According to the monitoring results at Zhongli monitoring station of Environmental Protection Administration (EPA), the pH value of rainfall during January-December in 2020 was only 4.96. According to the statistics of the Taoyuan Department of Environmental Protection (TYDEP), the average pH value of rainfall measured at seven monitoring stations in the city during January-June 2021 was 5.86, and the value measured at the Zhongli station was 5.52. All these values are higher than the acidic rain value at pH 5.0 as defined by EPA, suggesting that no more acidic rain is found in Zhongli.
According to Taoyuan City Mayor Wen-Tsan Cheng, EPA has only one monitoring station in Zhongli. In contrast, TYDEP has set up seven stations to monitor acidic rain in the city to bring more comprehensive and fuller data. According to the monitoring data for January-June 2021 of these seven stations, the average pH value of the city is 5.86. In addition, an annual rise in the pH value was also noted from 2017 to June 2021 (from 4.94, 5.04, and 5.10 to 5.86), suggesting an ongoing improvement every year. Despite the annual reduction to acidic rain, Mayor Cheng continues to direct TYDEP to form a task force. He invites air quality experts and scholars to hold regular discussion meetings to hear their recommendations in order to reduce and stabilize rainwater acidity.
According to TYDEP Director-General Dr. Li-Teh Lu, based on the average pH value at 5.52 measured at Zhongli station alone during January-June 2021, the condition is better than that of Yangmingshan station (average pH value at 4.66) in Taipei City and Wanli station (average pH value at 4.54) in New Taipei City, proving that there was no acidic rain so far in Zhongli in 2021.
According to TYDEP, the EPA report showed that Taoyuan’s effort in SOx emission control has borne fruit, and the sulfate intensity in rainwater has reduced significantly by 71% during 1991-2019. This result also matches with the continuous air pollution reduction measures (including reduction negotiation on air pollutant emissions with large factories, subsidization for replacement of old motorcycles and diesel vehicles, fuel change into natural gas of fossil fuel boilers, CEMS and CPMS monitoring) implemented in Taoyuan in recent years, enabling a significant improvement of plants (stationary pollution sources).
In addition, as the Zhongli monitoring station is located in Central University adjoining the freeway, it has higher exposure to mobile pollution sources (cars, trucks, and coaches) traveling north and south. Therefore, TYDEP has also adopted the following strategies against mobile pollution sources (cars and motorcycles). The subsidization for the replacement of electric scooters has reduced the number of one- and two-stroke motorcycles to the lowest among Taiwan’s six municipalities. The promotion of diesel vehicle replacement, maintenance-inspection integration, and enhancement of roadside random vehicle and motorcycle inspection has also effectively helped reduce the emissions of mobile pollution sources. These measures suggest that Taoyuan’s air quality policies are effective so that no more acidic rain is detected.