Application of copper(II)-based chemicals induces CHBr and CHCl emissions from soil and seawater.

Methyl bromide (CHBr) and methyl chloride (CHCl) are major carriers of atmospheric bromine and chlorine, respectively, which can catalyze stratospheric ozone depletion. However, in our current understanding, there are missing sources associated with these two species. Here we investigate the effect of copper(II) on CHBr and CHCl production from soil, seawater and model organic compounds: catechol (benzene-1,2-diol) and guaiacol (2-methoxyphenol). We show that copper sulfate (CuSO) enhances CHBr and CHCl production from soil and seawater, and it may be further amplified in conjunction with hydrogen peroxide (HO) or solar radiation. This represents an abiotic production pathway of CHBr and CHCl perturbed by anthropogenic application of copper(II)-based chemicals. Hence, we suggest that the widespread application of copper(II) pesticides in agriculture and the discharge of anthropogenic copper(II) to the oceans may account for part of the missing sources of CHBr and CHCl, and thereby contribute to stratospheric halogen load.