Maintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO₂ g⁻¹ day⁻¹) than in the expanded clay (1.0 µg CO₂ g⁻¹ day⁻¹). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIE_H = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day⁻¹) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

在修复人工湿地中受石油碳氢化合物污染的地下水期间，维持和支持完全生物降解对于污染物的最终破坏和去除至关重要。我们的目的是比较和深入了解生物降解，并探索不同过滤材料（沙子、生物炭改性沙子、膨胀粘土）可能存在的局限性。这些过滤器是在运行两年后从人工湿地收集的，并使用两种稳定同位素技术进行了批量实验； (i) 十六烷的碳同位素标记和 (ii) 癸烷的氢同位素分馏。十六烷和癸烷这两种碳氢化合物均可生物降解。砂质过滤材料（3.6 µg CO ₂ g ^-1 day ^-1 ）中十六烷的矿化率高于膨胀粘土（1.0 µg CO ₂ g ^-1 day ^-1 ）中的矿化率。构建的湿地微观世界的微生物群落以革兰氏阴性细菌和真菌为主，并且对于不同的过滤材料是特定的，而十六烷主要被细菌合成。观察到石油烃在膨胀粘土中的吸附/解吸，这可能不会阻碍但会延迟生物降解。在癸烷生物降解过程中，在膨胀粘土、沙子和生物炭过滤器中记录到的氢同位素分馏的情况非常少。在砂滤器中，癸烷的生物降解速度较慢，并且氢同位素分馏是可见的。尽管如此，砂滤器观察到的表观动力学氢同位素效应（AKIE _H = 1.072–1.500）和表观癸烷生物降解率（k = − 0.017 至 − 0.067 day ⁻¹ ）的范围较低。 总之，低生物降解率、小氢同位素分馏、零级矿化动力学和缺乏微生物生物质生长表明传质控制生物降解。