Method development estimating ambient oxidized mercury concentration from monitored mercury wet deposition

S Chen,P Blanchard,X Qiu,F Yang,L Zhang

doi:10.5194/acp-13-11287-2013

Abstract

Abstract. To quantify mercury dry deposition, the Atmospheric Mercury Network (AMNet) of the National Atmospheric Deposition Program (NADP) was established recently to monitor the speciated atmospheric mercury (i.e. gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM)). However, the spatial coverage of AMNet is far less than the long-established Mercury Deposition Network (MDN) for wet deposition monitoring. The present study describes the first attempt linking ambient concentration of the oxidized mercury (GOM + PBM) with wet deposition aiming to estimate GOM + PBM roughly at locations and/or times where such measurement is not available but where wet deposition is monitored. The beta distribution function is used to describe the distribution of GOM + PBM and is used to predict GOM + PBM from monitored wet deposition. The mean, median, mode, standard deviation, and skewness of the fitted beta distribution parameters were generated using data collected in 2009 at multiple monitoring superstations. The established beta distribution function from the 2009 GOM + PBM data is used to construct a model that predicts GOM + PBM from wet deposition data. The model is validated using 2010 data at multiple stations, and the predicted monthly GOM + PBM concentrations agree reasonably well with measurements. The model has many potential applications after further improvements and validation using different data sets.

Highlights

Atmospheric mercury (Hg) is operationally defined as gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM), and particulate-bound Hg (PBM)
Speciated atmospheric Hg data are useful in studies on various topics, for example, identifying Hg source–receptor relationships (Lynam et al, 2006; Swartzendruber et al, 2006; Choi et al, 2008; Rutter et al, 2009; Weiss-Penzias et al, 2009; Huang et al, 2010; Sprovieri et al, 2010; Cheng et al, 2012, 2013), understanding Hg cycling and partitioning (Engle et al, 2008; Steffen et al, 2008; Amos et al, 2012), evaluating Hg transport models (Baker and Bash, 2012; Zhang et al, 2012a), and quantifying Hg dry deposition budget (Engle et al, 2010; Lombard et al, 2011; Zhang et al, 2012b)
The spatial coverage of Atmospheric Mercury Network (AMNet), which has around 20 monitoring sites in USA and Canada, is far less than the long-established National Atmospheric Deposition Program (NADP)’s Hg wet deposition network – the Mercury Deposition Network (MDN) – which has more than 100 monitoring sites

Summary

Introduction

Atmospheric mercury (Hg) is operationally defined as gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM), and particulate-bound Hg (PBM). Such a classification practice has been used in field data collections as well as in Hg transport models simulations. While most Hg transport models could produce reasonable GEM values on various spatial and temporal scales, they frequently failed to capture the magnitudes of GOM and PBM values at both urban and rural locations (Baker and Bash, 2012; Zhang et al, 2012a). Considering that mercury collected in precipitation is mainly from oxidized mercury (GOM and PBM), it might be possible to generate some statistical relationships between the ambient concentration and the wet deposition. Monitored data from AMNet for ambient GOM and PBM concentrations and MDN for wet deposition were applied to the study

Relationship between ambient concentration and wet deposition

Statistical model with wet deposition

Estimate of ambient Hg concentration from wet deposition

Model validations

Conclusions and recommendations