Rainwater in Guangzhou, China: Oxidizing properties and physicochemical characteristics

Özet

This study analyzed urban wet deposition data collected during 81 rain events from October 2016 to September 2017 in Guangzhou, China. The oxidizing properties (H2O2 and ClO −), anions and cations (F−, Cl−, Br−,NO2 , NO3 , SO4 , PO4 , Li , Na , NH3 , K , Mg , and Ca2+), rainwater quality indicators (pH, re- duction potential (Eh), and electrical conductivity (EC)), and meteorological factors (precipitation, solar ra- diation intensity, relative humidity, and temperature) during wet deposition were measured and examined. The maximum concentration of H2O2 in rainwater was 118.7 μM, with an annual average of 20.1 μM. The seasonal changes in the average concentration of H2O2 followed the order spring (27.8 μM) > summer (18.4 μM) > winter (16.4 μM) > autumn (13.2 μM). The highest and lowest average H2O2 concentrations were recorded during spring and autumn, respectively. The ClO4− concentration ranged from 0.4 ppb to 110.3 ppb (average: 13.9 ppb). The highest ClO4− concentration was recorded in winter and was attributed to fireworks and firecrackers. The rainwater pH was weakly acidic (average pH: 6.3). The Eh ranged from 225.6 mV to633.0 mV (annual average: 395.8 mV). There were significant differences in the EC of wet deposition, which ranged from 8.8 μS/cm to 534.0 μS/cm. Strong determination correlations between EC and ion concentrations were observed, and significant changes in the EC of rainwater were related to differences in the total amount of ions in the rainwater. H2O2 concentration exhibited a weak positive correlation with relative humidity. No correlation between the H2O2 concentration and temperature was evident.