Seasonal characteristics of biogenic secondary organic aerosol tracers in a deciduous broadleaf forest in northern Japan.

We collected total suspended particulate (TSP) samples from January 2010 to December 2010 at Sapporo deciduous forest to understand the oxidation processes of biogenic volatile organic compounds (BVOCs). The gas chromatography-mass spectrometric technique was applied to determine biogenic secondary organic aerosols (BSOAs) in the TSP samples. We found the predominance of the isoprene SOA (iSOA) tracers (20.6 ng m-3) followed by α/ß-pinene SOA (pSOA) tracers (8.25 ng m-3) and ß-caryophyllene SOA (cSOA) tracer (1.53 ng m-3) in the forest aerosols. The results showed large isoprene fluxes and relatively high levels of oxidants in the forest atmosphere. The iSOA and pSOA tracers showed a clear seasonal trend with summer and autumn maxima and winter and spring minima. Their seasonal trends were mainly controlled by BVOCs emission from the local broadleaf deciduous forest. Additionally, the regional level of isoprene emissions from the oceanic sources may also be contributed during summertime aerosols. cSOA tracer showed high concentrations in the winter and spring, possibly due to an additional contribution of biomass burning (BB) aerosols from the local or regional BB activities. The biogenic secondary organic carbon (BSOC) was contributed mainly by the oxidation products of isoprene (136 ngC m-3) followed by ß-caryophyllene (63.0 ngC m-3) and α/ß-pinene (35.9 ngC m-3). The mass concentration ratio (0.92) of pinonic acid + pinic acid and 3-methyl-1,2,3-butanetricarboxylic acid ((PNA + PA)/3-MBTCA) indicates the photochemical transformation of first-generation oxidation products to the higher generation oxidation products. The average ratios of isoprene to α/ß-pinene (1.64) and ß-caryophyllene (18.6) oxidation products suggested a large difference in the emissions of isoprene and α/ß-pinene compared to ß-caryophyllene. The cSOA tracers in the forest aerosols are also contributed by BB during the winter and spring. Positive matrix factorization analyses of the BSOA tracers confirmed that organic aerosols of deciduous forests are mostly related to isoprene emissions. This study suggests that isoprene is a more significant precursor for the BSOA than α/ß-pinene and ß-caryophyllene in a broadleaf deciduous forest.

The long-term spatial and temporal distribution of aerosol optical depth and its associated atmospheric circulation over Southeast Africa.

Recent studies have revealed significant impact of anthropogenic aerosols to both climate and human health. Even though significant efforts have been made across the globe, studies related to aerosols over Southeast Africa remain scanty, hence causing high uncertainty in predicting and understanding the impacts of these aerosols. The present study therefore analyzed long-term spatial and temporal distribution of aerosol optical depth at 550 nanometer wavelength (AOD550) over the entire Southeast Africa. Relatively low AOD550 has been detected over the region in comparison to highly polluted regions across the globe. The highest annual average (>0.2) was observed over Lake Malawi, Zambezi valley, and the coastal areas of Central Mozambique while low annual values were recorded over northeast of Mozambique, and the eastern areas of Zimbabwe. In terms of seasonality, AOD550 was observed to be high (>0.3) during the dry months of September-October-November (SON) while being low (<0.1) during March-April-May (MAM) and June-July-August (JJA) in most areas. The seasonality of AOD550 was observed to be highly influenced by changes in seasonal biomass burning and seasonal atmospheric circulation. Statistical analyses revealed an insignificant change of AOD550 between 2002 and 2020 in most areas of the study domain. Regional open burning of biomass like bush fires and burning of crop residues during the dry months are the main sources of aerosol concentration. Therefore, the present study advocates the regulation and institutionalization of proactive and strategic mechanisms that curtail open burning activities within the region.

Seasonal and temporal variations of ambient aerosols in a deciduous broadleaf forest from northern Japan: Contributions of biomass burning and biological particles.

