Assessing acid rain and climate effects on the temporal variation of dissolved organic matter in the unsaturated zone of a karstic system from southern China

摘要

Highlights?The paper is the first comprehensive study on the effect of acid rain and climatic factors on dissolved organic matter variations in karst dripwaters over sub-annual to inter-annual time scale.?We report a continuous nine-year series of monthly dripwater fluorescence and discharge from two perennial drip sites.?The seasonality of fluorescence intensity mainly reflects the flushing of the soil zone and residence time of water governed by monsoonal rainfall; annual (effective) precipitation amount positively correlates with annual DOM concentration.?Current acid rain condition (～pH 5.6 to?～?4.5) has no discernable effect on quality and quantity of DOM in karst systems, which strongly buffer acidification from atmospheric rainfall.AbstractAcid rain has the potential to significantly impact the quantity and quality of dissolved organic matter (DOM) leached from soil to groundwater. Yet, to date, the effec