Kerfoot Henry B, Baker John A, Burt David M
GeoSyntecConsultants, 2100 Main Street, Huntington Beach, CA 92646, USA.
J Environ Monit. 2003 Dec;5(6):896-901. doi: 10.1039/b310351j.
An evaluation of the source of volatile organic compounds in groundwater samples was performed at a landfill in southern California. The 3H (tritium) content of the water in leachate and water from the gas-collection system (condensed water and entrained water droplets) and the delta 13C and 14C content of the inorganic carbon in landfill gas CO2, leachate, and gas-collection system water were used to characterize the dissolved inorganic carbon (DIC) inside the landfill, while the same parameters were monitored in groundwater samples from affected monitoring wells and an unaffected well. Tritium levels from leachate and gas-collection system condensate ranged from approximately 2000 TU to over 4000 TU, orders of magnitude higher than unaffected groundwater. The average 14C content of DIC in the landfill pore-water samples was 121 pMC and the 14C content of unaffected groundwater DIC was 93 pMC, while the 14C content of the dissolved inorganic carbon in groundwater with VOC detections ranged from 105 to 119 pMC. The delta 13C of DIC in pore water was consistently above 0 per thousand and the delta 13C of unaffected groundwater DIC was -20.3 per thousand, while the delta 13C of DIC in affected groundwater samples was increased from -17.3 to -13.2 per thousand. The increases in both delta 13C and 14C in landfill gas-impacted groundwater DIC generally correlated with the number of volatile organic compounds detected and their concentrations. Based on the tritium and DIC 14C levels in leachate and water from the gas-collection system compared to those of unaffected water, significant increases in the tritium content of the water would be expected to accompany VOC detections and increases in delta 13C and 14C caused by landfill water. The results rule out landfill water as the VOC source, leaving landfill gas as the source. The identities and concentrations of the specific VOCs in affected groundwater samples varied among wells as well as between two leachate samples, ruling out the use of a VOC "fingerprint" for leachate or landfill gas to be compared to groundwater VOC concentrations.
在加利福尼亚州南部的一个垃圾填埋场，对地下水样本中挥发性有机化合物的来源进行了评估。渗滤液中的水以及气体收集系统中的水（冷凝水和夹带的水滴）的3H（氚）含量，以及垃圾填埋气CO2、渗滤液和气体收集系统水中无机碳的δ13C和14C含量，被用于表征垃圾填埋场内的溶解无机碳（DIC），同时在受影响监测井和未受影响井的地下水样本中监测相同参数。渗滤液和气体收集系统冷凝液中的氚水平范围约为2000 TU至超过4000 TU，比未受影响的地下水高出几个数量级。垃圾填埋场孔隙水样本中DIC的平均14C含量为121 pMC，未受影响的地下水DIC的14C含量为93 pMC，而检测到挥发性有机化合物的地下水中溶解无机碳的14C含量范围为105至119 pMC。孔隙水中DIC的δ13C始终高于0‰，未受影响的地下水DIC的δ13C为-20.3‰，而受影响的地下水样本中DIC的δ13C从-17.3‰增加到-13.2‰。垃圾填埋气影响的地下水中DIC的δ13C和14C的增加通常与检测到的挥发性有机化合物的数量及其浓度相关。基于渗滤液和气体收集系统中的水与未受影响的水相比的氚和DIC 14C水平，预计水中氚含量的显著增加将伴随着挥发性有机化合物的检测以及由垃圾填埋水导致的δ13C和14C的增加。结果排除了渗滤液作为挥发性有机化合物来源的可能性，确定垃圾填埋气为来源。受影响的地下水样本中特定挥发性有机化合物的种类和浓度在不同井之间以及两个渗滤液样本之间有所不同，排除了使用渗滤液或垃圾填埋气的挥发性有机化合物“指纹”与地下水挥发性有机化合物浓度进行比较的可能性。
