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1.
Suspended particulate matter (SPM) and PM2.5 in the urban and suburban atmosphere of the Kanto Plain of Japan, which includes the Tokyo metropolitan area, during the period 22–26 July 2002 were characterized. Samples of SPM and PM2.5 were collected by low-volume samplers at 6-h intervals at Suginami, Saitama, and Kisai. At all the sites, the major components of SPM and PM2.5 were organic carbon (OC), elemental carbon (EC), and sulfate. The ion balance, the size distributions of the ionic species, and the high correlation between SO4 2? and NH4 + indicated that the main chemical form of sulfate was (NH4)2SO4. The OC/EC ratios were larger in the daytime than in the nighttime. The correlation coefficients of OC, OC/EC, and SO4 2? with ozone concentrations at inland sites (Saitama, Kisai) were higher than those at the coastal site (Suginami). Bound water and hydrogen and oxygen atoms associated with OC, the amounts of which were estimated with a mass closure model, contributed substantially to the total particle mass. The chemical characteristics of the particles indicated that two mechanisms led to high concentrations of SPM and PM2.5: (i) an active photochemical process produced high concentrations of OC and sulfate, leading to a high concentration of (NH4)2SO4 in the particles and to production of secondary organic aerosols; (ii) stable meteorological conditions resulted in accumulation of primary particles, mainly emitted from vehicle exhaust, resulting in high concentrations of OC and EC.  相似文献   

2.
Production of surface casts and the removal of plant litter from the soil surface by earth-worms had similar seasonal variations, with maximum values in May and minimum values occurring in July and August. Seasonal variations in the total nitrogen (TN) and oxidizable carbon contents of casts were closely related to variations in litter production. The C:N ratio of casts (10.7) was consistently smaller than that of underlying soil material (15.0 and 14.2 for the 0–5 and 18–22 cm depths, respectively), which is probably due to the mineralization of plant-derived organic material during passage through earthworms and utilization of low C:N ratio litter. Seasonal changes in the amounts of inorganic N forms in casts showed a build-up of NH4+N in the cooler winter months (July and August), attaining a maximum of 112 μg.g?1. with a decrease in autumn (April and May) and early spring (September and October), reaching a minimum of 54 μg.g?1. The opposite trend existed for seasonal variations in the NO3?-N content of the casts. Because only minor fluctuations in the amounts of N forms were obtained for underlying soil material during the casting period, the more dramatic changes observed in the casts could not be explained by soil variations. Seasonal variations in urease enzyme activity, associated with fluctuations in organic matter content, were more important than the effect of temperature on enzyme activity in accounting for seasonal variations in the NH4+-N content of casts. It was calculated that 73% of the TN content of litter removed from the surface by earthworms was accumulated in casts, indicating both the importance of earthworms in incorporating litter N with soil material and the inefficiency of N digestion by earthworms.  相似文献   

3.
《Geoderma》2006,130(1-2):35-46
Tropical soils are generally depleted in organic carbon (OC) due to environmental conditions favouring decomposition and mineralisation of soil organic matter (SOM). In Northern Laos, sloping soils are subjected to slash and burn agriculture, which leads to production of black carbon (BC), a stable SOM fraction. BC may directly influence the quantity and quality of SOM sequestered in tropical soils. The aim of this study was to quantify BC content and evaluate its impact on the chemical and stable isotope composition of SOM along a catena composed of Dystrochrepts at the bottom of the slope, Alfisols (midslope) and Inceptisols at the top of the slope for different burning frequencies. Six soil profiles, situated on a slope ranging from a river bank to the summit of a hill, were sampled. The stable isotope compositions (13C and 15N) of samples from both organo-mineral A and mineral B and C horizons were determined. The chemical composition of SOM analysed by 13C CPMAS NMR spectroscopy and the contribution of BC determined by dichromate oxidation were compared to OC and iron oxide content as well as land management including the burning cycle.The highest C contents were recorded at midslope positions. At any position on the slope, δ13C and δ15N ratios showed an enrichment in 13C and 15N with increasing soil depth. The OC content of soil horizons was related to their aryl C content, which is the component most likely driven by BC inputs. The BC contributions analysed by dichromate oxidation ranged from 3% to 7% of total OC. A positive correlation was obtained between aryl C and the BC content of SOM. Comparison of BC content and stable isotope composition of SOM showed that BC influenced the δ13C and the δ15N stable isotope ratios of these soils. BC was not associated with the mineral phase. The highest BC contents were measured under intensive slash and burn practice in the vicinity of the boundary of Alfisols at the top of the slope, where erosion was severe. Therefore, BC, a SOM component strongly influencing OC sequestration of these soils, is susceptible to translocation down the slope.  相似文献   

