Trace metals in the soils of Water Conservation Area of Florida Everglades: Considerations for ecosystem restoration

Dhaliwal, SalwinderS.; Toor, GurpalS.; Rodriguez-Jorquera, IgnacioA.; Osborne, ToddZ.; Newman, Susan

Trace metals in the soils of Water Conservation Area of Florida Everglades: Considerations for ecosystem restoration

2018

Dhaliwal, SalwinderS. | Toor, GurpalS. | Rodriguez-Jorquera, IgnacioA. | Osborne, ToddZ. | Newman, Susan

PURPOSE: Inorganic contaminants present a major challenge for the restoration of aquatic ecosystems. The objectives of this study were to determine the extent of trace metal contamination and investigate the influence of different plant communities on trace metal accumulation in the soils of the Florida Everglades. MATERIALS AND METHODS: Soil samples (n = 117) were collected from 0 to 10-cm depth using a stainless steel coring device from sites with three dominant plant communities—cattail, sawgrass, and slough—of Water Conservation Area-2A (43,281 ha) of Florida Everglades. RESULTS AND DISCUSSION: The mean pH in soils collected from three plant communities was 6.75–6.82, whereas electrical conductivity was slightly greater in the sawgrass (0.69 dS m⁻¹) than cattail (0.58 dS m⁻¹) and slough (0.40 dS m⁻¹). Mean reduction–oxidation potential was greatest in cattail (−113 mV) than sawgrass (−85.3 mV) and slough (−48.3 mV) soils. Among 11 trace metals (As, B, Co, Cr, Cu, Mn, Mo, Na, Ni, Pb, Zn) found in soil samples, Na had the greatest contents and was greater in cattail (2070 mg kg⁻¹) and sawgrass (1735 mg kg⁻¹) than slough (1297 mg kg⁻¹). Four trace metals (B, Cu, Mo, Ni) were significantly greater in cattail than sawgrass and slough. Whereas, Mn was significantly lower in cattail (31 mg kg⁻¹) than both sawgrass (84 mg kg⁻¹) and slough (51 mg kg⁻¹). Cattail also had significantly lower Cr (1.97 mg kg⁻¹) and Pb (10 mg kg⁻¹) than sawgrass (Cr 2.5 mg kg⁻¹; Pb 20.8 mg kg⁻¹). As (<6.9 mg kg⁻¹), Co (<1.3 mg kg⁻¹), and Zn (<17.2 mg kg⁻¹) were not significantly different among soils collected from three plant community-dominant sites. Contents of Cd and Se were below the method detection limits (Cd 0.01 mg L⁻¹; Se 0.2 mg L⁻¹) and are not reported. CONCLUSIONS: None of the trace metals in the soils exceeded the US Environmental Protection Agency sediment toxicity thresholds. Results from this study provided baseline concentrations of trace metals, which can be used to measure the success of restoration efforts in Florida Everglades.

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