Dissipation and evaluation of different treatments on the residues of different insecticides in/on cauliflower curd.

A field study to understand dissipation rates and effect of various washing treatments on the residues of seven different insecticides, i.e. tetraniliprole 200 SC, emamectin benzoate 5 SG, lufenuron 5.4 EC, indoxacarb 14.5 SC, thiodicarb 75 WP, profenofos 50 EC and cypermethrin 25 EC in/on cauliflower curd has been conducted. The results showed that initial deposits (just after the last insecticide application, i.e. 0 d) of tetraniliprole, emamectin benzoate, lufenuron, indoxacarb, thiodicarb, profenofos and cypermethrin were 0.43, 0.03, 0.25, 0.28, 0.38, 6.70 and 0.68 mg kg-1, respectively. The dissipation pattern of all the tested insecticides followed monophasic, first order kinetics with the half-lives of 6.25, 8.85, 3.27, 7.71, 4.36, 2.98 and 3.76 d, respectively. Proposed pre-harvest intervals for these insecticides are 6, 9, 3, 8, 4, 3 and 4 d, respectively. All the decontamination techniques showed reductions in residue levels. However, treatment by soaking in 5% sodium bicarbonate aqueous solution showed 54%, 42%, 53%, 48%, 22%, 54% and 77% maximum reductions in residues of tetraniliprole, emamectin benzoate, lufenuron, indoxacarb, profenofos and cypermethrin, respectively, in cauliflower curds. The next best treatment was soaking cauliflower curds in water at 45-50 °C for 10 min, which reduced the residues of cypermethrin, profenofos, tetraniliprole, thiodicarb, emamectin benzoate and lufenuron.

Analysis of visible and near infrared spectral reflectance for assessing metals in soil.

Visible and near infrared reflectance (VNIR; 350-2500 nm) spectroscopy has greatly been used in soils, especially for studying variability in spectrally active soil components (e.g., organic carbon, clays, and Fe/Al oxides) based on their diagnostic spectral features. In recent years, this technique has also been applied to assess soil metallic ions. In this research, the feasibility of VNIR spectroscopy for determination of soil metals was investigated with two soil data sets: (i) artificially metal-spiked and (ii) in situ metal-contaminated soils. Results showed that reflectance spectra of neither metal-spiked soils with Cd, As, and Pb even at their higher concentrations of 20, 900, and 1200 mg kg(-1), respectively, nor in situ metal-contaminated soils (with concentrations of 30 mg Cd, 3019 mg As, and 5725 mg Pb kg(-1) soil) showed any recognized absorption peaks that correspond to soil metal concentrations. We observed variations in reflectance intensity for in situ metal-contaminated soils only, showing higher reflectance across the entire spectrum for strongly and lower for less metal-contaminated soils. A significant correlation was found between surface soil metals' concentrations and continuum removed spectra, while soil metals were also found significantly associated with soil organic matter and total Fe. A partial least square regression with cross-validation approach produced an acceptable prediction of metals (R (2) = 0.58-0.94) for both soil data sets, metal-spiked and in situ metal-contaminated soils. However, high values of root mean square error ruled out practical application of the achieved prediction models.

Uptake of cadmium by hydroponically grown, mature Eucalyptus camaldulensis saplings and the effect of organic ligands.

The potential suitability of Eucalyptus camaldulensis for Cd phytoextraction was tested in a hydroponic study. Saplings were exposed to 4.5 and 89 microM Cd for one month, with and without EDTA and s,s-EDDS at 0.1, 1, and 5 mM. The saplings' growth was not affected at the 4.5 microM Cd concentration, yet it decreased 3-fold at 89 microM, and almost all the Cd taken up was immobilized in the roots, reaching 360 and 5300 mg Cd kg(-1), respectively (approximately 75% of which was non-washable in acid). The respective Cd root-to-shoot translocation factors were 0.14 and approximately 5*10(-4). At 0.1 mM concentration, EDTA and EDDS had no effect or even a positive effect on the saplings growth. This was reversed at 1 mM, and the chelants became lethal at the 5 mM concentration. At 89 microM Cd in the growth medium, 0.1 mM EDTA increased Cd translocation into the shoots by almost 10-fold, however it strongly reduced Cd content inside the roots. This hydroponic study indicates the feasibility of E. camaldulensis use for cleanup Cd-contaminated soils at environmental concentrations, both for site stabilization (phytostabilization) and gradual remediation (phytoextraction). EDTA was shown to be much more efficient in enhancing Cd translocation than s,s-EDDS.

Proximal spectral sensing to monitor phytoremediation of metal-contaminated soils.

Assessment of soil contamination and its long-term monitoring are necessary to evaluate the effectiveness of phytoremediation systems. Spectral sensing-based monitoring methods promise obvious benefits compared to field-based methods: lower cost, faster data acquisition and better spatio-temporal monitoring. This paper reviews the theoretical basis whereby proximal spectral sensing of soil and vegetation could be used to monitor phytoremediation of metal-contaminated soils, and the eventual upscaling to imaging sensing. Both laboratory and field spectroscopy have been applied to sense heavy metals in soils indirectly via their intercorrelations with soil constituents, and also through metal-induced vegetation stress. In soil, most predictions are based on intercorrelations of metals with spectrally-active soil constituents viz., Fe-oxides, organic carbon, and clays. Spectral variations in metal-stressed plants is particularly associated with changes in chlorophyll, other pigments, and cell structure, all of which can be investigated by vegetation indices and red edge position shifts. Key shortcomings in obtaining satisfactory calibration for monitoring the metals in soils or metal-related plant stress include: reduced prediction accuracy compared to chemical methods, complexity of spectra, no unique spectral features associated with metal-related plant stresses, and transfer of calibrations from laboratory to field to regional scale. Nonetheless, spectral sensing promises to be a time saving, non-destructive and cost-effective option for long-term monitoring especially over large phytoremediation areas, and it is well-suited to phytoremediation networks where monitoring is an integral part.