The mass concentration of soot aggregates is often estimated from mobility size distributions using a mobility-based effective density, ρeff. This ρeff changes with aggregate morphology. In ...particular, the ρeff of a soot core increases when it becomes compacted by the surface tension of condensing coatings, such as combustion-related vapours, secondary aerosols, and cloud water. The extent of this compaction is a function of coating volume, up to an asymptotic limit of complete compaction. While complete compaction has previously been shown to correspond to a universal, scale-invariant packing factor for sufficiently large aggregates, it has not previously been explicitly quantified. Here, we critically reanalyze multiple datasets compiled from the literature on the ρeff of completely compact soot. We show that, regardless of the coating material, soot aggregates generally become completely compacted following a 5-fold increase in volume. The final aggregate shape is more simply described by ρeff than by mobility diameter or shape factor. Below 140 nm diameter (about 20 aggregate monomers), the compacted ρeff obeys a power law; above 140 nm, it reaches a constant value of 651 ± 8 kg m−3. This ρeff is 3 times larger than that of freshly-produced soot at 140 nm. We provide a parameterization of the compacted ρeff for the estimation of soot mass concentration after coating, or, conversely, for use as a benchmark to estimate the extent of aggregate restructuring. Our parameterization can be easily adapted to other nanoparticle aggregates whose material density is known.
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•Soot aggregates are always completely compacted when coatings reach five-fold the initial aggregate volume.•Above the small-aggregate limit of ∼20 monomers, collapsed soot has a universal, constant effective density.•We synthesize equations describing soot's fractality and mass-mobility relationship across multiple studies and morphologies.
Traffic-loaded areas have been of increasing concern due to the potential risk of carcinogenic pollutants, including antimony (Sb), which accumulates mostly in atmospheric particles (PM) and can ...interact with soil organic matter (Corg). The stability of Sb in topsoils was studied via the adsorption mechanism using standard soils and Corg-reach vehicle-produced particles as the unique source of “traffic” Sb. The mixed adsorbents were prepared from loamy sand and clay standard soils, and braking abrasion dust and diesel engine soot as Sb sources in atmospheric PM. Whereas the black carbon (BC), as part of Corg, disposes of exceptional adsorption properties compared to the other Corg, all adsorption experiments were performed identically on the adsorbents prepared from the original standard soils and Sb source materials and on the adsorbents prepared from the same materials annealed at 375 °C to ensure only BC participation in adsorption processes. The concentration of the Sb model solution corresponded to the average Sb content in rainwater from traffic-loaded localities. In addition to Sb, the Corg and iron (Fe) were monitored. The sorbability of Sb on the loamy sand soil mixtures increased up to 90% compared with the pure soil due to new active surface sites for Sb binding created due to the Corg added with the source material. The clay soil mixture containing 10 times more Corg compared with the loamy sand soil accumulated the Corg from the source material, which resulted in blocking active sites and a decline in Sb sorbability by up to 20%. The processes performed identically with original and annealed materials showed the same trends and confirmed the key role of BC and soil quality in the accumulation and stability of Sb in traffic-loaded topsoils. The participation of Fe in Sb surface interactions was not observed.
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•Antimony (Sb) near traffic nodes represents environmental risk due to growing automotive traffic.•Brake abrasion dust poses actual Sb risk through atmospheric particles (PM) and following infiltration into local topsoils.•Black carbon (BC) plays key role in Sb interaction with organic matter (OM) in soils and PM.•Stability of Sb near traffic nodes is entirely controlled by topsoil texture and BC content.
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•Calligraphy ink treated with acid introduced oxygen groups into BC, maximizing active sites for H2O2 production.•Hydrothermal synthesis resulted in oxygen-functionalized BC ...(O-BC/ZnIn2S4), enhancing H2O2 production.•In ZnIn2S4-mediated H2O2 production, we observed a dual phenomenon of production and decomposition.•pH adjustments, especially under basic conditions, led to a ten-fold reduction in ionization, boosting H2O2 production by approximately 14%.
Hydrogen peroxide (H2O2), a powerful oxidizing agent, plays a critical role in various sectors including bleaching, wastewater treatment, sterilization, chemical manufacturing, healthcare, energy generation, and environmental cleanup. The conventional method for producing H2O2, known as the anthraquinone process, faces challenges due to its economic inefficiencies and significant safety concerns. This has spurred interest in developing safer and more environmental friendly photocatalysts for H2O2 production. These photocatalysts, when dispersed in water and exposed to sunlight, generate H2O2 by extracting oxygen from the air and hydrogen from water. Our research explores the use of zinc indium sulfide (ZnIn2S4), a material that is photoactive under visible light, which accounts for about 43 % of the solar spectrum. Initially, the pH of the solution was not modified, leading to the ionization of Zn and In. However, upon optimizing the experimental conditions, we observed a substantial reduction in particle ionization and an increase in H2O2 yield. Additionally, by integrating black carbon with oxygen functional groups into the ZnIn2S4 matrix, we achieved a 14 % increase in production efficiency compared to traditional methods.
