The researchers studied ozone pollution in the Pearl River Estuary in South China during autumn 2016. They measured ozone levels and its precursors at two sites, finding that ozone formation was limited by volatile organic compounds (VOCs) and nitrogen oxides (NOx). Isoprene, formaldehyde, xylenes, and trimethylbenzenes were key VOCs influencing ozone formation. Ozone production rates were high at both sites, indicating strong atmospheric oxidative capacity. In one pattern, ozone formation was VOC-limited at both sites, while in another pattern, it was co-limited by VOCs and NOx at one site but VOC-limited at the other. These findings help us understand ozone photochemistry in estuaries like the Pearl River Estuary.