Lead bioaccessibility in soil and mine wastes after immobilization with phosphate

CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe immobilization of lead by the reaction with phosphate bearing materials is a promising remediation method for contaminated soils. Low soluble neo-formed lead-phosphate phases similar to chloropyromorphite [Pb(5)(PO(4))(3)Cl], can control availability and mobility of lead in the environment, and consequently reduce human exposure, if soils are the main contamination pathway. We used three phosphate source materials [NaH(2)(PO(4))(3), commercial superphosphate and phosphate rock] to study lead immobilization in soil and mining waste samples. Products were examined after 1, 3 and 6 months of contact. The samples are from a contaminated area by former Pb mining and smelting activities, in southeastern Brazil, where epidemiological studies showed high lead blood levels in local population. The PBET (physiological based extraction test) bioaccessibility test was used to measure changes in the amount of soluble lead after sample treatment. Results show that the most efficient phosphate source was NaH(2)(PO(4))(3), which reduced lead solubility to 92% in acidic gastric conditions after the first month of contact. Superphosphate and phosphate rock also diminished Pb solubility, but the effect was more time dependent. None specific Pb-phosphate phases could be identified by XRD in whole treated samples, but the Pb-Ca-P elemental associations, observed on SEM images and EDS spectra of portions of the samples, combined with the reduced solubility, indicate that more insoluble lead phases were formed after the treatment. Based in these results, the in site phosphate application on soils to induce lead immobilization should be considered as a possible alternative to reduce human exposure at the area1951-4257273CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP [Nr.2002/00271-0]sem informaçãosem informaçãosem informaçã

Are Performance Differences of Interest Operators Statistically Significant?

The differences in performance of a range of interest operators are examined in a null hypothesis framework using McNemar’s test on a widely-used database of images, to ascertain whether these apparent differences are statistically significant. It is found that some performance differences are indeed statistically significant, though most of them are at a fairly low level of confidence, i.e. with about a 1-in-20 chance that the results could be due to features of the evaluation database. A new evaluation measure i.e. accurate homography estimation is used to characterize the performance of feature extraction algorithms.Results suggest that operators employing longer descriptors are more reliable