While dust from arid river beds during dry season has long compromised air quality in central and eastern Taiwan, the Environmental Protection Administration (EPA) yesterday touted its preliminary success in riverbed dust control with a cost-effective “step island plantation” method.
Responsibility for the dust problem at certain rivers has yet to be identified, however, since the pollution may not be a completely natural occurrence.
“In the past, dust suppression techniques at dried riverbeds such as gravel mulching and straw mulching have been tried, but the riverbed dust problem has only become worse over the years,” said Hsiao Hui-chuan (蕭慧娟), director-general of the EPA’s Air Quality Protection and Noise Control.
The riverbed dust situation is worst during the two dry seasons — November to December and February to March — when northeastern fronts sweep the island, she said.
In 2002 in Yunlin County’s Lunbei (崙背) and Hsienhsi (線西) townships, dust from the Chuoshui River (濁水溪) led to 14 percent of all days where coarse airborne pollutant particles, or particulate matters smaller than 10 micrometers, were over safety guideline limits. By last year the figure climbed to 27 percent, Hsiao said.
“This shows that previous mulching efforts had little effect,” she said.
Hsiao said the EPA began experimenting last year with the step island plantation method to curb dust problems at the Chuoshui River — said to have the most serious dust problem in the nation.
“The method has proven to be most effective the EPA has tried,” she said.
The method employs sand-trapping nets built onto river beds to create sufficient mounds of sand for grasses to grow and grab hold of the sand, Hsiao said, adding that within three to four months, the nets’ average sand collection was 35m³ to 51.73m³.
When asked if the river dusts were entirely natural pollutants, department technician Cecilia Swei (隋婉君) said a weir — or small dam — upstream, as well as the Sixth Naphtha Cracker (六輕) plant located at Mailiao (麥寮) in Yunlin County, had significantly contributed to the dust problem.
“Because the weir traps larger rocks of the river in its upper stream, and because the Sixth Naphtha Crackers plant extracts massive amounts of underground water for factory use, the Chuoshui River is both dry and full of sand,” Swei said.
Still, Hsiao said there was no plan to ask the plant to reimburse the community for the pollution local residents suffer.
“We just haven’t really evaluated how much [the plant] has contributed to the pollution yet,” she said.