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1.
Nitrous oxide (N 2O) is a potent greenhouse gas. Mitigating N 2O emission is critical for combating global climate change and improving the ecological environment. Many studies have focused on factors affecting N 2O emission from agricultural soils, but rarely on the relationship among these factors. In the present study, continuous measurement on N 2O emission was conducted in a maize system in Griffith, Australia and the relationships between N 2O emission, soil properties and weather conditions were examined. Principal component analysis and path analysis were used to analyze these data in correlation coefficient and the direct and indirect effects to N 2O emission. Results indicated that (1) the major factors affecting N 2O emission were WFPS, mineralized nitrogen (Mineral N), daily mean temperature ( T mean) and CO 2 concentration. The factors of direct influence N 2O emission were following Mineral N, CO 2, WFPS, and T mean. The indirect influence N 2O emission was following T mean, WFPS, Mineral N, and CO 2 concentration. (2) The standard multiple regression describing the relationship between N 2O emission and its major factors were Y = ?37.162 + 0.5267 X 1 + 0.4331 X 2 + 0.3014 X 3 + 0.2392 X 4 ( r = 0.924, p < 0.01, n = 151), where Y is N 2O emission, X 1 is Mineral N, X 2 is CO 2, X 3 is WFPS and X 4 is T mean. (3) N 2O emission from agricultural soils can be monitored and mitigated through improved management practices such as irrigation, straw retention and fertilizer application. 相似文献
2.
Pressure dependence of Néel temperature ( T N) in (Mg 0.20Fe 0.80)O, (Mg 0.25Fe 0.75)O, and (Mg 0.30Fe 0.70)O was newly measured up to 1.14 GPa, using superconducting quantum interference device magnetometer and piston–cylinder-type pressure cell under hydrostatic condition. The d T N/d P values of (Mg 0.20Fe 0.80)O, (Mg 0.25Fe 0.75)O, and (Mg 0.30Fe 0.70)O were determined as 4.0 ± 0.3, 2.7 ± 0.3, and 4.4 ± 0.4 K/GPa, respectively, in linear approximation; however, the T N deviated from the linearity under nonhydrostatic conditions. The compositional dependence of d T N/d P in (Mg 1?X Fe X )O showed a rapid decay with increasing Mg components at X ≥ 0.75 and the trend ended at X = 0.70. The estimated Néel transition pressure at room temperature by extrapolating these linearities are very similar to the rhombohedral distortion determined by previous X-ray diffraction studies for X ≥ 0.75, which suggests that the rhombohedral phase of (Mg 1?X Fe X )O ( X ≥ 0.75) at room temperature is antiferromagnetic under hydrostatic conditions. 相似文献
3.
In this study, AERMOD dispersion model has been applied for predicting the values of ambient concentrations of NO 2 emissions due to the stacks of fourth gas refinery located in South Pars Gas Complex in Asaluyeh, Iran. First, the values of NO 2 emissions from the stacks and the amounts of ambient concentrations of NO 2 in nine monitoring stations have been measured in four seasons in 2013. Then, dispersion of NO 2 emissions has been predicted by using AERMOD model in the region with the domain area of 10 × 10 km 2, in average times of 1 h. Finally, the simulated and observed values of ambient NO 2 concentrations in the nine receptors have been compared. Comparison of 1-h concentrations of the observed and predicted results with the international ambient standard levels shows that NO 2 concentrations are higher than the standard value. The results show that AERMOD model can be used effectively for predicting the amounts of pollutants’ concentrations in the study area. 相似文献
4.
