Polycyclic aromatic hydrocarbons in road dusts of a densely populated African city: spatial and seasonal distribution, source, and risk assessment

Characterization and risk assessment of polycyclic aromatic hydrocarbons from the emission of different power generator

Epileptic power supply in Sub-Saharan countries of Africa has warranted the use of power generators as an alternative source of power supply. Exhaust emission from these generators is associated with Polycyclic Aromatic Hydrocarbon (PAHs). Hence, this study focused on the determination of levels of PAHs in the emission of different brands of power generators used in Nigeria. Exhaust emissions of different power generators were sampled using a filter-sorbent sampling system with polyurethane foam (PUF) as an adsorbent material. Analysis of PAHs was carried out using a Gas Chromatograph coupled to a mass selective detector (GC- MS) operated on Electron Ionization (EI) mode. The results showed the ∑ PAHs range 14.91-26.0 μ g m - 3 . Bap was the most abundant of all the compounds with a concentration of 2.6 μ g m - 3 with a range of 2.08-3.07 μ g m - 3 . The Incremental Life Cancer Risk (ILCR) values of all the generator's emission sampled are higher than 10- 4 for both children and adult which indicate a high potential cancer risk from inhalation of emission from these generators while Hazard Quotient (HQ) values from all the power generating set in this study are all above 1 which indicated high associated non-carcinogenic. The study revealed the levels of PAHs associated with the emission of power generators in Nigeria.

Polycyclic aromatic hydrocarbons in dust from rural communities around gas flaring points in the Niger Delta of Nigeria: an exploration of spatial patterns, sources and possible risk

Indoor and outdoor dust from three rural communities (Emu-Ebendo, EME, Otu-Jeremi, OTJ, and Ebedei, EBD) around gas flaring points, and a rural community (Ugono Abraka, UGA) without gas flare points, in the Niger Delta of Nigeria, was analysed for the concentrations and distribution of polycyclic aromatic hydrocarbons (PAHs), their sources, and possible health risk resulting from human exposure to PAHs in dust from these rural communities. The PAHs were extracted from the dust with a mixture of dichloromethane/n-hexane by ultrasonication, and purified on a silica gel/alumina packed column. Gas chromatography-mass spectrometry was employed to determine the identity and concentrations of PAHs in the cleaned extracts. The Σ16PAH concentrations in the indoor dust ranged from 558 to 167 000, 6580 to 413 000, and 2350-37 500 μg kg-1 for EME, OTJ and EBD respectively, while those of their outdoor counterparts varied from 347 to 19 700, 15 000 to 130 000, and 1780 to 46 300 μg kg-1 for EME, OTJ and EBD respectively. On the other hand, the UGA community without gas flare points had Σ16PAH concentrations in the range of 444-5260 μg kg-1 for indoor dust, and 154-7000 μg kg-1 for outdoor dust. The lifetime cancer risk values for PAHs in these matrices surpassed the acceptable limit of 10-6 suggesting a potential carcinogenic risk resulting from human exposure to PAHs in indoor and outdoor dust from these rural communities. Principal component analysis suggested that PAH contamination of dust from these communities arises principally from gas flaring, combustion of wood/biomass, and vehicular emissions.

Concentration and sources of persistent organic pollutants within the vicinity of a scrap-iron smelting plant: Seasonal pattern and health risk assessment

Polychlorinated biphenyls (PCBs) are a class of ubiquitous and significant synthetic organic chemicals that pose deleterious threats to the environment and human health. This study examined the concentration, indoor-outdoor and seasonal change, sources, and health effects of PCBs in particulate-bound dust near a scrap iron recycling plant. PCBs levels were determined in samples using gas chromatograph mass spectrometer. The results indicated that 5 Cl atoms PCB constituted the majority of PCBs (41% overall), contributing 43% during the rainy season and 39% during the dry season. Dioxin-like PCBs (DLPCBs) contributed 38% during the rainy season and 33% during the dry season. In addition, DLPCB accounted for 26% and 40% of indoor and outdoor PCB emissions, respectively. Iron and steel production were identified as the highest identified contributing sources, accounting for 76% of PCB emissions in the rainy season, while plastic combustion had the highest contribution in the dry season, accounting for 44% of PCB emissions. Incremental Lifetime Cancer Risk assessment showed ingestion as the main exposure pathway for children and adults during the two seasons (74.42% and 58.24%, respectively), followed by dermal exposure, while inhalation had the least contribution. A multifaced approach involving relevant agencies, the industry, and the community is required to reduce exposure.

