Soil-plant transfer models for metals to improve soil screening value guidelines valid for São Paulo, Brazil.

In Brazil, there is a lack of combined soil-plant data attempting to explain the influence of specific climate, soil conditions, and crop management on heavy metal uptake and accumulation by plants. As a consequence, soil-plant relationships to be used in risk assessments or for derivation of soil screening values are not available. Our objective in this study was to develop empirical soil-plant models for Cd, Cu, Pb, Ni, and Zn, in order to derive appropriate soil screening values representative of humid tropical regions such as the state of São Paulo (SP), Brazil. Soil and plant samples from 25 vegetable species in the production areas of SP were collected. The concentrations of metals found in these soil samples were relatively low. Therefore, data from temperate regions were included in our study. The soil-plant relations derived had a good performance for SP conditions for 8 out of 10 combinations of metal and vegetable species. The bioconcentration factor (BCF) values for Cd, Cu, Ni, Pb, and Zn in lettuce and for Cd, Cu, Pb, and Zn in carrot were determined under three exposure scenarios at pH 5 and 6. The application of soil-plant models and the BCFs proposed in this study can be an important tool to derive national soil quality criteria. However, this methodological approach includes data assessed under different climatic conditions and soil types and need to be carefully considered.

Bioconcentration factors and the risk concentrations of potentially toxic elements in garden soils.

Empirical models describe soil-plant transfers to explain the variations in the occurrence of potentially toxic elements (PTE) in soils and to estimate the Bioconcentration Factor (BCF). In this study, results were selected based on data in the literature on soils of humid tropical and temperate regions to evaluate soil-plant transfer models, to calculate the BCF and to derive risk concentrations of Cu, Cr, Pb, Ni and Zn present in the exposure pathway leading to the consumption of contaminated vegetables. The Cetesb (Environmental Agency of the State of Sao Paulo, Brazil) mathematical model was used to derive the risk posed by soil concentrations in urban and rural exposure scenarios. The results of the pseudo total contents of PTE in the soil and the contents absorbed by plants were compared and the BCFs were calculated by the use of geometric means, including a correction factor appropriate to each particular type of soil. Differences were observed between BCFs calculated for each climate region: humid tropical (HTR) and temperate (TE), which the first one presented the highest values to BCF in leaves and the lowest BCF values for root, except Ni, compared to second one. The soil concentrations with the highest risk were found in humid tropical regions as compared with those found in temperate regions, except for Ni. The obtained BCFs may contribute to any future revisions of guideline values as well as help other state environmental agencies to establish their own guideline values.

Analysis of Mercury-Rich plants and mine tailings using the Hydride-Generation AAS method

A hydride-generation atomic absorption spectroscopy (AAS) method was developed for the analysis of total Hg in liquid matrices of mercury-rich plants and mine tailings samples. The detection limit for this method was as low as 11.4 ng/mL. The reproducibility of the mercury signals (in terms of relative standard deviation) was 4.6 percent. Accuracy of the method was verified by analyses of deionised water samples spiked with HgCl2 and HgNO3. Recovery values for total mercury ranged from 88.5 to 94.3 percent for both mercury species added. An external certified laboratory validated the analytical method with a maximum discrepancy of 15 percent. Optimal analytical response of the equipment for Hg analysis of plant samples was achieved when the sample volume added to the reaction vessel was 0.25 mL.

Um protocolo para análise do mercúrio (Hg) em amostras líquidas de solo e tecidos vegetais enriquecidos com Hg foi desenvolvido com base na técnica de geração de hidretos. O limite de detecção para este método foi de 11.4 ng/mL. A reproducibilidade do método (calculado com base no desvio padrão relativo) foi de 4.6 por cento. A precisão do método foi verificada pela análise de amostras de água deionizada contendo HgCl2 and HgNO3. Os valores de mercúrio total recuperados variaram de 88.5 a 94.3 por cento para ambas as espécies testadas. O método analítico foi validado por um laboratório externo certificado com discrepância máxima de 15 por cento. O desempenho analítico do equipamento para análise do mercúrio em tecidos vegetais foi considerado ótimo para volumes de amostra de até 0.25 mL.

Protocols for in vitro culture and phytochemical analysis of Phyllanthus species (euphorbiaceae).

We developed reproducible protocols for micropropagation, callus culture, and root culture of the medicinal plant Phyllanthus urinaria, P. niruri, P. tenellus, P. corcovadensis, P. caroliniensis, P. stipulatus, and P. fraternus by using single node explants. Genotype-linked differences are visible among the Phyllanthus species concerning shoot culture, callus culture, and root culture growth. The protocols developed for phytochemical screening of callus and root extracts of P. urinaria, P. caroliniensis, P. stipulatus, and P. fraternus have shown the production of sterols and triterpenes. Both compounds are known to account for the antinociceptive activity of the methanolic extracts as glochidone and stigmasterol have strong activity against neurogenic and inflammatory pain. Similarly, methanolic callus extracts of P. tenellus, P. niruri and P. corcovadensis have potent analgesic properties, however phenolics are major compounds isolated from these species. The optimized micropropagation, callus culture, and root culture protocols offer the possibility to use cell/root culture techniques for vegetative propagation and secondary metabolite studies.

Fitorremediacion de acuiferos contaminados por benceno y etanol utiliando "sauce lloron" (Salix babylonica)

El objetivo del trabajo fue investigar el potencial del sauce lloron (salix babylonica-Familia Salicaceae) en el proceso de adsorcion directa por las raices de etanol y benceno,como una etapa inicial en el estudio de la fitorremediacion.Los resultados obtenidos indicaron reducciones de hasta un 99 por ciento para ambos contaminantes,tanto a nivel balance de masa como a nivel de concentracion

Fitorremediacion de acuiferos contaminados por benceno y etanol utiliando "sauce lloron" (Salix babylonica)

El objetivo del trabajo fue investigar el potencial del sauce lloron (salix babylonica-Familia Salicaceae) en el proceso de adsorcion directa por las raices de etanol y benceno,como una etapa inicial en el estudio de la fitorremediacion.Los resultados obtenidos indicaron reducciones de hasta un 99 por ciento para ambos contaminantes,tanto a nivel balance de masa como a nivel de concentracion