Explore the vast range of titles available.

The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However, the absorption properties of BrC are poorly understood, leading to large uncertainties in modeling studies. To obtain observational constraints from measurements, a simple absorption Ångström exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new AAE method which improves upon previous approaches by using the information from the wavelength-dependent measurements themselves and by allowing for an atmospherically relevant range of BC properties, rather than fixing these at a single assumed value. We note that constraints on BC optical properties and mixing state would help further improve this method. We apply this method to multiwavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites. We estimate that BrC globally contributes up to 40 % of the seasonally averaged absorption at 440 nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with the BC ∕ OA mass ratio. Based on the variability in BC properties and BC ∕ OA emission ratio, we estimate a range of 0.05–1.5 m2 g−1 for OA-MAC at 440 nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388∕440 nm for BrC is generally  ∼ 4 worldwide, with a smaller value in Europe (< 2). Our analyses of observations at two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in urban-influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of  ∼ 1 day. This lifetime is comparable to previous observations within a biomass burning plume but much slower than estimated from laboratory studies. Given the large uncertainties associated with AERONET retrievals of AAOD, the most challenging aspect of our analysis is that an accurate, globally distributed, multiple-wavelength aerosol absorption measurement dataset is unavailable at present. Thus, achieving a better understanding of the properties, evolution, and impacts of global BrC will rely on the future deployment of accurate multiple-wavelength absorption measurements to which AAE methods, such as the approach developed here, can be applied.

The Himalayas and Tibetan Plateau (the HTP), referred to as “the third pole” with an excessive warming rate, exerts strong impacts on the global environment. As one of warming contributors, atmospheric brown carbon (BrC) remains limited scientific understanding in the HTP due to a scarcity of observations. In this study, we present a study of the light‐absorbing properties of methanol‐soluble brown carbon (MeS‐BrC) and water‐soluble brown carbon (WS‐BrC) during 2018–2021. Highly spatiotemporal variations of BrC light absorptions were observed. In the HTP marginal area, elevated BrC absorption coefficients at 365 nm (babs,365) and levoglucosan concentrations were obtained, and MeS‐BrC exhibits approximately 1.3–1.8 times higher absorption compared to WS‐BrC. We determined that BrC light absorptions was largely attributed to biomass burning (29%–35%). BrC can act as a potent warming agent in the HTP marginal area, with high direct solar absorption (25%–47% relative to black carbon). Plain Language Summary Atmospheric brown carbon (BrC) remains low scientific understanding in the HTP due to a scarcity of observations. Here, we present a plateau‐scale study of the light‐absorbing properties of methanol‐soluble brown carbon (MeS‐BrC) and water‐soluble brown carbon (WS‐BrC) during the period of 2018–2021. This study highlights the contribution of BrC to the HTP warming. Higher BrC light absorption was observed in the HTP marginal area compared with the central HTP. Enhanced radiative absorption effect of WS‐BrC was obtained in the HTP, with an annual average of ∼25% compared with BC in Qinghai Lake and Ngari, and as high as 46.5% in Purang. The results confirmed the importance of BrC from biomass burning in contributing to light‐absorbing aerosols in this region. Key Points Brown carbon (BrC) can be a strong warming agent in the marginal Himalayas and Tibetan Plateau Highly spatiotemporal variations of plateau‐scale BrC were observed BrC light absorptions was largely attributed to biomass burning

Varanasi district is comprised of eight administrative blocks. Owing to economic development, it has shown an increase in urban activities. Analysis of remotely sensed data for a period of two decades reveals that the built-up area increased by about 345% while vegetation decreased by 86% during 1993–2013. Contrary to other observations, land use changes, due to urban growth, increased not only the built area but also the agriculture class. Agricultural area increased by 39% in the two decades. Population density increased from 1217 to 1806 person/km 2 and household density grew from 152 to 273 households/km 2 during 1991–2011. Land absorption coefficient (LAC) and land consumption ratio (LCR) were calculated as demographic indices of land use land cover change (LULC). Vegetation delineation shows that sparse vegetation increased from 40.2 to 90.1 km 2 while dense vegetation decreased from 28.4 to 1.7 km 2 in 1993–2013. There was a distinct shift from agriculture, as a primary economic activity, towards non-agricultural pursuits. In order to frame better strategies for sustainable development and food security, this phenomenon of increasing urbanization around cities needs to be studied. This micro scale study can be helpful in formulating policy for urban areas in developing countries like India which heavily depend on agriculture to sustain their population and economy.

