Spatial distribution of heavy metals in sediments from the Gulf of Paria, Trinidad | Spatial distribution of heavy metals in sediments from the Gulf of Paria, Trinidad

Inglés. The Gulf of Paria receives heavy metal input from urban runoff, industrial and agricultural activity, sewage and domestic wastes: both from the west coast and from inland areas of Trinidad. Non-residual concentrations of nine metals, as well as total mercury concentrations, were used to determine spatial distributions of heavy metals in sediments in the Gulf of Paria. Surficial sediment samples were collected at 37 stations, which included the mouths of 11 major rivers that flow into the Gulf of Paria. Stations were sampled twice during the wet season (July 1998 and November/ December 1998) and twice during the dry season (March 1999 and April 1999). Sediments were analyzed for aluminium (Al), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn) and mercury (Hg). Total Organic Carbon (TOC) and grain size analyses were also performed on the sediments. Principal component analysis showed that sediments from river mouths subject to greatest land use and anthropogenic input, were distinct from other sediments in the Gulf of Paria. This was due to higher Pb, Zn, Cu and Hg concentrations (3.53-73.30 μg g-1, 45.8-313.9 μg g-1, 8.43-39.71 μg g-1 and 0.03-0.10 μg g-1, respectively). Sediments further from the coast were also distinct due to their higher Al, Fe, Cr and Mn concentrations (1.37-3.16 mg g-1, 9.51-18.91 mg g-1, 17.22-28.41 μg g-1 and 323.6–1,564.2 μg g-1, respectively). Cd and Pb were higher in the wet season while Ni was higher in the dry season. Pb, Zn, Cu and Hg were correlated with each other and with TOC. Correlation was also observed between Al, Fe, Cr, Mn and Ni. Al, Fe, Cr and Mn were correlated with percentage clay in sediments. The results suggest that Pb, Zn, Cu and Hg are preferentially removed by organic matter, which settles at the river-mouths, while Al, Fe, Cr, Mn, and Ni become associated with clay minerals and are transported away from the coast.

Español; castellano. El Golfo de Paria recibe metales pesados de zonas urbanas, industriales y agrícolas, además de aguas negras y aguas servidas, tanto de la costa occidental, como de tierra adentro de Trinidad. Se usaron concentraciones de metales pesados no residuales para determinar la distribución espacial de metales pesados en sedimentos en el Golfo de Paria. Se extrajeron muestras de sedimentos superficiales en 37 estaciones, que incluían la boca de 11 ríos principales que fluyen al golfo. Las estaciones fueron muestreadas dos veces durante la época lluviosa (julio 1998 y noviembre/ diciembre 1998) y dos en la época seca (marzo 1999 y abril 1999). Se analizó en los sedimentos cobre (Cu), cinc (Zn), plomo (Pb), mercurio (Hg), cadmio (Cd), níquel (Ni), cromo (Cr), hierro (Fe), manganeso (Mn), aluminio (Al), Carbón Orgánico Total (COT) y tamaño de grano. El análisis de componentes principales muestra que los sedimentos de las bocas de los ríos con cuencas más deforestadas y con mayor impacto antropogénico, son distintos del resto. Esto se debió a concentraciones mayores de Pb, Zn, Cu y Hg (3.53-73.30 μg g-1, 45.8-313.9 μg g-1, 8.43-39.71 μg g-1 y 0.03-0.10 μg g-1, respectivamente). Los sedimentos más alejados de la costa también eran distintos por sus mayores concentraciones de Al, Fe, Cr y Mn (1.37-3.16 mg g-1, 9.51-18.91 mg g-1, 17.22-28.41 μg g-1 y 323.6–1,564.2 μg g-1, respectivamente). Cd y Pb fueron mayores en la época húmeda, mientras que Ni fue mayor en la época seca. Matrices de correlación de Pearson muestran que Pb, Zn, Cu y Hg estaban correlacionados entre si y con el COT. Se observó correlación también entre Al, Fe, Cr, Mn y Ni. Estos metales estaban correlacionados con el porcentaje de arcilla en los sedimentos. Pb, Zn, Cu y Hg son removidos preferiblemente por la materia orgánica que se asienta en la boca de los ríos, mientras que Al, Fe, Cr, Mn y Ni se asocian con las arcillas y son transportados lejos de la costa.