Dry Deposition Monitoring
Atmospheric deposition is the process by which airborne pollutants are deposited to the earth. These pollutants include, but are not limited to, sulfur dioxide, nitrogen oxides, ammonia, and mercury. Total deposition consists of both wet and dry components.
Wet deposition occurs when pollutants are deposited in combination with precipitation, predominantly by rain and snow, but also by clouds and fog. The NPS monitors wet deposition through the National Atmospheric Deposition Program (NADP).
Dry deposition of particles and gases occurs by complex processes such as settling, impaction, and adsorption. Dry deposition is monitored through the Clean Air Status and Trends Network (CASTNet).
CASTNet measures weekly average atmospheric concentrations of sulfate, nitrate, ammonium, sulfur dioxide, and nitric acid; and meteorological conditions. Filter packs are exposed for 1-week intervals at a flow rate of 1.5 liters per minute (3.0 liters per minute for western sites), and sent to the contracted laboratory in Gainesville, Florida, for chemical analysis. Dry deposition rates are calculated using atmospheric concentrations, meteorological data, and information on land use, vegetation, and surface conditions.
|Metadata||what, where, and when monitors have operated in national parks||Monitoring History Database|
|Dry Deposition||sulfate, nitrate, ammonium, sulfur dioxide, and nitric acid concentration and deposition; and meteorological data||CASTNet website|
|CASTNet Total Deposition Charts||summary charts of total sulfur and nitrogen deposition||
*charts are found by clicking on a site under Site Information
The following maps show total deposition, including both wet and dry components for 2002. Dry deposition rates are calculated using the Multi-layer Leaf Model (MLM). Total deposition is reported below in terms of kilograms per hectare per year for sulfur and nitrogen.
|NPS Deposition Program Manager||Kristi Morris||(303) 987-6941|