Chemical Sink Research Articles

Rapid decline in carbon monoxide emissions and export from East Asia between years 2005 and 2016

Measurements of Pollution in the Troposphere (MOPITT) satellite and ground-based carbon monoxide (CO) measurements both suggest a widespread downward trend in CO concentrations over East Asia during the period 2005–2016. This negative trend is inconsistent with global bottom-up inventories of CO emissions, which show a small increase or stable emissions in this region. We try to reconcile the observed CO trend with emission inventories using an atmospheric inversion of the MOPITT CO data that estimates emissions from primary sources, secondary production, and chemical sinks of CO. The atmospheric inversion indicates a ~ −2% yr−1 decrease in emissions from primary sources in East Asia from 2005–2016. The decreasing emissions are mainly caused by source reductions in China. The regional MEIC inventory for China is the only bottom up estimate consistent with the inversion-diagnosed decrease of CO emissions. According to the MEIC data, decreasing CO emissions from four main sectors (iron and steel industries, residential sources, gasoline-powered vehicles, and construction materials industries) in China explain 76% of the inversion-based trend of East Asian CO emissions. This result suggests that global inventories underestimate the recent decrease of CO emission factors in China which occurred despite increasing consumption of carbon-based fuels, and is driven by rapid technological changes with improved combustion efficiency and emission control measures.

HYDROLOGICAL, PHYSICAL, AND CHEMICAL FUNCTIONS AND CONNECTIVITY OF NON-FLOODPLAIN WETLANDS TO DOWNSTREAM WATERS: A REVIEW.

We reviewed the scientific literature on non-floodplain wetlands (NFWs), freshwater wetlands typically located distal to riparian and floodplain systems, to determine hydrological, physical, and chemical functioning and stream and river network connectivity. We assayed the literature for source, sink, lag, and transformation functions, as well as factors affecting connectivity. We determined NFWs are important landscape components, hydrologically, physically, and chemically affecting downstream aquatic systems. NFWs are hydrologic and chemical sources for other waters, hydrologically connecting across long distances and contributing compounds such as methylated mercury and dissolved organic matter. NFWs reduced flood peaks and maintained baseflows in stream and river networks through hydrologic lag and sink functions, and sequestered or assimilated substantial nutrient inputs through chemical sink and transformative functions. Landscape-scale connectivity of NFWs affects water and material fluxes to downstream river networks, substantially modifying the characteristics and function of downstream waters. Many factors determine the effects of NFW hydrological, physical, and chemical functions on downstream systems, and additional research quantifying these factors and impacts is warranted. We conclude NFWs are hydrologically, chemically, and physically interconnected with stream and river networks though this connectivity varies in frequency, duration, magnitude, and timing.

Indoor Chemistry.

This review aims to encapsulate the importance, ubiquity, and complexity of indoor chemistry. We discuss the many sources of indoor air pollutants and summarize their chemical reactions in the air and on surfaces. We also summarize some of the known impacts of human occupants, who act as sources and sinks of indoor chemicals, and whose activities (e.g., cooking, cleaning, smoking) can lead to extremely high pollutant concentrations. As we begin to use increasingly sensitive and selective instrumentation indoors, we are learning more about chemistry in this relatively understudied environment.

Study on Chemical Heat Sink of Liquid Hydrocarbon Fuel under Supercritical Condition

Study on Chemical Heat Sink of Liquid Hydrocarbon Fuel under Supercritical Condition

Characterization and Comparison by Measurement of Properties Comparative Analysis about Traditional and Chemical Ink Sticks of Korea