The 19th Common Wealth Games was organized at Delhi, India, during October 3 to 14, 2010, where more than 8,000 athletes from 71 Commonwealth Nations have participated. In order to give them better environment information for proper preparedness, mass concentrations of particulate matters below 10 microns (PM 10) and 2.5 microns (PM 2.5), black carbon (BC) particles and gaseous pollutants such as carbon monoxide (CO) and nitrogen oxide (NO) were monitored and displayed online for ten different locations around Delhi, including inside and outside the stadiums. This extensive information system for air quality has been set up for the period from September 24 to October 21, 2010, and data have been archived at 5-min interval for further research. During the study period, average concentration of PM 10 and PM 2.5 was observed to be 229.7 ± 85.5 and 112.1 ± 56.0 μg m ?3, respectively, which is far in excess of the corresponding annual averages, stipulated by the national ambient air quality standards. Significant large and positive correlation ( r = 0.93) between PM 10 and PM 2.5 implies that variations in PM 10 mass are governed by the variations in PM 2.5 mass. The mass concentrations of PM 2.5 inside the stadium were found to be ~18 % lower than those outside; however, no large variations were observed in PM 10. Mean concentrations of BC, CO and NO for the observation period were 10.9 μg m ?3 (Min, 02 μg m ?3; Max, 31 μg m ?3), 1.83 ± 0.89 ppm (Min, 0.48 ppm; Max, 4.55 ppm) and 37.82 ppb (Min, 2.4 ppb; Max, 206.05 ppb), respectively. BC showed positive correlation ( r = 0.73) with CO suggests unified source for both of them, mainly from combustion emissions. All the measured parameters, however, show a significant diurnal variation with enhanced peaks in the morning and late night hours and lower values during daytime. 相似文献
5.
Sulfur oxides (SOX) emissions embodied in trade (SEET) may play an important role in affecting national responsibilities toward pollutant emission reduction within the context of global greenhouse gas emission policy. This paper analyzes the change of the SEET associated with energy consumption from the perspective of a country and a sector between 1995 and 2011, exploring the evolution characteristic of the sources and flows of the SEET for 39 countries, as well as measuring the production-based and consumption-based global SOX emissions’ inventory and investigating the impact of international trade on the allocation of national pollutant emissions’ reduction obligations. One important finding is that the volume of SOX emissions embodied in global trade increased dramatically from 1995 to 2011, and the global SOX emissions stemming from anthropogenic energy consumption are mostly from China and the USA. Another important finding is that, referring to specific sectors, whether seen from the total SEET or from the sources of SEET or from the total SOX emissions occurring from economic consumption and production, energy sectors, like electricity, gas, and water supply and coke, refined petroleum, and nuclear fuel, are the main contributors to the increase in the global SOX emissions. Notably, however, our results show that the sector of agriculture, hunting, forestry, and fishing should be allocated more SOX emission reduction responsibilities under a consumption-based emissions’ accounting inventory.
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6.
Atmospheric dust is considered to be the major cause of poor air quality due to its contribution to high particulate levels, but their interaction with the acidic gases helps in controlling the level of SO 2 and NO 2 through ambient neutralization reactions. In the present study, the interaction of acidic gases such as SO 2 and NO 2 with alkaline dust was investigated during October, 2013–July, 2014 at a site named as Babarpur located at the Trans-Yamuna region of Delhi. The concentration of SO 2 ranged from 10 to 170 μg/m 3 with an average of 36 μg/m 3 while that of NO 2 ranged from 15 to 54 μg/m 3 with an average of 26?±?8 μg/m 3. The results were observed to be well within the National Ambient Air Quality Standard (NAAQS) limits prescribed by the Central Pollution Control Board (CPCB). The average concentrations of SO 2 during day and night time were recorded as 31?±?18 and 43?±?53 μg/m 3 respectively while the mean concentrations of NO 2 during day and night time were recorded as 26?±?7 and 27?±?12 μg/m 3 respectively. A positive correlation between SO 42? and NO 3? was also observed indicating their secondary aerosol formation. In aerosol phase, average concentrations of SO 42? during day and night time were 3.9?±?0.3 and 6.5?±?2.3 μg/m 3 respectively while that of NO 3? were 9.5?±?1.5 and 7.3?±?0.5 μg/m 3 respectively. Molar ratios of Ca 2+/SO 42?, NH 4+/SO 42?, and NH 4+/NO 3? were observed as 8, 5, and 1.7 during daytime and 1.5, 0.4, and 0.8 during nighttime respectively. Such molar ratios confirmed high concentrations of sulphate (SO 4) 2? and low concentrations of nitrate (NO 3?) during night time, thereby indicating different pathway of aerosol formation during day and night time. Surface morphology and elemental composition of aerosol samples showed various oval, globular, and platy shapes where the diameter varied from few nm to ~5 μm depending on their precursors. There were certain shapes like grossularite, irregular aggregate, grape-like, triangular, and flattened which indicate the crustal origin of aerosols and their possible role in SO 2 and NO 2 adsorption. 相似文献
7.
