New biomimetic approach to determine the bioavailability of triclosan in soils and its validation with the wheat plant uptake bioassay

Effects of biochar on the fate of conazole fungicides in soils and their bioavailability to earthworms and plants

The study showed novel findings about changes in the fate and bioavailability of conazole fungicides (CFs) after biochar (BC) addition to soil. Two contrasting soils (low- and high-sorbing of CF; L soils, H soils) were amended by three BCs (low-, moderate-, and high-sorbing of CF; L-BC, M-BC, H-BC) at 0.2% and 2% doses. Epoxiconazole (EPC) and tebuconazole (TBC) were then added to the soil-BC mixtures, and their degradation, bioaccumulation in earthworms (Eisenia andrei), and bioconcentration in lettuce (Lactuca sativa) were studied for three months. Also, stir bar sorptive extraction (SBSE) was performed to determine CF (bio)accessibility. The EPC and TBC degradation in the soil-BC mixtures followed usually the first-order decay kinetics. The BC addition prevalently decreased the pesticides degradation in the L soil mixtures but often increased it in the H soil mixtures. In general, EPC degraded less than TBC. BC type and dose roles in the pesticides degradation were unclear. The BC addition significantly reduced pesticide uptake to the earthworms in the L soil mixtures (by 37-96%) and in the H soil mixtures (by 6-89%) with 2% BC. The BC addition reduced pesticide uptake to the lettuce roots and leaves significantly-up to two orders of magnitude, and this reduction was strong in H soil mixtures at 2% of BC. The BC addition reduced the CF (bio)accessibility measured by SBSE in all L soil mixtures and some H soil mixtures with 2% BC. Although not significant, it also seems that the pesticide bioaccumulation, bioconcentration, and (bio)accessibility were decreasing according to the BC type (L-BC > M-BC > H-BC). The pesticide concentrations in the earthworms and lettuce correlated significantly to the SBSE results, which indicates this technique as a possible predictor of biotic uptake. Our results showed that the interactions were hard to predict in the complex soil-BC-pesticide system.

Green method to determine triazine pesticides in water using Rotating Disk Sorptive Extraction (RDSE)

The following work presents the development of the solid phase extraction technique with rotary disk (RDSE) in which the analysis for seven triazines in surface waters was first implemented. All the variables involved in extraction have been studied and optimized using a solid phase of octadecyl (C18) deposited on surface of the disk. Triazines were analyzed quantitatively by gas chromatography with simple quadruple mass detector, recoveries obtained for seven triazines were between 80% and 120%, accuracy expressed as RSD was between 3.21% and 6.34%, and detection limit of the method was between 0.020-0.056 μgL^-1 according to each analyte, which indicates a good reproducibility and precision of the method. Finally, the method was applied to analyze the objective compounds in water samples obtained in the Bolo River (Palmira-Colombia), in which triazines were not detected.

Cork sheet as a sorptive phase to extract hormones from water by rotating-disk sorptive extraction (RDSE)

This work reports for the first time the use of laminar cork as a sorptive phase in a microextraction technique, rotating-disk sorptive extraction (RDSE). Typical hormones (estrone, estradiol, estriol and ethinyl estradiol) were selected as analyte models and extracted from wastewater samples on laminar cork with statistically equivalent extraction efficiency to that provided by Oasis HLB. The cork characterization was performed by confocal fluorescence microscopy (CLSM), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), allowing the identification of lignin, suberin and polysaccharides (cellulose and hemicellulose) as the main components of the cork. The best conditions for extraction were as follows: rotation velocity of the disk, 2000 rpm; extraction time, 45 min; and sample volume, 20 mL. The analytical features of the developed method show that calibration curves for all analytes have R² values higher than 0.99. The absolute recoveries were higher than 63%, and the precision, expressed as relative standard deviation, ranged from 2 to 16%. The LOD and LOQ ranges were 3-19 and 10-62 ng L^-1, respectively. The proposed method was applied to the analysis of wastewater, and the concentrations of hormones in a wastewater treatment plant in Santiago, Chile, ranged from <LOQ to 48 ng L^-1.

Released fraction of polychlorinated biphenyls from soil-biosolid system using a leaching procedure and its comparison with bioavailable fraction determined by wheat plant uptake

The bioavailability of polychlorinated biphenyls (PCBs) in soils amended with biosolids was estimated using an aqueous leaching process of the compounds combined with rotating disk sorptive extraction (RDSE), and compared with bioavailability determined through of PCB absorption in wheat plants growing in the same soil-biosolid matrix. The matrices consisted of soil amended with biosolids at doses of 30, 90, and 200 Mg/ha, which increase concomitantly the organic matter content of the matrix. Considering that PCBs were natively absent in both the biosolids and soil used, the compounds were spiked in the biosolids and aged for 10 days. For each biosolid dose, the aqueous leaching profile was studied and equilibrium time was calculated to be 33 h. The leaching fractions determined by RDSE, considering total PCBs studied, were 12, 7, and 6% and the bioavailable fractions absorbed by the wheat root were found to be 0.5, 0.3, and 0.2% for 30, 90, and 200 Mg/ha doses, respectively. Both fractions leachable and bioavailable decrease with both increasing hydrophobicity of the compound (Kow) and increasing in the biosolid dose. It was found that both fractions (leaching and bioavailable) correlated according to the bivariate least squares regression, represented by a coefficient of correlation of 0.86. Therefore, the application of the chemical method involving a leaching procedure is an alternative to estimate the bioavailable fraction of PCBs in wheat plants in a simpler and in a shorter time.

Effects of applying biosolids to soils on the adsorption and bioavailability of 17α-ethinylestradiol and triclosan in wheat plants

Biosolids contain inorganic and organic contaminants, including pharmaceutical and personal care products (PPCPs) that have accounted for a series of emerging contaminants, such as triclosan (TCS) and the hormone 17α-ethinylestradiol (EE2). The general aim of this study was to evaluate the effects of biosolid application on EE2 and TCS adsorption and bioavailability in soils through testing with wheat plants. For the bioavailability study, sand and two soils, Lampa and Lo Prado, were used. The sand and soils were treated using two biosolid application rates (0 and 90 mg ha^-1), and the EE2 and TCS concentrations in the biosolids were determined as 0.54 ± 0.06 and 8.31 ± 0.19 mg kg^-1, respectively. The concentration observed in wheat plants indicated that EE2 and TCS are mainly concentrated in the roots rather than in the shoots. Furthermore, the bioavailability of the compounds in plants depends on the properties of the contaminants and the soil. Adsorption studies showed that increasing the soil organic matter content increases the adsorption of TCS and EE2 on these substrates and that both compounds follow the Freundlich adsorption model. The desorption procedure indicated that availability for both TCS and EE2 depended on the soil type because TCS and EE2 were small in the Lampa soil with and without biosolid application and TCS increased by nearly 50% in the Lo Prado soil. The Lo Prado soil had an acidic pH (5.9) and the Lampa soil had a neutral pH of 7.3, and the organic carbon content was smaller.