우리나라의 전통먹은 화학먹에 의해 점차 사라져가고 있다. 이에 전통먹과 화학먹에 대한 과학적인 분석 방법을 통해 이화학적 성상을 비교 분석하여, 전통먹과 화학먹의 물성 차이를 확인해 전통먹의 대체 재료로서의 가능성을 확인해 보고자 한다. 분석 결과 화학먹인 c 먹이 가장 낮은 변화량을 보여주어 자외선에 의한 열화가 가장 미약하였으며, 전통먹인 송연먹이 가장 낮은 변색과 내구성을 보여주었다. 또한 e 먹의 화학먹이 가장 높은 원형도를 나타내어 잉크간 뭉침이 좋았으며, 전통먹인 b 먹은 원형도가 가장 낮아 퍼짐성이 좋았다. 이는 e 먹의 입도 크기가 평균 140.233㎛로 5종의 먹 중에서 가장 낮아 입자가 세밀하게 뭉쳐져 있어 원형도가 높게 나타난 결과로 판단된다. 원소 분석 결과 a 먹은 높은 C 함량과 낮은 N 함량으로 보아 나머지 4종의 먹 보다 적은 교질의 성분이 첨가되고 많은 양의 그을음으로 제작되었음을 확인할 수 있었고, b 먹은 그을음과 소가죽 아교를 혼합해 제조 하였으며, e 먹은 토끼 가죽 아교를 사용해 제작한 것으로 판단된다. 먹의 품질은 S와 O의 함량에 따라 다르게 나타나 각 실험과 분석 결과를 바탕으로 연구, 개발이 지속적으로 이루어진다면 보다 고품질의 먹을 개발할 수 있으며, 교착제의 종류 및 농도에 따라 달라지는 먹의 물성에 대한 연구 및 표준화 작업 등이 필요하다고 판단된다.Our country’s traditional meok (ink stick) is disappearing gradually these days replaced by chemical meok. So, this study conducted comparative analysis on physiochemical compositions using scientific analysis method for both quality and examined the difference in physical properties of the two meoks. In doing so, the study aimed at identifying traditional meok s potential as a replacement of chemical meok. As a result of analysis, c meok - chemical meok - showed the lowest variation resulting in the lowest ultraviolet ray degradation, while Songyon (charcoal) meok - traditional meok - showed the lowest discoloration and durability. e meok (chemical) showed the highest compactness with excellent effect of agglomeration between inks, whereas b meok (traditional) showed the lowest compactness resulting in good spreading effect. Particle size of e meok was 140.233㎛ on average showing the smallest size out of five meoks, which means particles were agglomerated closely resulting in the highest compactness. The result of elemental analysis showed a meok, given its high C content and low N content, was made with less colloid component additions and more amount of soot compared with the other four meoks. While, b meok was assessed to be made from soot and mixture of cowhide glues and e meok made from rabbit skin glues. Quality of meok depends on the contents of S and O. Therefore, if R&D on them can be made continually based on each experiment and analysis result, the study believes meok with better quality can be developed and also we need further research on and standardization of physical properties of meok that may differ depending on types and density of glues.

Reduced biomass burning emissions reconcile conflicting estimates of the post-2006 atmospheric methane budget

Several viable but conflicting explanations have been proposed to explain the recent ~8 p.p.b. per year increase in atmospheric methane after 2006, equivalent to net emissions increase of ~25 Tg CH4 per year. A concurrent increase in atmospheric ethane implicates a fossil source; a concurrent decrease in the heavy isotope content of methane points toward a biogenic source, while other studies propose a decrease in the chemical sink (OH). Here we show that biomass burning emissions of methane decreased by 3.7 (±1.4) Tg CH4 per year from the 2001–2007 to the 2008–2014 time periods using satellite measurements of CO and CH4, nearly twice the decrease expected from prior estimates. After updating both the total and isotopic budgets for atmospheric methane with these revised biomass burning emissions (and assuming no change to the chemical sink), we find that fossil fuels contribute between 12–19 Tg CH4 per year to the recent atmospheric methane increase, thus reconciling the isotopic- and ethane-based results.

Formaldehyde in the Tropical Western Pacific: Chemical sources and sinks, convective transport, and representation in CAM-Chem and the CCMI models.

