TAIPEI (Taiwan News) -- Taoyuan's Zhongli District has the dubious distinction of having recorded the highest level of acid rain in Taiwan last year.
The average pH value of the rain in Zhongli was 4.66, which is a similar level of acidity to tomato juice, reported Liberty Times. In Feb. 3 last year, the acidity level of rain in Zhongli was measured at pH 3.79, which is close to lemon juice (pH 2 to 3).
Rainfall with a pH value of less than 5.0 is considered acidic. Last year, the Environmental Protection Administration (EPA) commissioned the National Central University's (NCU's) Department of Atmospheric Sciences to carry out the "National Acid Rain Monitoring and Composition Analysis Survey."
After analyzing rainwater collected at 14 weather stations in northern, central, southern, and eastern Taiwan, the average pH level was found to be pH 5.72. The rainfall in northern Taiwan was found to be more acidic than in central and southern Taiwan.
The average pH value in northern Taiwan ranged between pH 4.66 and 5.38, followed by eastern Taiwan at pH 5.79, according to the report. Central Taiwan ranged between pH 5.83 and 6.37, while southern Taiwan had a range of between pH 5.6 and 6.28.
As for individual stations, The NCU weather station in Zhongli had the highest level of acidity at pH 4.66, a level of acidity similar to tomato juice (pH 4.1 to 4.6). On Feb. 3 of last year, the station recorded its highest level of acidity, which was pH 3.79, which is on par with lemon juice, reported the Liberty Times.
Two years ago, both Hsinchu and Zhongli had reported high levels of acidity. However, last year, the situation in Hsinchu improved significantly.
Based on data over the past several years, Zhongli held the record for the worst acid rain for five straight years from 2012 to 2016. In 2017, Hsinchu held the record for having the most acidic rain, only for Zhongli to again take the crown for worst acid rain again in 2018.
EPA Air Quality Protection and Noise Control Director-General Tsai Meng-yu (蔡孟裕) said that northern Taiwan, in general, has more scooters, which results in higher concentrations of nitrogen oxides, sulfur oxides, and other air pollutants. However, Tsai said that Zhongli has fewer calcium ions than other areas, which means there is less of an ability to neutralize the acid in the air, resulting in the lower pH levels, reported the Liberty Times.
Lin Neng-hui (林能暉), co-chair of the survey and professor of atmospheric science at NCU, told the Liberty Times that sulfate and nitrate ions are often transported from abroad to Taiwan in the fall and winter. He said that this leads to higher atmospheric acidity in northern counties and cities.
Lin said that the sulfate and nitrate ions are slightly higher in Zhongli than neighboring areas. However, he said that over the long-term, acid rain has actually been on the decline in Zhongli.
Based on data analysis of weather stations over the years, Lin said that sulfate ions have decreased significantly over the past 30 years, demonstrating that pollution reduction policies have been effective. However, the level of nitrate ions have remained the same or increased slightly over the years.
Lin suggested that in addition to fixed pollution sources, mobile pollution sources, such as scooters and industrial growth should be regulated to reduce acid rain in northern Taiwan.