Assessing bioaccumulation potential of sediment associated fipronil degradates in oligochaete Lumbriculus variegatus based on passive sampler measured bioavailable concentration.

The degradates of fipronil have equivalent or even more toxicity to non-target aquatic invertebrates. To assess their environmental risks, information of bioaccumulation is required. Currently, little is known about the bioaccumulative property of fipronil degradates in sediment, while it is well known that passive sampler may measure bioavailable concentration (Cfree) which links with the environmental effect more tightly than the total environment concentration. The goal of the present study was to characterize bioaccumulation potential in oligochaete Lumbriculus variegatus for a fipronil degradate sulfide. The sediment organic carbon-water partition coefficient (KOC) was measured with polymethyl methacrylate (PMMA) film passive sampler, and KOC was used to bridge the gap between biota-sediment accumulation factor (BSAF) and bioconcentration factor (BCF). The bioavailable concentration (Cfree)-based KOC values were 5371 ± 152 and 5013 ± 152 (mL/g OC) for fipronil sulfide (FSI) and sulfone (FSO), respectively. Since the two fipronil degradates were produced continuously in sediment by the parent compound, the time-weighted-average (TWA) concentration of FSI in the sediment was estimated from a bioassay with L. variegatus to calculate BSAF value (0.581 ± 0.211 g OC/g lipid) and BCF (3046 ± 1103 or log 3.48 ± 0.16 mL/g). This approach is able to estimate the Cfree-based KOC and BCF values of fipronil degradate in sediment with ongoing degradation of the parent compound.

Promoting the stability and adsorptive capacity of Fe3O4-embedded expanded graphite with an aminopropyltriethoxysilane-polydopamine coating for the removal of copper(ii) from water.

In this study, three magnetic graphites, namely, EGF, GAF, and GFA + KH550, were prepared, which were loaded either with Fe3O4 or with Fe3O4 and PDA or with Fe3O4, PDA, and KH550 onto expanded graphite. ATR-FTIR, XRD, XPS, SEM, TEM, and TGA characterization results showed that EGF, GAF, and GFA + KH550 were successfully prepared. Under the same initial copper concentration, the removal rates of copper ions by EGF, GFA, and GFA + KH550 were 86.2%, 96.9%, and 97.0%, respectively and the hazard index reductions of the three adsorbents were 2191 ± 71 (EGF), 1843 ± 68 (GFA), and 1664 ± 102 (GFA + KH550), respectively. Therefore GFA + KH550 exhibited better removal of Cu(ii) than EGF and GFA, for PDA and KH550 provided more adsorption-active sites like -OH and -NH. Here, the adsorption of GFA + KH550 fitted the pseudo-second-order kinetic and Langmuir models well within the testing range, which means that adsorption occurs on a monolayer surface between Cu(ii) and the adsorption sites. The intraparticle diffusion model and various thermodynamic parameters demonstrated that Cu(ii) was adsorbed on GFA + KH550 mainly via external surface diffusion and that the process was both endothermic and spontaneous. Recycling experiments show that GFA + KH550 has a satisfactory recyclability, and the way of direct recovery by magnets exhibits good magnetic induction. GFA + KH550 was applied in lake water and artificial seawater samples, and exhibited better removal of copper than that in DI water under the same environmental conditions for the existence of macromolecular organic matter. Furthermore, the adsorption capacity of copper ions was not relative to the salinity of water. The application of GFA + KH550 demonstrated the potential for application in water treatment procedures.

Measuring bioconcentration factors of sediment-associated fipronil in Lumbriculus variegatus using passive sampling techniques.

