The distribution, concentration, and ecological and health risk assessment of heavy metals in the seawater of Southwest Florida, USA

Southwest Florida is one of the fastest growing regions in the United States, heavily affected by anthropogenic activities, which may alter the composition of natural seawater. Polluted seawater may thus become a potential risk to coastal human populations and the ecosystem at large. The current study investigated seasonal variations in surface seawater along the Gulf coast of southwest Florida to determine potential anthropogenic inputs and the ecological impacts of heavy metals. Water samples were collected from 14 sampling locations at three different time points (October 2022, January 2023, and March 2023) following Hurricane Ian in September 2022. Samples were analysed for heavy metals (V, Cr, Mn, Ni, Zn, As, Rb, Mo, Cd, Sb, Pb, and U) using an Inductively Couple Plasma Mass Spectrometry (ICP-MS). The metal highest concentrations were found to be as follows, Zn (5096.81 ± 1.09 µg/L), Pb (387.84 ± 1.73 µg/L), Rb (237.46 ± 1.51 µg/L), Ni (131.29 ± 1.09 µg/L), Cr (32. 58 ± 1.29 µg/L), Mn (16.62 ± 1.22 µg/L), Mo (12.96 ± 0.43 µg/L), Cd (3.11 ± 8.87 µg/L), V (8.68 ± 0.76 µg/L), Sb (7.63 ± 0.31 µg/L), As (7.32 ± 0.47 µg/L), U (7.13 ± 0.00 µg/L). The Ecological risk index ranged from 1.01 to 83.75 in October 2022, 2.41–321.77 in January 2023, and 1.05–248.61 in March 2023, indicating high ecological risk due to the presence of heavy metals. Dermal hazard and ingestion indexes assessments were lower than one, indicating that no health risks to humans may result from dermal exposure at this stage. The presence of high concentrations of some heavy metals may be attributed to the impact of pollutants and possibly discharges from Hurricane Ian, thus the need for continuous monitoring. The present study may serve as baseline data for further research efforts to identify the source of these heavy metals in seawater as they may have detrimental effects on marine economically important organisms.