Trace elements and heavy metals in the Grand Bay National Estuarine Reserve in the northern Gulf of Mexico

Abstract

The objectives of this study are to investigate distribution of trace elements and heavy metals in the salt marsh and wetland soil and biogeochemical processes in the Grand Bay National Estuarine Research Reserve of the northern Gulf of Mexico. The results show that Hg, Cd and to some extent, As and Pb have been significantly accumulated in soils. The strongest correlations were found between concentrations of Ni and total organic matter contents. The correlations decreased in the order: Ni>Cr>Sr>Co>Zn, Cd>Cu>Cs. Strong correlations were also observed between total P and concentrations of Ni, Co, Cr, Sr, Zn, Cu, and Cd. This may be related to the P spilling accident in 2005 in the Bangs Lake site. Lead isotopic ratios in soils matched well those of North American coals, indicating the contribution of Pb through atmospheric fallout from coal power plants.

Keywords: Biogeochemical process; Environmental impact; Estuarine chemistry; Grand Bay Reserve; Lead isotopes; Trace elements.

Fig. 1

Location of the Grand Bay National Estuarine Reserve in the Gulf of Mexico and sampling sites (indicated by solid dots) (modified from Peterson et al. (2007)).

Fig. 2

Concentrations of trace elements and heavy metals in the Grand Bay Reserve, the Gulf of Mexico, USA.

Fig. 3

Variance in concentrations of trace elements and heavy metals in soils from the Grand Bay Reserve, the Gulf of Mexico, USA.

Fig. 4

Ratios of concentrations of trace elements and heavy metals in the Grand Bay Reserve, The Gulf of Mexico, USA over concentrations in the lithosphere and world soil (concentrations of trace elements and heavy metals in the world soil and global lithosphere are from Han et al. (2002a,b, 2003), Taylor and McLennan (1985), Ure and Berrow (1982), Aubert and Pinta (1977), Bowen (1982), Baur and Onishi (1969), Lide (1996), Bockris (1977)).

Fig. 5

Comparisons of trace elements and heavy metals in various sites from the Grand Bay Reserve, the Gulf of Mexico, USA (CB: Crooked Bayou site; BC: Bayou Cumbest site; BH: Bayou Heron site; and BL: Bangs Lake site).

Fig. 6

Strong correlations between concentrations of trace elements and organic matter content in soils from the Grand Bay Reserve in the Gulf of Mexico, USA.

Fig. 7

Phosphorous accumulation in sites of the Grand Bay Reserve (above) and strong correlations between concentrations of P and OM% in soils (CB: Crooked Bayou site; BC: Bayou Cumbest site; BH: Bayou Heron site; and BL: Bangs Lake site).

Fig. 8

Strong correlations between concentrations of trace elements/heavy metals and total phosphorus content in soils of Grand Bay Reserve, the Gulf of Mexico, USA.

Fig. 9

Distribution of Pb isotopes in the soil samples from the Grand Bay Reserve of the Gulf of Mexico (above) (BH: Bayou Heron site; CB: Crooked Bayou site; BL: Bangs Lake site and BC: Bayou Cumbest site) and their comparisons with reference samples (below). Pb isotopes in North American Coal, petroleum derived Pb, Chesapeake Bay sediments and South Florida lake sediments were from Díaz-Somoano et al. (2009), Landmeyer et al. (2003), Atkinson et al. (2011), Marcantonio et al. (2002) and Escobar et al. (2012), respectively.