Response of Freshwater Biofilms to Antibiotic Florfenicol and Ofloxacin Stress: Role of Extracellular Polymeric Substances

Antibiotic residues have been detected in aquatic environments worldwide. Biofilms are one of the most successful life forms, and as a result are ubiquitous in natural waters. However, the response mechanism of freshwater biofilms to the stress of various antibiotic residues is still unclear. Here, the stress of veterinary antibiotic florfenicol (FF) and fluoroquinolone antibiotic ofloxacin (OFL) on freshwater biofilms were investigated by determining the changes in the key physicochemical and biological properties of the biofilms. The results showed that the chlorophyll a content in biofilms firstly decreased to 46⁻71% and then recovered to original content under the stress of FF and OFL with high, mid, and low concentrations. Meanwhile, the activities of antioxidant enzymes, including superoxide dismutase and catalase, increased between 1.3⁻6.7 times their initial values. FF was more toxic to the biofilms than OFL. The distribution coefficients of FF and OFL binding in extracellular polymeric substances (EPS)-free biofilms were 3.2 and 6.5 times higher than those in intact biofilms, respectively. It indicated that EPS could inhibit the FF and OFL accumulation in biofilm cells. The present study shows that the EPS matrix, as the house of freshwater biofilms, is the primary barrier that resists the stress from antibiotic residues

Addition of Carbonaceous Material to Aquatic Sediments for Sorption of Lindane and <i>p,p</i>’-Dichlorodiphenyldichloroethylene

Isomers of hexachlorocyclohexanes (HCHs) and metabolites of dichlorodiphenyltrichloroethanes (DDTs) are still frequently detected worldwide in considerable amounts, even decades after their prohibition. Carbonaceous materials (CMs) have been shown to significantly reduce risks of propagation to humans by binding the hydrophobic organochlorine pesticides (OCPs) present in aquatic sediments. In the present study, black carbons extracted from natural sediments, and artificially produced black carbons, including black carbons by burning rice straw at 450 and 850 &#176;C, and a commercial activated carbon were compared to investigate the factors affecting the sorption of &#947;-HCH (lindane) and p,p&#8217;-dichlorodiphenyldichloroethylene (p,p&#8217;-DDE) on CMs. The results indicated that when the proportion of CMs to total organic carbon (&#402;CM/&#402;OC) was greater than 0.35, CMs played a leading role in the sorption of lindane and p,p&#8217;-DDE by the sediments. The sorption contribution rate of CMs could reach up to 64.7%. When the ratio of &#402;CM/&#402;OC was less than 0.10, CMs played a minor role in the sorption. In addition, the nonlinearity of the sorption isotherms was strengthened with the increasing the proportion of CMs to total organic carbon. Our findings show that &#402;CM/&#402;OC value is a principal parameter for assessing the sorption capacity of sediments added by CMs for OCPs

Low-temperature anode-free potassium metal batteries

Abstract In contrast to conventional batteries, anode-free configurations can extend cell-level energy densities closer to the theoretical limit. However, realizing alkali metal plating/stripping on a bare current collector with high reversibility is challenging, especially at low temperature, as an unstable solid-electrolyte interphase and uncontrolled dendrite growth occur more easily. Here, a low-temperature anode-free potassium (K) metal non-aqueous battery is reported. By introducing Si-O-based additives, namely polydimethylsiloxane, in a weak-solvation low-concentration electrolyte of 0.4 M potassium hexafluorophosphate in 1,2-dimethoxyethane, the in situ formed potassiophilic interface enables uniform K deposition, and offers K||Cu cells with an average K plating/stripping Coulombic efficiency of 99.80% at −40 °C. Consequently, anode-free Cu||prepotassiated 3,4,9,10-perylene-tetracarboxylicacid-dianhydride full batteries achieve stable cycling with a high specific energy of 152 Wh kg−1 based on the total mass of the negative and positive electrodes at 0.2 C (26 mA g−1) charge/discharge and −40 °C