PCDD/Fs and heavy metals in the vicinity of landfill used for MSWI fly ash disposal: Pollutant distribution and environmental impact assessment.

This study focused on the syngenetic control of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) and heavy metals by field stabilization/solidification (S/S) treatment for municipal solid waste incineration fly ash (MSWIFA) and multi-step leachate treatment. Modified European Community Bureau of Reference (BCR) speciation analysis and risk assessment code (RAC) revealed the medium environment risk of Cd and Mn, indicating the necessity of S/S treatment for MSWIFA. S/S treatment significantly declined the mass/toxic concentrations of PCDD/Fs (i.e., from 7.21 to 4.25 µg/kg; from 0.32 to 0.20 µg I-TEQ/kg) and heavy metals in MSWIFA due to chemical fixation and dilution effect. The S/S mechanism of sodium dimethyldithiocarbamate (SDD) and cement was decreasing heavy metals in the mild acid-soluble fraction to reduce their mobility and bioavailability. Oxidation treatment of leachate reduced the PCDD/F concentration from 49.10 to 28.71 pg/L (i.e., from 1.60 to 0.98 pg I-TEQ/L) by suspension absorption or NaClO oxidation decomposition, whereas a so-called "memory effect" phenomena in the subsequent procedures (adsorption, press filtration, flocculating settling, slurry separation, and carbon filtration) increased it back to 38.60 pg/L (1.66 pg I-TEQ/L). Moreover, the multi-step leachate treatment also effectively reduced the concentrations of heavy metals to 1-4 orders of magnitude lower than the national emission standards. Furthermore, the PCDD/Fs and heavy metals in other multiple media (soil, landfill leachate, groundwater, and river water) and their spatial distribution characteristics site were also investigated. No evidence showed any influence of the landfill on the surrounding liquid media. The slightly higher concentration of PCDD/Fs in the soil samples was ascribed to other waste management processes (transportation and unloading) or other local source (hazardous incineration plant). Therefore, proper management of landfills and leachate has a negligible effect on the surrounding environment.

Synthesis of bimetallic core-shelled nanoparticles modified by 2-mercaptoethanol as SERS substrates for detecting ferbam and thiabendazole in apple puree.

Modification of surface-enhanced Raman spectroscopy (SERS) substrates with thiol ligands is an emerging approach in enhancing the stability and sensitivity of metal substrates due to their good affinity with metals such as Au, Ag, and Cu. Thus, in the current study, 2-mercaptoethanol was used to modify the surface of silver-coated gold nanoparticles to develop a novel SERS substrate for the rapid assessment of fungicide residues in fruit samples. Results showed that the substrate could achieve the detection of ferbam and thiabendazole residues in apple puree with limits of detection of approximately 0.0042 and 0.0064 ppm, high coefficients of determination of 0.9946 and 0.9968, good recoveries ranging from 80 to 105 and 81 to 107% and relative standard deviations of 3.5-7.5 and 3.8-7.9 %, respectively. Therefore, the substrate developed could potentially be utilised to assess other toxic agrochemicals in future.

Development of cellulose Nanofiber-based substrates for rapid detection of ferbam in kale by Surface-enhanced Raman spectroscopy.

This study developed a novel surface-enhanced Raman spectroscopy (SERS) method coupled with cellulose nanofiber (CNF)-based SERS wipers that were fabricated on quartz papers coated with a mixture of silver nanoparticle (AgNP) and gold nanostar (AuNS). A "drop-wipe-test" protocol was developed for rapid detection of pesticide residues in vegetables by SERS. Tremendously enhanced Raman scattering signals were obtained from the quartz/CNF/mixture (AgNP + AuNS) substrate, which were much higher than the paper/mixture (AgNP + AuNS) substrate. This method was used to detect ferbam on kale leaves within a few minutes and the detection limit was 50 µg/kg based on the PLS models (R2 = 0.89). The enhancement factor of the SERS substrate was calculated to be ~ 104 with satisfactory reproducibility. Satisfactory SERS performance could be achieved within 1-month storage period. These results demonstrate that this CNF-based SERS/wiper method is a practical approach for rapid detection of chemical contaminants in fresh produce.

Analysis of Dithiocarbamate Fungicides in Vegetable Matrices Using HPLC-UV Followed by Atomic Absorption Spectrometry.

