Partition and Tempospatial Variation of Gaseous and Particulate Mercury at a Unique Mercury-Contaminated Remediation Site

Abstract

ABSTRACT This study investigated the seasonal variation and spatial distribution of gaseous and particulate mercury at a unique mercury-contaminated remediation site located at the near-coastal region of Tainan City, Taiwan. Gaseous elemental mercury (GEM), particulate mercury (PTM), and dustfall mercury (DFM) were measured at six nearby sites from November 2009 to September 2010. A newly issued Method for Sampling and Analyzing Mercury in Air (National Institute of Environmental Analysis [NIEA] Method A304.10C) translated from U.S. Environmental Protection Agency (EPA) Method IO-5, was applied for the measurement of atmospheric mercury in this particular study. One-year field measurements showed that the seasonal averaged concentrations of GEM and PTM were in the range of 5.56–12.60 and 0.06–0.22 ng/m3, respectively, whereas the seasonal averaged deposition fluxes of DFM were in the range of 27.0–56.8 g/km2-month. The maximum concentrations of GEM and PTM were 38.95 and 0.58 ng/m3, respectively. The atmospheric mercury apportioned as 97.42–99.87% GEM and 0.13–2.58% PTM. As a whole, the concentrations of mercury species were higher in the springtime and summertime than those in the wintertime and fall. The southern winds generally brought higher mercury concentrations, whereas the northern winds brought relatively lower mercury concentrations, to the nearby fishing villages. This study revealed that the mercury-contaminated remediation site, an abandoned chlor-alkali manufacturing plant, was the major mercury emission source that caused severe atmospheric mercury contamination over the investigation region. The hot spot of mercury emissions was allocated at the southern tip of the abandoned chlor-alkali manufacturing plant. On-site continuous monitoring of GEM at the mercury-contaminated remediation site observed that GEM concentrations during the open excavation period were 2–3 times higher than those during the nonexcavation period. IMPLICATIONS A manual and an auto-monitoring technique were successfully applied to sample gaseous and particulate mercury at a unique mercury-contaminated remediation site and further measured with a cold-vapor atomic fluorescence spectrometry (CVAFS). The mercury-contaminated remediation site was announced as a supersite of mercury contamination by the Environmental Protection Bureau (EPB) of Tainan City in 2003, causing significant contamination of atmospheric mercury over the investigation region. Both ambient temperature and prevailing wind direction played critical roles on the tempospatial variation and partition of gaseous and particulate mercury in the ambient atmosphere.