The seasonal variability of black carbon (BC) aerosols in India is studied using high resolution (10 km) BC simulations conducted using the Weather Research and Forecasting Model coupled with ...Chemistry. The model reproduces the observed seasonality of surface BC fairly well over most parts of India but fails to capture the seasonality in the Himalayas and deviates from the observed BC magnitude at several sites. The errors in modeled BC are attributed to uncertainties in BC emissions and their diurnal cycle, planetary boundary layer height underestimation, and aerosol processes. Model results show distinct but opposite seasonality of BC in the lower (LT) and free troposphere (FT) with BC showing winter maximum and summer minimum in the LT and vice versa in the FT. Our analysis shows that BC seasonality is not driven by seasonality of the anthropogenic emissions but by changes in the regional meteorology through weakening of the horizontal transport and strengthening of the vertical transport of BC during summertime compared to winter. BC in both the LT and FT comes mostly from anthropogenic emissions followed by biomass burning emissions except during winter when long‐distant sources become more important in the FT. BC in the FT is significantly affected by anthropogenic emissions from all parts of India. The source‐receptor relationship changes seasonally, but the regional transport remains a significant contributor to BC loadings in the LT of India, highlighting the necessity of considering nonlocal sources along with local emissions when designing strategies for mitigating BC impacts on air quality.
Key Points
Black carbon shows opposite seasonal cycle in the lower and free troposphere
The seasonal cycle of BC is driven mainly by seasonal changes in meteorology
Regional transport significantly impact BC distribution
Rapid industrial development and human activities have caused a degradation of soil quality and fertility. There is increasing interest in rehabilitating low fertility soils to improve crop yield and ...sustainability. Biochar, a carbonaceous material intentionally produced from biomass, is widely used as an amendment to improve soil fertility by retaining nutrients and, potentially, enhancing nutrient bioavailability. But, biochar is not a simple carbon material with uniform properties, so appropriate biochar selection must consider soil type and target crop. In this respect, many recent studies have evaluated several modification methods to maximize the effectiveness of biochar such as optimizing the pyrolysis process, mixing with other soil amendments, composting with other additives, activating by physicochemical processes, and coating with other organic materials. However, the economic feasibility of biochar application cannot be neglected. Strategies for reducing biochar losses and its application costs, and increasing its use efficiency need to be developed. This review synthesized current understanding and introduces holistic and practical approaches for biochar application to low fertility soils, with consideration of economic aspects.
•Biochar has potential to be the best management practice for low fertility soils.•Biochar coating with organic materials can result in enhanced crop nutrient supply.•Biochar may accelerate the composting process and improve the end-product quality.•The influence of biochar varies strongly according to the types of feedstock/soil.
Black carbon is a product of the incomplete combustion of carbonaceous fuels and has significant adverse effects on climate change, air quality, and human health. China has been a major contributor ...to global anthropogenic black carbon emissions. This study develops a black carbon inventory in China, using 2015 as the base year, and projects annual black carbon emissions in China for the period 2016–2050, under two scenarios: a Reference scenario and an Accelerated Reduction scenario. The study estimates that the total black carbon emissions in China in 2015 were 1100 thousand tons (kt), with residential use being the biggest contributor, accounting for more than half of the total black carbon emissions, followed by coke production, industry, agricultural waste burning, and transportation. This study then projects the total black carbon emissions in China in 2050 to be 278 kt in the Reference scenario and 86 kt in the Accelerated Reduction Scenario. Compared to the Reference scenario, the Accelerated Reduction scenario will achieve much faster and deeper black carbon reductions in all the sectors. The dramatic reductions can be attributed to the fuel switching in the residential sector, faster implementation of high-efficiency emission control measures in the industry, transportation, and coke production sectors, and faster phase-out of agricultural waste open burning. This analysis reveals the high potential of black carbon emission reductions across multiple sectors in China through the next thirty years.