Heat and mass transfer induced by alternating current during desorption of PAHs from soil using electrical resistance heating

The transfer of heat and contaminants by alternating current (AC) and the removal mechanism of polycyclic aromatic hydrocarbons (PAHs) in electrical resistance heating (ERH) need further study. The main factors affecting heat transfer and water evaporation in the ERH experiment were studied, and the desorption efficiency, temporal and spatial distribution and kinetic behavior under various conditions were analyzed. The results suggested that moisture content was a necessary condition to ensure effective heating of soil, and soil moisture content above 30% was recommended. Higher voltage intensity and/or ion concentration meant stronger input power, resulting in the rapider heating process and the shorter the boiling time. At a low desorption temperature (about 100°C), the Phe desorption mainly depended on the volatilization of surface Phe and the co-boiling of Phe-water. In ERH, the participation of AC would accelerate the diffusion of pollutants from the internal pores of soil particles and their redistribution with water phase, thus improving the Phe removed by co-boiling. It was noteworthy that AC just greatly promoted solid-liquid mass transfer, but it hardly promoted desorption directly, and the removal still depended on Phe-water co-boiling. The Phe desorption efficiency could be significantly improved from 14.0~18.4% to 59.6~70.8% under the combined action of current strengthening Phe diffusion and co-boiling. Thermogravimetric and product analysis confirmed that no new organic matter was generated, but only Phe entered the gas phase through phase change.

Parent and alkylated polycyclic aromatic hydrocarbon emissions from coal seam fire at Wuda, Inner Mongolia, China: characteristics, spatial distribution, sources, and health risk assessment

The Wuda coalfield in Inner Mongolia is a vital coal base in China, and it is the hardest-hit area for coal fires (spontaneous combustion of coal seams and coal gangue). Using gas chromatography-mass spectrometry, this work tested the concentration and analyzed the characteristics, distribution, sources, and health risks of polycyclic aromatic compounds (PACs) in the surface soil of the Wuda District, including the coal mine, coal fire, agricultural, and background areas. The soil of coal mine and coal fire area were heavily polluted with PACs, with mean concentrations of 9107 and 3163 µg kg-1, respectively, considerably higher than those in the agricultural (1232 µg kg-1) and background areas (710 µg kg-1). Alkyl polycyclic aromatic hydrocarbons (APAHs) were the dominant pollutants among these PACs, accounting for 60-81%. Alkyl naphthalenes and alkyl phenanthrenes are the primary pollutants in APAHs, accounting for 80-90% of the total amounts. Additionally, using the positive matrix factorization method, it can be concluded that the primary PAC sources are petrogenic sources, coal and biomass combustion, coal fires, and vehicle emissions. Finally, according to the cancer risk values of 16 PAHs, only the coal mine area showed a potential cancer risk. However, this result lacks a risk assessment of APAHs and underestimates the actual risk. The results of this study improved the understanding of PAC pollution in coal fire and surrounding areas and provided a reference for environmental and health risk investigations.

Integrative assessment of urban dust polycyclic aromatic hydrocarbons using ground and satellite data in Iran

Recently, for quick urbanization and industrialization, pollutants, especially urban dust, have posed many threats to the human environment. Polycyclic aromatic hydrocarbons (PAHs) are regarded as the main dangerous pollutants that are widespread, persistent, and carcinogenic. The present work aimed to investigate the contamination and sources of PAHs, as well as to assess the risk of cancer for 16 priority PAHs, in urban dust samples in Ahvaz, Isfahan, and Shiraz cities in Iran. We measured PAH concentrations by gas chromatography-mass spectrometry (GC-MS). The average concentrations of the 16 PAHs in Ahvaz, Isfahan, and Shiraz were 6215.11, 7611.03, and 7810.37 μg kg-1, respectively. The domination of low-molecular-weight (LMW) PAHs was observed in Ahvaz, while maximum contribution was observed for high-molecular-weight (HMW) PAHs in Esfahan and Shiraz. For PAHs' source identification, diagnostic ratio, correlation analysis, clustering, and positive matrix factorization (PMF) model were used. PAHs had a combustion (coal and wood, oil, fossil fuels) and gasoline/diesel engine emissions in all cities. Comparative studies suggest that the PAH compounds' level is higher in the research area than in other countries, except for China and India. Also, the pollution of urban dust PAHs has increased over time compared to previous studies in the same cities. The cancer risk from exposure to dust contaminated with PAHs was assessed using the Incremental Lifetime Cancer Risk (ILCR) model. According to the findings, a high risk of exposure to cancer was observed in Ahvaz, Isfahan, and Shiraz. However, compared to adults, children are at higher risk of cancer in their daily lives via dermal contact and unconscious ingestion. Based on the ILCR values, the risk of cancer is in the order of Shiraz > Isfahan > Ahvaz. To assess air pollutants and their effects on urban dust, TROPOMI onboard the Sentinel-5P data were used in the studied cities during 2018-2021. The results show that Ahvaz has different high levels of CO compared to the other 2 cities. Also, Isfahan has different high levels of NO2 compared to the other 2 cities, but Shiraz has different low levels of O3. According to satellite time series data, the trend of the Aerosol Absorbing Index (AAI) has been increasing, while there was a decreasing trend in AAI from the beginning of the COVID-19 pandemic until 12 months later. Therefore, the natural and anthropogenic sources of urban dust PAHs have been increasing in all studied cities. Our findings show that PAH compounds in urban dust pose a significant threat to human health. Therefore, strategic management and planning are vital in reducing urban dust pollution.

