The transition phase for the NADP/MDN covers the period of February 1995 to February 1996. The seventeen sites in the transition phase were concentrated in the Upper Midwest, the Northeast and along the Atlantic seaboard. A volume-weighted mean concentration of 10.25 ng/L total Hg for the seventeen sites was measured during this time. The most common concentrations range between 5 and 15 ng/L, with the highest value (50 ng/L) reported at Lewes, DE. The highest Hg concentration and deposition values are typically during the summer months with the lowest values reported for the winter months. A complete copy of this data report is available from the NADP Coordination Office.

Network coordination during the transition phase was contracted to Buffalo State College. The mercury analysis and preparation of the sample bottles were contracted to Frontier Geosciences, Inc. Clean sampling trains were shipped to the sites from Buffalo State College. A collection was made each week, on a Tuesday to Tuesday schedule, whether or not precipitation occurred. Site operators followed an established Standard Operating Procedure.

Quality assurance screening for the transition phase was conducted by the analytical laboratory and Buffalo State College. NADP/MDN samples collected in 1996 and in future years will undergo a thorough NADP quality assurance screening. During the transition phase at least one in every ten samples was analyzed in duplicate, one in every ten samples was analyzed with a matrix spike recovery, and a standard reference material DORM-2 was analyzed with each batch of samples. Reagent blanks were determined once for each batch of reagents. The reagent value is an introduced contaminant and is therefore subtracted from the sample concentration at the analytical laboratory.

Quality Assurance Codes for the Transition Phase

     W    Valid wet-only sample
     B    Operator purposely leaves the lid open to get a bulk sample
     U    Orifice exposed for an undefined time other than during precipitation
     NSI  Sample interval was greater 6 days and less than than 8 days, and not on Tuesday to Tuesday schedule 
     S    Sampling interval was less than 6 days 
     E    Sampling interval exceeded more than 8 days 
     V    Lab received sample volumes less than 23 mL (3 mL greater than original acid precharge 
     OF   Overflow water noted in overflow dish 
     NN   No information was reported 
     QP   System Blank clean water is poured through the funnel and tube into the sample bottle 
     FP   Funnel, capillary tube or bottle mishandled in field 
     SE   Site environment is compromised 
     C    Visible debris in sample bottle (i.e., insects, discolored water, plant matter) 
     f    Invalid for summary calculations 

Sites in the Mercury Deposition Transition Network

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