Visibility is a fundamental meteorological parameter critical for surface transportation, aviation, maritime navigation, and weather process investigation. Scattering visibility meters are extensively utilised for their simple design and rapid response; however, their measurement principle is inherently limited, as they only quantify the scattering coefficient without assessing the absorption coefficient, potentially causing measurement errors. The World Meteorological Organisation (WMO) posits that the atmospheric absorption coefficient is usually relatively small and can be neglected, justifying the approximation of the extinction coefficient by the scattering coefficient. However, as black carbon is the predominant light-absorbing component in the atmosphere, an increase in its mass concentration markedly alters the atmospheric absorption coefficient, considerably impacting the accuracy of scattering-based visibility meters. Based on Mie scattering theory and incorporating both field observations and laboratory data, we systematically examined the effects of black carbon and its interactions with other aerosol components on the measurement errors of scattering visibility meters. Our findings revealed that the impact of black carbon on measurement errors is substantial, and under certain conditions, particularly pronounced. This influence is not only dependent on the mass concentration of black carbon but also closely associated with aerosol size distribution, mixing state, and the characteristics of other scattering aerosols. Due to the spatiotemporal variability of these factors, the impact of black carbon on visibility errors is uncertain. Therefore, during the calibration of scattering-based visibility meters, the effects of black carbon and its associated factors must be considered to enhance measurement accuracy. We propose calibration recommendations for scattering-based visibility meters aimed at reducing measurement errors and improving the accuracy of visibility assessments.

The present paper deals with the evaluation of the impact of newly developed biofuels together with a comparison with conventionally produced fuel, diesel, in terms of their impact on the technical and emission condition of a studied vehicle. The main energy and emission parameters of the internal combustion diesel engine were evaluated. For laboratory experiments, a discrete test method was used for comprehensive assessment, the procedure of which is described in the methodology of the paper together with a description of the measurement chain designed to achieve the determined results. The paper deals with the evaluation of the measured results of power, torque, consumption, and emissions such as CO and absorption coefficient. Among the technical parameters, the power and torque drop were observed for each biofuel. The decrease is attributed to lower values of calorific value, viscosity, and density. A positive effect was observed for the CO and absorption coefficient emission parameters, i.e., a decrease for each of the newly developed biofuels studied.

Environmental pollution is escalating due to inadequate waste management, with the open burning of agricultural waste being a significant contributor. This process releases various harmful gases into the environment. This study introduces an innovative approach to creating sound absorption materials using agricultural by-products, specifically paddy straw and coconut coir, along with newspaper by-products. The research was conducted in two phases: first, the production of sound absorption panels with different densities and adhesive quantities, and second, the evaluation of these panels’ sound absorption capabilities through laboratory experiments. The impedance tube test was used to determine the sound absorption coefficient (SAC). The results showed effective sound absorption, especially at lower frequencies ranging from 125 Hz to 6300 Hz. Notably, paddy straw and coconut coir exhibited significant sound absorption values at 1,000 Hz (0.59 and 0.52, respectively). This study highlights the potential of paddy straw and coconut coir as sustainable, cost-effective materials for sound absorption panels. These natural materials demonstrate excellent sound-absorbing properties, making them suitable for various applications such as classrooms, sound recording rooms, auditoriums, and theaters at low to medium frequencies.

At present, there are still numerous unresolved questions concerning the mechanisms of light-absorbing organic aerosol (brown carbon, BrC) formation in the atmosphere. Moreover, there is growing evidence that chemical processes in the atmospheric aqueous phase can be important. In this work, we investigate the aqueous-phase formation of BrC from 3-methylcatechol (3MC) under simulated sunlight conditions. The influence of different HNO2/NO2− concentrations on the kinetics of 3MC degradation and BrC formation was investigated. Under illumination, the degradation of 3MC is faster (k2nd(global) = 0.075 M−1·s−1) in comparison to its degradation in the dark under the same solution conditions (k2nd = 0.032 M−1·s−1). On the other hand, the yield of the main two products of the dark reaction (3-methyl-5-nitrocatechol, 3M5NC, and 3-methyl-4-nitrocatechol, 3M4NC) is low, suggesting different degradation pathways of 3MC in the sunlight. Besides the known primary reaction products with distinct absorption at 350 nm, second-generation products responsible for the absorption above 400 nm (e.g., hydroxy-3-methyl-5-nitrocatechol, 3M5NC-OH, and the oxidative cleavage products of 3M4NC) were also confirmed in the reaction mixture. The characteristic mass absorption coefficient (MAC) values were found to increase with the increase of NO2−/3MC concentration ratio (at the concentration ratio of 50, MAC is greater than 4 m2·g−1 at 350 nm) and decrease with the increasing wavelength, which is characteristic for BrC. Yet, in the dark, roughly 50% more BrC is produced at comparable solution conditions (in terms of MAC values). Our findings reveal that the aqueous-phase processing of 3MC in the presence of HNO2/NO2−, both under the sunlight and in the dark, may significantly contribute to secondary organic aerosol (SOA) light absorption.

