From February 2008 to March 2009,event-based wet-only precipitation samples for mercury(Hg),trace elements,and major ions analysis were collected at a monitoring site on Mauna Kea,a dormant volcano in Hawaii,USA.The objectives of these measurements were to quantify the levels of Hg wet deposition,and to assess the temporal variability in deposition levels and atmospheric transport patterns.The measurement site was located in the Honohina Track of the Hakalau Forest National Wildlife Refuge(19.8212,-155.3293)at an elevation of 1937 meters on the windward eastern face of Mauna Kea Mountain.Because of the monitoring sites central tropical North Pacific location between zones of mid-latitude westerly flow to the north and tropical easterly flow to the south,the air mass transport to the site broadly consists of either long-range transport typically originating from the west over or near the Eurasian continent,and short-range transport typically originating from the east over the Pacific Ocean.Climatologically,the source regions of air masses arriving to the site reflect seasonal modulation; while the period October-June is characterized by both the short-and long-range transport pathways,with the latter more prominent,the period July-September is dominated by the short-range pathway with little long-range transport.As part of this work,event-based associations were assessed and quantified between Hg wet deposition and air mass back-trajectory,as well as associations with other trace elements and major ions.Historical rainfall rates at this location peak during the summer months(July-September).For the full measurement time period,Hg wet deposition totaled 5.94 ?g/m2.We observed the highest monthly deposition of 2.13 ?g/m2 to occur during July of 2008,which represented 36%of the annual Hg wet deposition at this global marine background location.HYSPLIT 7-day back-trajectories were completed for each precipitation event collected,followed by a cluster analysis to statistically categorize air mass transport regimes.Of the nine statistically significant transport clusters,three clusters represented half of the total number of precipitation events,66%of the total Hg wet deposition for the monitoring period,and the three highest volume-weighted-mean Hg concentration clusters(6.6,5.1,& 8.8 ng/L,respectively).Generally,all three of these transport clusters were characterized as having approached near the U.S.west coast before arriving at the monitoring site.In contrast,two other clusters did not approach the U.S.west coast and were determined to be the two lowest Hg concentration clusters(2.1 ng/L).