Formaldehyde (HCHO) directly affects the atmospheric oxidative capacity through its effects on HOx. In remote marine environments, such as the Tropical Western Pacific (TWP), it is particularly important to understand the processes controlling the abundance of HCHO because model output from these regions is used to correct satellite retrievals of HCHO. Here, we have used observations from the CONTRAST field campaign, conducted during January and February 2014, to evaluate our understanding of the processes controlling the distribution of HCHO in the TWP as well as its representation in chemical transport/climate models. Observed HCHO mixing ratios varied from ~500 pptv near the surface to ~75 pptv in the upper troposphere. Recent convective transport of near surface HCHO and its precursors, acetaldehyde and possibly methyl hydroperoxide, increased upper tropospheric HCHO mixing ratios by ~33% (22 pptv); this air contained roughly 60% less NO than more aged air. Output from the CAM-Chem chemistry transport model (2014 meteorology) as well as nine chemistry climate models from the Chemistry-Climate Model Initiative (free-running meteorology) are found to uniformly underestimate HCHO columns derived from in situ observations by between 4 and 50%. This underestimate of HCHO likely results from a near factor of two underestimate of NO in most models, which strongly suggests errors in NOx emissions inventories and/or in the model chemical mechanisms. Likewise, the lack of oceanic acetaldehyde emissions and potential errors in the model acetaldehyde chemistry lead to additional underestimates in modeled HCHO of up to 75 pptv (~15%) in the lower troposphere.

Current understanding of microplastics in the environment: Occurrence, fate, risks, and what we should do.

Microplastics pollution has been documented in the global environment, including at sea, in freshwater and in atmospheric fallout. Ingestion of microplastics by multiple kinds of organisms has been reported and has received increasing attention, because microplastics not only act as a source of toxic chemicals but also a sink for toxic chemicals. To better understand the great concerns about microplastics and associated toxic chemicals potential exposed to the organisms ingesting the debris, we should know more about the occurrence, fate, and risks of microplastics in the environment. What we should do depends on this better understanding. Integr Environ Assess Manag 2017;13:476-482. © 2017 SETAC.

A 15-year record of CO emissions constrained by MOPITT CO observations

Abstract. Long-term measurements from satellites and surface stations have demonstrated a decreasing trend of tropospheric carbon monoxide (CO) in the Northern Hemisphere over the past decade. Likely explanations for this decrease include changes in anthropogenic, fires, and/or biogenic emissions or changes in the primary chemical sink hydroxyl radical (OH). Using remotely sensed CO measurements from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument, in situ methyl chloroform (MCF) measurements from the World Data Centre for Greenhouse Gases (WDCGG) and the adjoint of the GEOS-Chem model, we estimate the change in global CO emissions from 2001 to 2015. We show that the loss rate of MCF varied by 0.2 % in the past 15 years, indicating that changes in global OH distributions do not explain the recent decrease in CO. Our two-step inversion approach for estimating CO emissions is intended to mitigate the effect of bias errors in the MOPITT data as well as model errors in transport and chemistry, which are the primary factors contributing to the uncertainties when quantifying CO emissions using these remotely sensed data. Our results confirm that the decreasing trend of tropospheric CO in the Northern Hemisphere is due to decreasing CO emissions from anthropogenic and biomass burning sources. In particular, we find decreasing CO emissions from the United States and China in the past 15 years, and unchanged anthropogenic CO emissions from Europe since 2008. We find decreasing trends of biomass burning CO emissions from boreal North America, boreal Asia and South America, but little change over Africa. In contrast to prior results, we find that a positive trend in CO emissions is likely for India and southeast Asia.

Detection of Semivolatile Organic Compounds in Permeable Pavement Infiltrate.

