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Soil Total Mercury Concentrations across the Greater Everglades
Author(s) -
Cohen Matthew J.,
Lamsal Sanjay,
Osborne Todd Z.,
Bonzongo Jean Claude J.,
Newman Susan,
Reddy K. Ramesh
Publication year - 2009
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2008.0126
Subject(s) - soil water , environmental chemistry , ecosystem , deposition (geology) , environmental science , organic matter , population , peat , wetland , chemistry , hydrology (agriculture) , zoology , ecology , soil science , geology , biology , sediment , geomorphology , geotechnical engineering , demography , sociology
Elevated Hg concentrations in the Everglades pose ecological and human health risks. We mapped soil total Hg concentrations per mass (THg M ) and area (THg A ) across the Everglades, and investigated relationships with soil properties (total P [TP] and organic matter content), community type, and hydrologic compartmentalization. Samples ( n = 600) from surface soils (0–10 cm) were selected from a population of 1405 sites spanning the Everglades. Overall, 168 sites had THg M levels >0.2 mg kg −1 ; interpolation suggests that 23% of the Greater Everglades exceeds this threshold. Hot spots (>0.4 mg kg −1 ) were observed in eastern Water Conservation Area (WCA) 1 and west‐central WCA3A; parts of WCA2A, WCA3AN, and WCA3B were locally high. Despite significant global differences in THg M among plant communities, differences evaluated using paired proximate sites were not significant, suggesting that large spatial scale depositional gradients govern ecosystem storage. Median THg A was 1.89 mg m −2 (range 0.07–12.05 mg m −2 ), representing approximately 100 yr of atmospheric deposition at contemporary rates (∼19 μg m −2 yr −1 ). Correlation between TP and THg M was positive in unimpacted areas (TP < 500 mg kg −1 , r = 0.69), but negative in impacted areas (TP > 500 mg kg −1 , r = ‐0.47), probably due to accelerated peat accretion rates in P‐enriched areas. Moreover, while reverse correlation with distance from a canal for THg M (0.70) and TP (−0.77) supports Hg enrichment via atmospheric deposition, THg M hotspots in WCA3AS, WCA1, and the Holeyland and Rotenberger tracts are suggestive of local enrichment mechanisms. Finally, despite dramatic regional emissions declines, the estimated mass of Hg in surface soils across the Everglades has increased ∼20% (11,000 vs. 13,100 kg) since 1996; while the statistical significance of this change is unknown, it provides a useful benchmark for future surveys.