Total suspended particulate (TSP) samples were collected in a deciduous broadleaf forest in Sapporo, Hokkaido, Japan, from January to December 2010 to understand the molecular composition and abundance of sugar compounds (SCs) in atmospheric aerosols. We analyzed the samples for anhydrosugars, primary sugars, and sugar alcohols using a gas chromatograph-mass spectrometer. The annual mean concentrations of total SCs ranged from 16.1 to 1748 ng m-3 (avg. 311 ng m-3) with maxima in spring (avg. 484 ng m-3) and minima in winter (avg. 28.2 ng m-3). Primary sugars and sugar alcohols followed the seasonal pattern of total SCs. High levels of anhydrosugars in winter (avg. 22.9 ng m-3) suggest a contribution of biomass burning from domestic heating due to lower ambient temperature. The high levels of arabitol and mannitol in spring followed by summer and autumn denote the contribution from multiple sources, i.e., growing vegetation and fungal spores in Sapporo forest. We observed an enhanced contribution of bioaerosols emitted from plant blossoms in spring and leaf decomposition in autumn. The identical seasonal trends of glucose and trehalose implied their similar sources in forest aerosols. Conversely, the highest concentration of sucrose in spring was due to the pollen emissions by blooming plants. Positive matrix factorization (PMF) analyses of the SCs suggested that organic aerosols in the deciduous forest are associated with the emissions from multiple sources, including vegetation, microbes, pollens, and wintertime biomass burning. The PMF analysis also suggested that vegetation is the primary carbon source in the forest atmosphere. The diagnostic mass ratios of levoglucosan to mannosan demonstrated the dominance of softwood burning. We noted that the meteorological parameters substantially affect the emission sources and seasonal concentrations of SCs in the deciduous forest.

Emission factors and global warming potential as influenced by fertilizer management for the cultivation of rice under varied growing seasons.

Greenhouse gas (GHG) emissions from paddy fields are intensified during rice production, and are generally reported based on single or double cropping. It needs to be known how emission factors, GHG emission patterns, and global warming potential are affected by growing three rice crops yearly under the principle of integrated plant nutrient system fertilization (IPNSF). Cowdung and vermicompost were used as IPNSF and compared with commercial fertilization alone. A static close chamber technique was used to measure GHG emissions. The peak periods of CH4 emissions were 20-37, 22-42, and 19-38 days after transplanting during dry, wet, and premonsoon seasons, respectively. The use of cow dung significantly enhanced total N2O, CH4, and CO2 fluxes by 5-10%, 15-23%, and 9-20%, respectively, compared to vermicompost. CH4 emissions for each kg grain production were 39-80, 45-63, and 43-57 gm in the dry, premonsoon, and wet seasons, respectively. Vermicompost significantly reduced CH4, CO2, and N2O fluxes by 13-19%, 17-21%, and 4-9%, respectively, along with a reduction in GHG emission factors by 8-17% and global warming potential by 13-17% compared to cow dung. Moreover, vermicompost and cow dung significantly improved rice grain yields in all three growing seasons compared to commercial fertilizer alone. In conclusion, the use of vermicompost as an IPNSF could be a viable technique for improving grain yield and for reducing GHG emissions from paddy fields during year-round rice cultivation.

Regional haze formation enhanced the atmospheric pollution levels in the Yangtze River Delta region, China: Implications for anthropogenic sources and secondary aerosol formation.

