Effect of surfactant application practices on the vertical transport potential of hydrophobic pesticides in agrosystems

Surfactants have the potential to modify the environmental behavior of hydrophobic pesticides leading to an enhanced or reduced mobility risk. This risk is often overlooked in registration procedures due to a lack of suitable methodologies to quantify the transport potential of pesticides with surfactants. In this study we present a novel methodology designed to study the surfactant facilitated transport of pesticides under controlled equilibrium and dynamic hydrologic conditions. Using this methodology, we investigated the risk of chlorpyrifos enhanced mobility for two common surfactant application practices in agrosystems: pesticide spraying and irrigation with waste water. With the dynamic experiments we showed that a single irrigation event with artificial reclaimed water containing the nonionic surfactant Triton X100 at a concentration of 15 mg/L reduced the leaching of chlorpyrifos by 20% while the presence of the same surfactant in the chlopyrifos spraying formulation reduced the leaching amount by 60%. However, in the first case 90% of the chlropyrifos fraction remaining in soil was retained in the upper 3 cm while in the second cas, 72% was transported to the bottom layers. The presence of Triton X100 in irrigation water or spraying formulation retards the leaching of chlorpyrifos but enhances its downward transport

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Antimicrobial precious-metal nanoparticles and their use in novel materials

Nanotechnology offers powerful new approaches to controlling unwanted microorganisms and other potential biohazards. Engineered nanoparticles with antifungal, antimicrobial, and antiviral properties are now being developed for a variety of applications, including manufacture and maintenance of sterile surfaces, prevention and control of biological contamination, food and water safety, and treatment of infectious diseases and cancer. The great potential of antimicrobial precious-metal nanoparticles is reflected by the high number of recent publications and patent applications, which is summarized, at least in part, in this paper. This review should provide an overview and offer guidance to the scientific community interested in nano(bio)technology, nanomedicine, and nanotoxicology, and may also be of interest to a broader scientific audience. Furthermore, this review covers specific topics in research and development addressing the effects of nanoparticles on microorganisms as well as novel nanotechnology-based approaches for controlling potentially pathogenic microorganisms

Simultaneous quantification of humic acid-water and silanized glass-water partition constants for PCBs, PCDDs and OCDF

Super-hydrophobic organic contaminants (SHOCs) such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and octachlorodibenzofuran (OCDF) can sorb to dissolved hydrophobic materials including humic acids (HAs), enhancing their apparent aqueous solubility and potentially resulting in increased groundwater contamination and offsite transport. To manage risks associated with transport of and contamination by SHOCs, modelling approaches incorporating partitioning data, i.e. dissolved organic carbon-water partition constants (K), are necessary. Measurement of K can however be compromised by SHOC sorption to glassware surfaces leading to an overestimation of experimental values resulting in larger K. A method for simultaneous derivation of K and glass-water partition constants (K) is described. It involves a mass balance approach combined with HA as a co-solvent at various concentrations and accounts for SHOC losses to silanized glassware. Measured log K values ranged from 5.28 to 7.64 for tetra- to decachlorinated PCBs, 6.67 to 7.93 for tetra- to octachlorinated PCDDs and 8.20 for OCDF. These data were linear functions of log K and consistent with relationships reported for more polar compounds. Log K (mm mm) values (1.62 to 4.06 for PCBs, 2.96 to 3.90 for PCDDs, 3.77 for OCDF) were one order of magnitude greater compared to literature PCB borosilicate glass-water partition constants. Techniques such as those presented in this work present simple, versatile means to provide prediction of the SHOC proportion remaining in aqueous solutions after loss to glassware that was inversely related to container surface area/volume ratio and log K in our study

Transport potential of super-hydrophobic organic contaminants in anionic-nonionic surfactant mixture micelles

