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1.
The atmospheric fluxes of N2O, CH4 and CO2 from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 μmol m−2 h−1, 11.9 to 5168.6 μmol m−2 h−1 and 0.69 to 20.56 mmol m−2 h−1 for N2O, CH4 and CO2, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N2O and CH4 fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N2O and CO2 fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH4+-N contents, as well as the soil porosity. However, only soil NH4+-N concentration had significant effects on CH4 fluxes. 相似文献
2.
We analyzed benthic fluxes of inorganic nitrogen, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in hypolimnetic sediments of lowland lakes. Two neighbouring mesotrophic (Ca' Stanga; CS) and hypertrophic (Lago Verde; LV) lakes, which originated from sand and gravel mining, were considered. Lakes are affected by high nitrate loads (0.2-0.7 mM) and different organic loads. Oxygen consumption, dissolved inorganic carbon, methane and nitrogen fluxes, denitrification and DNRA were measured under summer thermal stratification and late winter overturn.Hypolimnetic sediments of CS were a net sink of dissolved inorganic nitrogen (−3.5 to −4.7 mmol m−2 d−1) in both seasons due to high nitrate consumption. On the contrary, LV sediments turned from being a net sink during winter overturn (−3.5 mmol m−2 d−1) to a net source of dissolved inorganic nitrogen under summer conditions (8.1 mmol m−2 d−1), when significant ammonium regeneration was measured at the water-sediment interface. Benthic denitrification (0.7-4.1 mmol m−2 d−1) accounted for up to 84-97% of total NO3− reduction and from 2 to 30% of carbon mineralization. It was mainly fuelled by water column nitrate. In CS, denitrification rates were similar in winter and in summer, while in LV summer rates were 4 times lower. DNRA rates were generally low in both lakes (0.07-0.12 mmol m−2 d−1). An appreciable contribution of DNRA was only detected in the more reducing sediments of LV in summer (15% of total NO3− reduction), while during the same period only 3% of reduced NO3− was recycled into ammonium in CS.Under summer stratification benthic denitrification was mainly nitrate-limited due to nitrate depletion in hypolimnetic waters and parallel oxygen depletion, hampering nitrification. Organic enrichment and reducing conditions in the hypolimnetic sediment shifted nitrate reduction towards more pronounced DNRA, which resulted in the inorganic nitrogen recycling and retention within the bottom waters. The prevalence of DNRA could favour the accumulation of mineral nitrogen with detrimental effects on ecosystem processes and water quality. 相似文献
3.
M. Samer C. LoebsinM. Fiedler C. AmmonW. Berg P. SanftlebenR. Brunsch 《Energy and Buildings》2011,43(12):3718-3728
Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO2-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH3, CH4, CO2 and N2O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO2-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO2-balance. The AFRs, subject to TGT, were 0.12 m3 s−1 m−2, 1.15 m3 s−1 cow−1, 0.88 m3 s−1 LU−1, 56 h−1, 395 m3 s−1 and 470 kg s−1 through summer seasons, and 0.08 m3 s−1 m−2, 0.83 m3 s−1 cow−1, 0.64 m3 s−1 LU−1 39 h−1, 275 m3 s−1 and 328 kg s−1 through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h−1 cow−1; and through winter seasons were 4.8, 19, 2332 and 2.6 g h−1 cow−1, for NH3, CH4, CO2 and N2O, respectively. 相似文献
4.
Elemental and organic carbon in aerosols over urbanized coastal region (southern Baltic Sea, Gdynia) 总被引:2,自引:0,他引:2
Anita Lewandowska Lucyna Falkowska Dominika Murawiec Dorota Pryputniewicz Dorota Burska Magdalena Be?dowska 《The Science of the total environment》2010,408(20):4761-4769
Studies on PM 10, total particulate matter (TSP), elemental carbon (EC) and organic carbon (OC) concentrations were carried out in the Polish coastal zone of the Baltic Sea, in urbanized Gdynia. The interaction between the land, the air and the sea was clearly observed. The highest concentrations of PM 10, TSP and both carbon fractions were noted in the air masses moving from southern and western Poland and Europe. The EC was generally of primary origin and its contribution to TSP and PM 10 mass was on average 2.3% and 3.7% respectively. Under low wind speed conditions local sources (traffic and industry) influenced increases in elemental carbon and PM 10 concentrations in Gdynia. Elemental carbon demonstrated a pronounced weekly cycle, yielding minimum values at the weekend and maximum values on Thursdays. The role of harbors and ship yards in creating high EC concentrations was clearly observed. Concentration of organic carbon was ten times higher than that of elemental carbon, and the average OC contribution to PM 10 mass was very high (31.6%). An inverse situation was observed when air masses were transported from over the Atlantic Ocean, the North Sea and the Baltic Sea. These clean air masses were characterized by the lowest concentrations of all analysed compounds.Obtained results for organic and elemental carbon fluxes showed that atmospheric aerosols can be treated, along with water run-off, as a carbon source for the coastal waters of the Baltic Sea. The enrichment of surface water was more effective in the case of organic carbon (0.27 ± 0.19 mmol m−2 d−1). Elemental carbon fluxes were one order of magnitude smaller, on average 0.03 ± 0.04 mmol m−2 d−1. We suggest that in some situations atmospheric carbon input can explain up to 18% of total carbon fluxes into the Baltic coastal waters. 相似文献
5.
