Temporal and spatial variation in methyl bromide emissions from a salt marsh

Abstract

Methyl bromide (CH3Br) is a trace gas involved in stratospheric ozone depletion with both anthropogenic and natural sources. Estimates of natural source strengths are highly uncertain. In this study, >320 highly temporally and spatially resolved measurements of CH3Br emissions from a salt marsh in Scotland (56°00′N, 2°35′W) were made during one year using eight static enclosures. Net emissions showed both strong seasonal and diurnal cycles. Day-to-day maxima in emissions were associated with sunny days. Emissions dropped to zero when vegetation was removed. Mean measured CH3Br emission was 350 ng m−2 h−1, but a few “hot spots” (measured maximum 4000 ng m−2 h−1) dominated integrated emissions. A crude scale-up of the annual mean emission yields an estimate for global CH3Br emission of ∼1 (0.5–3) Gg y−1 (range uses annual mean from lowest and highest emitting enclosures), ∼10% the global salt marsh emission regularly quoted in the literature.