Sponsoring Organization: National Atmospheric Deposition Program
Description: The MDN is the only network providing a long term record of total mercury (Hg) concentration and deposition in precipitation in the United States and Canada.
Duration: 01/01/1996 to present (as of 08/29/2012)
Program Contact: David Gay
Program Contact Email: firstname.lastname@example.org
Program Contact Web URL: http://nadp.sws.uiuc.edu/NADP/contacts.aspx
Data Access Web URL: http://nadp.sws.uiuc.edu/data/mdndata.aspx
Data Access Policy: Data and information presented on this website (http://nadp.sws.uiuc.edu/) are in the public domain, unless otherwise indicated. Some images and graphics on this website have been created by other organizations and are used by the NADP with permission. Under copyright law, if you want to use images or graphics used by the NADP with permission, you first need to obtain the permission of the copyright holder.
Data Access Policy Web URL: http://nadp.sws.uiuc.edu/nadp/useConditions.aspx
Sampling Design: All MDN sites follow standard procedures and have uniform precipitation chemistry collectors and gages. The automated collector has the same basic design as the NTN collector but is modified to preserve mercury. Modifications include a glass funnel, connecting tube, bottle for collecting samples, and an insulated enclosure to house this sampling train. The funnel and connecting tube reduce sample exposure to the open atmosphere and limit loss of dissolved mercury. As an additional sample preservation measure, the collection bottle is charged with 20 mL of a one percent hydrochloric acid solution.
Sampling Frequency: Daily to Weekly
Sample Collection: Site operators collect samples Tuesday morning or daily within 24 hours of the start of precipitation.
Sample Processing: With each MDN sample, the entire sampling train is replaced with one that is cleaned by the Mercury Analytical Laboratory (HAL) at Frontier Global sciences, Inc., Seattle, Washington. Rigorous cleaning ensures that each sampling train component is essentially mercury-free. The HAL supplies the collection bottles already charged with the hydrochloric-acid preservative. By following those procedures and stringent sampling protocols, the MDN is able to report mercury concentrations below 1 part per trillion (<1 nanogram/liter).
Quality Assurance Plan: All MDN samples are sent to the HAL, which analyzes all forms of mercury in a single measurement and reports this as total mercury concentrations. At the end of 2005, 23 MDN sites also opted for methyl mercury analysis. The HAL reviews field and laboratory data for completeness and accuracy, and flags samples that were mishandled, compromised by precipitation collector failures, or grossly contaminated. The HAL delivers all data and information to the NADP Program Office for final checks and resolution of remaining discrepancies. Data then are made available on the NADP Web site.
Parameters Measured: Mercury (Hg) concentration
Monitoring Stations: 25 stations are registered in the database (search/display)