Recent decline in carbon monoxide levels observed at an urban site in Ahmedabad, India.

Carbon monoxide (CO) is a prominent air pollutant in cities, with far-reaching implications for both local air quality and global atmospheric chemistry. The long-term change in atmospheric CO levels at a specific location is influenced by a complex interplay of local emissions, atmospheric transport, and photochemical processes, making it a subject of considerable interest. This study presents an 8-year analysis (2014-2021) of in situ CO observations using a cutting-edge laser-based analyzer at an urban site in Ahmedabad, western India. The long-term observations reveal a subtle trend in CO levels, masked by contrasting year-to-year variations, particular after 2018, across distinct diurnal time windows. Mid-afternoon (12:00-16:00 h) CO levels, reflecting background and regional conditions, remained relatively stable over the study period. In contrast, evening (18:00-21:00 h) CO levels, influenced by local emissions, exhibited substantial inter-annual variability without discernible trends from 2014 to 2018. However, post-2018, evening CO levels showed a consistent decline, predating COVID-19 lockdown measures. This decline coincided with the nationwide adoption of Bharat stage IV emission standards and other measures aimed at reducing vehicular emissions. The COVID-19 lockdown in 2020 further resulted in a noteworthy 29% reduction in evening CO levels compared to the pre-lockdown (2014-2019) period, highlighting the potential for substantial CO reduction through stringent vehicular emission controls. The observed long-term changes in CO levels do not align with the decreasing emission estimated by various inventories from 2014 to 2018, suggesting a need for improved emission statistics in Indian urban regions. This study underscores the importance of ongoing continuous CO measurements in urban areas to inform policy efforts aimed at controlling atmospheric pollutants.

Disentangling the contribution of the transboundary out-flow from the Asian continent to Tokyo, Japan.

We assessed the contribution of transboundary air pollutants (TAPs) transported from China to Tokyo using the Pb(0.5

[Characteristics of Surface Ozone and Impact Factors at Different Station Types During the Autumn in Guangzhou].

Surface ozone (O3) has become the primary air pollutant in Guangzhou. Due to the influences of topography, meteorological conditions, and differences in precursor emissions, there are also large differences in the characteristics, formation mechanisms, and influencing factors of ozone in different areas of the same city. Based on the ground measurement data for October 2015 at four air quality monitoring stations that represent different types of regions in Guangzhou [urban area:Guangzhou Monitoring Center (GMC); upwind suburbs:Huadu Normal School (HNS); downwind suburbs:Panyu Middle School (PMS); Mountain area:Maofengshan (MFS)] and the WRF simulated meteorological data, the changing characteristics, influencing factors, and sensitivity of O3 were studied at each station. The results showed that the diurnal variation of O3 and NOx exhibit unimodal and bimodal characteristics (except for NOx at the MFS station). The peak ozone concentration appeared on Saturday at the GMC, HNS, and MFS stations, and on Thursday at the PMS station. The ozone concentration at the MFS station was the highest (98.61 µg·m-3), whereas that at the GMC station was the lowest (44.83 µg·m-3). The NOx inflection point intervals for O3 at different sites were:GMC:55-90 µg·m-3; PMS:30-60 µg·m-3; MFS:10-20 µg·m-3. The temperature inflection point intervals affecting the rate of O3 formation at different sites were:GMC:28-30℃; HNS:26-28℃; PMS:24-26℃; however, this was not obvious at the MFS station. The relative humidity inflection point intervals were:GMC:55%-65% ; HNS and PMS:60%-70% ; MFS:80%-85%. The wind speed(WS) of the light wind type was proportional to the O3 concentration. The O3 concentration at the PMS site was the highest in the northwest wind direction, and the O3 concentration at the MFS site was the highest in the other wind directions. By analyzing the multivariate linear fitting of impact factors on the O3 concentration, the main controlling factors at each site were:GMC:WS and T; PMS and HNS:T and RH; MFS:RH and WS. The ozone sensitivity at each site was as follows:GMC and HNS had a VOCs-limited regime, MFS had a NOx-limited regime, and PMS had a transition regime.

Evaluation of the Submicron Particles Distribution Between Mountain and Urban Site: Contribution of the Transportation for Defining Environmental and Human Health Issues.

