Balancing methane emission and alkalinity conservation: Insights from mineral amendments in coastal sediments.

With global climate warming and ocean acidification, mineral amendments in coastal areas have emerged as a promising strategy to bolster carbon sinks and alkalinity. However, most research has predominantly focused on carbon dioxide (CO2) absorption, with limited exploration of methane (CH4) reduction despite its more potent greenhouse effect. To address this gap, our study conducted a microcosm manipulative experiment employing coastal wetlands sediments to elucidate the regulatory effects of various mineral amendments on greenhouse gas emissions (including CO2 and CH4) and seawater alkalinity. The findings unveiled that olivine application effectively absorbed CO2, achieving a 175 % reduction (-342.0 mmol L-1 h-1) in the late stage, while gypsum application significantly reduced CH4 by 53 % (-6.06 mmol L-1 h-1) in the early stage. Nevertheless, applying gypsum led to a marked decrease in seawater alkalinity, potentially exacerbating ocean acidification and posing risks to marine ecosystems. Interestingly, the simultaneous application of both minerals showed promise in reducing CH4 emissions without compromising seawater alkalinity. This study presents a pioneering endeavor that contributes to the sustainable management of coastal wetlands and supports future initiatives at reducing CH4 emissions and alleviating ocean acidification.