Reduction of Ingestion Exposure to Trihalomethanes Due to Volatilization

详细信息    查看全文

• 作者：Stuart Batterman ; An-Tsun Huang ; Shugin Wang ; and Lian Zhang
• 刊名：Environmental Science & Technology
• 出版年：2000
• 出版时间：October 15, 2000
• 年：2000
• 卷：34
• 期：20
• 页码：4418 - 4424
• 全文大小：79K
• 年卷期：v.34,no.20(October 15, 2000)
• ISSN：1520-5851

文摘

Ingestion of tap water is one of the principal exposurepathways for disinfection byproducts (DBPs). One majorclass of DBPs, trihalomethanes (THM), are highly volatile,and volatilization will tend to lower ingestion exposures.This study quantifies volatilization rates of the four THMspecies that occur while drinking tap water, specifically,losses during the preparation, storage, and serving of water.A mass transfer model based on two-resistance theoryand quiescent conditions is presented, and parametrizationsof all variables are provided. Volatilization rate constantsare estimated in experiments representing common patternsof tap water consumption, i.e., storage of tap water inpitchers, pouring, and serving in glasses and mugsat temperatures from 4 to 100 C. Predicted and experimentalresults show comparable loss rates for the four THMs.Observed volatilization rates declined exponentially,as expected, and greatly exceeded model predictions thatassumed quiescent conditions in the liquid. Loss ratesincreased with temperature and mixing that resulted fromtemperature gradients and air currents. Overall, storage,pouring, and serving of tap water at temperatures below 30C caused minor (<20%) volatilization of THMs. Rapidlyheating water to 60 or 80 C also is not expected to resultin significant volatilization. However, volatilization lossesapproached 75% when water was boiled even for brief periodsof time and reached 90% when boiled water was pouredand served. For the typical adult who drinks nearly half oftheir water as hot beverages, volatilization will reduceingestion exposures of THMs by nearly a factor of 2. Toaccount for these losses, exposure estimates for THMs andother volatile chemicals should separate the consumptionof heated and unheated tap water.