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進入《TAIPEI TIMES》Rainwater samples collected in Hsinchu were most acidic in the nation last year
The Deji Reservoir in Taichung is pictured yesterday. Photo courtesy of a reader
NOT ALL BAD NEWS: While the rainwater had an average pH value of 5.29, long-term data showed that the rain quality in Hsinchu has significantly improved
By Chen Chia-i / Staff reporter
Samples of rainwater collected in Hsinchu last year had an average pH value of 5.29, the most acidic among all monitoring stations nationwide, Environmental Protection Administration （EPA） data showed.
The normal pH value of rainwater is about 5.6, and acid rain is defined as having a pH value below 5.0.
The average pH value of rainwater collected at Taiwan’s 14 monitoring stations was 5.75 last year, the data showed.
The five stations with the lowest pH levels were in northern Taiwan — Hsinchu; Nantou County’s Anbu （鞍部） area, with an average pH level of 5.36; Taoyuan’s Jhongli District （中壢） with 5.37; Keelung’s Pengjia Islet （彭佳嶼） with 5.41; and Yilan County with 5.48.
Previously, Jhongli had the most acidic rain for five consecutive years with average pH values below 5 in 2018 and 2020.
Hsinchu’s rain ranked fourth-most acidic in 2018 and second in 2019.
Acid rain fell more often in northern Taiwan, a National Central University Department of Atmospheric Sciences report commissioned by the EPA showed.
The frequency in 2021 was highest in Jhongli and Hsinchu, at 55 percent and 31 percent respectively, the report said.
The acidity of rainwater depends mainly on sulfate ions and nitrate ions, said Lin Neng-huei （林能暉）, a professor in the department who coauthored the report.
The population of Taoyuan and Hsinchu has continued to increase in the past few years, and more vehicles and scooter on the streets have resulted in more pollution, he said.
During the fall and winter, the northeast monsoon usually brings air pollution from Taipei, New Taipei City and overseas to Taoyuan and Hsinchu, resulting in more frequent acid rain, he said.
However, long-term data showed that the rain quality in Hsinchu and Jhongli has significantly improved, he added.
Less traffic at Taiwan Taoyuan International Airport during the COVID-19 pandemic led to less air pollution in the past two years, which might have contributed to better results in Jhongli, Lin said.
It remains to be seen whether the rainwater collected in Jhongli would become more acidic as flight traffic is increasing after pandemic restrictions were lifted, he said.
In related news, the Water Resources Agency yesterday said that southern Taiwan has enough water to last through next month thanks to the current plum rain front, although the total amount of rainfall was limited.
An estimated 25.49 million cubic meters of rain entered the nation’s reservoirs between 7am on Saturday and 4pm yesterday, as the first weather front of the plum rain season swept over Taiwan, agency data showed.
Additional reporting by staff writer
新聞來源：TAIPEI TIMES
A flooded parking lot by the Hsinchu County Government is pictured in an undated photograph. Photo: CNA
