Water-insoluble carbonaceous components in rainwater over an urban background location in Northern India during pre-monsoon and monsoon seasons

Weak transport of atmospheric water-insoluble particulate carbon from South Asia to the inner Tibetan Plateau in the monsoon season

Carbonaceous particles play a crucial role in atmospheric radiative forcing. However, our understanding of the behavior and sources of carbonaceous particles in remote regions remains limited. The Tibetan Plateau (TP) is a typical remote region that receives long-range transport of carbonaceous particles from severely polluted areas such as South Asia. Based on carbon isotopic compositions (Δ14C/δ13C) of water-insoluble particulate carbon (IPC) in total suspended particle (TSP), PM2.5, and precipitation samples collected during 2020-22 at the Nam Co Station, a remote site in the inner TP, the following results were achieved: First, fossil fuel contributions (ffossil) to IPC in TSP samples (28.60 ± 9.52 %) were higher than that of precipitation samples (23.11 ± 8.60 %), and it is estimated that the scavenging ratio of IPC from non-fossil fuel sources was around 2 times that from fossil fuel combustion during the monsoon season. The ffossil of IPC in both TSP and PM2.5 samples peaked during the monsoon season. Because heavy precipitation during the monsoon season scavenges large amounts of long-range transported carbonaceous particles, the contribution of local emissions from the TP largely outweighs that from South Asia during this season. The results of the IPC source apportionment based on Δ14C and δ13C in PM2.5 samples showed that the highest contribution of liquid fossil fuel combustion also occurred in the monsoon season, reflecting increased human activities (e.g., tourism) on the TP during this period. The results of this study highlight the longer lifetime of fossil fuel-sourced IPC in the atmosphere than that of non-fossil fuel sources in the inner TP and the importance of local emissions from the TP during the monsoon season. The findings provide new knowledge for model improvement and mitigation of carbonaceous particles.

Assessment of variability in PM2.5 and its impact on human health in a West African country

PM2.5 has become a global challenge threatening human health, climate, and the environment. PM2.5 is ranked as the most common cause of premature mortality and morbidity. Therefore, the current study endeavors to probe the spatiodynamic characteristics of PM2.5 in the Republic of Niger and its impacts on human health from 1998 to 2019. Based on remotely sensed satellite datasets, the study found that the concentration of PM2.5 continued to rise in Niger from 68.85 μg/m3 in 1998 to 70.47 μg/m3 in 2019. During the study period, the annual average PM2.5 concentration is far above the WHO guidelines and the interim target-1 (35 μg/m3). The overall annual growth rate of PM2.5 concentration in Niger is 0.02 μg/m3/year. The health risk (HR) due to PM2.5 exposure is also escalated in Niger, particularly, in Southern Niger. The extent of the extremely high-risk areas corresponding to 1 × 104-9.4 × 105 μg.persons/m3 is increased from 0.9% (2000) to 2.8% (2019). Niamey, southern Dakoro, Mayahi, Tessaoua, Mirriah, Magaria, Matameye, Aguié, Madarounfa, Groumdji, Madaoua, Bouza, Keita, eastern Tahoua, eastern Illéla, Bkomnni, southern Dogon-Doutchi, Gaya, eastern Boboye, central Kollo, and western Tillabéry are experienced high HR due to long-term exposure to PM2.5. These findings indicate that PM2.5 causes a serious health risk across Niger. There is an immediate need to carry out its regional control. Therefore, policymakers and the Nigerien government should make conscious efforts to identify the priority target areas with radically innovative appropriate mitigation interventions.

Profile of atmospheric particulate PAHs near busy roadway in tropical megacity, India

Objective: This study focuses on the profile of ambient particulate polycyclic aromatic hydrocarbons (PAHs), their seasonal distribution, source identification and human health risk assessment due to inhalation exposure of ambient PAHs in Delhi, India.Materials and Methods: Two sampling sites were chosen, one at roadway (MH) and other at urban background (JNU) site in Delhi. Determination of PAHs was carried with the help of HPLC with UV detector. Principal component analysis and Molecular diagnostic ratios were used for the source apportionment of PAHs. Health risks associated with inhalation of particulate PAHs were assessed using benzo(a)pyrene equivalent concentration and incremental lifetime cancer risk (ILCR) approach.Results: The results showed that the average mass concentration of Σ₁₆ PAHs near roadway (67.8 ± 40.2 ng m^-3) is significantly higher than urban background site (56 ± 30 ng m^-3). Moreover, source apportionment study indicated that major PAH-emission sources in Delhi NCR are traffic and coal combustion. ILCR values at both the sites fall in the range of 10^-2-10^-4 that corresponds to the priority risk level (10^-3) and higher than the acceptable risk level (10^-6).conclusions: The high PAHs concentration at MH site was due to it's nearness to busy traffic area. Thus, the spatial variations in PAHs were influenced by local emission sources. The high PAHs level during the winter season can be due to their higher emissions from local heating sources, shift of gas/particle partitioning toward the particulate phase at low temperature and reduced photochemical degradation of some PAHs in winter. The low level of PAHs in monsoon season can be attributed to their wet scavenging and higher percentage in vapor phase. PCA showed that the emissions from vehicles predominate at MH site; whereas, coal combustion and traffic both are the significant PAHs sources at JNU site. Health risk assessment revealed that the highest exposure risks occur at busy traffic site, thereby indicating a significantly higher health risk to the population of Delhi.

Investigation of Forest Fire Activity Changes Over the Central India Domain Using Satellite Observations During 2001-2020

Recurrent and large forest fires negatively impact ecosystem, air quality, and human health. Moderate Resolution Imaging Spectroradiometer fire product is used to identify forest fires over central India domain, an extremely fire prone region. The study finds that from 2001 to 2020, ∼70% of yearly forest fires over the region occurred during March (1,857.5 counts/month) and April (922.8 counts/month). Some years such as 2009, 2012, and 2017 show anomalously high forest fires. The role of persistent warmer temperatures and multiple climate extremes in increasing forest fire activity over central India is comprehensively investigated. Warmer period from 2006 to 2020 showed doubling and tripling of forest fire activity during forest fire (February-June; FMAMJ) and non-fire (July-January; JASONDJ) seasons, respectively. From 2015 JASONDJ to 2018 FMAMJ, central India experienced a severe heatwave, a rare drought and an extremely strong El Niño, the combined effect of which is linked to increased forest fires. Further, the study assesses quinquennial spatiotemporal changes in forest fire characteristics such as fire count density and average fire intensity. Deciduous forests of Jagdalpur-Gadchiroli Range and Indravati National Park in Chhattisgarh state are particularly fire prone (>61 fire counts/grid) during FMAMJ and many forest fires are of high intensity (>45 MW). Statistical associations link high near surface air temperature and low precipitation during FMAMJ to significantly high soil temperature, low soil moisture content, low evapotranspiration and low normalized difference vegetation index. This creates a significantly drier environment, conducive for high forest fire activity in the region.