Combustion-derived black carbon (BC) aerosols accelerate glacier melting in the Himalayas and in Tibet (the Third Pole (TP)), thereby limiting the sustainable freshwater supplies for billions of ...people. However, the sources of BC reaching the TP remain uncertain, hindering both process understanding and efficient mitigation. Here we present the source-diagnostic Δ(14)C/δ(13)C compositions of BC isolated from aerosol and snowpit samples in the TP. For the Himalayas, we found equal contributions from fossil fuel (46±11%) and biomass (54±11%) combustion, consistent with BC source fingerprints from the Indo-Gangetic Plain, whereas BC in the remote northern TP predominantly derives from fossil fuel combustion (66±16%), consistent with Chinese sources. The fossil fuel contributions to BC in the snowpits of the inner TP are lower (30±10%), implying contributions from internal Tibetan sources (for example, yak dung combustion). Constraints on BC sources facilitate improved modelling of climatic patterns, hydrological effects and provide guidance for effective mitigation actions.
Emissions from biomass burning contribute significantly to water-soluble organic carbon (WSOC) and light-absorbing organic carbon (brown carbon). Ambient atmospheric samples were collected at an ...urban site in Beijing during winter and summer, along with source samples from residential crop straw burning. Carbonaceous aerosol species, including organic carbon (OC), elemental carbon (EC), WSOC and multiple saccharides as well as water-soluble potassium (K+) in PM2.5 (fine particulate matter with size less than 2.5 μm) were measured. Chemical signatures of atmospheric aerosols in Beijing during winter and summer days with significant biomass burning influence were identified. Meanwhile, light absorption by WSOC was measured and quantitatively compared to EC at ground level. The results from this study indicated that levoglucosan exhibited consistently high concentrations (209 ± 145 ng m−3) in winter. Ratios of levoglucosan/mannosan (L/M) and levoglucosan/galacosan (L/G) indicated that residential biofuel use is an important source of biomass burning aerosol in winter in Beijing. Light absorption coefficient per unit ambient WSOC mass calculated at 365 nm is approximately 1.54 ± 0.16 m2 g−1 in winter and 0.73 ± 0.15 m2 g−1 in summer. Biomass burning derived WSOC accounted for 23 ± 7% and 16 ± 7% of total WSOC mass, and contributed to 17 ± 4% and 19 ± 5% of total WSOC light absorption in winter and summer, respectively. It is noteworthy that, up to 30% of total WSOC light absorption was attributed to biomass burning in significant biomass-burning-impacted summer day. Near-surface light absorption (over the range 300–400 nm) by WSOC was about ∼40% of that by EC in winter and ∼25% in summer.
•High and relatively stable levoglucosan concentrations were found in Beijing in winter.•Light absorption from biomass burning to WSOC was evaluated in Beijing.•Light absorption (300–400 nm) by WSOC relative to EC was ∼40% (winter) and ∼25% (summer).•Residential biomass burning is non-negligible source to fine PM in Beijing winter.
Organic aerosol (OA) constitutes a substantial fraction of fine particles and affects both human health and climate. It is becoming clear that OA absorbs light substantially (hence termed Brown ...Carbon, BrC), adding uncertainties to global aerosol radiative forcing estimations. The few current radiative-transfer and chemical-transport models that include BrC primarily consider sources from biogenic and biomass combustion. However, radiocarbon fingerprinting here clearly indicates that light-absorbing organic carbon in winter Beijing, the capital of China, is mainly due to fossil sources, which contribute the largest part to organic carbon (OC, 67 ± 3%) and its sub-constituents (water-soluble OC, WSOC: 54 ± 4%, and water-insoluble OC, WIOC: 73 ± 3%). The dual-isotope (Δ
C/δ
C) signatures, organic molecular tracers and Beijing-tailored emission inventory identify that this fossil source is primarily from coal combustion activities in winter, especially from the residential sector. Source testing on Chinese residential coal combustion provides direct evidence that intensive coal combustion could contribute to increased light-absorptivity of ambient BrC in Beijing winter. Coal combustion is an important source to BrC in regions such as northern China, especially during the winter season. Future modeling of OA radiative forcing should consider the importance of both biomass and fossil sources.
