Mercury hotspot identification in Water Conservation Area 3, Florida, USA

Abstract

A significant amount of science and effort has been placed on understanding the biogeochemical cycle of mercury within the Florida everglades. The range of resolution for these studies include regional (Everglades Protection Area) and site-specific scales, with very little attention being given to the landscape scale. However, a lot of questions still exist regarding methyl mercury (MeHg) synthesis, bioaccumulation and environmental accumulation. I used the Geti–Ord Gi * spatial clustering statistic to describe and evaluate soil total mercury (THg) and MeHg data collected by U.S. Environmental Protection Agency Regional Environmental Monitoring and Assessment Program between 1995 and 2005. Soil mercury (total and methyl) displayed distinct spatial clustering within Water Conservation Area 3 (WCA3) and was dependent on canal density, water control structure density and hydroperiod. THg hotspots were identified consistently within the southern portion of WCA3A and WCA3B in areas with prolonged hydroperiods (360.9 ± 0.7 days), low canal densities (0.064 ± 0.008 canals/km2) and low structure densities (0.008 ± 0.001 structures/km2). MeHg hotspots consistently occurred within the northern portion of WCA3A and during the last year of sampling in WCA3B. MeHg hotspots occurred in areas with shorter hydroperiods (282.0 ± 8.8 days), lower canal density (0.109 ± 0.013 canals/km2) and higher structure density (0.029 ± 0.005 structures/km2). Results presented in this study provide further understanding to Hg hotspot dependence on hydrological factors and potentially help guide water management decisions.