Richard Matthews Michael Winson John Scullion 《The Science of the total environment》2009,407(8):2557-2564
Biological ammoniacal-nitrogen (NH4+-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH4+-N reduction (0.126-0.159 g m− 2 d− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m− 2 d− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m− 2 d− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH4+-N m− 2 d− 1 and 0.033-0.251 g C m− 2 d− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH4+-N and TOC respectively. For the weak leachates (NH4+-N < 140 mg l− 1) complete oxidation of NH4+-N was achieved. For the strong leachates (NH4+-N 883-1150 mg l− 1) a biphasic treatment response resulted in NH4+-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH4+-N to TON in bulk leachate. The temporal decoupling of NH4+-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH4+-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH4+-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors. 相似文献
6.
Wood ash (3.1, 3.3 or 6.6 tonnes dry weight ha− 1) was used to fertilize two drained and forested peatland sites in southern Sweden. The sites were chosen to represent the Swedish peatlands that are most suitable for ash fertilization, with respect to stand growth response. The fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the forest floor, measured using opaque static chambers, were monitored at both sites during 2004 and 2005 and at one of the sites during the period 1 October 2007-1 October 2008. No significant (p > 0.05) changes in forest floor greenhouse gas exchange were detected. The annual emissions of CO2 from the sites varied between 6.4 and 15.4 tonnes ha− 1, while the CH4 fluxes varied between 1.9 and 12.5 kg ha− 1. The emissions of N2O were negligible. Ash fertilization increased soil pH at a depth of 0-0.05 m by up to 0.9 units (p < 0.01) at one site, 5 years after application, and by 0.4 units (p < 0.05) at the other site, 4 years after application. Over the first 5 years after fertilization, the mean annual tree stand basal area increment was significantly larger (p < 0.05) at the highest ash dose plots compared with control plots (0.64 m2 ha− 1 year− 1 and 0.52 m2 ha− 1 year− 1, respectively). The stand biomass, which was calculated using tree biomass functions, was not significantly affected by the ash treatment. The groundwater levels during the 2008 growing season were lower in the high ash dose plots than in the corresponding control plots (p < 0.05), indicating increased evapotranspiration as a result of increased tree growth. The larger basal area increment and the lowered groundwater levels in the high ash dose plots suggest that fertilization promoted tree growth, while not affecting greenhouse gas emissions. 相似文献
7.
A sustainable, carbon neutral methane oxidation by a partnership of methane oxidizing communities and microalgae 总被引:1,自引:0,他引:1
Effluents of anaerobic wastewater treatment plants are saturated with methane, an effective greenhouse gas. We propose a novel approach to treat such effluents using a coculture of methane oxidizing communities and microalgae, further indicated as methalgae, which would allow microbial methane oxidation with minimal CO2 emissions. Coculturing a methane oxidizing community with microalgae in sequence batch reactors under continuous lightning yielded a factor of about 1.6 more biomass relative to the control without microalgae. Moreover, 55% less external oxygen supply was needed to maintain the methane oxidation, as oxygen was produced in situ by the microalgae. An overall methane oxidation rate of 171 ± 27 mg CH4 L−1 liquid phase d−1 was accomplished in a semi-batch setup, while the excess CO2 production was lower than 1 mg CO2 L−1 d−1. Both nitrate and ammonium were feasible nitrogen sources for the methalgae. These results show that a coculture of microalgae and methane oxidizing communities can be used to oxidize dissolved methane under O2-limiting conditions, which could lead to a novel treatment for dissolved methane in anaerobic effluents. 相似文献
8.
