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The National Atmospheric Deposition Program (NADP) developed and operates a collaborative network of atmospheric-mercury-monitoring sites based in North America - the Atmospheric Mercury Network (AMNet). The justification for the network was growing interest and demand from many scientists and policy makers for a robust database of measurements to improve model development, assess policies and programs, and improve estimates of mercury dry deposition. Many different agencies and groups support the network, including federal, state, tribal, and international governments, academic institutions, and private companies. AMNet has added two high-elevation sites outside of continental North America in Hawaii and Taiwan because of new partnerships forged within NADP. Network sites measure concentrations of atmospheric mercury fractions using automated, continuous mercury speciation systems. The procedures that NADP developed for field operations, data management, and quality assurance ensure that the network makes scientifically valid and consistent measurements. AMNet reports concentrations of hourly gaseous elemental mercury (GEM), two-hour gaseous oxidized mercury (GOM), and two-hour particulate-bound mercury less than 2.5 microns in size (PBM2.5). As of January 2012, over 450 000 valid observations are available from 30 stations. AMNet also collects ancillary meteorological data and information on land use and vegetation, when available. We present atmospheric mercury data comparisons by time (3 yr) at 21 individual sites and instruments. Highlighted are contrasting values for site locations across the network: urban versus rural, coastal versus high elevation and the range of maximum observations. The data presented should catalyze the formation of many scientific questions that may be answered through further in-depth analysis and modeling studies of the AMNet database. All data and methods are publically available through an online database on the NADP website (http://nadp.sws.uiuc.edu/amn/). Future network directions are to foster new network partnerships and continue to collect, quality assure, and post data, including dry deposition estimates, for each fraction. [ABSTRACT FROM AUTHOR]

Dry deposition of speciated mercury, i.e., gaseous oxidized mercury (GOM), particulate-bound mercury (PBM), and gaseous elemental mercury (GEM), was estimated for the year 2008--2009 at 19 monitoring locations in eastern and central North America. Dry deposition estimates were obtained by combining monitored two- to four-hourly speciated ambient concentrations with modeled hourly dry deposition velocities (Vd) calculated using forecasted meteorology. Annual dry deposition of GOM+PBM was estimated to be in the range of 0.4 to 8.1 µgm-2 at these locations with GOM deposition being mostly five to ten times higher than PBM deposition, due to their different modeled Vd values. Net annual GEM dry deposition was estimated to be in the range of 5 to 26 µgm-2 at 18 sites and 33 µgm-2 at one site. The estimated dry deposition agrees very well with limited surrogate-surface dry deposition measurements of GOM and PBM, and also agrees with litterfall mercury measurements conducted at multiple locations in eastern and central North America. This study suggests that GEM contributes much more than GOM+PBM to the total dry deposition at the majority of the sites considered here; the only exception is at locations close to significant point sources where GEM and GOM+PBM contribute equally to the total dry deposition. The relative magnitude of the speciated dry deposition and their good comparisons with litterfall deposition suggest that mercury in litterfall originates primarily from GEM, which is consistent with the limited number of previous field studies. The study also supports previous analyses suggesting that total dry deposition of mercury is equal to, if not more important than, wet deposition of mercury on a regional scale in eastern North America. [ABSTRACT FROM AUTHOR]

Three sets of model predicted values for speciated mercury concentrations and dry deposition fluxes over the Great Lakes region were assessed using field measurements and model intercomparisons. The model predicted values were produced by the Community Multiscale Air Quality Modeling System for the year 2002 (CMAQ2002) and for the year 2005 (CMAQ2005) and by the Global/Regional Atmospheric Heavy Metals Model for the year 2005 (GRAHM2005). Median values of the surface layer ambient concentration of gaseous elemental mercury (GEM) from all three models were generally within 30% of measurements. However, all three models overpredicted surface-layer concentrations of gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) by a factor of 2–10 at the majority of the 15 monitoring locations. For dry deposition of GOM plus PBM, CMAQ2005 showed a clear gradient with the highest deposition in Pennsylvania and its surrounding areas while GRAHM2005 showed no such gradient in this region; however, GRAHM2005 had more hot spots than those of CMAQ2005. Predicted dry deposition of GOM plus PBM from these models should be treated as upper-end estimates over some land surfaces in this region based on the tendencies of all the models to overpredict GOM and PBM concentrations when compared to field measurements. Model predicted GEM dry deposition was found to be as important as GOM plus PBM dry deposition as a contributor to total dry deposition. Predicted total annual mercury dry deposition were mostly lower than 5 μg m−2 to the surface of the Great lakes, between 5 and 15 μg m−2 to the land surface north of the US/Canada border, and between 5 and 40 μg m−2 to the land surface south of the US/Canada border. Predicted dry deposition from different models differed from each other by as much as a factor of 2 at regional scales and by a greater extent at local scales. [Copyright &y& Elsevier]

Between 2005 and 2(1(19, millions of U.S. and Canadian soybean acres that would have received fungicide application remained untreated for soybeait rust due to information disseminated through the Integruted Pest Managensent Pest Information Platform for Extension and Edttcaton (ipmPlPE), ittcreasing North American producers' profits by hundreds of millions of dollars each year. The results of our attalysis of Phakopsora podtyrhizi uredittiospores itt rain collections, aerobiology model output, and observations of soybean rust sprertd in 2007 and 2008 sltow a steno0 correspottdeuce betsveen spore collections and model predictions for the continental interior of North America, where soybean is an intportant crop. The analysis suggests that cotttrol petettces based on up-to-dale maps of soybean rust observtttions and associated comntentary trout Exteosiott Specialists delivered by the ipmPIPE nay have suppressed tlte number and strength of tnoculutit sottrce streas in the southern states and retarded tlte northward progress of seasonal soybean rust incursions into conttncntal North America. The analysis further indicates that spore trapping and aerobiological modeling catt reduce our reliance on the costly Sentinel Plot Network white maintaining the effectiveness of the iptttPlPE system for soybean rust management. [ABSTRACT FROM AUTHOR]