Understanding UK Air Quality with a Chemistry Transport Model

Ambient air pollution exposure was associated with 4.2 million premature deaths globally in 2019. In the UK, it is considered the single biggest environmental health issue, with particular concern regarding pollution from nitrogen dioxide (NO2), Ozone (O3) and Particulate Matter (PM2.5). Numerical representations (models) allow us to interrogate our understanding of processes controlling pollution but are inherently simplified representations. This work uses the GEOS-Chem atmospheric chemistry transport model run in both its nested and stretched grid configuration to extend our understanding of air pollution over the UK. Compared to observations, the model systematically underestimates Nitrogen Oxides (NOx) in non-rural environments, potentially due to spatial resolution. This underestimate could lead to an overestimation of O3 concentrations in these environments, but is balanced by a model underestimate in background O3 flowing into the UK. It is estimated that 78% of UK O3comes from outside of the UK. Reducing UK NOx emissions increases wintertime O3 by reducing NO titration, and reduces overall summertime O3 production. Higher spatial resolutions reduce bias and improve correlations with observations for both NOx and O3, due to better representation of local emissions and lower O3 production rates. Despite capturing the average concentrations of ammonia and sulphur dioxide reasonably, model overestimates in inorganic aerosols lead to an overestimate of PM2.5. Changes to Industrial SO2 emission injection heights improve estimates for SO2, with small improvements for PM2.5 and aerosol sulfate. Population-weighted PM2.5 violates both the WHO 5 ugm-3 and UK's 10 ugm-3 guidelines in the standard model. Removal of all UK anthropogenic and agricultural emissions reduces the population exceeding the WHO guideline from 95% to 27%, but highlights the challenge of complying with the guideline. Higher spatial resolutions increase PM2.5 bias overall, but model-observation correlations continue to improve with higher resolutions

Basin-scale, integrated observations of the early 21st century multiyear drought in southeast Australia

The Murray-Darling Basin in southeast Australia is experiencing one of the most severe droughts observed recently in the world, driven by several years of rainfall deficits and record high temperatures. This paper provides new basin‐scale observations of the multiyear drought, integrated to a degree rarely achieved on such a large scale, to assess the response of water resources and the severity of the drought. A combination of Gravity Recovery and Climate Experiment (GRACE) data with in situ and modeled hydrological data shows the propagation of the water deficit through the hydrological cycle and the rise of different types of drought. Our observations show the rapid drying of soil moisture and surface water storages, which reached near‐stationary low levels only ∼2 years after the onset of the drought in 2001, with a loss of ∼80 and ∼12 km3 between January 2001 and January 2003, respectively. The multiyear drought has led to the almost complete drying of surface water resources which account for most of the water used for irrigation and domestic purposes. High correlation between observed groundwater variations and GRACE data substantiates the persistent reduction in groundwater storage, with groundwater levels still declining 6 years after the onset of the drought (groundwater loss of ∼104 km3 between 2001 and 2007). The hydrological drought continues even though the region returned to average annual rainfall during 2007

The role of the glucocorticoid receptor in anti-hormone resistance in breast cancer

