Abstract

Microplastics (MP) are ubiquitous in the environment; their atmospheric relevance is being increasingly recognized. Because of their atmospheric concentrations, there is the question of whether MP can act as ice nucleating particles in the atmosphere. This study investigates the immersion freezing activity of lab-prepared MP of four different compositions─low density polyethylene (LDPE), polypropylene (PP), poly(vinyl chloride) (PVC), and poly(ethylene terephthalate) (PET)─using droplet freezing assays. The MP are also exposed to ultraviolet light, ozone, sulfuric acid, and ammonium sulfate to mimic environmental aging of the plastics to elucidate the role that these processes play in the ice nucleating activity of MP. Results show that all studied MP act as immersion nuclei, and aging processes can modify this ice nucleating activity, leading, primarily, to decreases in ice nucleating activity for LDPE, PP, and PET. The ice nucleating activity of PVC generally increased following aging, which we attribute to a cleaning of chemical defects present on the surface of the stock material. Chemical changes were monitored with infrared spectroscopy (ATR-FTIR), and the growth of a peak at 1650–1800 cm–1 was associated with a decrease in ice nucleating activity while loss of an existing peak in that region was associated with an increase in ice nucleating activity. The studied MP have ice nucleating activities sufficient to be a non-negligible source of ice nucleating particles in the atmosphere if present in sufficiently high concentrations.

Highlights

Acute exposure to phthalates affects fundamental aspects of adult brain function.

The effects are massive both with DEHP and its substitute DINP.

Both plasticizers affect neuronal signaling and central information processing.

Both offset the balance between excitation and inhibition.

Both cause a massive decline in conduction speed and potentially impact neuroglia.

Abstract

Phthalates are key additives in many plastic products and among the most frequently used plasticizers. The release of some of them into the environment has been shown to have serious effects on development and reproduction. Based on such effects, diisononyl phthalate (DINP) has been advocated as a safer alternative to di-2-ethylhexyl phthalate (DEHP). Recently, it has been suggested that DEHP may affect the vertebrate blood-brain barrier. This could have serious consequences not only for the developing, but also for the adult brain. Here we tested for such impact on neuronal function and demonstrate acute exposure effects of both plasticizers on fundamental aspects of brain function in an adult vertebrate. We used the Mauthner neuron in the hindbrain of fish and its diverse inputs from various sensory systems as a model. After exposing intact goldfish to environmentally relevant plasticizer concentration (either 100 µg L–1, or 10 µg L–1), we show from in vivo intracellular recording that one month of environmental exposure to DEHP or DINP affected the sensory input to this central neuron, offset the balance between excitation and inhibition, and reduced its conduction speed by 20 %. The effects of both plasticizers were strong even at the concentration of 10 µg L–1. In an adult vertebrate, our findings thus demonstrate a previously neglected high sensitivity of various crucial brain functions to the acute exposure to phthalates.

Abstract

The growth rate of the atmospheric abundance of methane (CH4) reached a record high of 15.4 ppb yr−1 between 2020 and 2022, but the mechanisms driving the accelerated CH4 growth have so far been unclear. In this work, we use measurements of the 13C:12C ratio of CH4 (expressed as δ13CCH4) from NOAA’s Global Greenhouse Gas Reference Network and a box model to investigate potential drivers for the rapid CH4 growth. These measurements show that the record-high CH4 growth in 2020–2022 was accompanied by a sharp decline in δ13CCH4, indicating that the increase in CH4 abundance was mainly driven by increased emissions from microbial sources such as wetlands, waste, and agriculture. We use our box model to reject increasing fossil fuel emissions or decreasing hydroxyl radical sink as the dominant driver for increasing global methane abundance.

Sustainable planet for all, for very small values thereof.