In this study, the sound absorption characteristics of hexagonal close-packed and face-centered cubic lattices were estimated by theoretical analysis. Propagation constants and characteristic impedances were obtained by dividing each structure into elements perpendicular to the incident direction of sound waves and by approximating each element to a clearance between two parallel planes. Consequently, the propagation constant and the characteristic impedance were treated as a one-dimensional transfer matrix in the propagation of sound waves, and the normal incident sound absorption coefficient was calculated by the transfer matrix method. The theoretical value of the sound absorption coefficient was derived by using the effective density applied to the measured tortuosity. As a result, the theoretical value was becoming closer to the measured value. Therefore, the measured tortuosity is reasonable.

The ultrabasic soils exhibit sources of natural geogenic contamination and potential to contaminate soil and water resources. In Ranau basin area, Malaysia, there are three sub-basins which locate adjacent to the ultrabasic soil. The transport of metals concentration can be assessed using the riverine heavy metal flux analysis based on the empirical erosion models. The erosion models such as the Revised Universal Soil Loss Equation (RUSLE) give a common and extensive framework for evaluating soil erosion and its causative factors. RUSLE examined rainfall (R), topography (LS), soil erodibility (K), cover management (C), and support practice (P) as prominent factors influencing soil erosion. Several heavy metals (Co, Cr, Ni, Pb, Cu, and Zn) and a toxic element (As) were analyzed in this study using the standard laboratory analysis. Results of study revealed the average of soil erosion rates in the sub-basins was higher than the national standard of soil erosion rate were 215.10 ton/ha year (very high class, > 150 ton/ha year), 113.29 ton/ha year (high class, 100–150 ton/ha year), and 67.53 ton/ha year (moderate high class, 50–100 ton/ha year) in the Langanan, Liwagu, and Lohan respectively. The riverine heavy metal flux was the highest for Ni, Cu, Pb, and Zn in the Langanan (1.51 kg/ha year, 2.77 kg/ha year, 6.71 kg/ha year, and 118.95 kg/ha year, respectively). The heavy metal flux was highest for Cr and Co in the Liwagu (311.57 kg/ha year and 10.91 kg/ha year). The concentration of heavy metals in rice grains in descending order was Cr > Ni > Zn > Cu > Pb > Co. The biological absorption coefficient (BAC) values for all of the heavy metals were below 0.12 which indicated that rice plants in the study area did not accumulate heavy metals. These results have a prominent notion to discover the distribution and transport of heavy metals in the sub-basins to arrange the best solution in controlling of source heavy metal pollution due to ultrabasic soil.

Black carbon (BC) is a pollutant aerosol affecting climate and human health. Light absorption coefficients of black carbon (Babs) were measured using an aethalometer model AE33 at wavelengths 370, 470,520,660,880, and 950 nm. Babs for the seven wavelengths at seven sites in Jordan fluctuated with time and peaked at rush hours. The daily average values for all sites were inversely proportional to the wavelength. The average daily visibility values in the seven Jordan sites varied between 72 km and 211km. In the Irbid site, the daily average visibility values for 7-13 Nov. 2021 varied between 43 km and 107 km. BC varied from hour to hour and from day to day. The daily average values of BC in Irbid for the period of 7 -13 Nov. 2021 varied between 2.24 μg.m-3 and 4.66 μg.m-3. BC peaked at the rush hour and had the lowest values on Friday. About 90% of the measured BC was from fossil fuel sources and 10% from biomass-burning sources.