Impact of bacterial and fungal processes on 14C-hexadecane mineralisation in weathered hydrocarbon contaminated soil

In this study, the impact of bacterial and fungal processes on ¹⁴C-hexadecane mineralisation was investigated in weathered hydrocarbon contaminated soil. The extent of ¹⁴C-hexadecane mineralisation varied depending on the bioremediation strategy employed. Under enhanced natural attenuation conditions, ¹⁴C-hexadecane mineralisation after 98days was 8.5±3.7% compared to <1.2% without nitrogen and phosphorus additions. ¹⁴C-hexadecane mineralisation was further enhanced through Tween 80 amendments (28.9±2.4%) which also promoted the growth of a Phanerochaete chyrsosporium fungal mat. Although fungal growth in weathered hydrocarbon contaminated soil could be promoted through supplementing additional carbon sources (Tween 80, sawdust, compost, pea straw), fungal ¹⁴C-hexadecane mineralisation was negligible when sodium azide was added to soil microcosms to inhibit bacterial activity. In contrast, when fungal activity was inhibited through nystatin additions, ¹⁴C-hexadecane mineralisation ranged from 6.5±0.2 to 35.8±3.8% after 98days depending on the supplied amendment. Bacteria inhibition with sodium azide resulted in a reduction in bacterial diversity (33-37%) compared to microcosms supplemented with nystatin or microcosms without inhibitory supplements. However, alkB bacterial groups were undetected in sodium azide supplemented microcosms, highlighting the important role of this bacterial group in ¹⁴C-hexadecane mineralisation.