A simple method combining ion-pair methylation, high-performance liquid chromatography (HPLC) analysis with detection at 272 nm and atomic absorption spectrometry was developed in order to determine 10 dithiocarbamate fungicides (Dazomet, Metam-sodium, Ferbam, Ziram, Zineb, Maneb, Mancozeb, Metiram, Nabam and Propineb) and distinguish ethylenbisdithiocarbamates (EBDTCs) Zineb, Maneb and Mancozeb in diverse matrices. This method associates reverse phase analysis by HPLC analysis with detection at 272 nm, with atomic absorption spectrometry in order to distinguish, with the same extraction protocol, Maneb, Mancozeb and Zineb. The limits of detection (0.4, 0.8, 0.5, 1.25 and 1.97) and quantification (1.18, 2.5, 1.52, 4.2 and 6.52) calculated in injected nanogram, respectively, for Dazomet, Metam-Na, dimethyldithiocarbamates (DMDTCs), EBDTCs and propylenebisdithiocarbamates (PBDTCs) justify the sensitivity of the method used. The coefficients of determination R2 were 0.9985, 0.9978, 0.9949, 0.988 and 0.9794, respectively, for Dazomet, Metam-Na, DMDTCs, EBDTCs and PBDTCs, and the recovery from fortified apple and leek samples was above 90%. Results obtained with the atomic absorption method in comparison with spectrophotometric analysis focus on the importance of the atomic absorption as a complementary specific method for the distinction between different EBDTCs fungicides.

Primary risk assessment of dimethyldithiocarbamate, a dithiocarbamate fungicide metabolite, based on their probabilistic concentrations in a coastal environment.

The primary ecological risk of dimethyldithiocarbamate (DMDC), a dithiocarbamate fungicide (DTC) metabolite, was evaluated based on their probabilistic environmental concentration distributions (ECDs) in the coastal environment, Hiroshima Bay, Japan. And their behavior and temporal trends was further considered. This is the first report of the identification of DMDC from environmental seawater and sediment samples. DMDC concentrations in bottom seawater were substantially higher than those in surface seawater, which are associated with the leachability from sediments in bottom seawaters, and with photodegradation in surface seawaters. Furthermore, seasonal risks are dominated by higher concentrations from April to June, indicating temporal variation in the risk to exposed species. Hierarchical Bayesian analysis offered DMDC ECD medians and range (5th to 95th percentiles) of 0.85 ng L(-1) (0.029, 22), 12 ng L(-1) (3.2, 48) and 110 ng kg dry(-1) (9.5, 1200) in surface seawater, bottom seawater and sediment, respectively. Considering that DMDC and DTCs have similar toxicological potential to aquatic organisms, the occurrence of the compound in water is likely to be of biological relevance. In summary, this work provides the first demonstration that the ecological risk of DMDC and its derived DTCs in Hiroshima Bay is relatively high, and that DTCs should be a high priority for future research on marine contamination, especially in bottom seawaters.

Feasibility of using terahertz spectroscopy to detect seven different pesticides in wheat flour.

This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature. Five of the seven pesticides exhibited specific absorption peaks in the low-energy THz range. The two remaining pesticides had no specific absorption peaks in this frequency range, but they exhibited different frequency-dependent refractive indices. The absorption coefficients of imidacloprid increased with its increasing weight ratio in high-density polyethylene, and the fitted power absorptions and refractive indices using a Maxwell-Garnett effective medium model were comparable to the measured data. Imidacloprid was also identified from its characteristic absorption peaks in wheat flour mixtures, and a linear relationship between the absorption coefficient and the weight ratio was observed. Our results show the potential of detection of selected pesticides in foods, such as wheat flour, using THz spectroscopy.

Gold nanorods as surface enhanced Raman spectroscopy substrates for sensitive and selective detection of ultra-low levels of dithiocarbamate pesticides.

We report the use of gold nanorods as solution-based SERS substrates for the detection of ultralow-levels of three different dithiocarbamate fungicides: thiram, ferbam and ziram. Gold nanorods are attractive to use as SERS substrates due to the ability to tune the surface plasmon resonance of the nanoparticles to the laser excitation wavelength of the Raman spectrometer equipped with a 785 nm diode laser. The gold nanorods are synthesized using a seed-mediated growth method and characterized using UV-Visible spectroscopy, zeta potential, and TEM. The gold nanorods have an aspect ratio of 2.19 ± 0.21 and have an average length of 37.81 ± 4.83 nm. SERS spectra are acquired at different concentrations of each fungicide and calibration curves are obtained by monitoring the intensity of the band arising from the ν(C-N) stretching mode coupled to the symmetric δ(CH(3)) motion. The limits of detection and limits of quantitation are obtained for each fungicide. The limits of detection are 11.00 ± 0.95 nM, 8.00 ± 1.01 nM, and 4.20 ± 1.22 nM for thiram, ferbam, and ziram respectively. The limits of quantitation are 34.43 ± 0.95 nM, 25.61 ± 1.01 nM, and 12.94 ± 1.22 nM for thiram, ferbam, and ziram respectively. It can be seen that the three different dithiocarbamates can be detected in the low nM range based on the limits of detection that are achieved.

