Temporal trends in bromide release following rewetting of a naturally drained gully mire

Recently, there has been interest in the occurrence of bromide (Br ‐ ) in natural waters since it has been demonstrated that Br ‐ , in association with humic substances in raw waters, is readily incorporated into haloacetic acids in the form of organically bound bromine (Br) during water chlorination. We report results of the effects of experimentally rewetting a naturally drained gully mire on the hydrochemistry of Br ‐ , iron (Fe) and dissolved organic carbon (DOC) in the peat water. Results obtained over a three year period showed that rewetting substantially increased the concentrations of these solutes in the pore water, with peak values of 1 mg dm ‐3 (Br ‐ ), > 60 mg dm ‐3 (Fe) and > 300 mg dm ‐3 (DOC) detected in some samples after rewetting, compared with typical values < 0.05 mg dm ‐3 (Br ‐ ), < 1 mg dm ‐3 (Fe) and < 15 mg dm ‐3 (DOC) under the drained conditions. Bromide, Fe and DOC release were highly seasonal, with the largest concentrations observed in late‐summer to autumn. However, whereas seasonal peak concentrations of Fe and DOC have since remained at these higher levels, seasonal peak concentrations of Br ‐ were progressively attenuated over time, suggesting the latter phenomenon is a flush effect, with no longer‐term consequences for water quality.