The relationship between phosphine, methane, and ozone over paddy field in Guangzhou, China

Abstract

Greenhouse effect has been attracting more and more attention in the world. Carbon dioxide (CO2) and methane (CH4) are the most important greenhouse gases. Phosphine (PH3) may have a potential greenhouse effect because it can react with hydroxyl radicals (·OH) in competition with other reducing gases. The aim of this study is to discover the relationship among PH3, ozone (O3) and CH4 in paddy fields and estimate the potential greenhouse effect of PH3 by field experiment. The results reveal that there was a significant negative correlation between O3 and PH3 (r = −0.494, p = 0.001, n = 42) during the whole period of rice growth. Similarly, CH4 was also negatively correlated with PH3, but not significant (r = −0.283, p = 0.069, n = 42). However, it was found that PH3 and CH4 corresponded to the reciprocal model. These results show that there was a certain competition relationship between PH3 and CH4. It was widely speculated that PH3 and CH4 were similar in the photochemical elimination process. ·OH could react with PH3, resulting in PH bond break. Then PH3 was oxidized to phosphate and other oxidation substances. Through Pearson correlation analysis and multiple stepwise linear regression analysis, light intensity was the principal factor affecting PH3 levels over the paddy field. The regression equation was [PH3] = -0.0003*[L] +20.025 (R2 = 0.243; F = 5.177; P < 0.01). These discoveries in this study have great reference values for the future investigation of greenhouse effect.