Necrophytoremediation of aliphatic hydrocarbons in contaminated soil (#303)
Petroleum hydrocarbons represent the most common environmental contaminants in the world which threaten the health of living organisms. As a consequence, there is a need to develop cost effective and environmentally friendly techniques to clean up these contaminants. One such promising method is necrophytoremediation; using plant dead biomass (e.g. straw) to remove or degrade contaminants from environments. The aim of this study was to evaluate the efficacy of necrophytoremediation using 4 types of plant residues (alfalfa hay, pea straw, wheat straw and various residues (combination of residues) on the degradation of aliphatic hydrocarbons (1%, w/w) in a contaminated soil. In addition, traditional microbial methods (plate counting and most probable number; MPN) in conjunction with PCR-Denaturing Gradient Gel Electrophoresis (DGGE)-sequencing methods was used to further assess the impact of this technology on the soil microbial community. The result showed that the addition of all plant residues led to a significant increase in the removal of total petroleum hydrocarbons (TPH). Addition of pea straw resulted in an 83% reduction in TPH, compared to 57% for the control soil. Plate counting and MPN results showed that the presence of plant residues increased the population of bacteria and hydrocarbon degraders; for example, a 12-fold increase in hydrocarbon degraders was observed in contaminated soils mixed with pea straw. DGGE analysis revealed that addition of most plant residues (e.g. pea straw) led to significant changes in the bacterial community structure with increased hydrocarbonoclastic activity. The mechanisms underlying this enhanced remediation may include the release of nutrients into the soil, improving soil structure and aeration and the addition of additional degradative microflora into the soil.