Restoration of Brine and Oil Contaminated Marshlands by Cationic Exchange and Chemical-Biological Stabilization

Organic rich soil, containing 21 % and 56 % organic matter, was collected from a marshy area in southeastern Mexico from a tropical environment. The marsh had been contaminated by brine and oily water over several decades. The soil was treated serially by cationic exchange and chemical-biological stabilization. Cationic exchange resulted in a 60 % reduction in electrical conductivity (EC) , ~ 65 % reduction in de sodium adsorption ratio (SAR), and ~ 70 % reduction in the sodium ion concentration [Na + ]. Treatment by chemicalbiological stabilization resulted not only in the remediation of of hydrocarbon-caused impacts to the soil, but also mitigated brine caused impacts, reducing the EC roughly 30 % more, reducing the SAR 20 – 30 %, and the [Na + ] ~ 25 %. Final values were EC = 1.8 dS/m, a SAR of 0.5 – 0.6, a [Na + ] of 3.5 – 3.7 cmol(+)/Kg, and a pH of 8.3. The chemical-biological stabilization also resulted in the elimination of of hydrocarbon leachates (< 1 mg/L TPH), and reduced toxicity to background levels. Comparison with data from other studies, indicated that the final values are appropriate for the type of salt marsh/mangrove vegetation native to this area. Subsequent planting with marsh fimbry resulted in establishment, vigorous growth and reproduction.