Surfactant mixtures are commonly used in agricultural and soil remediation applications, necessitating an understanding of their micellization behavior and associated impact on the fate of co-existing chemicals in the subsurface. A polymer-water sorption isotherm approach was shown to present an alternative to traditional methods for quantifying, understanding and predicting surfactant mixture properties. Micelle compositions were measured for anionic-nonionic surfactant mixtures. This is important since micelle composition can alter the apparent aqueous solubility of super-hydrophobic organic contaminants (SHOCs) resulting in surfactant facilitated transport (SFT). A key parameter in predicting SFT for SHOCs is their micelle-water partition constant (KMI). These were determined for polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated biphenyls (PCBs) with representative anionic-nonionic surfactant mixtures using a polymer depletion method. These previously unreported constants were intermediate between those for pure anionic and nonionic surfactant solutions, with magnitude depending on micelle composition. Separate linear relationships were found between log KMI and log KOW for PCDDs and PCBs. This work provides new methods and preliminary results relating to binary surfactant mixtures (e.g. critical micelle concentration and micelle composition) and SHOCs (KMI) that are important in the evaluation of the fate and transport of SHOCs in the subsurface environment and provide insight into the environmental mobility of these important contaminants

Solubility enhancement of dioxins and PCBs by surfactant monomers and micelles quantified with polymer depletion techniques

Partitioning of super-hydrophobic organic contaminants (SHOCs) to dissolved or colloidal materials such as surfactants can alter their behaviour by enhancing apparent aqueous solubility. Relevant partition constants are, however, challenging to quantify with reasonable accuracy. Partition constants to colloidal surfactants can be measured by introducing a polymer (PDMS) as third phase with known PDMS-water partition constant in combination with the mass balance approach. We quantified partition constants of PCBs and PCDDs (log K 5.8-8.3) between water and sodium dodecyl sulphate monomers (K) and micelles (K). A refined, recently introduced swelling-based polymer loading technique allowed highly precise (4.5-10% RSD) and fast

The importance of growth kinetic analysis in determining bacterial susceptibility against antibiotics and silver nanoparticles

Routine antibiotics susceptibility testing still relies on standardized cultivation-based analyses, including measurement of inhibition zones in conventional agar diffusion tests and endpoint turbidity-based measurements. Here, we demonstrate that common off-line monitoring and endpoint determination after 18-24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48 h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07) as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 μg mL of vancomycin and 8 μg mL of fosfomycin, after which pronounced growth was observed. Despite the delayed onset of growth, treatment with fosfomycin, daptomycin, fusidic acid, cefoxitin, or gentamicin resulted in higher maximum growth rates and/or higher final optical density values compared with antibiotic-free controls, indicating that growth stimulation and hormetic effects may occur with extended exposure to sublethal antibiotic concentrations. Whereas neither maximum growth rate nor final cell density correlated with antibiotic concentration, the lag phase duration for some antibiotics was a more meaningful indicator of dose-dependent growth inhibition. Our results also reveal that non-temporal growth profiles are only of limited value for cultivation-based antimicrobial silver nanoparticle susceptibility testing. The exposure to Ag(0) nanoparticles led to plasma membrane damage in a concentration-dependent manner and induced oxidative stress in Enterococcus faecium UKI-MB07, as shown by intracellular ROS accumulation

The measurement of food safety and security risks associated with micro- and nanoplastic pollution

Abstract: Agricultural systems are increasingly impacted by micro- and nanoplastic (MNP) pollution raising concerns for food safety and security. To understand the scale of the problem and develop mitigation strategies, there is a need to characterise the effects and impacts of MNP. Here, we discuss the main MNP entry pathways into the human food chain and their effects/impact on food and feed sources, identifying major research gaps hindering robust risk assessments of MNP pollution. We identified emerging and current analytical methods to facilitate the closing of those gaps. An interdisciplinary approach combining omics strategies with novel methods for fast and reliable MNP measurement and plastic additive leaching characterisation across multiple dynamic environments can accurately quantify MNP pollution risks. Data of this type is essential to support policy development and legislation to prevent further MNP pollution from causing food safety and security problems worldwide