Pasture reduction in oil-contaminated soil is important for petroleum areas with cattle raising. To address this, soils representative of southeastern Mexico were artificially contaminated with heavy crude (15°API, 10,000–80,000mg/kg) and pasture reduction measured, being logarithmically correlated to petroleum concentrations (R2=0.95-0.99). Smectite-rich clayey soils (Gleysol, Vertisol) were least affected, with reductions of 10% and 26%, respectively, at 10,000mg/kg, and 12% and 34% at 20,000mg/kg. Sandy coastal soil (Psamment) showed moderate impacts (21%) at 10,000mg/kg, but high impacts (45% reduction) at 20,000mg/kg. An alluvial soil (Fluvent) and red-clay soil (Ultisol) suffered abrupt reductions in pasture productions even at low concentrations (10,000mg/kg): 50% and 59% respectively.
The gradual reduction in pasture in clayey and sandy soils may be due to decreases in field capacity and/or formation of water repellency: more soil microsites become covered with petroleum at increasing concentrations. Whereas the more abrupt reduction in alluvial and red-clay soils may also involve agglomeration of soil particles, causing compaction, reducing root penetration, water infiltration and soil gas exchange. To overcome this, much lower cleanup levels are needed, or post-remediation activities to improve field capacity, reduce water repellency and reduce compaction, such as adding organic amendments and establishing a complete vegetative cover (site restoration).

Primary Author:
Juan Pablo Montero-Velez
Universidad Juarez Autonoma de Tabasco
Villahermosa, Tabasco

Co-Author/Conference Presenter:
Randy H. Adams
Universidad Juarez Autonoma de Tabasco, Tabasco, Mexico

Veronica Isidra Dominguez-Rodriguez