IntroductionAs key industries in energy supply, oil refineries play a pivotal role in national economic development, however, their operations are associated with significant environmental consequences. The processes of oil extraction and refining release a range of pollutants—including greenhouse gases, sulfur and nitrogen oxides, and volatile organic compounds—contributing to climate change, acid rain, and adverse human health effects such as respiratory disorders (Mani et al., 2021, Dutta et al., 2020). Moreover, the discharge of untreated wastewater and accidental oil spills into surface and groundwater systems poses serious threats to aquatic ecosystems, leading to reduced biodiversity and habitat degradation (Olokani et al., 2022). Refineries also generate hazardous wastes that contaminate soil and water resources, resulting in long-term ecological damage (Rao et al., 2021). To mitigate these impacts, the implementation of stringent environmental regulations and the adoption of cleaner production technologies are essential (Khan et al., 2023). In Iran, the oil and gas sector holds strategic importance for the economy, yet it remains a major source of environmental degradation through the pollution of air, water, and soil (Pourian & Khalili, 2017). Environmental Impact Assessment (EIA) has long been recognized as an effective tool for identifying, predicting, and mitigating the adverse effects of industrial projects such as refineries. While EIA has been systematically applied in many developed countries, its formal implementation in Iran dates back to 1994 (Qaderi et al., 2015). Numerous studies have documented the environmental footprint of refineries in Iran, highlighting issues such as air and water pollution, degradation of natural resources, and public health risks (Askarzadeh-Torqabeh et al., 2003, Azizpour & Ghasemi, 2010, Tavakol & Nozari, 2012, Sadeghian & Sahba, 2012, Ghasemi et al., 2014). These findings underscore the urgent need for improved waste management practices, continuous environmental monitoring, and the integration of sustainable development principles in industrial planning. Despite these efforts, challenges remain, particularly in rural and ecologically sensitive areas, where regulatory enforcement is often weak and environmental data are limited—highlighting the importance of localized, evidence-based assessments to guide policy and practice. Methodology The research methodology employed a descriptive-analytical approach with an applied objective, integrating both documentary and field-based data collection methods. In the documentary phase, relevant literature, reports, and official records pertaining to the Fajr Gas Refinery in Jam County and the broader oil and gas industry were reviewed. For the field investigation, primary data were collected directly from refinery units, and a structured environmental questionnaire was developed and administered to local residents. The validity and reliability of the questionnaire were rigorously assessed and confirmed through expert review and statistical tests (Cronbach’s alpha). Data analysis was performed using SPSS software, employing descriptive statistics and inferential statistical tests—including the one-sample t-test—to evaluate the environmental impacts of the refinery on the study area. This integrated approach enabled a comprehensive assessment of the ecological consequences associated with the refinery’s operations. FindingThe findings of the present study entitled "Investigation and Analysis of the Environmental Impacts of the Fajr Gas Refinery" clearly indicate significant negative impacts resulting from the establishment and operation of the Fajr Gas Refinery in Jam County on the regional environment, particularly in surrounding rural areas. These impacts manifest across multiple dimensions—hydrological, atmospheric, soil, biological, and socio-economic—and are substantiated by statistical data, inferential statistical tests, and local residents’ observations. In terms of water quality analysis, sampling results from the refinery, steam effluent, treatment plants, and downstream qanats reveal a marked deterioration in water quality. Key indicators of this degradation include elevated salinity, high electrical conductivity, excessive water hardness, high concentrations of nitrate and ammonium ions, and severe microbial contamination (with MPN > 1100). Notably, data from the downstream qanat—showing 10. 17% salinity, electrical conductivity of 17, 440 µS/cm, and total hardness of 2, 240 mg/L—indicate highly unsuitable conditions for drinking, agricultural, and industrial uses. These conditions clearly stem from the infiltration of industrial effluents and inadequate management of refinery waste. Furthermore, increased levels of organic pollutants (such as high COD) in both the refinery and steam effluent, coupled with declining groundwater levels, are additional signs of a growing water crisis in the region. Findings from Tables 5 and 6, based on a one-sample t-test assessing 13 environmental indicators, scientifically and statistically confirm that the establishment of the refinery has been associated with significant adverse effects. The significance value (Sig = 0. 003), which is well below the 0. 05 error threshold, decisively rejects the null hypothesis and supports the primary research hypothesis that negative environmental impacts have occurred. All assessed components—from reduced water resources to noise pollution and land-use changes—exhibit mean values exceeding permissible limits, reflecting serious concerns among local residents and environmental experts alike. Discussion and ResultsThe findings of this study clearly confirm that the establishment of the Fajr Gas Refinery in Jam County has led to extensive negative environmental impacts, including air pollution, degradation of water quality and quantity, depletion of groundwater aquifers, destruction of vegetation cover, soil and noise contamination, and shifts in agricultural practices. These impacts not only threaten the natural ecosystem but also severely affect the health, livelihoods, and overall quality of life of local residents. In order to transform the current situation and taking into account the environmental impacts of the refinery, the following key recommendations can be proposed: Comprehensive Industrial Wastewater ManagementContinuous Environmental MonitoringRestoration of Degraded EcosystemsPublic Education and Community EngagementBalanced and Sustainable DevelopmentThis study emphasizes that without immediate and structured interventions, the environmental consequences of the Fajr Gas Refinery could escalate into an irreversible crisis. Therefore, it is imperative that policymakers, industrial managers, and local communities collaborate proactively to restore the environment and promote sustainable development in the region.