4.
Air pollution represents a significant fraction of the total mortality estimated by the World Health Organization (WHO) global burden of disease projec?t (GBD). The present paper discusses the characteristics of trace gases (O3, NO, NO2, and CO) and particulate matter (PM10 and PM2.5) in two Asian megacities, Delhi (India) and Beijing (China). A continuous measurement of trace gases and particulate matter are considered from 12 measuring sites in Beijing and 8 sites in Delhi. Over Beijing, the annual average of PM2.5, PM10, O3, NO2, and CO is, respectively, 85.3, 112.8, 58.7, and 53.4 μg/m3 and 1.4 mg/m3, and, respectively, over Delhi 146.5, 264.3, 24.7,and 19.8 μg/m3 and 1.73 mg/m3. From the spatial variations of pollutants, the concentrations of particulate matter and trace gases are observed to be much higher in the urban areas compared to the suburban areas. The higher average concentrations of PM10 and PM2.5 over Delhi and Beijing are observed during winter season compared with other seasons. The maximum diurnal variation of PM10 concentration is observed during winter season over Beijing and Delhi. The comparison of trace gases shows that the O3 concentrations during daytime are obviously higher compared with nighttime, and the highest diurnal variation of O3 is observed during summer. The concentrations of CO are highest during winter season, and higher concentrations are observed during nighttime compared to daytime. The O3 and CO show negative correlation over Beijing and Delhi. The negative correlation between O3 and NO2 is merely observed over Beijing, while CO and NO2 concentrations, in contrast, show positive correlation over Beijing.  相似文献   

5.
The occurrence of substantial quantities of black carbon (BC) in urban soil due to local dispersal following incomplete combustion of fossil fuel complicates the determination of labile soil organic carbon (SOC). Estimates of SOC content were made from loss on ignition (LOI) analyses undertaken on samples (0–15 cm depth) from comprehensive soil geochemical surveys of three UK urban areas. We randomly selected 10 samples from each decile of the LOI distribution for each of the surveys of Coventry (n = 808), Stoke‐on‐Trent (n = 737) and Glasgow (n = 1382) to investigate the proportions of labile SOC and BC. We determined their total organic carbon (TOC) and BC contents, and by difference the labile SOC content, and investigated the linear relationship of the latter with SOC estimates based on LOI analyses. There was no evidence for a difference in the slope of the regression for the three urban areas. We then used a linear regression of labile SOC based on LOI analyses (r2 = 0.81) to predict labile SOC for all survey samples from the three urban areas. We attribute the significantly higher median BC concentrations in Glasgow (1.77%, compared with 0.46 and 0.59% in Coventry and Stoke‐on‐Trent) to greater dispersal of coal ash across the former. An analysis of the 30 samples showed that LOI at 450 °C accounts for a consistent proportion of BC in each sample (r2 = 0.97). Differences between TOC (combustion at 1050 °C after removal of inorganic carbon) and an LOI estimate of SOC may be a cost‐effective method for estimation of BC. Previous approaches to estimation of urban SOC contents based on half the mean SOC content of the equivalent associations under pasture, underestimate the empirical mean value.  相似文献   

6.
A monitoring program of particulate matter was conducted at eight sampling sites in four highly industrialized cities (Shenyang, Anshan, Fushun, and Jinzhou) of Liaoning Province in Northeast China to identify the major potential sources of ambient PM2.5. A total of 814 PM2.5 and PM2.5–10 samples were collected between 2004 and 2005. All PM samples were collected simultaneously in four cities and analyzed gravimetrically for mass concentrations. A sum of 16 elemental species concentrations in the PM samples were determined using inductively coupled plasma atomic emission spectroscopy. Annual means of PM2.5 concentrations ranged from 65.0 to 222.0 μg m?3 in all the eight sampling sites, and the spatial and seasonal variations were discussed. Enrichment factors were calculated, and Cr, Cu, Zn, As, Cd, and Pb will be pollution-derived elements. Site-to-site comparisons of PM2.5 species in each city were examined using coefficient of divergence, revealing that the two sites in each city are similar in elemental species. Principle component analysis was used for preliminary source analysis of PM2.5. Three or four factors in each city were isolated, and similar sources (crustal source, coal combustion, vehicle exhaust, iron making, or some other metallurgical activities) were identified at four cities.  相似文献   