Pollution and ecological risk assessments for heavy metals in coastal, river, and road-deposited sediments from Apia City in Upolu Island, Samoa

This study was the first to investigate the pollution and ecological risks of heavy metals in coastal, river/stream and road-deposited sediments (RDS) from Apia in Samoa. Cr and Ni concentrations in sediment samples were higher than those of other metals. River sediments and RDS had relatively high EF values around the intensive commercial areas, with a moderate to significant enrichment of Cu, Zn, Cd, and Pb. The results indicate that Cr and Ni have a natural origin from volcanic parent materials, while Cu, Zn, Cd, and Pb originated from anthropogenic activities, such as traffic emissions and the discharge of municipal wastewater. The assessments of pollution and ecological risk revealed that coastal sediments adjacent to the river are anthropogenically contaminated and present a moderate ecological risk. This study demonstrates that metals that have accumulated in the urban impermeable layer and river/stream bed have flowed into the coastal environment through runoff.

Distribution, Source Apportionment and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediments at the Basin Scale: A Case Study in Taihu Basin, China

As a systematic research at basin scale, this study investigated the spatial distribution, source apportionment and ecological risks of eighteen polycyclic aromatic hydrocarbons (PAHs) in surface sediments at different functional regions (rivers, lakes and reservoirs) from Taihu basin. Results showed that the mean values of 18 PAHs (defined as ∑₁₈PAHs) in river sediments (1277 ng/g) was much higher than those observed in lake sediments (243 ng/g) and reservoir sediments (134 ng/g). The accumulation of PAHs in river sediments was largely impacted by the local social-economic development and energy consumption. The positive matrix factorization (PMF) and isomer ratios analysis of PAHs suggest that relative contributions to PAHs in sediments were 15% for gasoline and heavy oil combustion, 9% for oil spills, 30% for coal combustion, 23% for traffic source, and 23% for diagenetic source. Ecological risk assessment based upon risk quotient (RQ) method indicated that sediments at Taihu basin have suffered moderate risk of PAHs.

Alkylated Polycyclic Aromatic Hydrocarbons Are the Largest Contributor to Polycyclic Aromatic Compound Concentrations in the Topsoil of Huaibei Coalfield, China

Alkyl polycyclic aromatic hydrocarbons (APAHs) are more toxic and persistent than their parent compounds. Here, the concentrations, composition profiles, and spatial distribution of polycyclic aromatic compounds (PACs) in 127 topsoil samples from Huaibei coalfield were analyzed. The PAC concentrations in different functional areas were significantly different: mining area > industrial area > residential area > agricultural area. APAHs were the major contributors to PACs, accounting for 71-83% of total PACs. Alkylnaphthalenes and alkylphenanthrenes were the primary APAH components, accounting for 83-87% of APAHs. Principal component analysis showed that petrogenic source, coal and biomass combustion, and vehicle emissions were the primary sources of PACs. By comparing the fingerprint information of soil, coal, and coal gangue, it was hypothesized that the petrogenic source of PAC pollution in typical mining areas and surrounding areas are coal particle scattering and coal gangue weathering. Some coal mining and industrial areas potentially pose risks to children, whereas others do not. There are limited evaluation criteria for alkyl PAHs; hence, the estimated risk is likely lower than the actual risk. In addition to the conventional 16 PAHs, it is critical to consider a broader range of PACs, especially APAHs.