The experiment was conducted to ascertain net production and consumption rates of 15NH 4 + and 15NO 3 ? for water and sediment in a wetland. This was done using 15N isotope pool dilution methodology under ambient and elevated atmospheric CO 2 concentrations in experimental riparian wetlands to obtain the gross N transformation rates. The 15N budget for sediment was also estimated. The results suggested that the differences in high proportion of 15N concentration in the overlying water body under elevated CO 2 could be attributed to the low production and high consumption rates of 15NH 4 + in sediment. The elevated CO 2 effect on production and consumption of NH 4 + decreased by 144 % ( P = 0.014) and increased by 153 % ( P = 0.009), respectively. Thereby, 15NH 4 + production rates are negatively related with 15NO 3 ? consumption rates and this accounted for the decreases in net 15NO 3 ? consumption under CO 2 enrichment in the wetland sediment by 11 % ( P = 0.528). Therefore, 15NO 3 ? production and consumption rates may strongly depend on NH 4 + production. Inorganic 15N and total 15N exported from sediment to overlying water body by the effect of CO 2 were 41 % ( P = 0.071) and 18 % ( P = 0.000), respectively. Therefore, low net 15NH 4 + production and high 15NH 4 + consumption rates under elevated CO 2 may partly explain the significant reduction of N from the sediment. 相似文献
8.
Reverse dispersion modelling was employed to quantify sulphur dioxide (SO 2) and nitrogen dioxide (NO 2) emissions from brick firing clamp kilns and spontaneous combustion from a coal discard dump. Reverse dispersion modelling technique integrates ambient monitoring and dispersion simulation to calculate actual emission rates from an assumed rate of 1 g per second (g/s). Emission rates and emission factors were successfully quantified for SO 2, but not for NO 2, due to the influence of external sources and the complexity regarding the varying proportion of nitrogen oxides released from the kiln. Quantified emission factor for clamp kiln firing ranged from 1.91–3.24 g of SO 2 per brick fired and 0.67–1.14 g of SO 2 per kilogram of bricks fired. The variation in SO 2 emission factors was linked to high variability in energy input. The source configuration input to the dispersion model, assumed to represent the kiln, was changed from a volume source to a more effective “bi-point” source situated at the top of the kiln, with buoyancy calculated from the carbon combustion rate. In addition, SO 2 emission rate for spontaneous combustion from the discard dump was quantified as 0.35 g/s. 274 tons of discard material was estimated to burn annually, assuming that the emission rate is consistent over a year. Consequently, the reverse dispersion modelling and the elevated “bi-point” source technique may be considered a novel approach for quantifying emissions from combustion of materials or mixture of materials where knowledge of source parameters is limited. 相似文献
9.
