 |
| Titel |
Bioavailability and Sources of Lead in the Terrestrial Environment of Egypt |
| VerfasserIn |
Ezzat Marzouk, Waleed Shetaya, Mohamed Elkassas, Elham Mohamed, Elizabeth Bailey, Scott Young |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122626
|
| Publikation (Nr.) |
 EGU/EGU2016-1711.pdf |
|
|
|
|
|
| Zusammenfassung |
| Lead (Pb) is considered a major contemporary eco-toxicological threat with smelting
operations and fossil fuel combustion regarded as the major sources in the environment.
The majority of studies characterising Pb in soil have sought to determine: (i) its
source, from 206,207,208Pb isotope ratios, (ii) its distribution among operationally
defined soil fractions and (iii) its lability as defined by chemical extraction or isotopic
exchangeability. The objectives of the current work were: (i) to source-apportion the
soil Pb burden in Egypt between petrol, geological and other origins over a wide
range of soil characteristics and diverse locations; (ii) to quantify the isotopically
exchangeable fraction of Pb (PbE) as a measure of Pb reactivity; and (iii) to develop
multivariate relationships to predict soil Pb lability. Combined determinations of SEP
fractionation, isotopic lability and natural isotopic abundances were used as a means of
characterizing Pb in ∼ 150 Egyptian soils (selected to cover a wide range of soil
properties, locations and Pb exposure). Results showed a wide range of % PbEvalues (∼
5 – 40 % of the total soil Pb concentration, Pbtotal). However, PbE showed no
consistent correspondence to any single fraction of the SEP. Non-labile Pb (Pbtotal –
PbE) showed reasonable agreement with the SEP ‘residual’ fraction in relatively
uncontaminated soils from both inland and shoreline soils. However, in other soils,
notably those from contaminated peri-urban and urban locations, the non-residual
fractions (bound to oxides and humus) included non-labile forms of Pb. Up to 90% of
the observed variability in the %PbE in soils from the inland and shoreline areas
(uncontaminated) could be explained by soil factors, including variation in soil pH,
soil organic matter content, total Pb and P concentrations. However, in the case of
the contaminated peri-urban and urban soils the figure was only 33% implying a
significant contaminant ‘source’ effect on Pb lability. Isotopic ratios (206Pb/207Pb and
208Pb/207Pb) fell on a mixing line between end-members attributed to petrol and regional
geogenic Pb sources and clearly showed a distinction between Pb from geogenic and
anthropogenic sources (mainly petrol-derived Pb). In contaminated locations, there was clear
evidence that petrol-derived Pb, in average, remained considerably more labile
than Pb from the soil parent material. However, in all samples, both petrol-derived
and geogenic Pb contributed to the labile fraction depending on soil conditions. |
|
|
|
|
|
|