation. This has allowed us to reliably quantify both small and large trends in several chemical species. Results from our measurements will be provided. It is clear that the addition of acidic compounds to ecosystems has dropped drastically over the past three decades, but that certain regions are still experiencing high acidic compound loading. Our data also show that nitrogen deposition is increasing, and in particular to very sensitive ecosystems. We are noting the heavy regional increases in nitrogen deposition are due to ammonium increases.
A new direction for NADP is the evaluation of Critical Loading of anions, which is being directed by our Scientific Subcommittee Critical Loads of Atmospheric Deposition subcommittee. The goal of the committee is to determine total deposition (wet and dry) of specific anions. This data is used to compare to estimated critical load definitions that cause changes in the ecosystem. Specific output from this effort will be presented.
Additionally, NADP would encourage participation in our network operations by researchers and/or government agencies in Mexico that would like to be part of our network. The addition of sites in Mexico would improve our coverage of the continent, and improve data for all North American scientists. In the talk, i will cover some of these aspects.