An assessment of heavy metal and pesticide pollution at a commercial airport.

Abstract

An assessment of heavy metal and pesticide pollution was conducted at a commercial airport in Pietermaritzburg, which is the base for a local crop spraying operation, as well as a small-scale aircraft maintenance centre. The study investigated the presence of heavy metals from the aircraft activities (tyre wear, emission and aircraft body attrition) along the edges of the runway. In addition, the study assessed the pollution of the soil in different parts of the airport (areas adjacent to the crop sprayer hangar and maintenance hangars drainage ditch) caused by organic chemicals (pesticides) originating from the washing and maintenance of the crop spraying aircrafts. A total of 37 samples were taken from the top soil (0-15 cm) adjacent to both sides of the runway, approximately 100 meters apart, for heavy metal assessment. Total metal concentrations were determined on a 1:1 HNO3 acid extract analysed using inductively coupled plasma spectroscopy and the results compared with the baseline concentrations of heavy metals in the soils of South Africa. The average levels of the heavy metals in the soils were: Cd - 4.4, Co - 76, Cr - 142, Mn - 6580, Pb - 64 and Zn - 70 mg/kg. The Cd and Co concentrations of all samples and the Pb and Zn concentrations of 86% of the samples were above the South African guidelines for the maximum permissible contents of these metals (2 mg/kg Cd, 20 mg/kg Co, 6.6 mg/kg Pb, 46.5 mg/kg Zn) in soils. In addition, the concentration of Cr was significantly above these guidelines (80 mg/kg Cr ) in 51% of the samples. All the metals, except zinc, were highly correlated with one another indicating the source for these heavy metals is the same. In addition the concentration of these metals was high at sampling points adjacent to the runway where pronounced aircraft tyre wear marks were observed, suggesting that the aircraft activities are the sources of these heavy metals. A total of 13 samples were collected from areas adjacent to the crop sprayer hangar and the drainage ditch (at the maintenance hangars) in order to determine the qualitative presence of organic pollutants. The samples were prepared using soxhlet extraction. Cypermethrin, deltamethrin, azoxystrobin, fusillade and fluazifop-p-butyl as well as fuel oils Jet Al and Avgas were qualitatively determined using GC/MS. Only fusillade and fluazifop-p-butyl were detected, in some of the samples. No quantitative analysis of the organic chemicals was attempted due to time constraints.