School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; National Engineering Research Centre for Distillation Technology, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China.
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Department of Environmental Science and Technology, School of Applied Science, Cranfield University, Cranfield MK43 0AL, UK.
Chemosphere. 2014 Aug;109:71-6. doi: 10.1016/j.chemosphere.2014.03.005. Epub 2014 Apr 12.
In this study, we investigate specifically the influence of soil grain size and water content on the degradation of n-alkane fractions and the formation of aldehydes and carboxylic acid during ozonation. 15 g of quartz sand spiked with diesel (25 g kg(-1)) were exposed to ozone for 20 h at concentrations of 10, 30 and 50 mg L(-1), respectively. Results indicated that ozonation of the n-alkanes in fine grain size sand (0.15-0.25 mm) was 1.2 times faster than coarse sand due to higher surface contact area between O3 and sand particles. Soil moisture below 18% w/w did not influence the ozonation efficiency. In contrast the ozonation led to an increase of acidity of the sand samples (pH=3.0) after 20 h treatment. This was due to the formation of carboxylic acid. Formaldehyde, one of the key by-products of ozonation, was always <13 mg kg(-1) after the treatment which is below the industrial soil clean-up target level. While the aldehydes and carboxylic acid further reacted with O3 and their ozonation rate were slower than those of the alkanes suggesting that the hydroxylated by-products accumulated in the sand during the process. Overall the findings demonstrated that not only the alkanes but also aldehydes and carboxylic acid should be considered when defining remediation end-points.
在这项研究中，我们专门研究了土壤粒径和含水量对烷烃降解以及臭氧氧化过程中醛和羧酸形成的影响。将 15 克掺有柴油（25 g kg(-1)）的石英砂分别暴露于浓度为 10、30 和 50 mg L(-1)的臭氧中 20 小时。结果表明，由于 O3 和砂粒之间的表面接触面积较大，细粒径砂（0.15-0.25 毫米）中的烷烃臭氧氧化速度比粗砂快 1.2 倍。土壤水分低于 18%w/w 不会影响臭氧氧化效率。相比之下，臭氧氧化会导致砂样的酸度增加（pH=3.0），经过 20 小时处理后。这是由于羧酸的形成。甲醛是臭氧氧化的关键副产物之一，处理后始终<13 mg kg(-1)，低于工业土壤清理目标水平。而醛和羧酸进一步与 O3 反应，其臭氧氧化速率比烷烃慢，表明在该过程中羟基化副产物在砂中积累。总的来说，研究结果表明，在定义修复终点时，不仅要考虑烷烃，还要考虑醛和羧酸。