Fipronil and its degradates have been detected ubiquitously in aquatic environment worldwide, yet little is known about its bioaccumulation potential. The goal of the present study was to measure bioconcentration factor (BCF) of sediment-associated fipronil in a benthic invertebrate, Lumbriculus variegatus using passive sampling techniques. Three passive samplers including polymethyl methacrylate (PMMA) film, poly(dimethylsiloxane) fiber and polyacrylate fiber were evaluated. PMMA film was identified as the preferred method and was applied to determine fipronil log KOC (3.77 ±â€¯0.04). BCF of sediment-associated fipronil in L. variegatus was obtained through measuring freely dissolved concentration (Cfree). Because fipronil degraded in sediment, time weighted average (TWA) Cfree was estimated for calculating BCFTWA (1855 ±â€¯293 mL/g lipid). Fipronil BCF was also measured in a water-only bioaccumulation test of L. variegatus under constant exposure condition. This BCF value (1892 ±â€¯76 mL/g lipid) was comparable with the BCFTWA, validating effectiveness of the passive sampling method for the measurement of sediment Cfree. Fipronil was bioaccumulative in L. variegatus according to the USEPA's criteria. The combination of Cfree and TWA concentration measurements was demonstrated to properly determine BCF value for moderately hydrophobic and degradable chemicals in sediment.

One-pot route to synthesize HNTs@PVDF membrane for rapid and effective separation of emulsion-oil and dyes from waste water.

Water-purification membranes with high water flux, excellent recycling ability, good anti-fouling property, wide range for different oil/water emulsions separation, and strong water-soluble dyes removal ability are highly desirable for water purification but still a challenge to be realized. In this work, we show a simple method to address this challenge, in which halloysite nanotubes (HNTs) have been decorated on the poly (vinylidene fluoride) (PVDF) membrane surface through one-pot method via the aid of KH550 and dopamine. The HNTs@PVDF composite membrane exhibits superhydrophilic and under-water superoleophobic performance. In addition, our membrane can separate wide oil/water emulsions (including surfactant-stabilized and surfactant-free emulsions) from wastewater with high efficiency (>99.65%), outstanding recycle ability with good flux recovery rate (FRR > 95%) and good anti-fouling performance (the underwater oil contact angle (OCA) is 155.8 ±â€¯1.8° with low oil adhesion) and high water flux (7994 ±â€¯150 L m-2 h-1). Interestingly, our membrane also removes different water-soluble dyes (e.g., Congo red, methylene blue, and rhodamine B) from waste water by simply filtering. Those outstanding properties make our membrane hold great potential applications in real-world water purification and environmental protection.

Enantioselective degradation and bioaccumulation of sediment-associated fipronil in Lumbriculus variegatus: Toxicokinetic analysis.

Enantioselective degradation and biotransformation are critical processes affecting the bioaccumulation and toxicity of chiral pesticides in the environment. In the present study, enantioselective uptake, biotransformation and elimination of a current use pesticide, fipronil in a benthic invertebrate, Lumbriculus variegatus were assessed using a sediment bioaccumulation test. Toxicokinetic models were constructed to quantitatively describe kinetic processes of fipronil enantiomers. The degradation of fipronil in sediment significantly affected chemical uptake, thus degradation kinetic model was incorporated into toxicokinetic modeling. It was shown that S-(+)-fipronil degraded faster than R-(-)-fipronil in sediment, with dissipation rate constants being 0.090 ±â€¯0.008 and 0.023 ±â€¯0.006 1/d, respectively. As a result, R-(-)-enantiomer preferentially accumulated in sediment over time. Similarly, higher concentrations of R-(-)-fipronil were detected in L. variegatus compared with S-(+)-fipronil. Toxicokinetic modeling showed R-(-)-fipronil had larger uptake and elimination rate coefficients and apparent maximum reaction rate, but a smaller apparent half-saturation constant than S-(+)-fipronil. Preferential uptake of R-(-)-fipronil from sediment to L. variegatus was the main reason for greater R-(-)-fipronil concentrations in organism. Biotransformation of fipronil in L. variegatus was also enantioselective, yet it played fewer roles on enantioselective bioaccumulation than uptake. Overall, our findings highlight the importance of selective degradation, uptake and biotransformation of sediment-associated fipronil on its enantioselective bioaccumulation in benthic invertebrates, which helps to improve the accuracy for assessing aquatic toxicity of the chiral pesticide. CAPSULE: Enantioselective bioaccumulation of sediment-associated fipronil in Lumbriculus variegatus was quantitatively explained by selective degradation, uptake, biotransformation and elimination parameters using a combination of degradation and toxicokinetic modeling.