Capillary electrophoretic-ultraviolet method for the separation and estimation of zineb, maneb, and ferbam in food samples.

A simple and sensitive capillary electrophoretic method with ultraviolet detection has been developed for the separation and determination of ferbam [iron(III)-dimethyldithiocarbamate], maneb [manganese(II)-ethylenebisdithiocarbamate] and zineb [zinc(II)-ethylenebisdithiocarbamate], in borate buffer, after their acidic decomposition and complexation with CDTA (trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid monohydrate), as CDTA-metal complexes of Fe+3, Mn +2, and Zn+2. The determination is dependent on the pH and the nature of the buffer solutions. In this method, the detection limit (signal-to-noise ratio = 3) is 0.0013, 0.0022, and 0.0023 mM for ferbam, maneb, and zineb, respectively. The relative standard deviation for the analysis of 1 mM of each was found to be 1.5 +/- 0.2%. The method was successfully applied for the analysis of red beans and grain samples spiked with ferbam, maneb, and zineb. The applicability of capillary electrophoresis as a useful tool for the simultaneous determination and analysis of ferbam, maneb, and zineb is demonstrated.

Historical estimation of exposure to 1,3-butadiene, styrene, and dimethyldithiocarbamate among synthetic rubber workers.

Quantitative estimates of exposure to 1,3-butadiene (BD), styrene (STY), and dimethyldithiocarbamate (DMDTC) were developed for a follow-up study of workers at six North American synthetic rubber plants. Procedures entailed identifying tasks and jobs involving exposure, identifying factors influencing historical changes in exposure potential, and using mathematical models to calculate job- and time-period-specific exposures. Exposure metrics included 8-hour time-weighted average (TWA) intensity, the annual number of peak exposures (BD: >100 ppm, STY: >50 ppm) and TWA intensity below and above the peak threshold. The 5th and 95th percentiles of the approximate probability distribution of each exposure estimate served as its 90% uncertainty interval. Job- and year-specific estimates were linked with subjects' work histories to obtain cumulative exposure indices. Exposure estimates varied among tasks, jobs, plants, and time periods. BD TWAs were approximately 10 ppm during the 1940s-1960s and declined during the 1970s and 1980s. STY TWAs were always <2 ppm. DMDTC exposure began in the 1950s, was high through the 1960s, and later declined. BD peak exposure accounted for a large proportion of cumulative BD exposure, whereas almost none of the STY exposure was experienced at levels >50 ppm. Exposure indices were correlated. Exposures were higher than previously estimated. Multiple correlations among DMDTC, BD, and STY exposure estimates make it difficult to estimate agent-specific effects. Limitations of the methodology include the potential inaccuracy of the estimates, the lack of adequate industrial hygiene data to validate the estimates, the additional inaccuracy of linkage with poorly specified job groups, and the potential for differential exposure misclassification because the jobs and work areas where excess leukemia mortality occurred were well-known at the time of this study. Nevertheless, the new exposure estimates were highly correlated with the old, yielding equivalent exposure ranking of workers and were comparable to limited industrial hygiene data published by NIOSH.

Fourth-derivative spectrophotometric determination of fungicide ferbam (iron(III) dimethyldithiocarbamate) in a commercial sample and wheat grains using 2,2'-bipyridyl.

A procedure has been developed for the direct fourth-derivative spectrophotometric determination of iron(III) dimethyldithiocarbamate by converting it into an iron(II) 2,2'-bipyridyl complex, which is then dissolved in Triton X-100. Beer's law is obeyed over the concentration range 0.5-20 microg mL(-1 )in the final solution. Various parameters such as the effect of pH and interference of large number of ions on the determination of ferbam have been studied in detail. The method is sensitive, highly selective and can be used for the determination of ferbam in a commercial sample and in mixtures with various dithiocarbamates (ziram, zineb, maneb, etc.) and from wheat grains.

Determination of the fungicide ferbam in wheat grains after adsorption onto microcrystalline naphthalene.