The multi-annual carbon budget of a peat-covered catchment 总被引:1,自引:0,他引:1
This study estimates the complete carbon budget of an 11.4 km2 peat-covered catchment in Northern England. The budget considers both fluvial and gaseous carbon fluxes and includes estimates of particulate organic carbon (POC); dissolved organic carbon (DOC); excess dissolved CO2; release of methane (CH4); net ecosystem respiration of CO2; and uptake of CO2 by primary productivity. All components except CH4 were measured directly in the catchment and annual carbon budgets were calculated for the catchment between 1993 and 2005 using both extrapolation and interpolation methods. The study shows that: Over the 13 year study period the total carbon balance varied between a net sink of − 20 to − 91 Mg C/km2/yr. The biggest component of this budget is the uptake of carbon by primary productivity (− 178 Mg C/km2/yr) and in most years the second largest component is the loss of DOC from the peat profile (+ 39 Mg C/km2/yr). Direct exchanges of C with the atmosphere average − 89 Mg C/km2/yr in the catchment. Extrapolating the general findings of the carbon budget across all UK peatlands results in an approximate carbon balance of − 1.2 Tg C/yr (± 0.4 Pg C/yr) which is larger than previously reported values. Carbon budgets should always be reported with a clear statement of the techniques used and errors involved as this is significant when comparing results across studies. 相似文献
9.
Organic and inorganic carbon concentrations and fluxes from managed and unmanaged boreal first-order catchments 总被引:1,自引:0,他引:1
Miitta Rantakari Tuija Mattsson Sirpa Piirainen Marketta Ahtiainen 《The Science of the total environment》2010,408(7):1649-1658
Seasonal and between stream variation (catchment dependent variation) in losses of organic and inorganic carbon via downstream transport and outgassing of CO2 into the atmosphere were studied in 11 small boreal catchments situated in close proximity to each other. Of these catchments four were undrained peatland rich catchments, four drained peatland rich catchments and three managed mineral soil-dominated catchments. Downstream export of total inorganic carbon (TIC) varied between 870 and 1400 kg km− 2 a− 1 and was rather consistent between the catchments, except in the case of the mineral soil-dominated catchment Kangaslampi, where export was only 420 kg km− 2 a− 1. The export of total organic carbon (TOC) varied between 2300 and 14,800 kg km− 2 a− 1 and was highest in peatland rich catchments. Peatland drainage decreased TIC and TOC concentrations in the long term, but did not affect lateral carbon export due to increased runoff from the catchments. Partial pressure of CO2 in streams was the highest in undrained peatland rich catchments, but the outgassing of CO2 into the atmosphere was also high from drained peatlands due to the higher discharge rate and long ditch networks. In mineral soil-dominated catchments both downstream export of carbon and emission into the atmosphere were low. TOC exports were compared in two climatically different years (2003 and 2007). The results indicate that climate change might alter the timing of the TOC export from the catchments, the importance of the spring ice melt diminishing and both snow cover and snow free period export increasing. 相似文献
10.
The study focuses on the role of the fired clay brick making industry (BMI) on deforestation and greenhouse gas (GHG) emissions in Sudan. The BMI is based on numerous kilns that use biomass fuel, mainly wood which is largely harvested unsustainably. This results in potential deforestation and land degradation. Fuelwood consumption data was collected using interviews and questionnaires from 25 BMI enterprises in three administrative regions, namely Khartoum, Kassala and Gezira. Annual fuelwood consumption data (t dm yr− 1) was converted into harvested biomass (m3) using a wood density value of 0.65 t dm m− 3. For annual GHG estimations, the methodological approach outlined by the Intergovernmental Panel on Climate Change (IPCC) was used. According to our results, the annual deforestation associated with the BMI for the whole of Sudan is 508.4 × 103 m3 of wood biomass, including 267.6 × 103 m3 round wood and 240.8 × 103 m3 branches and small trees. Total GHG emissions from the Sudanese BMI are estimated at 378 028 t CO2, 15 554 t CO, 1778 t CH4, 442 t NOX, 288 t NO and 12 t N2O per annum. The combined CO2-equivalent (global warming potential for 100-year time horizon) of the GHG emissions (excluding NOX and NO) is 455 666 t yr− 1. While these emissions form only a small part of Sudan's total GHG emissions, the associated deforestation and land degradation is of concern and effort should be made for greater use of sustainable forest resources and management. 相似文献
11.
