Application of copper(II)-based chemicals induces CH3Br and CH3Cl emissions from soil and seawater

Abstract

Methyl bromide (CH3Br) and methyl chloride (CH3Cl) 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 CH3Br and CH3Cl production from soil, seawater and model organic compounds: catechol (benzene-1,2-diol) and guaiacol (2-methoxyphenol). We show that copper sulfate (CuSO4) enhances CH3Br and CH3Cl production from soil and seawater, and it may be further amplified in conjunction with hydrogen peroxide (H2O2) or solar radiation. This represents an abiotic production pathway of CH3Br and CH3Cl 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 CH3Br and CH3Cl, and thereby contribute to stratospheric halogen load.

Global methyl halide emissions from biomass burning during 2003–2021

“…Besides, a new CH 3 Cl emission source was discussed by Jiao et al. [ 39 ], who found that the use of pesticides based on Cu 2+ resulted in CH 3 Cl emissions via an abiotic pathway from soil and seawater. Re-evaluating emissions from known sources and finding new sources are thus necessary to improve our understanding of the global CH 3 Cl budget.…”

Rapid Release of Halocarbons from Saline Water by Iron-Based Photochemistry

“…CH 3 Cl formed from the combination of • CH 3 and Cl • that resulted from the transformation of Cl – by • OH. Compared with the dark abiotic redox process involving Fe­(III), ,, sunlight irradiation may exert an enhancement effect on the formation of • CH 3 . On the other hand, under sunlight irradiation, the redox cycling of iron triggered by the Fenton reaction may amplify the role of Fe­(III) in CH 3 Cl production and greatly enhance the utilization efficiency of Fe­(III).…”

“…Guaiacol contains simultaneously hydroxyl and methoxy groups, which have been implicated as the basic functional elements in the lignin structure . It has been extensively used as a representative monomer of lignin for the study of methyl halide formation. ,, …”

“…51 It has been extensively used as a representative monomer of lignin for the study of methyl halide formation. 26,27,39 The experiments were conducted to monitor the production of CH 3 Cl from the aqueous solution containing guaiacol and chloride under three different conditions, including simulated solar light irradiation in the absence of Fe(III), dark treatment in the presence of Fe(III), and simulated solar light irradiation in the presence of Fe(III), respectively. Approximately 0.10 μM CH 3 Cl was formed after Fe(III) was introduced in the presence of simulated solar light.…”

“…Liu et al have reported that Fe­(III) significantly promoted CH 3 Br production during irradiation of humic acid . Recently, copper­(II) was reported to enhance CH 3 Br and CH 3 Cl production from soil and seawater and further amplified in conjunction with hydrogen peroxide or solar radiation . However, few studies focus on the effect of sunlight on the production of halocarbons in the presence of Fe­(III).…”