The dual carbon isotope signatures and optical properties of carbonaceous aerosols have been investigated simultaneously for the first time in the South Asian outflow during an intensive campaign at ...the Maldives Climate Observatory on Hanimaadhoo (MCOH) (February and March 2012). As one component of the Cloud Aerosol Radiative Forcing Dynamics Experiment, this paper reports on the sources and the atmospheric processing of elemental carbon (EC) and water‐soluble organic carbon (WSOC) as examined by a dual carbon isotope approach. The radiocarbon (Δ14C) data show that WSOC has a significantly higher biomass/biogenic contribution (86 ± 5%) compared to EC (59 ± 4%). The more 13C‐enriched signature of MCOH‐WSOC (−20.8 ± 0.7‰) compared to MCOH‐EC (−25.8 ± 0.3‰) and megacity Delhi WSOC (−24.1 ± 0.9‰) suggests that WSOC is significantly more affected by aging during long‐range transport than EC. The δ13C‐Δ14C signal suggests that the wintertime WSOC intercepted over the Indian Ocean largely represents aged primary biomass burning aerosols. Since light‐absorbing organic carbon aerosols (Brown Carbon (BrC)) have recently been identified as potential contributors to positive radiative forcing, optical properties of WSOC were also investigated. The mass absorption cross section of WSOC (MAC365) was 0.5 ± 0.2 m2 g−1 which is lower than what has been observed at near‐source sites, indicating a net decrease of WSOC light‐absorption character during long‐range transport. Near‐surface WSOC at MCOH accounted for ~1% of the total direct solar absorbance relative to EC, which is lower than the BrC absorption inferred from solar spectral observations of ambient aerosols, suggesting that a significant portion of BrC might be included in the water‐insoluble portion of organic aerosols.
Key Points
Fossil fuel contribution to PM2.5 EC and WSOC is 41% and 14% respectivelyAerosol LRT leads to 13C enrichment and a less absorbing WSOC aerosolWSOC accounts for only ~ 1% of direct solar absorbance relative to EC
Industrial chlorinated solvents continue to be among the most significant issues in groundwater (GW) pollution worldwide. This study assesses the effectiveness of eight novel oxidation treatments, ...including persulfate (PS), ferrous sulfate, sulfidated nano-zero valent iron (S-nZVI), and potassium ferrate, along with their combinations, for the potential in situ remediation of GW polluted with chlorinated solvents (1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene). Our bench-scale results reveal that the combined addition of PS and S-nZVI can effectively eliminate trichloroethylene (10 µg/L), achieving removal rates of up to 80% and 92% within 1 h, respectively, when using synthetic GW. In the case of real GW, this combination achieved removal rates of 69, 99, and 92% for cis-1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene, respectively, within 24 h. Therefore, this proposed remediation solution resulted in a significant reduction in the environmental risk quotient, shifting it from a high-risk (1.1) to a low-risk (0.2) scenario. Furthermore, the absence of transformation products, such as vinyl chloride, suggests the suitability of employing this solution for the in situ remediation of GW polluted with chlorinated solvents.
Black carbon (BC) aerosols impact climate and air quality. Since BC from fossil versus biomass combustion have different optical properties and different abilities to penetrate the lungs, it is ...important to better understand their relative contributions in strongly affected regions such as South Asia. This study reports the first year-round 14C-based source apportionment of elemental carbon (EC), the mass-based correspondent to BC, using as regional receptor sites the international Maldives Climate Observatory in Hanimaadhoo (MCOH) and the mountaintop observatory of the Indian Institute of Tropical Meteorology in Sinhagad, India (SINH). For the highly-polluted winter season (December-March), the fractional contribution to EC from biomass burning (fbio) was 53 5% (n = 6) at MCOH and 56 3% at SINH (n = 5). The fbio for the non-winter remainder was 53 11% (n = 6) at MCOH and 48 8% (n = 7) at SINH. This observation-based constraint on near-equal contributions from biomass burning and fossil fuel combustion at both sites compare with predictions from eight technology-based emission inventory (EI) models for India of (fbio)EI spanning 55-88%, suggesting that most current EI for Indian BC systematically under predict the relative contribution of fossil fuel combustion. A continued iterative testing of bottom-up EI with top-down observational source constraints has the potential to lead to reduced uncertainties regarding EC sources and emissions to the benefit of both models of climate and air quality as well as guide efficient policies to mitigate emissions.
