Keep those umbrellas ready, acid rain is worst in 5 years

Rain almost as acidic as vinegar fell in Yuen Long, Central and Western last year.

The level of acidity was the worst in five years and even worse than that recorded in Guangdong, Environmental Protection Department figures revealed.

The average annual pH level of rain - a measure of its alkalinity or acidity - was 4.39 in Central and Western, and 4.29 in Yuen Long last year, more acidic than the 4.71 average recorded in Guangdong.

Rain collected in Yuen Long showed levels as severe as 3.1, while 3.2 was recorded in Central and Western. Rain with a pH level below 5.6 is regarded as acidic, with three or below indicating an acidity similar to vinegar.

The department's principal environmental officer, Raymond Leung Pak-ming, said the average acidity was 'moderate' and comparable to levels in places such as London. He said that the differences in the levels over the past five years were not significant.

The current levels of acid rain - which contains pollutants such as sulfates, mainly produced by the burning of fossil fuels - would not have a significant impact on the ecosystem, Mr Leung said.

But Ho Kin-chung, of the Open University's environmental science programme, said that while acid rain in Hong Kong did not pose an immediate threat, it might change the ecosystem in the long term.