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Impad reaction with hydroxyl radicals(half-life,i-18 hr).The dominant removal process in water is volatilization.Xylenes are moderately mobile in soil and may leach into groundwater where they are known to persist for several years,despite some evidence that they biodegrade in both soil and groundwater.Bioconcentration is not expected to be significant.The primary source of exposure is from air,especially at occupational sites where xylenes are used and in areas with high traffic. TERRESTRIAL FATE:When spilled on land,xylenes will volatilize and leach into the ground.Xylenes may be degraded during their passage through soil.The extent of the degradation will undoubtedly depend on their concentration,residence time in the soil,the nature of the soil,and whether resident microbial populations have been acclimated.AQUATIC FATE:In surface waters,volatilization appears to be the dominant removal process (half-life 1- 5.5 days(2,SRC). Some adsorption to sediment will occur.Although xylenes are biodegradable and have been observed havirollmental to degrade in seawater, there is insufficient data to access the rate of this process in surface waters.Although they have Fate been observed to degrade in groundwater in one study,they are known to persist for many years in groundwater at least at sites where the concentration might have been quite high.In a field study of an oil spill from the Trans-Alaskan Pipeline which leaked into the Atigun River on June 10, 1979,aromatic hydrocarbons including xylenes were absent from the 40 km long river in contaminated area 18 days after the spill.ATMOSPHERIC FATE:When released into the atmosphere,xylenes may degrade by reaction with photochemically produced hydroxyl radicals (half-life 1.0-1.7 hr in summer and 10-18 hr in winter).However,ambient levels are detected because of large emissions. Biological oxygen demand 5(after 5 days @ 20 deg C): 0.64(no stated isomer). 1190] DRINKING WATER:According to a federal survey of drinking water from groundwater supplies,xylenes are present in<5%of supplies.Xylenes have been detected in the drinking water in Canada with mean values of< 1 ppb and in several USA cities including Washington,DC,Philadelphia,PA,Cleveland,OH,Tuscaloosa,AL(6),Houston,TX(6),and New Orleans,LA(9). Xylenes at 0.1-2.9 ppb have been found in drinking water wells in the vicinity of a landfill(7).A max of 0.1 ppb has been found in bank-filtered Rhine R water in the Netherlands(8).Detected in all 14 drinking water supplies studies, 10 surface and 4 ground in Great Britain(10).GROUNDWATER:Xylene isomers have been found in groundwater under landfills risking Water and in the hundreds ppb range under a coal gasification site, 15 months after gasification was completed. SURFACE Impact WATER:Detected,not quantified in the Mississippi River near New Orleans,the Black Warrior River in Tuscaloosa, � AL,and the Glatt River in Switzerland.Xylenes have been found in Lakes Eire and Michigan . Detected at avg conch of < 1 ppb in the raw water sources of 30 Canadian cities .Detected in only 1 of 204 surface water samples in the USA(6). SEAWATER:In Vineland Sound,MA and the Gulf of Mexico.Valdez Harbor-Trans Alaskan Pipeline Terminal-0.2 and 0.7 ppb in 2 of 7 sampling sites.RAINISNOW:West Los Angeles,part per trillion rouge.EFFL:Low-level radioactive waste disposal site at Maxey Flats 0.12 and 0.48 ppm in 2 of 3 trench leachates .Industrial plant in Philadelphia area 1000 ppb including all C2 benzenes. Effluent from containing ponds in Atigun River,Alaska 1.2 ppb, including ethyl benzene. Treated effluents from offshore oil drilling platforms in the Gulf of Mexico 0.3 ppm avg(conn includes ethylbenzene). DISCLAIMER -Please Read Return to Alphabetical.Lis,t of Com ounds List of Campounds.by CAS Number +` .;, List of Services Spectrum Laboratories Homepage 1