Hành vi của chất lỏng giai đoạn dày đặc ở dưới bề mặt Nonaqueous 7,1 DNAPL TÍNH Dày đặc các chất lỏng pha nonaqueous (DNAPLs) là chất lỏng duy nhất đó là hơi hòa tan trong nước và tồn tại trong do dưới bề mặt như là một giai đoạn riêng biệt không thể trộn lộn dịch với nước và không khí .* Cả Mật độ của DNAPL là rất tốt hơn nước (DNAPL mật độ = 1 g cm3 tại 48C) và di động của họ ở dưới bề mặt là Chi phối nhiều hơn bởi lực hấp dẫn và các. | 7 Behavior of Dense Nonaqueous Phase Liquids in the Subsurface DNAPL PROPERTIES Dense nonaqueous phase liquids DNAPLs are liquids that are only slightly soluble in water and therefore exist in the subsurface as a separate fluid phase immiscible with both water and air. The density of DNAPLs is greater than water DNAPL density 1 g cm3 at 4 C and their mobility in the subsurface is governed more by gravity and the properties of the DNAPL and surrounding soil than it is by groundwater movement. Unlike light nonaqueous phase liquids LNAPLs such as gasoline diesel fuel and heating oil which are less dense than water DNAPLs released into soils can sink below the water table where their more-soluble components can slowly dissolve into flowing groundwater giving rise to dissolved contaminant plumes. A release of DNAPL at the ground surface can therefore lead to long-term contamination of both the vadose and saturated zones at a site. DNAPLs such as wood preservatives like creosote transformer and insulating oils containing polychlorinated biphenyls PCBs coal tar and a variety of chlorinated solvents such as trichloroethene TCE and tetrachloroethene PCE have been widely used in industry since the beginning of the twentieth century. However their importance as soil and groundwater contaminants was not recognized until the 1980s mainly because of the limitations of early analytical methods. As a result chemical material safety data sheets MSDS distributed as late as early 1970 sometimes recommended that waste chlorinated solvents be discarded by spreading them onto dry ground and allowing them to evaporate. These early MSDSs acknowledged the volatile nature of many DNAPL chemicals but did not recognize their ability to infiltrate rapidly into the subsurface causing soil and groundwater pollution. It is not surprising that DNAPLs are the contaminants of greatest concern at many Superfund and other hazardous waste sites. Table lists many of the DNAPLs commonly found at
