Mcfarlandhiggins6123

Although environmental research has recently begun to focus on the ubiquity of microplastics in terrestrial systems, there is still lack of comprehensive data which describe microplastics levels in soils and the factors influencing the distribution of this contaminant. Here, we show that microplastics contamination (3877 ± 2356 p kg1) is omnipresent in numerous soil samples collected along the Yangtze River. Subsoils (4005 ± 2472 p kg1) showed higher levels of microplastics than topsoils (3748 ± 2301 p kg1), while polyamide (32%) was the most commonly found polymer in the samples. Small microplastics particles ( less then 200 µm) accounted for approximately 70% of the microplastics detected in subsoils. In terms of shape, microfragments were the most common type of microplastic particle, accounting for 34% of total microplastics, followed by microfibers (30%). Furthermore, microplastics contamination was found to be positively correlated with both the population of the study area and precipitation, yet negatively correlated with the elevation of the sampling site. Our study represents the first large-scale study of microplastic contamination in riparian soils along the Yangtze River, and provides important data regarding the ecotoxicology and ecosystem effects of microplastics in terrestrial environments.Manganese (Mn) in acidic paddy soil has large potential in emigrating from the soil and pollute adjacent ecosystems. Single microorganisms modulate the biogeochemistry process of Mn via redox reactions, while the roles of microbial aggregates (e.g. Phospho(enol)pyruvic acid monopotassium in vivo periphytic biofilm) in modulating its biogeochemical cycle is poorly constrained. Here we collected a series of periphytic biofilms from acidic paddy fields in China to explore how periphytic biofilm regulates Mn behavior in paddy fields. We found that periphytic biofilms have large Mn accumulation potential Mn contents in periphytic biofilm ranged from 176 ± 38 to 797 ± 271 mg/kg, which were 1.2-4.5 folds higher than that in the corresponding soils. Field experiments verified the Mn accumulation potential, underlining the biofilms function as natural barriers to intercept Mn emigrating from soil. Extracellular polymeric substances, especially the protein component, mediated adsorption was the main mechanism behind Mn accumulation by periphytic biofilm. Microorganisms in periphytic biofilms in general appeared to have inhibitory effects on Mn accumulation. Climatic conditions and nutrients in floodwater and soil affect the microorganisms, thus indirectly affecting Mn accumulation in periphytic biofilms. This study provides quantitative information on the extent to which microbial aggregates modulate the biogeochemistry of Mn in paddy fields.Reliable quantification of per- and polyfluoroalkyl substances (PFAS) adsorption and mobility in geomedia provides critical information (i.e., evaluation and prediction) for risk characterization and mitigation strategy development. Given the limited PFAS data available and various competing theories for modeling pollutant kinetics, it is indispensable to better understand and quantify the adsorption and transport of PFAS in geomedia using generalized models built upon a consistent physical theory. This study proposed a universal physical law (called the tempered stable law) in PFAS adsorption/transport by interpreting PFAS adsorption kinetics and nonideal transport as a nonequilibrium process dominated by adsorption/desorption with multiple rates following the tempered one-sided stable density (TOSD) distribution. This universal TOSD function led to novel TOSD-based models which were then tested by successfully simulating PFAS adsorption kinetics, adsorption isotherms, and nonideal transport data reported in the literature. Model comparisons and extensions were also discussed to further check the feasibility of the TOSD models and their adaptability to capture PFAS transport in more complex geomedia at all scales.A novel process involving the simultaneous electrochemical-oxidation (EO) and electrosynthesis of ferrate has been investigated for the treatment of the commonly detected and recalcitrant pesticide, atrazine. The present study considered the electrosynthesis of ferrate, in neutral pH, using low concentration iron (Fe2+) representative of raw water levels and its subsequent effect on atrazine degradation. Ferrate synthesis was unaffected by current density (10-80 mA cm-2), indicating mass transport limitations. Synthesis was affected by the initial iron concentration, whereby 0.051, 0.108 and 0.332 mg L-1 was generated with an Fe2+ concentration of 0.5, 1.0 and 3.0 mg L-1, respectively. When operating under simultaneous EO and ferrate oxidation, atrazine degradation exceeded that of a solely EO process. From an initial concentration of 2.00 mg L-1, atrazine was degraded to 1.34, 1.05 and 0.51 mg L-1 during 10, 40 and 80 mA cm-2, characterised by pseudo-first-order kinetics. Degradation with electrochemically-generated ferrate could be described by second-order kinetics, and yielded a degradation rate constant of 23.5 M-1 s-1. The effect of natural organic matter (NOM) on atrazine degradation was also investigated. Ferrate was observed to be mostly scavenged by resorcinol, a representative NOM compound, having a second-order reaction rate constant of 9.71 × 102 M-1 s-1.The present paper reports the application of augmented simplex-centroid mixture design to obtain a high BET surface area activated carbon using as reactants KOH, K2CO3 and K2C2O4. The optimum mixture composition was 2.51 g of KOH, 0.49 g of K2CO3 and absence of K2C2O4, generating an optimized AC (ACop) with SBET value equals to 1984 m2 g-1. The results herein obtained show that low amounts of K2CO3 can catalyze the pore development in the presence of KOH, increasing the surface area. Furthermore, the fractal dimensions of ACop are greater than 2.72, indicating the material has a complex pore structure with irregularities self-similar upon variations of resolution, as seen by SEM images. The TPD curves showed that the ACop has different oxygenated molecular fragments, which agrees with the pHPZC value (5.05). The ACop was applied in the adsorption of rhodamine B (RhB) and metformin (Met) in both binary and monocomponent systems. The simultaneous adsorption at 30 °C reveals that the adsorption capacity of RhB is 630.