7.
Marine ecosystems are a known net source of greenhouse gases emissions but the atmospheric gas fluxes, particularly from the mangrove swamps occupying inter-tidal zones, are characterized poorly. Spatial and seasonal fluxes of nitrous oxide (N2O) and carbon dioxide (CO2) from soil in Mai Po mangrove swamp in Hong Kong, South China and their relationships with soil characteristics were investigated. The N2O fluxes averaged from 32.1 to 533.7 μg m−2 h−1 and the CO2 fluxes were between 10.6 and 1374.1 mg m−2 h−1. Both N2O and CO2 fluxes in this swamp showed large spatial and seasonal variations. The fluxes were higher at the landward site than the foreshore bare mudflat, and higher fluxes were recorded in warm, rather than cold, seasons. The landward site had the highest content of soil organic carbon (OC), total Kjeldahl nitrogen (TKN), nitrate (NO3−–N) and total phosphorus (TP), while the bare mudflat had the highest ammonium nitrogen (NH4+–N) concentration and soil denitrification potential activity. The N2O flux was related, positively, to CO2 flux. Soil NO3−–N and TP increased N2O flux, while soil OC and TP concentrations contributed to the CO2 flux. The results indicated that the Mai Po mangrove swamp emitted significant amounts of greenhouse gases, and the N2O emission was probably due to soil denitrifcation.  相似文献   

8.
Particulate matter measurements (PM10, PM2.5) using a beta radiation attenuation monitor were performed at the Akrotiri research station (May 2003–March 2006) on the island of Crete (Greece). The mean PM10 concentration during the measuring period (05/02/03–03/09/04) was equal to 35.0?±?17.7 μg/m3 whereas the mean PM2.5 concentration (03/10/04–04/02/06) was equal to 25.4?±?16.5 μg/m3. The aerosol concentration at the Akrotiri station shows a large variability during the year. Mean concentrations of particulate matter undergo a seasonal change characterised by higher concentrations during summer [PM10, 38.7?±?10.8 μg/m3 (2003); PM2.5, 27.9?±?8.7 μg/m3 (2004) and 27.8?±?9.7 μg/m3 (2005)] and lower concentrations during winter [PM10, 28.7?±?22.5 μg/m3 (2003/2004); PM2.5, 21.0?±?13.0 μg/m3 (2004/2005) and 21.4?±?21.9 μg/m3 (2005/2006)]. Comparative measurements of the PM10 concentration between the beta radiation attenuation monitor, a standardized low volume gravimetric reference sampler and a low volume sequential particulate sampler showed that PM10 concentrations measured by the beta radiation attenuation monitor were higher than values given by the gravimetric samplers (mean ratio 1.17?±?0.11 and 1.21?±?0.08, respectively). Statistical and back trajectory analysis showed that elevated PM concentrations (PM10, 93.8?±?49.1 μg/m3; PM2.5: 102.9?±?59.9 μg/m3) are associated to desert dust events. In addition regional transport contributes significantly to the aerosol concentration levels whereas low aerosol concentrations were observed during storm episodes.  相似文献   

9.
Samples of airborne particulate matter (PM2.5) were collected at a site in Lahore, Pakistan from November 2005 to January 2006. A total of 129 samples were collected using an Andersen Reference Ambient Air Sampler 2.5-400 sampler and analyzed for major ions, trace metals, and organic and elemental carbon concentrations. The data set was then analyzed by positive matrix factorization (PMF) to identify the possible sources of the atmospheric PM collected in this urban area. Six factors reproduced the PM2.5 sample compositions with meaningful physical interpretation of the resolved factors. The sources included secondary PM, diesel emissions, biomass burning, coal combustion, two-stroke vehicle exhaust, and industrial sources. Diesel and two-stroke vehicles contributed about 36%, biomass burning about 15%, and coal combustion sources around 13% of the PM2.5 mass. Nearly two thirds of the PM2.5 mass is carbonaceous material. Secondary particles contributed about 30% of PM2.5 mass. The conditional probability function (CPF) was then used to help identify likely locations of the sources present in this area. CPF analysis point to the east and northeast, which are directions of urban and industrial areas located across the border near Amritsar, India as the most probable source for high PM2.5 concentration from diesel and two-stroke vehicles exhaust in Lahore. Analysis of those days within three different ranges of PM2.5 concentration shows that most of the measured high PM2.5 mass concentrations were driven by diesel and two-stroke vehicle emissions including the associated primary sulfate. The use of the potential source contribution function (PSCF) to find the source locations of regionally transported particles is inapplicable in situations when high PM2.5 concentrations are dominated by local sources and local meteorology.  相似文献   