Thermal degradation of individual glucosinolates within the plant matrix was studied. Red cabbage samples were heated at different temperatures for various times. To rule out the influence of ...enzymatic breakdown and to focus entirely on the thermal degradation of glucosinolates, myrosinase was inactivated prior to the thermal treatments. All identified glucosinolates degradation when heated at temperatures above 100
°C. The indole glucosinolates 4-hydroxy-glucobrassicin and 4-methoxyglucobrassicin showed the highest degree of showed degradation, even at temperatures below 100
°C.
Kinetic parameters have been estimated for the degradation that could be described by first-order kinetics. At temperatures below 110
°C indole glucosinolates have a significant higher degradation rate constant as compared to aliphatic glucosinolates. The breakdown of 4-hydroxyglucobrassicin seems to consist of two parallel reaction pathways. Based on the proposed degradation kinetics and the estimated parameters, the degree of thermal degradation of all individual glucosinolates at standardized heating conditions (blanching, cooking and canning) was simulated. Glucosinolates are expected to be not very susceptible to thermal degradation during blanching conditions. Cooking will cause more thermal degradation to indole glucosinolates (38%) as compared to aliphatic glucosinolates (8%). Canning, the most severe heat treatment, will result in significant thermal degradation (73%) of the total amount of glucosinolates.
Introducción: La popularidad de que gozan las bebidas energéticas entre los adolescentes y jóvenes, ha aumentado en los últimos años. El aumento del consumo entre los estudiantes motivó el diseño de ...un taller educativo en un grupo de adolescentes, con el objetivo de aumentar el nivel de conocimientos sobre las características de estos refrescos y sobre sus posibles efectos para la salud; así como de evaluar el impacto del taller respecto a estos conocimientos.Material y Métodos: Se realizó un estudio de intervención con evaluación pre- y post- intervención en un instituto de Manresa, Barcelona. Se aplicó un cuestionario de conocimientos sobre las Bebidas Energéticas antes y después de realizar un taller educativo, en el que se emplearon técnicas de enseñanza afines a los Estilos de Aprendizaje preferentes de los participantes.Resultados: Las técnicas de enseñanza, correspondieron a las estrategias preferentes para los estilos auditivo (32,3%) y quinestésico (23,7%) predominantes en el colectivo. En la evaluación previa: el 76,3% de los adolescentes definen las Bebidas Energéticas como isotónicas para deportistas, la mayoría reconocen su elevado contenido en cafeína (95%), el 61,3% considera que aportan energía para el deporte, el 76,3% que pueden provocar nerviosismo y el 28% creen que no han de ser consumidas por adolescentes. En la evaluación posintervención aumentó el número de estudiantes que respondió correctamente en todas las preguntas del cuestionario.Conclusiones: Un gran número de adolescentes tiene poco o nulo conocimiento sobre las características de las bebidas energéticas y las consecuencias de su consumo para la salud, que mejora significativamente tras la realización de un taller a través de técnicas de enseñanza participativas y cooperativas afines a las estrategias de aprendizaje preferente de los participantes.
Comentarios de erudición (libro decimosexto) Bartolomé Jiménez Patón / María del Carmen Bosch, Jaime Garau, Abraham Madroñal, Juan Miguel Monterrubio / María del Carmen Bosch, Jaime Garau, Abraham Madroñal, Juan Miguel Monterrubio
2011
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