Moinești, nestled within the Bacău County of Romania, occupies a geographically interesting position in the sub-Carpathian hills. Situated at coordinates 46.4333, 26.4833, the city’s terrain is characterised by rolling hills and valleys, typical of the Moldavian Plateau. The elevation, while not extreme, contributes to localized meteorological conditions influencing air dispersion. The Bistrița River flows nearby, offering a potential, though limited, moderating influence on local temperatures and humidity. Historically, Moinești developed around the oil extraction industry, and remnants of this industrial past, alongside associated infrastructure, remain a significant feature of the surrounding landscape. The urban-rural gradient is relatively sharp; the city centre gives way quickly to agricultural land, primarily used for crop cultivation and livestock farming. This proximity to agricultural activities introduces potential sources of particulate matter from field work and fertilizer use. The surrounding hills can trap pollutants during periods of calm weather, exacerbating air quality issues. The regional climate is continental, with cold winters and warm summers, impacting pollutant behaviour. The city’s location within a valley system further influences wind patterns and pollutant concentration, creating microclimates that affect air quality variability.

Moinești experiences a distinct seasonal air quality pattern dictated by Romania’s continental climate. Winter (December-February) typically sees the poorest air quality. Low temperatures encourage increased use of solid fuels for heating – wood and coal – releasing significant particulate matter (PM2.5 and PM10) and sulfur dioxide. Temperature inversions, common in the valley setting, trap these pollutants near ground level. Spring (March-May) brings gradual improvement as heating demand decreases, but agricultural activities begin, contributing to dust and ammonia emissions. Summer (June-August) generally offers the cleanest air, aided by higher temperatures, increased wind speeds, and rainfall which helps to wash pollutants from the atmosphere. However, prolonged heatwaves can lead to increased ozone formation. Autumn (September-November) sees a return to poorer conditions as heating resumes, and stagnant air masses become more frequent. October and November are particularly problematic. Sensitive individuals – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during winter and autumn months. Monitoring wind direction is crucial; winds from industrial areas will carry higher pollutant loads. Fog, common in autumn and winter, can exacerbate particulate matter concentrations.