The rapid and continuous monitoring of gaseous elemental mercury (GEM) behavior in ambient air

Abstract

In order to examine the environmental behavior of elemental mercury (GEM or Hg°) at varying time scales, Hg concentration data were obtained at 1-s intervals using a rapid Hg monitoring system (Lumex Hg analyzer). The Hg data sets obtained from a total of 24 experiments were analyzed in two different manners—either as raw data (collected at 1-s intervals) or after modification into two arbitrarily extended intervals (i.e., 10 s and 1 min). To meaningfully interpret those rapidly monitored Hg data, we evaluated both the raw and modified data sets in varying respects. The environmental behavior of Hg, while exhibiting clear distinctions over diurnal and/or seasonal scales, was found to experience sharp changes for a very short time period, usually less than a few tens of seconds to a minute. During such a short duration, a five- to ten-fold increase in Hg concentration was commonly found. As a means to evaluate the temporal factors associated with Hg behavior, the correlation analysis was made using both the original and modified data sets between the various statistical parameters (mean, median, min, and max). The overall results of this study confirm that the temporal variability of Hg, while maintaining highly stable and systematic patterns (e.g., over diurnal or seasonal scale), can be dramatically dynamic over very short time intervals such as a few tens of seconds or minutes.