A mesocosm evaluation of processed drill cuttings for wetland restoration

Abstract

Many areas of coastal Louisiana are experiencing rapid wetland loss, largely due to an elevated rate of relative sea-level rise. Efforts to restore these deteriorated wetlands often include some form of sediment addition for successful rehabilitation. The earthen materials generated during petrochemical exploration (drill cuttings) may prove to be an ancillary sediment source for restoration efforts, while also reducing the load of oil-field waste. This study assessed two differently processed drill cuttings (DC-A and DC-B), dredge spoil and topsoil (control) in conjunction with three hydrologic regimes and five vegetative conditions ( Spartina alterniflora, Spartina patens, Spartina cynosuroides, Avicennia germinans, and an unvegetated control) at four salinity levels to determine sediment characteristics and capacity for supporting wetland plant growth. The DC-A and the dredge treatments demonstrated similar soil physico-chemical characteristics, which fell within acceptable ranges, and were comparable to the control in supporting plant growth. DC-B under fresh conditions demonstrated a high interstitial pH (∼11.0) that became ameliorated (∼8.3) under all saline conditions. Plant photosynthetic response was minimal in DC-B under fresh conditions, but comparable to the control under saline conditions. These results are promising and warrant further evaluations under a wider range of environmental conditions prior to field implementation.