Size distribution of PM 10 mass aerosols and its ionic characteristics were studied for 2 years from January 2006 to December 2007 at central Delhi by employing an 8-stage Andersen Cascade Impactor sampler. The mass of fine (PM 2.5) and coarse (PM 10?2.5) mode particles were integrated from particle mass determined in different stages. Average concentrations of mass PM 10 and PM 2.5 were observed to be 306 ± 182 and 136 ± 84 μg m ?3, respectively, which are far in excess of annual averages stipulated by the Indian National Ambient Air Quality Standards (PM 10: 60 μg m ?3 and PM 2.5: 40 μg m ?3). The highest concentrations of PM 10?2.5 (coarse) and PM 2.5 (fine) were observed 505 ± 44 and 368 ± 61 μg m ?3, respectively, during summer (June 2006) period, whereas the lower concentrations of PM 10?2.5 (35 ± 9 μg m ?3) and PM 2.5 (29 ± 13 μg m ?3) were observed during monsoon (September 2007). In summer, because of frequent dust storms, coarse particles are more dominant than fine particles during study period. However, during winter, the PM 2.5 contribution became more pronounced as compared to summer probably due to enhanced emissions from anthropogenic activities, burning of biofuels/biomass and other human activities. A high ratio (0.58) of PM 2.5/PM 10 was observed during winter and low (0.24) during monsoon. A strong correlation between PM 10 and PM 2.5 ( r 2 = 0.93) was observed, indicating that variation in PM 10 mass is governed by the variation in PM 2.5. Major cations (NH 4 +, Na +, K +, Ca 2+ and Mg 2+) and anions (F ?, Cl ?, SO 4 2? and NO 3 ?) were analyzed along with pH. Average concentrations of SO 4 2? and NO 3 ? were observed to be 12.93 ± 0.98 and 10.33 ± 1.10 μg m ?3, respectively. Significant correlation between SO 4 2? and NO 3 ? in PM 1.0 was observed indicating the major sources of secondary aerosol which may be from thermal power plants located in the southeast and incomplete combustion by vehicular exhaust. A good correlation among secondary species (NH +, NO 3 ? and SO 4 2?) suggests that most of NH 4 + is in the form of ammonium sulfate and ammonium nitrate in the atmosphere. During winter, the concentration of Ca 2+ was also higher; it may be due to entrainment of roadside dust particles, traffic activities and low temperature. The molar ratio (1.39) between Cl ? and Na + was observed to be close to that of seawater (1.16). The presence of higher Cl ? during winter is due to western disturbances and probably local emission of Cl ? due to fabric bleaching activity in a number of export garment factories in the proximity of the sampling site. 相似文献
10.
Hydrothermal experiments with H 2O-CO 2 fluids at Pfluid = 6 kbar yielded the following quilibrium conditions for reactions important in metamorphosed siliceous dolomites ( T = ° C; X = Xco2): (3) dolomite + 2 quartz = diopside + 2 CO 2T = 620 ± 8 X = 0.73 ± 0.03 (5) 5 dolomite + 8 quartz + H 2O = tremolite + 3 calcite + 7 CO 2T = 600 ± 5 550 ±5 540±5 500±5 X = 0.66 ± 0.03 0.21 ± 0.03 0.21 ± 0.04 0.06 ± 0.02 (7) 3 dolomite + 4 quartz + H 2O = talc + 3 calcite + 3 CO 2T = 550±5 500±5 450 ±5 X = 0.25 ± 0.05 0.07 ± 0.02 0.03 ± 0.02 (8) 2 dolomite + talc + 4 quartz = tremolite + 4 CO 2T = 550 ± 5 540 ±5 500 ± 5 X = 0.22 ± 0.03 0.21 ± 0.02 0.06 ± 0.02 A thermodynamically self-consistent 6 kbar T- XCO2, topology results by extrapolating equilibria from experimental brackets using a modified Redlich-Kwong equation for activities in H 2O-CO 2 mixtures. This topology restricts the assemblage talc + calcite to a narrow stability band in T- XCO2 space at XCO2 < 0.55 and T < 590° C. Accordingly, the occurrence of talc + calcite in pure siliceous dolomites metamorphosed at Pfluid = 6 kbar implies correspondingly water-rich fluids. 相似文献
11.
