Got dirty air? Try wash­ing it

China Daily (Canada) - - ACROSS AMERICA - By ELIANA KIR­SHEN­BLAT in New York elianakir­shen­blat@ chi­nadai­

Some 350,000 to 500,000 pre­ma­ture deaths oc­cur in China ev­ery year due to out­door air pol­lu­tion, ac­cord­ing to a re­port by 21st Cen­tury Busi­ness Her­ald re­leased on Tues­day. New air qual­ity mea­sures are con­stantly im­ple­mented and air pol­lu­tion re­duc­tion tar­gets have re­cently been set for lo­cal gov­ern­ments.

But one re­searcher may have found a way to sim­ply and dras­ti­cally re­duce the air pol­lu­tion prob­lem — wa­ter China’s cities, just like a gar­den.

Yu Shao­cai of Zhejiang Univer­sity in China, and North Carolina State Univer­sity in the US, de­tailed his idea in an ar­ti­cle pub­lished online Jan 7 in Springer’s jour­nal En­vi­ron­men­tal Chem­istry Let­ters. His pro­posal is straight­for­ward, put a sprin­kler sys­tem in place that could wa­ter China’s at­mos­phere and thus clean it.

In his pa­per Yu pre­dicts that this method could help re­duce the fine par­ti­cle load in the at­mos­phere to a safer level of 35 mi­cro­grams per cu­bic me­ter. And it could be done in a short time, de­pend­ing how the wa­ter is sprayed. He said that the idea came to him “while watch­ing a gar­den be­ing wa­tered, I im­me­di­ately thought that we can clean air pol­lu­tion by spray­ing wa­ter into the at­mos­phere like wa­ter­ing a gar­den”.

As sim­ple as it sounds, his re­search backs up the ef­fec­tive­ness of this so­lu­tion.

The haze in China is caused by fine par­ti­cles — or par­tic­u­late mat­ter — that are larger than 2.5 mi­crom­e­ters in di­am­e­ter, Yu writes in his pa­per.

Fur­ther, “it is well known that pre­cip­i­ta­tion scav­eng­ing is the sin­gle most ef­fi­cient way of re­mov­ing aerosol pol­lu­tion in the at­mos­phere”.

Pre­cip­i­ta­tion scav­eng­ing refers to the nat­u­ral process when at­mo­spheric mois­ture like rain, fog or snow re­moves sub­stances from the air.

Yu cites in his pa­per re­search done at a Bei­jing ur­ban at­mo­spheric en­vi­ron­men­tal mon­i­tor­ing sta­tion that shows a marked de­crease in air pol­lu­tion di­rectly af­ter a heavy rain­fall, as well as an in­crease in pol­lu­tants dur­ing the dry spell di­rectly be­fore the rain.

“When we have rain, es­pe­cially heavy rain, rain­wa­ter can clean the air pol­lu­tion in a very short time pe­riod from a few min­utes to hours or days, de­pend­ing on the pre­cip­i­ta­tion rates,” Yu writes.

Spray­ing wa­ter into the at­mos­phere can re­sult in scav­eng­ing air pol­lu­tion quickly, he writes.

Work­ing with emis­sion con­trol pro­to­cols this can be a per­ma­nent so­lu­tion to air qual­ity prob­lems in China’s megac­i­ties.

Not only is this idea sim­ple but China al­ready has what it needs to make it hap­pen, he ar­gues: Tall build­ings to place the sprin­klers on, wa­ter, air­craft for al­ter­na­tive dis­tri­bu­tion and sprin­klers.

It would also be cost-ef­fec­tive. “The low-tech na­ture of this geo-engineering ap­proach has led us to be­lieve that it will cost much less than many other in­ter­ven­tions, such as cut­ting emis­sions,” Yu said in his pa­per. There are even some bonus ben­e­fits like re­mov­ing harm­ful gases from the at­mos­phere and clean­ing the city’s streets.

The drop size also mat­ters so that the drops do not evap­o­rate be­fore hit­ting the ground, which could re­lease harm­ful par­tic­u­lates back into the at­mos­phere. But by en­sur­ing a large enough drop size this can eas­ily be avoided, wrote Yu.

“The wa­ter could be col­lected and reused, mean­ing it would not ex­ac­er­bate cur­rent wa­ter short­ages,” he writes. “If the wa­ter col­lected has been pol­luted be­cause of very pol­luted air, then we will need some treat­ment.”

The sprin­klers would need to be used daily to avoid the ac­cu­mu­la­tion of air pol­lu­tion in the at­mos­phere and the oc­cur­rence of haze. Yu is con­fi­dent that this would not be prob­lem for the pub­lic.

“If you can of­fer a half hour wa­ter­ing your gar­den, then you can of­fer a half hour wa­ter­ing your am­bi­ent at­mos­phere to keep air clean,” he wrote.


A tourist with a pro­tec­tive mask takes a self-por­trait at the Bund un­der heavy haze in Shang­hai on Dec 9. The dirty air that has gripped Shang­hai and its neigh­bor­ing prov­inces for days is at­trib­uted to coal burn­ing, car ex­haust, fac­tory pol­lu­tion and weather pat­terns, and is a stark re­minder that pol­lu­tion is a se­ri­ous chal­lenge in China.

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