Direct Seawater Analysis by High-Resolution ICP-MS Provides Insights into Toxic Metal Accumulation in Marine Sediments

In this study, new insights into the contamination of marine ecosystems are provided by the simultaneous analysis of concurrently collected bottom seawater and upper sediment layer samples with inductively coupled plasma mass spectrometry (ICP-MS). Precise and interference-free quantification of the trace levels of selected heavy metals in seawater diluted 100 times was directly obtained by high-resolution ICP-MS, with the recovery (from 94 to 109% against the certified reference material CASS-6), repeatability (3-5%), intermediate precision (averaging 6.5%), and limits of detection (0.002-0.3 mu g L-1) being systematically assessed. The same metal contaminants accumulated in the surface sediments were determined - after sample digestion prior to measurements - by quadrupole ICP-MS using a previously optimized and validated protocol. Both sets of metal concentration data expressed as a function of distance from the coast show a decline, followed by a flattening where the transfer of insoluble material and the associated metal fluxes carried by the river watercourse tend to end an action. This occurrence was confirmed by quantifying the natural seawater constituents, such as potassium and lithium, whose concentrations remained constant after the distance of 250 km from the estuary due to a reduced dilution by freshwater.

Automated summary

This study provided new insights into marine ecosystem contamination by analyzing bottom seawater and upper sediment samples simultaneously using high-resolution ICP-MS and quadrupole ICP-MS. The study quantified trace levels of heavy metals in seawater and sediment, revealing a decline in metal concentrations as distance from the coast increases.