10.
The carbon dynamics in soils is of great importance due to its links to the global carbon cycle. The prediction of the behavior of native soil organic carbon (SOC) and organic amendments via incubation studies and mathematical modeling may bridge the knowledge gap in understanding complex soil ecosystems. Three alkaline Typic Ustochrepts and one Typic Halustalf with sandy, loamy sand, and clay loam texture, varying in percent SOC of 0.2; S1, 0.42; S2, 0.67; S3 and 0.82; S4 soils, were amended with wheat straw (WS), WS + P, sesbania green manure (GM), and poultry manure (PM) on 0.5% C rate at field capacity (FC) and ponding (P) moisture levels and incubated at 35 °C for 1, 15, 30 and 45 d. Carbon mineralization was determined via the alkali titration method after 1, 5, 7 14, 21, and 28 d. The SOC and inorganic carbon contents were determined from dried up (50 °C) soil samples after 1, 15, 30, and 45 d of incubation. Carbon from residue mineralization was determined by subtracting the amount of CO2-C evolved from control soils. The kinetic models; monocomponent first order, two-component first order, and modified Gompertz equations were fitted to the carbon mineralization data from native and added carbon. The SOC decomposition was dependent upon soil properties, and moisture, however, added C was relatively independent. The carbon from PM was immobilized in S4. All the models fitted to the data predicted carbon mineralization in a similar range with few exceptions. The residues lead to the OC build-up in fine-textured soils having relatively high OC and cation exchange capacities. Whereas, fast degradation of applied OC in coarse-textured soils leads to faster mineralization and lower build-up from residues. The decline in CaCO3 after incubation was higher at FC than in the P moisture regime.  相似文献   

11.
The study of mineral components in respirable particles (particulate matter with diameter less than 10 μm, PM10) in ambient air is important in understanding and improving air quality. In this study, PM10 samples were collected in various areas around Beijing during 2002～2003, including an urban setting, a satellite city and a rural area. The mineralogical composition of these PM10 samples was studied by X-ray diffraction (XRD), environmental scanning electron microscopy / and energy-dispersive X-ray analyzer (ESEM/EDX). The results indicated that mineral composition of PM10 in different seasons and in different region varied significantly. Mineral mass concentration in Beijing PM10 reached the highest percentage in the spring and fell to the lowest level in the autumn. The minerals in the spring PM10 were dominated by clay minerals and quartz, followed by plagioclase, K-feldspar, calcite, dolomite, hematite, pyrite, magnesite, gypsum and laumontite as well as some unidentified materials. Fewer mineral types were collected in summer, however some new components, including K(NH4)Ca(SO4)2·H2O, NH4Cl and As2O3·SO3 were noted to be present, suggesting that atmospheric chemical reaction in Beijing air were more active in summer than in other seasons. Mineral components in Beijing urban air were at a higher percentage with fewer phases than that in satellite city air. In conclusion, there was considerable variation in mineral components in PM10 samples collected in different seasons and areas, which reflects the related air quality of sampling areas.  相似文献   

12.
The Industrial Source Complex Short Term (ISCST3) model was used to discern the sources responsible for high PM10 levels in Kanpur City, a typical urban area in the Ganga basin, India. A systematic geographic information system-based emission inventory was developed for PM10 in each of 85 grids of 2?×?2 km. The total emission of PM10 was estimated at 11 t day?1 with an overall breakup as follows: (a) industrial point sources, 2.9 t day?1 (26%); (b) vehicles, 2.3 t day?1 (21%); (c) domestic fuel burning, 2.1 t day?1 (19%); (d) paved and unpaved road dust, 1.6 t day?1 (15%); and the rest as other sources. To validate the ISCST3 model and to assess air-quality status, sampling was done in summer and winter at seven sampling sites for over 85 days; PM10 levels were very high (89?C632 ??g m?3). The results show that the model-predicted concentrations are in good agreement with observed values, and the model performance was found satisfactory. The validated model was run for each source on each day of sampling. The overall source contribution to ambient air pollution was as follows: vehicular traffic (16%), domestic fuel uses (16%), paved and unpaved road dust (14%), and industries (7%). Interestingly, the largest point source (coal-based power plant) did not contribute significantly to ambient air pollution. The reason might be due to release of pollutant at high stack height. The ISCST3 model was shown to produce source apportionment results like receptor modeling that could generate source apportionment results at any desired time and space resolution.  相似文献   

