Alkyllead species in the coastal waters of Alexandria, Egypt

Abstract

Fourteen locations were sampled along the Alexandria coast to assess the occurrence and fate of alkyllead compounds in water, sediments and biota. Tetraalkyllead was not observed in any of the samples analyzed. PbMe 3 + dominated the methyllead species in water (constituting 62–64% of total alkyllead) reaching 1506 ng kg −1 opposite the alkyllead production plant. PbEt 3 + dominated the ethyllead species constituting 18–20% of total alkyllead species with a maximum concentration of 902 ng kg −1 PbEt 2 +2 > PbMe 2 +2 > PbMe 2Et + > PbMeEt 2 + appeared mostly in nearshore stations with maximum levels being reached opposite to the alkyllead production plant and traffic light locations on the highway running parallel to the seashore, especially during summer. Seasonal variations were mainly related to traffic activity. The average concentration ratio of PbMe 3 + : PbEt 3 + is 3.2 ± 2.4 reflecting the use of PbMe 4 as a petrol additive. Alkyllead compounds behaved nonconservatively on reaching seawater due to their removal from solution by uptake onto suspended particles. The PbMe 3 + :PbMe 2 +2 concentration ratio in sediments fluctuated between 30:1 for nearshore to 5:1 for offshore samples while that for PbEt 3 + :PbEt 2 + was 1.6:1 and 2.9:1 for the same areas. Methylethyllead species were not detected in offshore sediments. Low triand dialkyllead levels were observed for anaerobic sediments. Alkyllead species concentration in biota inhabiting the coastal waters of Alexandria increased in the following order: Mixed plankton < Mugil capito (pelagic fish) < Mullus burbatus (demersal fish) < Donax trunculus (bivalve) < Ulva rigida (algae) < Neptunus pelagicus (crab) indicating higher levels in demersal rather than pelagic organisms. The maximum concentration factors for crabs are: 2850, 4985, 12970 and 6690 for PbMe 3 +, PbEt 3 +, PbMe 2 +2 and PbEt 2 +2, respectively, during summer. Alkyllead concentrations in some individuals reached high levels. These levels are considered hazardous with respect to the future discharge strategy of alkyllead to coastal waters, rendering these compounds more bioavailable. However, a health hazard criterion has not yet been established.