A procedure was developed for the determination of iron(III) dimethyldithiocarbamate by converting it into iron(II)-bathophenanthroline-tetraphenylborate complex, which was then adsorbed onto microcrystalline naphthalene. The absorbance was measured at 534 nm against a reagent blank. Beer's Law was obeyed over the concentration range of 0.4-20 microg mL in final solution. Ten replicate determinations on 70 microg ferbam solutions gave a mean absorbance of 0.36, with a relative standard deviation of 0.91%. The method is sensitive and highly selective. It was applied for the determination of ferbam in a commercial sample and in mixtures with various dithiocarbamates (ziram, zineb, maneb) and wheat grains.

Spectrophotometric determination of ferbam [iron(III) dimethyl dithiocarbamate] in commercial sample and wheat grains after extraction of its bathophenanthroline tetraphenylborate complex into molten naphthalene.

A procedure has been developed for the determination of iron(III) dimethyldithiocarbamate by converting it into a iron(III)-bathophenanthroline-tetraphenylborate complex, which was then extracted into molten naphthalene, and the absorbance was measured at 534 nm against a reagent blank. Beer's law is obeyed over the concentration range 0.4-20 microg mL(-)(1) in final solution. The method is sensitive and highly selective and is applied for the determination of ferbam in a commercial sample, in mixtures with various dithiocarbamates (ziram, zineb, maneb, etc.), and from wheat grains.

Direct spectrophotometric determination of ferbam (Iron(III) dimethyldithiocarbamate) in commercial sample and wheat grains using 4,7-diphenyl-1,10-phenanthroline.

A procedure has been developed for the determination of iron(III) dimethyldithiocarbamate by converting it into the iron(II)-bathophenanthroline complex, which is then dissolved in acetone-water (1:1), and the absorbance is measured at 534 nm against a reagent blank. Beer's law is obeyed over the concentration range 0.5-20 microg x mL(-1) in the final solution. The method is sensitive and highly selective and is used for the direct determination of ferbam in a commercial sample and in mixtures with various dithiocarbamates (ziram, zineb, maneb, etc.) and from wheat grains.

Simple and sensitive spectrophotometric determination of ziram, zineb and ferbam in commercial samples and foodstuffs using phenylfluorone.

A procedure has been developed for the determination of ziram, zineb and ferbam dithiocarbamate pesticides by converting ziram and zineb into a zinc-phenylfluorone complex and ferbam into an iron phenylfluorone complex, which are then dissolved in water in the presence of cetylpyridinium bromide and pyridine as a surfactant. The method is sensitive, highly selective and can be used for the determination of ziram, zineb and ferbam in commercial samples and in foodstuffs.

Spectrophotometric determination of ferbam (iron(III) dimethyldithiocarbamate) in commercial sample and wheat grains using 4,7-diphenyl-1,10-phenanthroline after extraction into mesityl oxide.

A procedure has been developed for the determination of iron(III) dimethyldithiocarbamate by converting it into iron(II)-bathophenanthroline complex, which is then extracted into mesityl oxide in the presence of potassium perchlorate. The absorbance is then measured at 534 nm against a reagent blank. Beer's law is obeyed over the concentration range 0.5-20 microg ml(-1) in the final solution. The method is sensitive, highly selective and can be used for the determination of ferbam in a commercial sample, and in mixtures with various dithiocarbamates (ziram, zineb, maneb, etc.) and in wheat grains.

Capillary electrophoretic determination of ferric dimethyldithiocarbamate as iron(III) chelate of EDTA.

A simple and sensitive capillary electrophoretic method with UV detection has been developed for the determination of Ferbam (ferric dimethyldithiocarbamate) in boric acid buffer after its acidic decomposition and complexation with EDTA as Fe-EDTA- complex. The determination is dependent on the pH and the nature of the buffer solutions. In this method the detection limit (S/N = 3) is 1.8 x 10(-6) mol/L (0.7 mg/kg) of Ferbam. The relative standard deviation for the analysis of 50 microg/ml was found to be 2.9%. The method was successfully applied for the analysis of wheat grain samples spiked with Ferbam. The applicability of capillary electrophoresis as a useful tool for the analysis of Ferbam is demonstrated.

High-performance liquid chromatographic determination of dimethyldithiocarbamate residues in some agricultural products.

Dimethyldithiocarbamates are widely used in agriculture as active fungicides. The degradation of dimethyldithiocarbamates (ferbam, thiram) confirmed the fact that they are not stable and decompose very rapidly. The aim of this work was to apply the results obtained in high-performance liquid chromatographic quantitative analysis of residues of dithiocarbamate fungicides in some agricultural products (strawberries, maize, tobacco). The developed method enables very simple control analysis of low concentrations of dimethyldithiocarbamate residues in very short time. All limits of detection correspond with the criteria of FAO (Codex Alimentarius).