High-time-resolution (3-hour) PM2.5 samples were collected simultaneously from the rural and urban areas in the Yangtze River Delta region during winter. The aerosol samples were analyzed for carbonaceous components, organic tracers, water-soluble inorganic ions and stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions of total carbon and total nitrogen. The values of PM2.5 and secondary organic carbon (SOC) for both sampling sites were observed 2 times higher in haze events compare to those in clear days, implying severe pollution occurred by photochemical oxidation during haze periods. The PM mass of rural samples showed similar temporal trend and significant correlation with the urban PM, reflecting pollution sources or their formation process are most likely identical. Diurnal variations of PM2.5 and carbonaceous components revealed that pollution levels increased at daytime due to the photochemical oxidation. In addition, SOC and OC were influenced by the relative humidity (RH%) and temperature (T °C), indicating that such meteorological factors play important roles in the occurrence of regional air pollution. The concentrations of levoglucosan, polycyclic aromatic hydrocarbons, hopanes, and n-alkanes were 625 ± 456 and 519 ± 301 ng m-3, 32.6 ± 24.7 and 28.7 ± 20.1 ng m-3, 1.83 ± 1.51 and 1.26 ± 1.34 ng m-3, and 302 ± 206 and 169 ± 131 ng m-3 for rural and urban samples, respectively. Levoglucosan is the most abundant organic compounds, exhibited 2-3 times higher in haze than clear days, suggesting biomass burning (BB) emission substantially affects the haze pollution in winter. Furthermore, NO3- was the dominant ionic species followed by SO42-, NH4+, Cl- and other minor species for both sites. The δ13C and δ15N values demonstrate that anthropogenic activities such as fossil fuel combustion and BB are the major sources for carbonaceous and nitrogenous aerosols. This study implies that both the regional anthropogenic emissions and meteorological conditions influenced the regional haze formation, leading enhancement of pollution levels in eastern China during winter.

Effective Suppression of Methane Emission by 2-Bromoethanesulfonate during Rice Cultivation.

2-bromoethanesulfonate (BES) is a structural analogue of coenzyme M (Co-M) and potent inhibitor of methanogenesis. Several studies confirmed, BES can inhibit CH4 prodcution in rice soil, but the suppressing effectiveness of BES application on CH4 emission under rice cultivation has not been studied. In this pot experiment, different levels of BES (0, 20, 40 and 80 mg kg-1) were applied to study its effect on CH4 emission and plant growth during rice cultivation. Application of BES effectively suppressed CH4 emission when compared with control soil during rice cultivation. The CH4 emission rates were significantly (P<0.001) decreased by BES application possibly due to significant (P<0.001) reduction of methnaogenic biomarkers like Co-M concentration and mcrA gene copy number (i.e. methanogenic abunadance). BES significantly (P<0.001) reduced methanogen activity, while it did not affect soil dehydrogenase activity during rice cultivation. A rice plant growth and yield parameters were not affected by BES application. The maximum CH4 reduction (49% reduction over control) was found at 80 mg kg-1 BES application during rice cultivation. It is, therefore, concluded that BES could be a suitable soil amendment for reducing CH4 emission without affecting rice plant growth and productivity during rice cultivation.

Long-term (2001-2012) observation of the modeled hygroscopic growth factor of remote marine TSP aerosols over the western North Pacific: impact of long-range transport of pollutants and their mixing states.

In order to assess the seasonal and annual variability of long-range transported anthropogenic pollutants from East Asia and their effect on the hygroscopicity and precipitation process over the western North Pacific, we conducted long-term calculations of bulk hygroscopicity, g(90%)ZSR, based on the ZSR model using chemical composition data from 2001-2012 at Chichijima Island. We found that sea-salts (Na(+) and Cl(-)) are the major mass fraction (65%) of the total water-soluble matter followed by SO4(2-) (20%) and WSOM (6%). The seasonal variation of g(90%)ZSR was high in summer to autumn and low in winter to spring months, probably due to the influence of the long-range transport of anthropogenic SO4(2-), dust, and organics from East Asia and their interaction with sea-salts through heterogeneous reactions. On the other hand, annual variations of g(90%)ZSR showed a decrease from 2001 to 2006 and then an increase from 2007 to 2012. Interestingly, the annual variations in SO4(2-) mass fractions showed an increase from 2001 to 2006 and then a decrease from 2007 to 2012, demonstrating that SO4(2-) seriously suppresses the hygroscopic growth of sea-salt particles over the western North Pacific. This is further supported by the strong negative correlation between SO4(2-) and g(90%)ZSR. Based on the MODIS satellite data, the present study demonstrates that long-range transported anthropogenic pollutants from East Asia to the North Pacific can act as efficient cloud condensation nuclei but significantly suppress the precipitation by reducing the size of cloud droplets over the western North Pacific.