The ~ 570 Ma old Khantaishir ophiolite is built by up to 4 km harzburgitic mantle with abundant pyroxenites and dunites followed by ~ 2 km of hornblende-gabbros and gabbronorites and by a ~ 2.5 km thick volcanic unit composed of a dyke + sill complex capped by pillow lavas and some volcanoclastics. The volcanics are mainly basaltic andesites and andesites (or boninites) with an average of 58.2 ± 1.0 wt% SiO 2, X Mg = 0.61 ± 0.03 ( X Mg = molar MgO/(MgO + FeO tot), TiO 2 = 0.4 ± 0.1 wt% and CaO = 7.5 ± 0.6 wt% (errors as 2 σ). Normalized trace element patterns show positive anomalies for Pb and Sr, a negative Nb-anomaly, large ion lithophile elements (LILE) concentrations between N- and E-MORB and distinctly depleted HREE. These characteristics indicate that the Khantaishir volcanics were derived from a refractory mantle source modified by a moderate slab-component, similar to boninites erupted along the Izu-Bonin-Mariana subduction system and to the Troodos and Betts Cove ophiolites. Most strikingly and despite almost complete outcrops over 260 km 2, there is no remnant of any pre-existing MORB crust, suggesting that the magmatic suite of this ophiolite formed on completely denudated mantle, most likely upon subduction initiation. The architecture of this 4–5 km thick early arc crust resembles oceanic crust formed at mid ocean ridges, but lacks a sheeted dyke complex; volcanic edifices are not observed. Nevertheless, low melting pressures combined with moderate H 2O-contents resulted in high-Si primitive melts, in abundant hornblende-gabbros and in a fast enrichment in bulk SiO 2. Fractional crystallization modeling starting from the observed primitive melts (56.6 wt% SiO 2) suggests that 25 wt% pyroxene + plagioclase fractionation is sufficient to form the average Khantaishir volcanic crust. Most of the fractionation happened in the mantle, the observed pyroxenite lenses and layers in and at the top of the harzburgites account for the required cumulate volumes. Finally, the multiply documented occurrence of highly depleted boninites during subduction initiation suggests a causal relationship of subduction initiation and highly depleted mantle. Possibly, a discontinuity between dense fertile and buoyant depleted mantle contributes to the sinking of the future dense subducting plate, while the buoyant depleted mantle of the future overriding plate forms the infant mantle wedge. 相似文献
12.
Methane is one of the potential greenhouse gases contributing to global climate change, with a global warming potential of about 25 times than that of carbon dioxide. Aerobic methane oxidation (methanotrophy) is the key process that counteracts emission of methane to atmosphere. In this study, methane oxidation capacity of different methane-oxidizing bacteria (methanotrophs) isolated from six different ecosystems was investigated. Methanotrophic consortium isolated from dumpsite proved to be most effective in oxidizing methane. Initially, methane oxidation rate was found to be 0.72 ± 0.036 mM/day; in course of the study consortium M5 showed an increase in methane oxidation rate up to 1.7 ± 0.016 mM/day. A maximum of 0.78 mol of CO 2 production was found during methane oxidation in methanotrophs from dumpsite (M5). While varying temperatures, methane oxidation rate was in the range of 1.3–1.7 mM/day which has been found in the temperature range of 30–40 °C. Even at higher temperature (50 °C), 0.076 ± 0.14 mM of the methane was utilized per day. Methane oxidation was assessed by Michaelis–Menten kinetics. By varying the methane concentration, methane oxidation was studied and kinetic parameters such as V max and K m were derived using Lineweaver–Burk plot and found to be 1.497 mM/day and 2.23 mM, respectively. In methane mitigation approach, Methane soil sink is very essential because a balance between methane production by methanogens and consumption by methanotrophs plays an important role in methane emission reduction. Enhancing the methane soil sink will be a cost-effective method to cut down methane emission. 相似文献
13.
