ASSESSMENT OF INORGANIC LEAD SPECIES AND TOTAL ORGANO-ALKYLLEAD IN SOME EGYPTIAN AGRICULTURAL SOILS

This study was carried out to assess the amounts of (ii total Pb in so il, (ii) inorganic Pb species: exchangeable (EXCH), carbonate (CARB), easily reducible (EASR), moderately reducible (MODR), organic matter a nd sulfides (ORGS), and residual (RESD) bound Pb, and (iii) total orga no-lead as alkyllead in alluvial and lacustrine soils of the Nile delt a, Egypt. Wide ranges of soil Pb were found in the alluvial (18.2-1850 mu g g(-1)) and the lacustrine (39-1985 mu g g(-1)) soils. The topsoi l was highly enriched with Pb relative to the subsurface soils, especi ally in highly contaminated soils. There was no significant relationsh ip between soil type and Pb content. Amounts of soil Pb gl eater than the background level (14 mu g g(-1)) are due to Pb deposited from vari ous anthropogenic activities. The partitioning of soil Pb into differe nt species varied according to the intensity of contamination. It foll owed the sequence: RESD > ORGS > CARB > MODR > EASR in the slightly co ntaminated alluvial as well as lacustrine soils. In the highly contami nated soils, it followed the sequence: ORGS > MODR > CARB > EASR > RES D in the alluvial soils, and the sequence. ORGS > CARB > MODR > EASR > RESD in the lacustrine soils. There is high binding capacity of organ ic matter and sulfides to Pb, especially in the highly contaminated so ils. The concentrations of total alkyllead in soils varied markedly an d were related to both intensity of contamination and depth in the soi l. The subsurface soil (15-30 cm) was highly enriched by alkyllead (me ans 224 and 353 ng g(-1) in the alluvial and lacustrine soils, respect ively relative to the surface and deeper soils. The proportion of tota l alkyllead as a percentage of total Pb in the soil was generally very low. It did not exceed 1.6% in the slightly contaminated soils, and 0 .6% in the highly contaminated ones.