Black carbon (BC), pyrogenic residues resulting from the incomplete combustion of organics, are liberated from wildfires at high rates. Subsequent introduction to aqueous environments via atmospheric ...deposition or overland flow results in the formation of a dissolved fraction, called dissolved black carbon (DBC). As wildfire frequency and intensity increases along with a changing climate, it becomes imperative to understand the impact a concurrent increase in DBC load might have to aquatic ecosystems. In the atmosphere BC stimulates warming by absorbing solar radiation, and similar processes may occur with surface waters that contain DBC. In this work we investigated whether the addition of environmentally relevant levels of DBC could impact surface water heating dynamics in experimental settings. DBC was quantified at multiple locations and depths in Pyramid Lake (NV, USA) during peak fire season while two large, proximal wildfires burned. DBC was detected in Pyramid Lake water at all sampled locations at concentrations (3.6–18 ppb) significantly higher than those reported for other large inland lakes. DBC was positively correlated (R2 = 0.84) with chromophoric dissolved organic matter (CDOM) but not bulk dissolved or total organic carbon (DOC, TOC), suggesting that DBC is a significant component of the optically active organics in the lake. Subsequent lab-based experiments were conducted by adding environmentally relevant levels of DBC standards to pure water, exposing the system to solar spectrum radiation, and creating a numerical model of heat transfer based on observed temperatures. The addition of DBC at environmentally relevant orders of magnitude caused reductions to shortwave albedo when exposed to the solar spectrum, which resulted in 5–8 % more incident radiation being absorbed by water and changes to water heating dynamics. In environmental settings, this increase in energy absorption could translate to increased heating of the epilimnion in Pyramid Lake and other wildfire-impacted surface waters.
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•High levels of dissolved black carbon were detected in a wildfire-impacted lake.•Dissolved black carbon correlated to optically active organics in the lake.•Dissolved black carbon caused accelerated water heating in lab experiments.•Wildfire-derived dissolved black carbon may impact surface water heating dynamics.
Russia has a particularly important role regarding black carbon (BC) emissions given the extent of its territory above the Arctic Circle, where BC emissions have a particularly pronounced effect on ...the climate. This study presents a comprehensive review of BC estimates from a range of studies. We assess underlying methodologies and data sources for each major emissions source based on their level of detail, accuracy and extent to which they represent current conditions. We then present reference values for each major emissions source. In the case of flaring, the study presents new estimates drawing on data on Russian associated petroleum gas and the most recent satellite data on flaring. We also present estimates of organic carbon (OC) for each source, either based on the reference studies or from our own calculations. In addition, the study provides uncertainty estimates for each source. Total BC emissions are estimated at 689 Gg in 2014, with an uncertainty range between (407-1,416), while OC emissions are 9,228 Gg (with uncertainty between 5,595 and 14,728). Wildfires dominated and contributed about 83% of the total BC emissions, however the effect on radiative forcing is mitigated by OC emissions. We also present an adjusted estimate of Arctic forcing from Russian OC and BC emissions. In recent years, Russia has pursued policies to reduce flaring and limit particulate emissions from on-road transport, both of which appear to significantly contribute to the lower emissions and forcing values found in this study.
Previous studies indicated that using CO2 as a reaction agent in the pyrolysis of biomass led to an enhanced generation of syngas via direct reaction between volatile organic carbons (VOCs) evolved ...from the thermal degradation of biomass and CO2. In addition, the physico-chemical properties of biochar in CO2 were modified. In this current study, biochars generated from red pepper stalks in N2 and CO2 (RPS-N and RPS-C, respectively) were tested for their effects on the immobilization of Pb, Cd, Zn, and As in contaminated soils. Soils were incubated for one month with 2.5% of RPS, and two biochars (i.e., RPS-N and RPS-C) at 25°C. After the incubation period soils were analyzed to determine the amendment effects on the behavior of metal(loid)s. The potential availability and mobility kinetics of metal(loid)s were assessed by single extraction of ammonium acetate and consecutive extraction of calcium chloride, respectively. Sequential extraction was used to further examine potential changes in geochemical fractions of metal(loid)s. The increased soil pH induced by application of the biochars reduced the potentially available Pb, Cd, and Zn, while RPS-C significantly reduced Pb due to the high surface area and aromaticity of RPS-C. However, RPS-C mobilized potentially available As compared to RPS-N due to the increased soil pH. Biochars reduced the mobility kinetics of Pb, Cd, and Zn, and RPS-N effectuated the greatest reduction of As mobility. The RPS-C increased the Fe and Mn oxides, hydroxide, and organically bound Pb, while both biochars and RPS-N increased residual Cd and Zn, and organically bound As, respectively. When considering the two biochars, RPS-C was highly effective for immobilization of Pb in soils, but it had no effect on Cd and Zn and a negative effect on As. In addition, RPS-C significantly increased the total exchangeable cations in soils.
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•Biochars markedly reduced Cd, Pb and Zn mobility in soils.•Biochar pyrolyzed in CO2 most effectively immobilized Pb.•Biochar pyrolyzed in CO2 increases As mobility more.•More siloxane groups present in biochar pyrolysed in CO2.
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