Biotreatment of methylparathion ( O, O-dimethyl- O-4-nitrophenyl phosphorothioate) was studied in aqueous mineral salts medium containing fungal culture to demonstrate the potential of the pure culture (monoculture) of Fusarium sp in degrading high concentration of methylparathion. A statistical Box–Behnken design of experiments was performed to evaluate the effects of individual operating variables and their interactions on the methylparathion removal with initial concentration of 1,000 mg/L as fixed input parameter. A full factorial Box–Behnken design of experiments was used to construct response surfaces with the removal, the extent of methylparathion biodegradation, removal of chemical oxygen demand and total organic carbon, and the specific growth rate as responses. The temperature ( X 1), pH ( X 2), reaction time ( X 3) and agitation ( X 4) were used as design variables. The result was shown that experimental data fitted with the polynomial model. Analysis of variance showed a high coefficient of determination value of 0.99. The maximum biodegradation of methylparathion in terms of the methylparathion removal ( Y 1), chemical oxygen demand removal ( Y 2) and total organic carbon removal ( Y 3) were found to be 92, 79.2 and 57.2 % respectively. The maximum growth in terms of dry biomass ( Y 4) was 150 mg/L. The maximum biodegradation corresponds to the combination of following factors of middle level of temperature ( X 1 = 30 °C), pH ( X 2 = 6.5), agitation ( X 4 = 120 rpm) and the highest level of reaction time ( X 3 = 144 h). The removal efficiency of methylparathion biodegradation was achieved 92 %. It was observed that optimum biotreatment of methylparathion can be successfully predicted by response surface methodology. 相似文献
14.
Open burning of scrap (bicycle, motorcycle, car and truck) tyres (OBST) was simulated in the laboratory to investigate their impact on the ambient air quality. The tyre samples were burnt in combustion chamber, and gaseous pollutants (CO, NO 2 and SO 2) emitted were quantified, while concentrations and elemental compositions of emitted total suspended particulates (TSP) were determined. Emission level of SO 2 from all the tyre samples exceeded USEPA allowable (156.74 µg/m 3) limit. CO due to car and truck tyres exceeded USEPA allowable (10,285.71 µg/m 3) limit, while NO 2 concentration was below the allowable limit (56.33 µg/m 3) only in bicycle tyre. 25% of all the gaseous pollutants emitted are within the Air Quality Index range of 101–150. TSP concentrations from all the tyre samples were higher than the Federal Ministry of Environment standard (250 µg/m 3) for ambient TSP. There is strong correlation ( R) of 0.885, 0.949 and 0.802 among all the gaseous (CO/NO 2, CO/SO 2 and NO 2/SO 2) pollutants, respectively, while the highest (0.999) and lowest (0.079) positive correlations were observed between Mg and Mn as well as Cd and Zn, respectively. The results of this study show that OBST emits hazardous pollutants, which pose serious threat to human health and environment. 相似文献
15.
While the Intergovernmental Panel on Climate Change classifies coal as anthracite, bituminous coal, and sub-bituminous coal, Korea only distinguishes coal as anthracite and bituminous coal while sub-bituminous coal is considered bituminous coal. As a result, Korea conducted research in the CO 2 emission factors of anthracite and bituminous coal, but largely ignored sub-bituminous coal. Therefore, the purpose of this research is to develop the CO 2 emission factor of sub-bituminous coal by classifying sub-bituminous coal from resources of bituminous coal activities collected in Korea between 2007 and 2011. The 2007–2011 average carbon content of sub-bituminous coal was analyzed to be 69.63 ± 3.11 %, the average hydrogen content 4.97 ± 0.37 %, the inherent moisture 12.60 ± 4.33 %, the total moisture 21.91 ± 5.45 %, and the dry-based gross calorific value was analyzed to be 5,914 ± 391 kcal/kg; using these analyzed values, the as-received net calorific value was found to be 20.75 ± 7.59 TJ/Gg and the CO 2 emission factor was found to be 96,241 ± 4,064 kg/TJ. In addition, the 62.7 million ton amount for the 2009 greenhouse gas emission from sub-bituminous coal as estimated with the analyzed value of this study is an amount that is equivalent to 11.1 % of the 2009 total greenhouse gas emission amount of 564.7 million tons, and this amount is larger than the 9.3 % for the industrial processes sector, 3.3 % for the agricultural sector and 2.5 % for the waste sector. Therefore, it is important to reflect the realities of Korea when estimating the greenhouse gas emission from such sub-bituminous coals. 相似文献
16.