The U.S. Environmental Protection Agency's Edison Environmental Center (EEC) has a research and demonstration permeable parking lot comprised of three different permeable systems: permeable asphalt, pervious concrete, and permeable interlocking concrete pavers. Water quality and quantity analysis has been ongoing since January 2010. This paper describes analysis of semivolatile organic compounds (SVOCs) to determine if hydrocarbons were in water that infiltrated through the permeable surfaces. SVOCs were analyzed in samples collected from 11 dates over a 3-year period, from February 8, 2010 to April 1, 2013. Results are broadly divided into three categories: 42 chemicals were never detected; 12 chemicals (11 chemical test) were detected at a rate of less than 10% or less; and 22 chemicals were detected at a frequency of 10% or greater (ranging from 10 to 66.5% detections). Fundamental and exploratory statistical analyses were performed on the 22 most observed chemicals. The statistical analyses were limited due to low frequency of detections and dilutions of samples, which impacted detection limits. The infiltrate data through three permeable surfaces were analyzed as nonparametric data by the Kaplan-Meier estimation method for fundamental statistics; there were some statistically observable differences in median concentration between pavement types when using Tarone-Ware comparison hypothesis test. A result was that three groups could be identified based on whether observed porous asphalt infiltrate concentration were greater than, similar to, or less than permeable interlocking concrete pavers infiltrate concentration. Identifying these three groups allowed one-way analysis on chemical attributes; the octonal water partitioning (logK OW), number of benzene rings, and molecular complexity were all significant. These 22 most observed chemicals in the infiltrate were further tested by Spearman rank order nonparametric for correlations between frequency of detection and chemical attributes; significant correlations were observed for porous asphalt frequency of detection and molecular weight (MW), Henry's constant, log K OW and molecular complexity, while both permeable concretes did not have any significant correlations between frequency of detection and chemical parameters. Conclusions from the statistical analyses on the 22 most frequently observed SVOCs in the infiltrate indicate that porous asphalt acts as a source for chemicals with low log K OW and MW and a sink for chemicals with high log K OW and MW, while no significant pattern was observed in the SVOC infiltrate concentrations of the two types of concrete.

An experimental and simulated investigation on pyrolysis of blended cyclohexane and benzene under supercritical pressure

The pyrolysis characteristics of blended cyclohexane and benzene mixture are investigated under supercritical pressure. The experimental results show that cyclohexane pyrolysis is greatly easier than thermal cracking of benzene, and the addition of cyclohexane can significantly promote the benzene pyrolysis, while the thermal cracking of cyclohexane itself is weakened by the addition of benzene. A simulation of the blended fuel is carried out by using Chemkin program, indicating that the chemical heat sink of cyclohexane pyrolysis can account for nearly 50% of its total heat absorption capacity, while benzene is inactive in thermal cracking process.

Energy absorption and reaction mechanism for thermal pyrolysis of n-decane under supercritical pressure

In this work, the behavior of mild thermal cracking n-decane was investigated experimentally and numerically. A developed experimental method of electrical heating tube was used to analyze the thermal cracking of n-decane under various temperatures and pressures. The results showed that, at low cracking conversion of 12%, the selectivities of all cracked products are approximately equal to constant values. A one-step global reaction model consisting of 11 species was established for mild-cracking n-decane and a novel on-line density measurement method was developed to improve the precision of residence time calculation, thus the kinetics parameters. The reliability of the reaction model was confirmed through comparing the experimental results with simulated values by using Chemkin program with the deviation less than 10%. The chemical heat sink of thermal cracking n-decane was evaluated and the result showed that the heat absorption provided by chemical endothermic reactions is unnegligible even at low conversion.

