Dissolved metal concentrations in coastal seawater and groundwater in Saipan, Commonwealth of the Northern Mariana Islands, USA.

Abstract

Saipan, the largest and most populated island of the Commonwealth of the Northern Mariana Islands, has coastal areas with high submarine groundwater discharge (SGD) and heavy metal pollution of sediments. Here, we measured metal concentrations in coastal Saipan groundwater and surface water and explored spatial correlations with pollution sources. Concentrations of Cd, Pb, Cu, and Zn were highest in inland wells, with 3 wells exceeding USEPA guidelines for Cu or Pb. Concentrations tended to be highest in well groundwater, intermediate in beach groundwater and surface water, and lowest in offshore reef areas, suggesting that SGD could transport metals to coastal waters, although surface water dissolved metal concentrations were not elevated in high-SGD areas. High Cu and Cd in Laolao Bay suggested a possible threat to aquatic life. More research is needed on metal concentrations in water supply wells, including the possible influences of dumpsites and other pollution sources.