High pressure in situ synchrotron X-ray diffraction experiment of strontium orthophosphate Sr 3(PO 4) 2 has been carried out to 20.0 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P– V data yields a volume of V 0 = 498.0 ± 0.1 Å 3, an isothermal bulk modulus of K T = 89.5 ± 1.7 GPa, and first pressure derivative of K T ′ = 6.57 ± 0.34. If K T ′ is fixed at 4, K T is obtained as 104.4 ± 1.2 GPa. Analysis of axial compressible modulus shows that the a-axis ( K a = 79.6 ± 3.2 GPa) is more compressible than the c-axis ( K c = 116.4 ± 4.3 GPa). Based on the high pressure Raman spectroscopic results, the mode Grüneisen parameters are determined and the average mode Grüneisen parameter of PO 4 vibrations of Sr 3(PO 4) 2 is calculated to be 0.30(2). 相似文献
17.
The Pan-African tectonothermal activities in areas near Sittampundi, south India, are characterized by metamorphic changes in an interlayered sequence of migmatitic metapelites, marble and calc-silicate rocks. This rock sequence underwent multiple episodes of folding, and was intruded by granite batholiths during and subsequent to these folding events. The marble and the calc-silicate rocks develop a variety of skarns, which on the basis of mineralogy; can be divided into the following types: Type I: wollastonite?+?clinopyroxene (mg#?=?71–73)?+?grandite (16–21 mol% Adr)?+?quartz?±?calcite, Type II: grandite (25–29 mol% Adr )?+?clinopyroxene (mg#?=?70)?+?calcite? +?quartz, and Type III: grandite (36–38 mol% Adr)?+?clinopyroxene (mg#?=?55–65)?+?epidote?+?scapolite?+?calcite?+?quartz. Type I skarn is 2–10 cm thick, and is dominated by wollastonite ( >70 vol%) and commonly occurs as boudinaged layers parallel to the regional foliation Sn 1 related to the Fn 1 folds. Locally, thin discontinuous lenses and stringers of this skarn develop along the axial planes of Fn 2 folds. The Type II skarn, on the other hand, is devoid of wollastonite, rich in grandite garnet (40–70 vol%) and developed preferentially at the interface of clinopyroxene-rich calc-silicates layers and host marble during the later folding event. Reaction textures and the phase compositional data suggest the following reactions in the skarns: 1. calcite?+?SiO 2?→?wollastonite?+?V, 2. calcite?+?clinopyroxene?+?O 2?→?grandite?+?SiO 2?+?V, 3. scapolite?+?calcite?+?quartz?+?clinopyroxene?+?O 2?→?grandite?+?V and 4. epidote?+?calcite?+?quartz?+?clinopyroxene?+?O 2?→?grandite?+?V Textural relations and composition of phases demonstrate that (a) silica metasomatism of the host marble by infiltration of aqueous fluids (X CO2?<?0.15) led to production of large volumes of wollastonite in the wollastonite-rich skarn whereas mobility of FeO, SiO 2 and CaO across the interface of marble and calc-silicate and infiltration of aqueous fluids (X CO2?<?0.35) were instrumental for the formation of grandite skarns. Composition of minerals in type II skarn indicates that Al 2O 3 was introduced in the host marble by the infiltrating fluid. Interpretation of mineral assemblages observed in the interlayered metapelites and the calcareous rocks in pseudosections, isothermal P-X CO2 and isobaric T-X CO2 diagrams tightly bracket the “peak” metamorphic conditions at c.9?±?1 kbar and 750°?±?30°C. Subsequent to ‘peak’ metamorphic conditions, the rocks were exhumed on a steeply decompressive P–T path. The estimated ‘peak’ P–T estimates are inconsistent with the “extreme” metamorphic conditions (>11 kbar and >950°C) inferred for the Pan-African tectonothermal events from the neighboring areas. Field and petrological attributes of these skarn rocks are consistent with the infiltration of aqueous fluid predominantly during the Fn 1 folding event at or close to the ‘peak’ metamorphic conditions. Petrological features indicate that the buffering capacity of the rocks was lost during the formation of type I and II skarns. However, the host rock could buffer the composition of the permeated fluids during the formation of type III skarn. Aqueous fluids derived from prograde metamorphism of the metapelites seem to be the likely source for the metasomatic fluids that led to the formation of the skarn rocks. 相似文献
18.