The world-class Jinding Zn–Pb deposit: ore formation in an evaporite dome, Lanping Basin, Yunnan, China

The Jinding Zn–Pb sediment-hosted deposit in western Yunnan, China, is the fourth largest Zn deposit in Asia. Based on field observations of the ore textures, breccias, and the sandstone host rocks, the ores formed in a dome that was created by the diapiric migration of evaporites in the Lanping Basin during Paleogene deformation and thrust loading. Most of the ore occurs in sandstones that are interpreted to be a former evaporite glacier containing a melange of extruded diapiric material, including breccias, fluidized sand, and evaporites that mixed with sediment from a fluvial sandstone system. A pre-ore hydrocarbon and reduced sulfur reservoir formed in the evaporite glacier that became the chemical sink for Zn and Pb in a crustal-derived metalliferous fluid. In stark contrast to previous models, the Jinding deposit does not define a unique class of ore deposits; rather, it should be classified as MVT sub-type hosted in a diapiric environment. Given that Jinding is a world-class ore body, this new interpretation elevates the exploration potential for Zn–Pb deposit in other diapir regions in the world.

Thermal behavior in the cracking reaction zone of scramjet cooling channels at different channel aspect ratios

To study the thermal behavior in the cracking reaction zone of regeneratively cooled scramjet cooling channels at different aspect ratios, 3-D model of fuel flow in terms of the fuel's real properties and cracking reaction is built and validated through experiments. The whole cooling channel is divided into non-cracking and cracking reaction zones. Only the cracking reaction zone is studied in this article. The simulation results indicate that the fuel conversion presents a similar distribution with temperature because the fuel conversion in scramjet cooling channels is co-decided by the temperature and velocity but the temperature plays the dominate role. For the cases given in this paper, increasing the channel aspect ratio will increase the pressure drop and it is not beneficial for reducing the wall temperature because of the much severer thermal stratification, larger conversion non-uniformity, the corresponding M-shape velocity profile which will cause local heat transfer deterioration and the decreased chemical heat absorption. And the decreased chemical heat absorption caused by stronger temperature and conversion non-uniformities is bad for the utilization of chemical heat sink, chemical recuperation process and the ignition performance.

Coupling relationship analysis between flow and pyrolysis reaction of endothermic hydrocarbon fuel in view of characteristic time correlation in mini-channel

In order to study the coupling relationship between flow and pyrolysis of endothermic hydrocarbon fuel in mini-channel of regeneratively cooled advanced aeroengines, characteristic time was defined to describe the time scales for flow and pyrolysis reaction in pyrolysis reaction flow field. The DamkÖhler number (Da) was used to quantitatively describe the relationship and degree of coupling between flow and pyrolysis reaction in mini-channel in terms of characteristic time. A 1D model was established to describe the coupling relationship of flow and pyrolysis reaction, and validated through experimental data. Simulation and experimental results indicated that: relationship and degree of coupling between flow and pyrolysis reaction could be quantitatively described using Da. The flow field could be divided into three regions according to the distributions of Da and chemical heat sink: frozen flow, non-equilibrium flow and equilibrium flow. Each region exhibited the different coupling characteristics between flow and pyrolysis reaction, which resulted in different distribution of chemical heat sink. There was a maximum rate of chemical heat sink releasing between non-equilibrium region and equilibrium region in particular. And the variation of flow had no influence on the maximum rate of chemical heat sink releasing.

Deformation-induced trace element redistribution in zircon revealed using atom probe tomography.

Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal–plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials.

Experimental Study of CaO Facilitated Cellulose Pyrolysis in a Drop Tube Pyrolyzer

The direct deoxygenation effect of CaO on bio-oil from cellulose pyrolysis was studied in a series of drop tube experiments together with gas chromatography-mass spectrometry analysis. The oxygen contents of the bio-oils were found to decrease from 44.4% for CaO-free cellulose to 40.7% when the CaO/cellulose mass ratio (R) was 2. The relative variation of the oxygen content of the bio-oils reached –8.4% for this mass ratio. The relative abundance of levoglucosan decreased sharply from 85.72 to 42.75% with an increase of R from 0 to 2. The decrease of the relative abundance of levoglucosan and an increase of the relative abundance of acetol and other small molecule products indicated a dominant shift of the parallel competitive reactions from the glycosidic bond rupture pathway to the decomposition and reforming route. The direct fixation of active quasi-CO2 intermediates, functioning as a ‘chemical sink’ in the decomposition and reforming route, caused this shift.