13.
PM2.5 and PAHs bound to PM2.5 were investigated in downtown Bologna, from January to June 2003, in order to determine the burden of the fine fraction in the aerosol of a typical urban environment of the Po Valley, a critical area in Northern Italy in terms of atmospheric pollution. The sampling campaign was divided into three parts: a winter sub-campaign, an intermediate campaign where PM2.5 and PM10 were simultaneously sampled and which identified PM2.5 as the major component of PM10, and a summer sub-campaign. Critical concentrations of both PM2.5 and PAHs were observed in winter time; for example, in January 2003 the mean value for the 24-h average PM2.5 concentration was 58 μg/m3, much higher than the annual arithmetic mean of 15 μg/m3 established by the US ambient air quality standard (NAAQS). Correspondingly, the mean value for benzo[a]pyrene (BAP) in PM2.5 was 1.79 ng/m3, again higher than the annual mean of 1 ng/m3, required by European regulations for BAP in PM10. In summer time the BAP concentration considerably decreases to 0.10 ng/m3 as the likely effect of photolysis and dilution on a higher boundary layer; PM2.5 decreases too, but the mean concentration (22 μg/m3) is still higher than the NAAQS value. Further analysis included TEM microscopy of collected particles and correlations between PM2.5, PAHs and gases (benzene, O3, CO, NO2, SO2). All these observations identified on-road mobile sources as the main source of emissions and, in general, of the poor air quality level in the city of Bologna.  相似文献   

14.
Ten selected metals (Na, K, Fe, Zn, Pb, Mn, Cr, Co, Ni & Cd) were estimated in total suspended particulate (TSP) samples collected on glass fibre filters in urban Islamabad, Pakistan, from October 2002 to May 2003, using a high volume sampling technique. The wet digestion method (HNO3/HClO4) was used for metal analysis by the flame atomic absorption spectrophotometry (FAAS) method. Maximum mean contribution was noted for Na (1.949 μg m?3), followed by K (0.900 μg m?3), Zn (0.603 μg m?3), Fe (0.584 μg m?3) and Pb (0.214 μg m?3). The particle size determination on % volume basis for four fractions (PM< 2.5, PM2.5–10, PM10–100& PM> 100) was also carried out. PM10–100 were found to be the most abundant in the local atmosphere followed by PM2.5–10, while the respirable fraction (PM< 2.5) and giant fraction (PM> 100) showed comparable and lower levels. The trace metals were found to be mainly associated with PM< 2.5 and PM2.5–10. The influence of climatic variables on toxic trace metals and particle size fractions was also investigated statistically and it was revealed that temperature has a significant correlation with fine particle fractions and airborne trace metal levels. The source identification was carried out by Principal Component Analysis and Cluster Analysis. Four metal sources were identified: industrial (32.6%), soil-derived dust (21.9%), traffic/road dust (19.8%), and metallurgical/garbage incineration (12.4%). The metal levels were also compared with those reported for other parts around the world.  相似文献   

15.
辽宁西北部主要绿化树种对空气颗粒物滞留能力研究   总被引：1，自引：0，他引：1  
采用洗脱法测定了辽西北地区阜新市15种常见绿化树种单位叶面积滞留粗颗粒物(TSP)及细颗粒物(PM_(2.5))的质量,分析比较了15种树种叶片去除TSP和PM_(2.5)能力以及随着空间变化的规律。结果表明:(1)不同树种单位叶面积TSP和PM_(2.5)滞留量均存在显著差异,变化范围分别为3.68~5.94g/m~2和0.47~0.92g/m~2,树种间滞留能力的差值可达2倍左右。(2)在同一个功能区不同树种滞留TSP和PM_(2.5)的差异由树冠高度(绿篱灌木乔木)和叶表面粗糙度(叶表面沟槽宽度的不同可能是沟槽宽度过宽和过窄均不利于叶片捕集颗粒物,且颗粒物滞留量随沟槽深度增加而增大)以及叶片比叶重(比叶重大的滞尘量大)等所引起。(3)在不同功能区同一树种单位叶面积滞留TSP量的排序为工业区商业交通区露天矿区清洁区,而PM_(2.5)滞留量则无明显差异。乔木中新疆杨、灌木中紫丁香的单位叶面积滞留量与单株滞留量都较高,起到明显的降尘作用,是沙尘频发的辽西北地区城市绿化树种的优先之选。  相似文献   

