Abstract
Carbon dioxide (CO2) removal from the atmosphere is essential to all scenarios of limiting global warming to 2°C or below [1]. Suspended organic particulate matter from the entire North Sea is deposited in the sediments of the Skagerrak between Norway and Denmark representing a natural key process for long-term carbon storage within the North Sea.
Marine Carbon Dioxide Removal (CDR) approaches such as Ocean alkalinity enhancement (OAE) represents a further method under debate, with potential to increase the long-term natural storage of CO2 in the ocean, which is already the biggest natural CO2 sink.
Natural storage processes can be influenced by climate change induced effects on the biogeochemical properties of the sediment e.g. via oxygen availability and resulting redox conditions, which could also have strong side effects on the mobility of e.g. legacy pollutants stored in the sediments.
OAE utilizes natural materials like olivine, however, bearing also the risk of simultaneously enhancing the presence of (toxic) trace metals in the marine environment.
Hence, the utilization of coastal zones as sinks for CO2 requires a solid understanding of coastal ecosystems and knowledge on the current baselines in terms of trace metal pollution is required to assess ecological risks, to identify most vulnerable regions as well as to minimize any unintended side effects of the described approaches.
Here we describe the combined application of multielement analysis via ICP-MS/MS as well as isotopic fractionation analysis of Mo (δ98/95Mo) as redox tracer using MC-ICP-MS to study the ongoing processes as well as mobility of pollutants, which represents a possible unintended side effect of such measures.
In combination with trace element concentrations, δ98/95Mo ratios allowed to distinct between different organic matter oxidation pathways and their impacts on the remobilization of different toxicologically relevant elements such as copper, lead or nickel.
