Mavia Anjum

Fine particulate matter (PM _2.5 ) is a leading environmental risk factor for human health, driven in the interior Pacific Northwest by summertime wildfire smoke and wintertime residential wood combustion trapped by valley inversions. This study characterized the seasonal, spatial and temporal structure of PM _2.5 across Idaho, USA, over 2005 to 2024, and inferred its dominant source regimes using statistical and geospatial tools. The complete daily PM _2.5 record of the US Environmental Protection Agency Air Quality System was aggregated to 4,260 site-months for 32 sites, and Mann-Kendall and Theil-Sen trend analysis, Pearson correlation, principal component analysis (PCA) and inverse distance weighting (IDW) interpolation were applied. The regional mean was 7.53 µg m ^− 3 , with a site range of 3.16 to 12.08 µg m ^− 3 . The climatology was bimodal, with an August to September wildfire maximum and a November to February wood-smoke and inversion maximum separated by a clean spring background, and July to September carried 36.6% of the annual mass. The cold-season and background series declined significantly, whereas the fire-season series rose at 2.54 µg m ^− 3 per decade, which held the annual mean flat. PCA separated the network into two source regimes explaining 57.5% of the between-site variance, and a temporal mode was dominated by July to September episodes, identifying wildfire smoke as the dominant driver. It was found that 32.7% of site-years exceeded the 2024 annual standard of 9.0 µg m ^− 3 , and the two regimes are diverging under a warming climate, so that season and source specific management is required.

Radon (²²²Rn) migrates from soil to the atmosphere by molecular diffusion and pressure-driven advection while decaying with a 3.82-day half-life. Surface exhalation varies seasonally because the two governing soil properties, the effective diffusion coefficient and the radon source strength, both depend on soil moisture and temperature. Existing one-dimensional models are typically solved at steady state or with static properties, and few openly available tools ingest meteorological forcing to resolve the flux as a time-evolving signal. We present a model that solves the full transient diffusion–advection–decay equation in a layered 1-D soil column (0–200 cm) using an implicit Crank–Nicolson scheme. The effective diffusion coefficient follows the Rogers–Nielson moisture relation with a gas-kinetic temperature correction; pore air–water partitioning uses the temperature-dependent Ostwald coefficient; emanation responds to moisture and temperature; and a damped analytical thermal wave plus a leaky-bucket moisture model translate monthly climate inputs into depth- and time-resolved forcing. The solver matches the exact analytical steady state to a root-mean-square error of 0.0003%. Under idealized seasonal forcing representative of a humid subtropical highland (Murree-type) climate, the modelled flux is strongly bimodal: a pre-monsoon June maximum from warm, drying soil, a pronounced July–August monsoon minimum where high saturation collapses diffusivity and traps radon at depth, and an autumn recovery. The annual mean is ~ 245 Bq m⁻² h⁻¹ with a peak-to-peak range near 40%. Sensitivity analysis shows near-linear scaling with radium activity, emanation and bulk density, and nonlinear response to porosity and moisture. A factorial attribution experiment shows the two controls act nearly additively, moisture contributing a larger variance share (≈ 60%) than temperature (≈ 40%); moisture alone reproduces the bimodal shape, temperature alone a single summer maximum. This competition between moisture-enhanced emanation and moisture-suppressed diffusion reconciles the apparent paradox that wetting raises soil-air radon yet can reduce exhalation, providing a reproducible, climate-forced framework for interpreting exhalation time series and generating hypotheses about climate-driven change.

The objective of this study was to evaluate the extent of radon contamination in twenty-six drinking water samples from natural springs were collected from Dhirkot Azad Kashmir, along with four bottled mineral water samples. Radon gas escapes from the earth’s crust due to uranium ores and diffuses into the atmosphere. This study assessed the levels of radon concentration, the yearly effective radiation dose, and carcinogenic risk from radon exposure in drinking water samples. The radon concentration varied from 0.28 to 30.25 Bq/L. The mean radon concentration of all samples was found to be 7.86 ± 2.3 Bq/L. The radon concentrations in bottled drinking water were found to be lower than those in natural springs. The statistical and GIS analyses included the use of interpolation and Pearson’s correlation matrix. Seven samples had radon concentration that surpassed the standard limit established by the US-EPA, which is 11 Bq/L. The average annual effective dose from inhalation and ingestion was found to be lower than the value (0.1 mSv/y) provided by the WHO, but for some natural spring water samples, it exceeded the risk limit. The cancer risk revealed that 40% of the samples had an elevated lifetime cancer risk from radon exposure. Overall, the majority of the results obtained aligned with the worldwide guidelines established by the US-EPA. However, there were a few instances where the limits were exceeded, and constant monitoring is recommended. This study establishes a baseline for radon concentration in the area and provides a basis for future studies.