Background: Approximately 75% of all breast cancer diagnoses are oestrogen receptor a (ERa) positive. In such ERa positive subtypes, anti-hormones such as fulvestrant and tamoxifen are a mainstay therapy. However, the efficacy of these agents is severely limited by subsequent development of resistance. The glucocorticoid receptor (GR) has been implicated as a possible resistance mechanism owing to transcription of pro-proliferative and anti-apoptotic genes in breast cancer cells. A similar contributory role to resistance has also been observed in anti-hormone resistant prostate cancer suggested by increased GR expression and tumour progression. These associations are of particular concern given the use of glucocorticoids as an adjuvant treatment in breast cancer. This research aims to assess the impact of fulvestrant and tamoxifen on GR expression in the anti-hormone treated and resistant MCF-7 ERa positive breast cancer cell line. Methods: mRNA and protein expression of the GR were investigated by reverse transcription polymerase chain reaction and Western blotting respectively, in the ERa-positive MCF-7 breast cancer cell line. Expression in wild-type cells was compared to cells following short-term (7 day) oestrogen (1nM) and fulvestrant (100nM) treatment, and in cells with acquired resistance to fulvestrant and tamoxifen. Results: Both fulvestrant -treated and -resistant MCF-7 cells exhibited increased GR mRNA and protein expression which was statistically significant in resistant cells at the protein (p=0.0345) but not mRNA level. Tamoxifen-resistant cells also exhibited increased GR protein expression. Conclusions: These data demonstrate up-regulation of the GR during treatment with, and following acquisition of resistance to, the anti-hormone fulvestrant. This supports potential for increased expression of GR-regulated pro-survival genes in resistance, indicating a potential role for the GR in anti-hormone resistant breast cancer. Further research into this area is warranted to improve clinical outcomes

Global impact of COVID-19 restrictions on the surface concentrations of nitrogen dioxide and ozone

Social distancing to combat the COVID-19 pandemic has led to widespread reductions in air pollutant emissions. Quantifying these changes requires a business-as-usual counterfactual that accounts for the synoptic and seasonal variability of air pollutants. We use a machine learning algorithm driven by information from the NASA GEOS-CF model to assess changes in nitrogen dioxide (NO2) and ozone (O3) at 5756 observation sites in 46 countries from January through June 2020. Reductions in NO2 coincide with the timing and intensity of COVID-19 restrictions, ranging from 60 % in severely affected cities (e.g., Wuhan, Milan) to little change (e.g., Rio de Janeiro, Taipei). On average, NO2 concentrations were 18 (13-23) % lower than business as usual from February 2020 onward. China experienced the earliest and steepest decline, but concentrations since April have mostly recovered and remained within 5 % of the business-as-usual estimate. NO2 reductions in Europe and the US have been more gradual, with a halting recovery starting in late March. We estimate that the global NOx (NO + NO2) emission reduction during the first 6 months of 2020 amounted to 3.1 (2.6-3.6) TgN, equivalent to 5.5 (4.7-6.4) % of the annual anthropogenic total. The response of surface O3 is complicated by competing influences of nonlinear atmospheric chemistry. While surface O3 increased by up to 50 % in some locations, we find the overall net impact on daily average O3 between February-June 2020 to be small. However, our analysis indicates a flattening of the O3 diurnal cycle with an increase in nighttime ozone due to reduced titration and a decrease in daytime ozone, reflecting a reduction in photochemical production. The O3 response is dependent on season, timescale, and environment, with declines in surface O3 forecasted if NOx emission reductions continue

Multiplication of microbes below 0.690 water activity: implications for terrestrial and extraterrestrial life

Since a key requirement of known life-forms is available water (water-activity; aw), searches for signatures of past life in terrestrial and extraterrestrial environments have recently targeted places known to have contained significant quantities of biologically available water. The lower limit of water activity that enables cell division is ~0.605 which, until now, was only known to be exhibited by a single eukaryote; the sugar-tolerant, fungal xerophile Xeromyces bisporus. The first forms of life on Earth were, however, prokaryotic. Furthermore, early life on Earth inhabited high-salt environments, suggesting an ability to withstand low water activity. Recent evidence indicates that some halophilic Archaea and Bacteria have water activity limits more or less equal to those of X. bisporus. Regardless of species, cellular systems are sensitive to minute differences in water activity (of w-units) so there is a need to determine water-activity values to three decimal places. We discuss water activity in relation to the limits of Earth’s present-day biosphere; the possibility of microbial multiplication by utilizing water from thin, aqueous films or non-liquid sources; whether prokaryotes were the first organisms able to multiply at the 0.605-aw limit; and whether extraterrestrial aqueous milieu of ≥0.605 aw can resemble fertile microbial habitats found on Earth