SHORT-RANGE VARIABILITY OF FALLOUT PB IN A CONTAMINATED SOIL

Studies about Pb variability in contaminated soils, especially in the case of fallout from smelters or facilities, are few and the relevance of geostatistical technique for studying contaminated soil as well as the surface area required for investigation are unclear. Few studies have been conducted on short-range variability of trace elements in so ils, and some of them have shown these elements to be randomly distrib uted while others pointed out the spatial dependence between sample lo cations. Therefore, the main objective of this study is to document th e short-range variability of Pb in an area contaminated by fallout, us ing a case study in France. Soil lead in this site arises from a histo ry of industrial use. No other metals were detected in Pb emissions. O n this site, we conducted a statistical and a geostatistical study of ph content in soil, and of soil characteristics that may affect it. Th e aims of this work are (i) to separate the spatial structure due to h igh Pb fallout from a content and diffuse pollution, (ii) to separate the variability due to analytical measurements from ones related to sp atial variations, (iii) to point out the soil characteristics correlat ed with Pb, (iv) to optimize sampling design for monitoring the long-t erm changes following remedial action. Results demonstrated that in th is highly contaminated soil, fallout Pb was mainly located in the surf ace layer (0-0.2 m depth). The geostatistical study suggested that the study of the spatial structure may help in discriminating fallout Pb from Pb coming from diffuse pollution or geochemical content. However, the large spatial variability of Pb, partly due to microheterogeneity made the monitoring of this toxic element very difficult, and require d a larger surface for sampling. Using correlation techniques to detec t causations appeared not to be relevant. Therefore, other statistical techniques such as path analysis should be tested. Additionally, micr oanalysis, mobility and bioavailability studies, as well as lab or ben ch scale remediation studies should be conducted.