16.
Widespread drought and record maximum temperatures in eastern Australia produced a large dust storm on 23 October, 2002 which traversed a large proportion of eastern Australia and engulfed communities along a 2000 km stretch of coastline from south of Sydney (NSW) to north of Mackay (Queensland). This event provided an opportunity for a study of the impacts of rural dust upon the air quality of four Australian cities. A simple model is used to predict dust concentrations, dust deposition rates and particle size characteristics of the airborne dust in the cities. The total dust load of the plume was 3.35 to 4.85 million tones, and assuming a (conservative) plume height of 1500 m, 62–90% of this dust load was deposited in-transit to the coast. It is conservatively estimated that 3.5, 12.0, 2.1 and 1.7 kilotonnes of dust were deposited during the event in Sydney, Brisbane, Gladstone and Mackay, respectively. In the South East Queensland region, this deposition is equivalent to 40% of the total annual TSP emissions for the region. The event increased TSP, PM10 and PM2.5 concentrations and reduced the visibility beyond the health and amenity guidelines in the four cities. For example, the 24-h average PM10 concentrations in Brisbane and Mackay, were 161 and 475 μg m?3 respectively, compared with the Australian national ambient air quality standard of 50 μg m?3. The 24-h average PM2.5 concentration in Brisbane was 42 μg m?3, compared with the national advisory standard of 25 μg m?3. These rural dusts significantly increased PM10/TSP ratios and decreased PM2.5/PM10 ratios, indicating that most of the particles were between PM2.5 and PM10.  相似文献   

17.
Incomplete combustion of organics such as vegetation or fossil fuel led to accumulation of charred products in the upper soil horizon. Such charred products, frequently called pyrogenic carbon or black carbon (BC), may act as an important long-term carbon (C) sink because its microbial decomposition and chemical transformation is probably very slow. Direct estimations of BC decomposition rates are absent because the BC content changes are too small for any relevant experimental period. Estimations based on CO2 efflux are also unsuitable because the contribution of BC to CO2 is too small compared to soil organic matter (SOM) and other sources.We produced BC by charring 14C labeled residues of perennial ryegrass (Lolium perenne). We then incubated this 14C labeled BC in Ah of a Haplic Luvisol soil originated from loess or in loess for 3.2 years. The decomposition rates of BC were estimated based on 14CO2 sampled 44 times during the 3.2 years incubation period (1181 days). Additionally we introduced five repeated treatments with either 1) addition of glucose as an energy source for microorganisms to initiate cometabolic BC decomposition or 2) intensive mixing of the soil to check the effect of mechanical disturbance of aggregates on BC decomposition. Black carbon addition amounting to 20% of Corg of the soil or 200% of Corg of loess did not change total CO2 efflux from the soil and slightly decreased it from the loess. This shows a very low BC contribution to recent CO2 fluxes. The decomposition rates of BC calculated based on 14C in CO2 were similar in soil and in loess and amounted to 1.36 10−5 d−1 (=1.36 10−3% d−1). This corresponds to a decomposition of about 0.5% BC per year under optimal conditions. Considering about 10 times slower decomposition of BC under natural conditions, the mean residence time (MRT) of BC is about 2000 years, and the half-life is about 1400 years. Considering the short duration of the incubation and the typical decreasing decomposition rates with time, we conclude that the MRT of BC in soils is in the range of millennia.The strong increase in BC decomposition rates (up to 6 times) after adding glucose and the decrease of this stimulation after 2 weeks in the soil (and after 3 months in loess) allowed us to conclude cometabolic BC decomposition. This was supported by higher stimulation of BC decomposition by glucose addition compared to mechanical disturbance as well as higher glucose effects in loess compared to the soil. The effect of mechanical disturbance was over within 2 weeks. The incorporation of BC into microorganisms (fumigation/extraction) after 624 days of incubation amounted to 2.6 and 1.5% of 14C input into soil and loess, respectively. The amount of BC in dissolved organic carbon (DOC) was below the detection limit (<0.01%) showing no BC decomposition products in water leached from the soil.We conclude that applying 14C labeled BC opens new ways for very sensitive tracing of BC transformation products in released CO2, microbial biomass, DOC, and SOM pools with various properties.  相似文献   