Model validation and parametric study of fluid flows and heat transfer of aviation kerosene with endothermic pyrolysis at supercritical pressure

The regenerative cooling technology is a promising approach for effective thermal protection of propulsion and power-generation systems. A mathematical model has been used to examine fluid flows and heat transfer of the aviation kerosene RP-3 with endothermic fuel pyrolysis at a supercritical pressure of 5MPa. A pyrolytic reaction mechanism, which consists of 18 species and 24 elementary reactions, is incorporated to account for fuel pyrolysis. Detailed model validations are conducted against a series of experimental data, including fluid temperature, fuel conversion rate, various product yields, and chemical heat sink, fully verifying the accuracy and reliability of the model. Effects of fuel pyrolysis and inlet flow velocity on flow dynamics and heat transfer characteristics of RP-3 are investigated. Results reveal that the endothermic fuel pyrolysis significantly improves the heat transfer process in the high fluid temperature region. During the supercritical-pressure heat transfer process, the flow velocity significantly increases, caused by the drastic variations of thermophysical properties. Under all the tested conditions, the Nusselt number initially increases, consistent with the increased flow velocity, and then slightly decreases in the high fluid temperature region, mainly owing to the decreased heat absorption rate from the endothermic pyrolytic chemical reactions.

Heterogeneity of ion irradiation-induced hardening in A533B reactor pressure vessel model alloys

Reactor pressure vessels comprise bainitic steel structures, and are heterogeneous on the mesoscale. Nanoindentation techniques were used to evaluate the hardness of these structures on the micrometer scale, and to evaluate the heterogeneity in a specimen using the distribution of the hardness. Three A533B model alloys were irradiated by 2.8 MeV Fe2+ ions at 563 K, and the effects of ion fluence, ion flux, and chemical composition on the change in the hardness distribution were examined. Heterogeneity of the hardening is observed in high-copper specimens irradiated up to (2–10) × 1014 ions/cm2, where the average hardness increases the most. In these specimens, the hardness distribution broadens, and demonstrates that the hardening in certain positions (possibly where the initial hardness is high) is greater than in other positions. Variation in initial chemical composition (especially copper and carbon) or sink strength may cause a difference in the curing behavior.

Thermal mineralization behavior of PFOA, PFHxA, and PFOS during reactivation of granular activated carbon (GAC) in nitrogen atmosphere.

Waste disposal site is one of the important sinks of chemicals. A significant amount of perfluoroalkyl and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexanoic acid (PFHxA) have been brought into it. Because of their aqueous solubility, PFASs are released to landfill effluent waters, from which PFASs are efficiently collected by adsorption technique using granular activated carbon (GAC). The exhausted GAC is reactivated by heating processes. The mineralization of PFASs during the reactivation process was studied. Being thermally treated in N2 atmosphere, the recovery rate of mineralized fluorine and PFC homologues including short-chained perfluorocarboxylic acids was determined. If the reagent form of PFOA, PFHxA, and PFOS were treated at 700°C, the recovery of mineralized fluorine was less than 30, 46, and 72%, respectively. The rate increased to 51, 74, and 70%, if PFASs were adsorbed onto GAC in advance; moreover, addition of excess sodium hydroxide (NaOH) improved the recovery to 74, 91, and 90%. Residual PFAS homologue was less than 1% of the original amount. Steamed condition did not affect destruction. The significant role of GAC was to suppress volatile release of PFASs from thermal ambient, whereas NaOH enhanced destruction and retained mineralized fluorine on the GAC surface. Comparing the recovery of mineralized fluorine, the degradability of PFOS was considered to be higher than PFOA and PFHxA. Whole mass balance missing 9~26% of initial amount suggested formation of some volatile organofluoro compounds beyond analytical coverage.