The Effect of Hydrocarbon Pollution on Niger Delta Root Crops: A Case Study of Cocoyam [Colocasia Esculenta]

Abstract

This paper investigates effects of re-occurring oil spillages on cocoyam, Colocasia esculenta (L.). It studies changes in petiole lengths, leaf blades, chlorophyll concentrations in leaves, and PAH and BTEX concentrations in tubers for three generations under diverse conditions. 8 10-gallon grow bags were used: Grow bags 5–8 were treated with a controlled quantity (4 L/cubic metre) of liquid crude hydrocarbon in the months of June 2019–2021; with 2 replications, after a 2-3-day interval within a week. In grow bags 3, 4, 7, and 8, poultry manure were applied once in 2 months after small seedlings emerged from soil surfaces. Grow bags 1 and 2, 3, and 4 served as “controls” for non-contaminated growth. Grow bags 7 and 8 were treated with hydrocarbons and poultry manure. In the first generation, coco yams planted in grow bags 7-8 showed growth responses (average values of 1.04 m, 51 cm, 4.45 mg/g for petiole length, leaf blade length, and chlorophyll concentration, respectively) very similar to coco yams planted in pristine soil with poultry manure with average values of 1.00 m, 50 cm, 3.45 mg/g. The cocoyams planted in pristine organic rich soils showed similar response with or without fertilizers (average values of 0.98 m, 48 cm 1.83mg/g and 1.00m, 50 cm, 3.45mg/g) with progressively smaller leaves as generation increases. The cocoyams in hydrocarbon impacted soils generally perform poorer than uncontaminated soil with or without poultry manure by the second and third generation. Poultry manure on soils with re-occurring hydrocarbon contamination exacerbates soil weakening. Mean PAH and mean BTEX concentrations in tubers were 0.001-0.0035 mg/kg and <0.001mg/kg respectively. Cocoyams are not strong BTEX bioactive scavenger but gradually became more concentrated in PAH.