Deployment of the Monitor for AeRosols and GAses in ambient air (MARGA) at a CASTNET Site in Beltsville, MD to Identify Potential Artifacts in Historic Filterpack Data

摘要

Two MARGA systems were collocated over an eight month period. The MARGA performance on hourly time scale by a collocated pulsed fluorescence SO_2 analyzer. Additionally the MARGA units performed very well when compared against one another. A change in inlet height and length was made to one of the MARGAs to determine the effect on instrument performance and it was found that the shortened inlet had a significant impact on NH_3 recovery in cold weather. Future studies with the MARGA will use the shortened inlet. The MARGA data was then integrated into week-long periods to compare with traditional CASTNET measurements made with the filterpack and the passive NH_3 sampling for the AMoN network. Comparisons showed good agreement for SO_2, total nitrate, NH_4~+, and SO_4~(-2), but indicate some biases and potential sampling artifacts for HNO_3, NH_3, and the base cations. Inorganic ratios were calculated and compared and indicate potential seasonal differences. This work will expand on previous studies of precision of the CASTNET network and comparisons to other networks, by including hourly resolved measurements rather than comparison of only integrated methods. If artifacts are consistent enough to be quantified, algorithms will be proposed to correct past site-specific and possibly network-wide CASTNET filterpack data.