Transportation is one of the main causes of atmospheric pollution, especially in downtown big cities. Researchers usually point their attention to gaseous and/or particulate matter pollutants. This paper investigated the role of submicron particles, particularly the fraction ranging between 5-560 nm, in aerosol chemistry for identifying the contribution of autovehicular traffic and investigating the doses deposited in the human respiratory tract. Measurements carried out by two Fast Mobility Particle Sizer (FMPS, TSI) analyzers were simultaneously performed at two different sampling sites (an urban and a mountain site) during workdays and weekends in July. The total particle number (2-2.5 times higher in the urban site), the aerosol size distribution (different modes during the day), and the ultrafine/non-ultrafine particle ratios (ranging between 2-4 times between two sites) were investigated and discussed in relationship to the high autovehicular traffic in Rome and the almost null anthropogenic emissions at the mountain site, as well as the differing contributions of both to the "fresh nucleation" and to "aged aerosol". Furthermore, the regional cumulative number doses deposited in the human respiratory tract were studied for both sites: The difference between the urban/mountain site was very high (up to 15 fold), confirming the pollutant role of transportation.

Ambient mercury source identification at a New York State urban site: Rochester, NY.

Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) were measured continuously in Rochester, NY (NY43) from January 2012 to December 2014. Continuous measurements of ozone (O3), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO2), particulate matter (PM2.5), and meteorological data were also made at this site. A principal component analysis (PCA) of the resulting 15 variables showed that the ambient mercury in Rochester was primarily produced by non-local sources in contrast to earlier studies that showed that local sources were present. Positive matrix factorization (PMF) analysis of the atmospheric mercury and other pollutant species concentrations showed that transport and atmospheric processes have become the major source of mercury in Rochester. Conditional bivariate probability function (CBPF) and potential source contribution function (PSCF) were used to identify local and distant mercury sources. The results in this study showed that the closure of a coal-fired power plant and promulgation of several fuel quality policies reduced local mercury emissions making long-distance transport the major source of mercury in Rochester.

Examining Sense of Community among Hispanic Catholic Parishes by Economic Status, Location-Site, and Family Size.

In the present study, Roman Catholic deacons at one of the 216 Hispanic parishes across the U.S. reported on their parish sense of community (P-SOC), using the SCI-2, within the congregation. P-SOC was assessed among socioeconomic status of lower/working class (n = 109) or middle class (n = 107) Latino parishes, located in either an urban (n = 152) or urban cluster (n = 64) site, with the number of families within the parish to reflect a tiny (n = 76), small (n = 46), moderate (n = 38), or large (n = 54) size. A 2 × 2 × 4 MANOVA on four P-SOC sub-scale scores found no significant main or interaction effect for status, site, or size. It appears per public perception that a sense of connectedness and closeness exists in the Hispanic parishes that are poor, urban, and large congregations is a myth at best.

Contributions of vehicular emissions and secondary formation to nitrous acid concentrations in ambient urban air in Tokyo in the winter.

Nitrous acid (HONO) plays an important role in the formation of OH radicals, which are involved in photochemical oxidation. HONO concentrations in ambient air at urban sites have previously been measured, but very few studies have been performed in central Tokyo. In this study, HONO concentrations in ambient air in southeast central Tokyo (near Tokyo Bay) in winter were determined by incoherent cavity enhanced absorption spectroscopy. The O3, NO, NO2, and SO2 concentrations were simultaneously determined. The NO concentrations were used to classify the parts of the study period into types I (high pollution), II (medium pollution), and III (low pollution). The maximum HONO concentrations in the type I, II, and III periods were 7.1, 4.5, and 3.0ppbv, respectively. These concentrations were comparable to concentrations previously found in other Asian megacities. The mean HONO concentration varied diurnally, and HONO was depleted between 00:00 and 03:00 each day. The sampling site is surrounded by roads with high traffic loads, but vehicular emissions were estimated to contribute <10% of the HONO concentrations. Two positive and negative relative humidity dependences of the HONO to NO2 ratio were confirmed, implying the existence of the two different secondary formation process of HONO. The NO2 to HONO conversion rates at night in the type I, II, and III periods were 6.3×10-3, 7.6×10-3, and 4.2×10-3h-1, respectively.