INVERKAN AV HAVSFÖRSURNING PÅ PROTONERBARA ORGANISKA FÖRORENINGARAS EKOTOXICITET

Abstract

Resulting from anthropogenic carbon dioxide emissions, average surface seawater pH is estimated to decline from today's approximately 8.05 to between 7.78 and 8.03 towards 2100. For ionisable organic pollutants, changes in pH can lead to a change in the degree of ionisation, which could influence the ecotoxicity of a compound by altering its bioavailability. In this study, potential changes in ecotoxicity of ionisable organic compounds resulting from ocean acidification are examined. This is achieved partly by conducting a literature review, analysing existing literature that investigates this relationship. Potential changes are also evaluated by examining marine ecotoxicity data for ionisable organic compounds on the watch list pursuant to Directive 2008/105/EC of the European Parliament and of the Council, as well as on the list of priority substances according to the 2022 proposal for amending the Water Framework Directive (2000/60/EC). These data are related to the ionisation-degree for different pH when possible. Results from the literature review indicate that ocean acidification can modulate the marine ecotoxicity of ionisable organic compounds. This modulation is seemingly dependent on the acidic or basic properties of a substance. In some cases there were uncertainties as to whether an increased toxicity was a result of an increased sensitivity of the test organism due to an acidic environment. The substances investigated in relation to ocean acidification so far are few and often had a pKa indicating only small changes in ionisation-degree would occur. This lack of data was also reflected in the results from examining EU-relevant ionisable organic compounds, where existing data on marine ecotoxicity linked to pH was very limited. Ionisation-degree seemed to correspond with toxicity for an acid on the priority list. Combined results indicate a need for more marine data on ecotoxicity and bioaccumulation under future ocean acidification scenarios, specifically for ionisable organic comounds with pKa close to 8, in order to estimate risks these polluntants pose under ocean acidification.