Do surfactants influence the growth of Rhizophora mangle during restoration of contaminated soil with emulsified oil?

摘要

Mangrove forests are ecosystems subject to contamination by oil spills. The objective of this study was to evaluate the developmentof Rhizophora mangle plants in soil contaminated with oil emulsified with surfactants. These ecosystems have diverse andeconomically valuable ecological functions. Mangrove soil and propagules were collected in southeastern Mexico. The propaguleswere sown under greenhouse conditions and the plants were grown for 3 months. Two bioassays were applied: (1) the soilwas contaminated by oil emulsified with a biosurfactant synthesized by Azospirillum lipoferum, and (2) the soil was contaminatedwith oil emulsified with a surfactant based on pine essential oil. Emulsified oil was applied to the substrate in containerswith 3-month-old plants until several concentrations were reached (0, 30,000, 40,000, 50,000, 60,000, and 70,000 ppm). Subsequently,5 plants for each treatment were randomly extracted every 30 days for 12 months, and the stem length and diameter,root length, leaf area, and fresh and dry weights of the plants were evaluated. Plant development was evaluated through ananalysis of variance and a test of means. At the end of the bioassay, the treatments with oil emulsified with pine oil yieldedno surviving plants, whereas the treatments with oil emulsified with the biosurfactant yielded a 100 survival rate. Treatmentwith 30,000 ppm of oil emulsified with the biosurfactant yielded the greatest increases in the leaf area and total dry biomass.The heavy oil fraction concentration decreased by 93.9 with the 30,000 ppm treatment and by 82.64 with the70,000 ppm treatment.