18.
The decrease of NMR visibility of the C signal in soil samples due to the association between organic carbon (OC) and the topsoil mineral surface was investigated. CPMAS 13C‐NMR spectra were obtained for soil particle‐size fractions (< 2 μm, 2–20 μm, > 20 μm) and bulk soils from an agricultural topsoil (Chernozem) that had received three different amendments (no fertilization, mineral fertilization (NPK), mineral (NPK) and organic (cattle manure) fertilizations) at Bad Lauchstädt, Germany. The soil organic carbon content of the three soils depended on the degree of soil fertilization. There was no constant relationship between the total NMR signal intensity and the total amount of organic carbon (TOC) for all size fractions. Indeed, a key role played in the C signal intensity by the paramagnetic ferric ion from the clay content in soil fractions and bulk soils was confirmed. Thus, we describe the variations of C signal intensity by taking into account the distribution of clay‐associated OC and non‐associated OC pools. Depending on the amendment, the C signal visibility was weakened by a factor of 2–4 for the clay‐associated OC. This estimation was rendered possible by combining mineral specific surface area (SSA) measurements with the N2 gas adsorption method (BET method) and determination of TOC and iron concentrations. This approach contributes to the quantitative evaluation of the CPMAS 13C‐NMR detection.  相似文献   

19.
The evaluation of the contribution of natural sources to PM10 and PM2.5 concentrations is a priority especially for the countries of European south strongly influenced by Saharan dust transport events. Daily PM2.5 concentrations and composition were monitored at an urban site at 14 m above ground level, at the National Technical University of Athens campus from February to December 2010. The typical dust constituents Si, Al, Fe, K, Ca, Mg, and Ti were determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF). Sulfur, a tracer of anthropogenic origin and major constituent of PM2.5, was determined by both WDXRF and ionic chromatography. The contribution of dust and sulfates in PM2.5 was calculated from the analytical determinations. An annual mean of 20 μg/m3 was calculated from the mean daily PM2.5 concentrations data. Twenty-two per cent of daily concentrations of PM2.5 reached or exceeded the EU annual target concentration of 25 μg/m3. The exceedances occurred during 13 short periods of 1–4 days. Back-trajectory analysis was performed for these periods in order to identify the air masses origin. From these periods, ten periods were associated to Saharan dust transport events. The most intense dust transport event occurred between February 17th and 20th and was responsible for the highest recorded PM2.5 concentration of 100 μg/m3 where the dust contribution in PM2.5 reached 96 %. The other dust transport events were less intense and corresponded to less pronounced enhancements of PM2.5 concentrations, and their contribution ranged from 15 to 39 % in PM2.5 concentrations. Air masses originated from northwest Africa while the influence of central Sahara was quite smaller.  相似文献   

20.
We used four vegetation types located along an urban–suburban–rural gradient in Nanchang, China to study how the deposition of nitrogen (N) and phosphorus (P) in the urban area affected soil carbon (C) cycling. We found that total P, nitrate (NO3−–N), available P, and the abundances of culturable bacteria, actinobacteria, and nitrifying bacteria in soils, collected to 15 cm depth in August of 2008, decreased along the urban-to-rural gradient (P < 0.05); the C/P and N/P ratios, ammonium (NH4+–N), and culturable fungi abundance showed the reverse trends; whereas soil organic C, total N, C/N, mineral N, and the activities of sucrase and neutraland acid phosphatase showed no pattern with gradient and vegetation type. Compared to suburban and rural sites, total and available P in soil increased 168% and 131%, 47% and 139%, respectively in urban sites. The cumulative amount of CO2 emission per gram of soil (Cmin, incubated from 2 to 43 days) varied little along the urban-to-rural gradient, but showed positive correlations with organic C, total N, total P, nitrate, mineral N concentrations, C/N, bacteria and actinobacteria abundances, sucrase and acid phosphatase activities. In contrast, the cumulative amount of CO2 produced per gram organic C (Cmin/OC) within the incubation period was influenced by gradient, vegetation type, and their interaction, and values were about 35% greater in the urban than in suburban and rural sites. The relationship between elevated Cmin/OC in urban vegetations and the enrichment of P in organic matter (P/C ratio) suggests that P coming from urban household waste can degrade the stability of organic C in urban soils.  相似文献   

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