Seasonal and spatial variations of atmospheric depositions-bound elements over Tehran megacity, Iran: Pollution levels, PMF-based source apportionment and risks assessment

A total of 32 atmospheric depositions (ADs) samples were collected from eight sampling sites from April 2018 to March 2019 in the Tehran megacity. Elemental concentration, pollution characteristics, ecological and human health risks, and source apportionment of ADs in the < 63 μm fraction were investigated. Descriptive statistical analysis revealed that the average concentration of Zn, Cd, Pb, and Cu had the highest values over the upper continental crust (UCC). The influence of anthropogenic activities on the level of elements pollution was determined using the Geo-accumulation index (Igeo), Enrichment factor (EF), and Pollution index (PI). The findings revealed the highest Igeo values for Cd at the “extremely contaminated” level due to great influence from Cd emission sources, especially in spring. The extremely high EF values for Zn in 18.8% of samples could be attributed to the low distance of these sampling sites from the nearby industrial areas and adjacent road traffic density. PI values in the range of “considerable to extremely high” pollution were in the order of Zn > Cd > Pb > Cu > Ni > Cr. Eventually, The pollution load index (PLI) indicated the higher than unity of PLI values for all sampling sites reflecting considerable polluted sites across the study area. The ecological risk index (RI) indicated a considerable ecological risk, with the highest monomial risk values for Cd and Pb. The cumulative hazard index (HI) results showed that children encounter higher non-carcinogenic (NCR) risks than adults. However, the cumulative carcinogenic risk (CCR) of adults was 2.25 times higher than for children. The positive matrix factorization (PMF) model extracted four factors, including traffic-related sources (29.7%), local soils and crustal dust resuspension sources (24.8%), demolition and construction activities (23.5%), and industry-related emissions (22%). Among the identified sources, traffic-related sources showed the largest contribution to elements and ecological risks

Heavy Metal Pollution in the Floor Dust of Yazd Battery Repairing Workshops in 2014

Background and Objectives: The presence of industrial workshops has increased urban pollution. This study aimed to investigate the heavy metal pollutants of Yazd battery repairing workshops and to identify the ecological and environmental effects resulted. Materials and Methods: This descriptive cross-sectional study was carried out in Yazd. In this regard, the city was divided into three parts on the basis of geographical features. Then, 30 workshops were selected from each part through stratified random sampling method. Heavy metals (Pb, Cd, Cr, Zn, Cu, Fe, Mn) in the floor were measured using atomic absorption spectrophotometry (AAS). The impacts assessment of heavy metals was evaluated using environmental potential risk index (RI), cumulative pollution index (IPI), pollution coefficient factor (Cf), and the degree of modified contamination (mCd) and Pearson’s correlation statistical test. Results: The trend of heavy metals concentrations in floor dust particles of workshops was as Fe>Cu>Pb>Zn>Mn>Cr>Cd. Therefore, the average concentrations of Fe and Cd in the samples were 27011.52 ±4721.05 and 78.25±21.07 mg/kg respectively. The results of the RI showed that heavy metal of floor dust had very high danger (2816.29). The mCd value was as 63.35 indicating these workshops were at severe contamination class. The value of Cf was as 304.17 revealing that these workshops were at very severe contamination class. Conclusions: This research showed that the high concentration of heavy metals in battery repairing workshops is due to the interaction of heavy metals of industrial wastes components, including electrical wastes and battery with the dust having mankind origin

Using a hybrid approach to apportion potential source locations contributing to excess cancer risk of PM2.5-bound PAHs during heating and non-heating periods in a megacity in the Middle East

Polycyclic aromatic hydrocarbons (PAHs) represent one of the major toxic pollutants associated with PM2.5 with significant human health and climate effects. Because of local and long-range transport of atmospheric PAHs to receptor sites, higher global attentions have been focused to improve PAHs pollution emission management. In this study, PM2.5 samples were collected at three urban sites located in the capital of Iran, Tehran, during the heating and non-heating periods (H-period and NH-period). The US EPA 16 priority PAHs were analyzed and the data were processed to the following detailed aims: (i) investigate the H-period and NH-period variations of PM2.5 and PM2.5-bound PAHs concentrations; (ii) identify the PAHs sources and the source locations during the two periods; (iii) carry out a source-specific excess cancer risk (ECR) assessment highlighting the potential source locations contributing to the ECR using a hybrid approach. Total PAHs (TPAHs) showed significantly higher concentrations (1.56–1.89 times) during the H-period. Among the identified PAHs compounds, statistically significant periodical differences (p-value < 0.05) were observed only between eight PAHs species (Nap, BaA, Chr, BbF, BkF, BaP, IcdP, and DahA) at all three sampling sites which can be due to the significant differences of PAHs emission sources during H and NH-periods. High molecular weight (HMW) PAHs accounted for 52.7% and 46.8% on average of TPAHs during the H-period and NH-period, respectively. Positive matrix factorization (PMF) led to identifying four main PAHs sources including industrial emissions, petrogenic emissions, biomass burning and natural gas emissions, and vehicle exhaust emissions. Industrial and petrogenic emissions exhibited the highest contribution (19.8%, 27.2%, respectively) during the NH-period, while vehicle exhaust and biomass burning-natural gas emissions showed the largest contribution (40.7%, 29.6%, respectively) during the H-period. Concentration weighted trajectory (CWT) on factor contributions was used for tracking the potential locations of the identified sources. In addition to local sources, long-range transport contributed to a significant fraction of TPHAs in Tehran both during the H- and NH-periods. Source-specific carcinogenic risks assessment apportioned vehicle exhaust (44.2%, 2.52 × 10−4) and biomass burning-natural gas emissions (33.9%, 8.31 × 10−5) as the main cancer risk contributors during the H-period and NH-period, respectively. CWT maps pointed out the different distribution patterns associated with the cancer risk from the identified sources. This will allow better risk management through the identification of priority PAHs sources