| 词条 | Shade balls |
| 释义 |
Shade balls are small plastic spheres floated on top of a reservoir for environmental protection and to slow evaporation. Also known as bird balls, they were developed initially to prevent birds from landing on toxic tailing ponds produced by mining operations. They have been used by airports to prevent birds from being attracted to drainage ponds and thus risking collisions with planes. HistoryShade balls were originally known as bird balls, as they were developed initially to prevent birds from landing on toxic tailing ponds produced by mining operations.[1] They have been used by airports to prevent birds from being attracted to drainage ponds and thus risking collisions with planes.[2] Usage by LADWPStarting in mid-2008, the Los Angeles Department of Water and Power deployed about 400,000 of these devices in the Ivanhoe reservoir with the main objective of preventing the formation of a carcinogenic chemical, bromate, which forms when naturally occurring bromine reacts with chlorine in the presence of sunlight.[1][3] In the original release by the LADWP, there is no mention of water conservation as an objective, and the project was planned for a five year life span, until a Griffith Park project was completed. However, the reduction in evaporation led to an estimated savings of about 1.1 billion liters (290 million gallons) of water in one year.[1] In 2014 and 2015, the LADWP deployed 96 million shade balls on its largest reservoir in response to the United States Environmental Protection Agency's surface water treatment rule,[4] which requires large reservoirs of treated water to be covered.[5][6] The LADWP claims that in addition to reducing evaporation, they will also reduce UV radiation by-products and algae growth.[7] The balls saved 1.7 million cubic metres of water from evaporating during their deployment from August 2015 to March 2017. However they required 2.9 million cubic metres of water in their manufacture. Nevertheless, the balls have a lifespan of ten years, and the plastic may be reused after that.[8] ConstructionThe shade balls used in the Los Angeles project are made of high-density polyethylene (HDPE) with carbon black additive to protect the plastic from ultraviolet radiation. [9][10][11][12] Adding carbon black also prevents the formation of bromate, a suspected human carcinogen.[13][14]They are about {{convert|4|in|cm}} in diameter, and are partially filled with water to avoid being blown by wind. HDPE plastic is commonly used for food and beverage containers as well as water distribution pipes.[9] The black coating on the balls, called carbon black, is a petroleum derivative which is classified as a carcinogen if inhaled as dust. The black color balls have been claimed to prevent UV light from reaching the water more effectively than lighter color balls. References1. ^1 2 Marco Chown Oved, [https://www.pressreader.com/canada/toronto-star/20161112/282952449774508 "Shade Balls - Just Add Water"], Toronto Star, October 23, 2016 2. ^[https://www.npr.org/2015/08/12/431959386/los-angeles-unleashes-shade-balls-to-protect-reservoir-water-quality Los Angeles Unleashes 'Shade Balls' To Protect Reservoir Water Quality] 3. ^{{cite web|last1=Vara-Orta|first1=Francisco|title=A reservoir goes undercover|url=http://articles.latimes.com/2008/jun/10/local/me-balls10|website=Los Angeles Times|publisher=Los Angeles Times|accessdate=27 December 2015}} 4. ^{{cite web|url = http://water.epa.gov/lawsregs/rulesregs/sdwa/lt2/basicinformation.cfm|title = Water: Long Term 2 Enhanced Surface Water Treatment Rule|accessdate = 2015-08-13|date = 2013-02-11|publisher = United States Environmental Protection Agency}} 5. ^{{cite web|url=https://www.npr.org/2015/08/12/431959386/los-angeles-unleashes-shade-balls-to-protect-reservoir-water-quality|title=Los Angeles Unleashes 'Shade Balls' To Protect Reservoir Water Quality|publisher= National Public Radio|accessdate=2015-08-13|date=2015-08-12}} 6. ^{{cite news |last=Walton |first=Alice |last2=Grad |first2=Shelby |url=http://www.latimes.com/local/lanow/la-me-ln-shade-ball-water-20150812-htmlstory.html |title=The 36-cent 'shade ball' that could save $250 million and keep L.A. water clean |work=The Los Angeles Times |location=Los Angeles |publisher=The Los Angeles Times |date=2015-08-12 |accessdate=2015-08-12 |quote=Shade balls are used to protect water quality, prevent algae growth and slow evaporation from the city’s reservoirs.}} 7. ^{{cite news|last1 = Walton|first1 = Alice|title = L.A.'s shade balls go viral — but the Internet has mixed opinion|url = http://www.latimes.com/local/cityhall/la-me-balls-first-and-spring-20150824-story.html|accessdate = 24 August 2015|publisher = Los Angeles Times|date = August 23, 2015}} 8. ^https://www.sciencealert.com/la-reservoir-shade-balls-manufacture-use-more-water-than-they-saved 9. ^1 "Shade Balls: Sustainable Drought Prevention", retrieved 3-31-2016, Precision Plastic Ball 10. ^"Los Angeles Reservoir Covered With 96 Million Shade Balls to Conserve Water Amidst Drought" (Aug 12, 2015) ABC News 11. ^[https://www.cnbc.com/2015/08/13/shade-balls-protect-la-water-supply-during-drought.html {{"'}}Shade balls' protect LA water supply during drought"] (13 Aug 2015) CNBC 12. ^[https://www.npr.org/sections/thetwo-way/2015/08/11/431670483/la-rolls-out-water-saving-shade-balls "LA Rolls Out Water-Saving 'Shade Balls{{'"}}] (August 11, 2015) NPR 13. ^{{cite web| url= http://www.inchem.org/documents/iarc/vol73/73-17.html| work= International Agency for Research on Cancer: Summaries and Evaluations| title= Potassium Bromate (Group 2B)| publisher= Canadian Centre for Occupational Health and Safety| accessdate= 2008-03-09}} 14. ^{{cite journal| pmc=1567851| title= Toxicity and carcinogenicity of potassium bromate—a new renal carcinogen| journal= Environmental Health Perspectives| date=July 1990| volume= 87| pages= 309–35| doi= 10.1289/EHP.9087309| author= Kurokawa, Yuji| pmid= 2269236| last2=Maekawa| first2=A| last3=Takahashi| first3=M| last4=Hayashi| first4=Y| publisher=Environmental Health Perspectives, Vol. 87| jstor=3431039}} External links{{commonscat|Shade balls}}
3 : Balls|Water supply infrastructure|Reservoirs |
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