C and N accumulations in soil aggregates determine nitrous oxide emissions from cover crop treated rice paddy soils during fallow season.

Combination of leguminous and non-leguminous plant residues are preferably applied in rice paddy soils to increase the rate of organic matter mineralization and to improve plant growth. However, organic matter addition facilitates methane (CH4) emission from rice paddy soil. Mineralization of organic nitrogen (N) increases NO3-N concentrations in soil, which are precursors for the formation of nitrous oxide (N2O). However, N2O is a minor greenhouse gas emitted from submerged rice field and hence is not often considered during calculation of total global warming potential (GWP) during rice cultivation. The hypothesis of this study was that fluxes of N2O emissions might be changed after removal of flooded water from rice field and the effect of cover crops on N2O emissions in the fallow season might be interesting. However, the effects of N-rich plant residues on N2O emission rates in the fallow season and its effect on annual GWP were not studied before. In this experiment, combination of barley (non-leguminous) and hairy vetch (leguminous) biomasses were applied at 9 Mg ha(-1) and 27 Mg ha(-1) rates in rice paddy soil. Cover crop application significantly increased CH4 emission flux while decreased N2O emissions during rice cultivation. The lowest N2O emission was observed in 27 Mg ha(-1) cover crop treated plots. Cover crop applications increased N contents in soil aggregates especially in smaller aggregates (<250 µm), and that proportionately increased the N2O emission potentials of these soil aggregates. Fluxes of N2O emissions in the fallow season were influenced by the N2O emission potentials of soil aggregates and followed opposite trends as those observed during rice cultivation. Therefore, it could be concluded that the doses of cover crop applications for rice cultivation should not be optimized considering only CH4, but N2O should also be considered especially for fallow season to calculate total GWP.

Secondary metabolites from the stem of Ravenia spectabilis Lindl.

BACKGROUND: Ravenia spectabilis is a medium tall shrub found widespread in South America. It also found in India, Pakistan, Bangladesh etc. Few alkaloid and steroid compounds were reported from the plant previously. MATERIALS AND METHODS: Methanol extract from the stems of Ravenia spectabilis were partitioned into n-hexane, carbon tetrachloride, chloroform and aqueous soluble fractions, respectively. The crude methanol extract, carbon tetrachloride fraction and chloroform fraction were fractionated by column chromatography of Silica gel and Sephadex LH-20 for isolation and purification of compounds. The structures of the isolated compounds were determined by extensive NMR spectral analysis, including 2D NMR, mass spectroscopy etc. RESULTS: Ten compounds, γ-fagarine (1), ravenoline (2), N-methyl atanine (3),2,3,3,5-tetramethyl-2,3,4,5- tetrahydrofurano [3,2-c] quinolin-4-one (4), arborinine (5), 3-geranyl indole (6), atanine (7), steroids sitosta-4-en- 3-one (8), stigmasterol (9) and 3-methoxy-4-hydroxy cinnamic acid (10) were isolated from the stems of Ravenia spectabilis. CONCLUSION: Compounds N-methyl atanine (3), 2,3,3,5-tetramethyl-2,3,4,5-tetrahydrofurano [3,2-c] quinolin-4-one (4), 3-geranyl indole (6), sitosta-4-en-3-one (8) and 3-methoxy-4-hydroxy cinnamic acid (10) were isolated from this plant for the first time. 3-geranyl indole (6) was also isolated second time from natural sources.