Mobility and ecological risk assessment of trace metals in polluted estuarine sediments using a sequential extraction scheme.

The three-stage sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb, and Zn, proposed by the Commission of the European Communities Bureau of Reference, was applied to sediment five samples collected from the Sal estuary, Sergipe State, northeast Brazil, in September 2009. The method showed satisfactory recoveries, detection limits, and standard deviations for determinations of trace metals in the sediments. Cd and Pb were the metals most prevalent in the bioavailable fractions (carbonates, Fe and Mn oxides, organic matter, and sulfides), while Ni, Zn, Cu, and Cr showed higher percentages in the inert fraction. The order of mobility of the metals was Cd (66%) > Pb (65%) > Zn (59%) > Ni (57%) = Cr (57%) > Cu (56%). Possible toxicity related to these metals was examined using the risk assessment code, and by comparing the chemical data with sediment quality guideline ERL-ERM values. Results obtained using the two methods were in agreement, and showed low to medium risk for all metals, indicating that adverse effects on aquatic biota should rarely occur.

Determination of glyphosate in water samples by IC.

Agricultural development and its associated impacts on the environment are resulting in increasingly restrictive guidelines and legislation concerning the use of chemicals in agro-ecosystems. The herbicide glyphosate is widely used for weed control in both cultivated and uncultivated areas and is considered to show low toxicity to mammals. It is highly water-soluble, and its monitoring in surface, underground, and potable waters is recommended by the United States Environmental Protection Agency. This work presents a method for the inclusion of glyphosate determination within routine anion analysis using ion chromatography in water sampler without any kind of extraction, clean-up, or preconcentration step. The equipment used was a Dionex Model ICS-3000 ion chromatograph fitted with a 25-microL loop, Ion Pac AG19 guard and AS19 analytical columns, ASRS-300 (2 mm) suppressor, and conductivity detector. The method showed a linear response to glyphosate between 0.05-0.75 mg/L with a correlation coefficient of 0.999, and a detection limit below the maximum levels permitted by Brazilian legislation. Recoveries in the range 90-105% were achieved in tests using surface, well, potable, and ultrapure water samples.

Biosorption of Cr(III) using in natura and chemically treated tropical peats.

The physicochemical characteristics of three Brazilian peats were investigated using elemental analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD) and studies of Cr(III) biosorption based on adsorption isotherms. Adsorption of Cr(III) by in natura peat from Santo Amaro das Brotas (Sergipe State) was much greater than by peats from either Ribeirão Preto (São Paulo State) or Itabaiana (Sergipe State), with adsorption capacities (q) of 4.90+/-0.01, 1.70+/-0.01 and 1.40+/-0.01 mg g(-1), respectively. Pre-treatments with HCl and NaOH+HCl reduced adsorption by the Santo Amaro das Brotas peat, showing that adsorption efficiency was associated with the amount of organic matter present. Conversely, increase in the mineral content following pre-treatment increased adsorption of Cr(III) by the Ribeirão Preto and Itabaiana peats. Highest adsorption (retention >95.0%) was achieved at equilibrium pH 4.0 using the Santo Amaro das Brotas peat. Experimental data for the adsorption of Cr(III) from aqueous solution onto this peat were fitted to the Langmuir equation, from which an equilibrium adsorption capacity, q(max), of 5.60 mg g(-1) was obtained, which was close to the experimentally determined value.