Pollution from urban centers and fossil fuel combustion can decrease forest growth and interfere with physiological processes. To evaluate whether tree growth and the carbon isotope ratio (δ 13C) and nitrogen isotope ratio (δ 15N) in tree rings can serve as proxies for air pollution, this study compared these indices for poplar ( Populus cathayana) growing at urban and suburban locations in Lanzhou, in northwestern China. Basal area increment values were much lower at the urban site than in the suburbs from 1985 to 2009, were negatively correlated with NO 2 ( r = ?0.56, p < 0.01) and SO 2 ( r = ?0.52, p < 0.05) emissions from 1990 to 2009, and increased abruptly after the Lanzhou urban steel factory closed. Urban tree-ring δ 13C values were not significantly correlated with NO 2 and SO 2 concentrations, and did not differ significantly between the two sites, indicating that other environmental effects (such as precipitation) masked the pollution effects. Tree-ring δ 15N values in the urban samples were much higher than the suburban values. Such differences may be attributable to uptake of 15N-enriched compounds caused by a higher urban N deposition rate. Tree growth is a promising tool for detecting ecophysiological responses of trees to both diffuse and point-source air pollution, but δ 13C and δ 15N in poplar were not sensitive to point-source air pollution in a heavily polluted environment. 相似文献
19.
The objective of the study is to investigate spatio-temporal variations of PM 10, PM 2.5, and PM 1 concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM 10 in the range 215 ± 169–526 ± 412 μg m ?3, PM 2.5 in the range of 91 ± 79–297 ± 107 μg m ?3, PM 1 in the range of 68 ± 60–247 ± 84 μg m ?3 were obtained. Coarse fractions (PM 2.5–10) varied from 27 to 58% whereas fine fractions (PM 1–2.5 and PM 1) varied in the range of 51–73%. PM 2.5 concentration was 41–74% of PM 10 concentration, PM 1 concentration was 31–62% of PM 10 concentration, and PM 1 concentration was 73–83% of PM 2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM 10, PM 2.5, PM 1, CO, CO 2) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area. 相似文献
20.
Based on data from ground-based air quality stations, space–time variations of six principal atmospheric pollutants, such as particulate matter (PM 2.5 and PM 10) and gas pollutants (SO 2, NO 2, СО, and O 3), obtained from January 1, 2014 to December 31, 2017 in the city of Lanzhou, have been studied. Average total concentrations of PM 2.5 and PM 10 were 53.2?±?26.91 and 124.54?±?82.33 µg/m 3, respectively; however, the results showed that in 75.53% and 84.85% days, concentrations of these pollutants exceeded Chinese National Ambient Air Quality Standard and in 100% days exceeded World Health Organization guidelines standards. Daily mean values of aerosol optical depth and Ångström exponent based on data, received by satellite Moderate Resolution Imaging Spectroradiometer, show a broad range of values for aerosol optical depth (from 0.018 to 1.954) and Ångström exponent (from 0.003 to 1.8). Results of principal components analysis revealed three factor loadings. Thus, Factor 1 has the relevant loadings for PM 2.5, PM 10, CO, SO 2, and NO 2 (36%) and closely associated with transport emissions and industrial sources, which contribute to air pollution in Lanzhou. Factor 2 was heavily loaded with temperature and visibility (16.94%). Factor 3 consisted of relative humidity (14.11%). Cluster analysis revealed four subgroups: cluster 1 (PM 2.5, NO 2, SO 2), cluster 2 (CO), cluster 3 (PM 10) and cluster 4 (relative humidity, visibility, temperature, O 3, wind speed), which were compliant with results, obtained from principal components analysis. Positive correlation was found among all pollutants, other than O 3. According to processed backward trajectories obtained by Hybrid Single-Particle Lagrangian Integrated Trajectory model, it was found that movement of air masses occur from north, northwest, and west directions—the location of principal natural sources of aerosols. 相似文献
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