Trace metal

About: Trace metal is a research topic. Over the lifetime, 5125 publications have been published within this topic receiving 181046 citations.

Remineralization and recycling of iron, thorium and organic carbon by heterotrophic marine protists in culture

Abstract: To characterize trace metal cycling in marine systems as mediated by heterotrophic pro- tists, we conducted a series of laboratory experiments in 2-organism model systems consisting of bac- teria and protistan grazers. Trace metal isotopes ( 59 Fe and 234 Th), 14 C, and bulk organic carbon mea- surements were used to follow the chemical transformation of bacterial carbon and associated trace metals by several different grazer species. Results indicate that grazers were able to cause reparti- tioning of Th and regeneration of Fe from bacterial prey into the dissolved phase (<0.2 µm), even in particle-rich laboratory cultures. For both Th and Fe, protist grazing led to the formation of relatively stable dissolved and colloidal metal-organic species. Metal/carbon ratios of the particle pool in some model systems with grazers were significantly altered, indicating a decoupling of trace metal and organic carbon cycling through the grazing process. Different protist species exhibited substantial variation (up to a factor of 10) in their ability to quantitatively remobilize trace metals from bacterial prey. The implications of these findings for trace metal cycling in marine systems are discussed.

A review of sediment contamination by trace metals in the Humber catchment and estuary, and the implications for future estuary water quality

Abstract: This paper reviews what is presently known about sediment contamination in the macro-tidal Humber estuary on the east coast of the UK, with particular reference to the trace elements arsenic, copper, lead and zinc. The Humber is a post-industrial estuary, with an industrial and mining legacy of contaminated sediments throughout the river catchment. Surface and near-surface sediments in the estuary also show significant contamination of trace metals over background values. Inputs of dissolved and particulate trace elements to the estuary from the rivers are reviewed, and atmospheric deposition to the catchment and estuary calculated as a potential additional source of contamination. The necessity of maintaining the sediment balance within the estuary means that contaminated sediments dredged from the estuary harbours are deposited to other sites within the estuary, rather than being removed. Trace metal concentrations in recent dredged sediments, and sediments from the period of peak contamination in the 1970s, are compared with background values. Current inputs to the estuary from point sources, and trends over the last decade are considered. Our calculation of the current depositional fluxes of trace metals to the estuary intertidal sediments, and comparison with the inputs, reveals that the estuary sediments are today capable of storing 55–97% of the input load of As, 15–27% of the Cu, 17–50% of the Pb and 11–12% of the Zn annually. Sediment quality in the estuary is currently far from its 'background' state with respect to trace metals. This has implications for the future water and sediment quality of the Humber under the terms of the EU Water Framework Directive. One management option being considered to improve sea defences in the estuary, managed realignment, may also act to dilute contaminated sediments in the estuary, and thereby to improve future water quality. We look at the effect on sediment contaminant storage of three possible future managed realignment scenarios.