Why comparison between different chemical extraction procedures is necessary to better assess the metals availability in sediments

Single and sequential extractions are current useful tools for estimating the availability of metals in soils or sediments. Many chemical extraction procedures have been proposed literature, making comparison difficult. This study compares data consistency potential given by four commonly found literature: two single (using dilute HCl EDTA as reactant) (the modified standardized 3-steps procedure Standards, Measurements Testing Programme (SMTP), namely BCR-extraction, 7-steps Leleyter Probst (1999), LP-extraction). The leaching all performed on reference lake sediment CRM BCR-701, used a to assess accuracy Rauret et al. (1999). results show similar availabilities between leaches Zn, Cu, Cr Pb BCR Ni. LP-extraction is most aggressive tested (except extraction), mainly due better exchangeable fraction, dissolution acido-soluble phase particularly amorphous crystalline Fe-oxides. reveals major problem extraction, potentially formation lead precipitates during LP-extractions, even if an overestimation cannot be excluded.