Abstract

TRUJILLO-NARCIA, Antonio et al. Effect of the restoration of a fluvisol contaminated with crude oil. Rev. Int. Contam. Ambient [online]. 2012, vol.28, n.4, pp.360-374. ISSN 0188-4999.

Soils adjacent to oil facilities in Mexico could potentially be affected by crude-oil or oil-derivative spills or leaks. While the environmental legal framework sets forth, through Mexican official standards, the maximum allowable limits of hydrocarbons in soil and the remediation guidelines, the geochemical parameters used are no guarantee that the original conditions of soil are recovered. The functioning and resilience of the altered properties of remediated oil-polluted soil require measuring the efficiency of commercial remediation through parameters not included in NOM-138-SEMARNAT/SA1-2008. For this reason, the aim of this investigation was to identify the physical and chemical properties of remediated soil to prove the recovery of soil quality relative to the parameters of an adjacent and taxonomically similar soil. Parameters determined include total petroleum hydrocarbons (TPH), eight physical and 10 chemical properties of a remediated soil in an area of 0.85 ha and these were compared with figures obtained from samples collected in 0.377 ha of an adjacent control Fluvisol. Samples were collected at two depths (0-15 and 15-30 cm). Statistical differences (p < 0.01) were observed between both soil types for TPH, resistance to penetration (RP), bulk density (Bd), moisture at field capacity (MFC), water retention (WR), basic infiltration (Bi), clay and silt; also, on the following chemical properties: hydrogen potential (pH), electrical conductivity (EC), organic matter (OM), total nitrogen (N), usable phosphorus (P), exchangeable potassium (K), exchangeable calcium (Ca), exchangeable magnesium (Mg), exchangeable sodium (Na) and cation-exchange capacity (CEC). A negative correlation (p < 0.01) was identified beween TPH and 10 physical and chemical variables, among them Bi (-0.926) and MFC (-0.914), evidencing that remediated soil remains affected. A significant (p < 0.01) posi-tive correlation was found between TPH and six physical and chemical variables, such as Bd (0.935) and RP (0.928), which reveals the origin of soil degradation. The data show that soil quality remains affected, and hence the physical and chemical remediation was ineffective, so that new remediation processes are required, preferably biological ones. This study provides information for selecting physical and chemical indicators of soil to enable a better follow-up of the remediation process until soil is deemed remediated.

Keywords : compaction; bulk density; moisture; basic infiltration; water retention; texture.