Kinetics of nitrate and perchlorate reduction in ion-exchange brine using the membrane biofilm reactor (MBfR) 总被引:2,自引:0,他引:2
Van Ginkel SW Ahn CH Badruzzaman M Roberts DJ Lehman SG Adham SS Rittmann BE 《Water research》2008,42(15):4197-4205
Several sources of bacterial inocula were tested for their ability to reduce nitrate and perchlorate in synthetic ion-exchange spent brine (30-45 g/L) using a hydrogen-based membrane biofilm reactor (MBfR). Nitrate and perchlorate removal fluxes reached as high as 5.4 g N m−2 d−1 and 5.0 g ClO4 m−2 d−1, respectively, and these values are similar to values obtained with freshwater MBfRs. Nitrate and perchlorate removal fluxes decreased with increasing salinity. The nitrate fluxes were roughly first order in H2 pressure, but roughly zero-order with nitrate concentration. Perchlorate reduction rates were higher with lower nitrate loadings, compared to high nitrate loadings; this is a sign of competition for H2. Nitrate and perchlorate reduction rates depended strongly on the inoculum. An inoculum that was well acclimated (years) to nitrate and perchlorate gave markedly faster removal kinetics than cultures that were acclimated for only a few months. These results underscore that the most successful MBfR bioreduction of nitrate and perchlorate in ion-exchange brine demands a well-acclimated inoculum and sufficient hydrogen availability. 相似文献
12.
Hourly mean time series of dust concentration (PM10) measured at 3 m high and a sonic-anemometer measured momentum and kinematic heat fluxes at 8 m high above the surface have been obtained from a 20-m monitoring tower located at Erdene in the Asian dust source region of Mongolia for years of 2009 and 2010. These time series were used to identify dust events and to develop optimal regression equations for the dust concentration of dust events with the friction velocity (u*) and the convective velocity scale (w*). In total, 68 dust events were identified in 2009 (except for November) and 43 dust events for the period from March to August in 2010. The duration of each dust event ranged from 3-29 h in 2009 and 5-35 h in 2010. The maximum hourly mean dust concentration of the dust event was found to be 4,107 μg m− 3 in May in 2009 and 4,708 μg m− 3 in March in 2010 while a minimum of 251 μg m− 3 in August in 2009 and 662 μg m− 3 in June in 2010. The optimal regression equation for the dust concentration (C) of dust events was found to have the form of log C = a + b(u* + cw*)n, where a, b, c and n are constants that vary month to month. The convective velocity scale (w*) that has not been taken into account in most dust modelings was found to enhance the dust concentration of dust events during the cold period from December to March when the soil temperature was below the freezing level for both the stable (w* < 0) and unstable (w* > 0) stratifications, whereas the convective velocity caused a reduction in the dust concentrations during the warm period from April to October, suggesting the importance of the convective velocity to estimate dust concentration of dust events. 相似文献
13.
Muñoz-Leoz B Antigüedad I Garbisu C Ruiz-Romera E 《The Science of the total environment》2011,409(4):763-770
Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO2 and N2O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO3− L− 1 solution (rate: 90 mL day− 1) for 125 days at two different temperatures (10 and 20 °C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO3− concentration, NH4+ concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO2 and N2O) were determined in the undisturbed soil columns. The A horizon at 20 °C showed the highest rates of NO3− removal (1.56 mg N-NO3− kg−1 DW soil day− 1) and CO2 and N2O production (5.89 mg CO2 kg−1 DW soil day− 1 and 55.71 μg N-N2O kg−1 DW soil day− 1). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO3− ha− 1 year− 1, and potential greenhouse gas emissions of 5620 kg CO2 ha− 1 year− 1 and 240 kg N-N2O ha− 1 year− 1. 相似文献
14.
Treatment of fresh air in ventilation systems for air-conditioned offices consumes a significant amount of energy and affects the indoor air quality (IAQ). In this study, energy impact on the ventilation systems was examined against certain IAQ objectives for indoor airborne bacteria exposure risk in air-conditioned offices of Hong Kong. The relationship between thermal energy consumptions and indoor airborne bacteria exposure levels based on regional surveys was investigated. The thermal energy consumptions of ventilation systems operating for carbon dioxide (CO2) exposure concentrations between 800 and 1200 ppmv for typical office buildings and the corresponding failure probability against some target bacteria exposure levels were evaluated. The results showed that, for a reference indoor environment at a CO2 exposure concentration of 1000 ppmv, the predicted average thermal energy saving of ventilation system for a unit increment of the expected risk of unsatisfactory IAQ of 1% was 55 MJ m−2 yr−1 and for a unit decrement of 1%, the predicted additional thermal energy consumption was 58 MJ m−2 yr−1 respectively. This study would be a useful source of reference in evaluation of the energy performance of ventilation strategies in air-conditioned offices at a quantified exposure risk of airborne bacteria. 相似文献
15.
The role of atmospheric urea on the biogeochemical cycle of Water Soluble Organic Nitrogen (WSON) in the Eastern Mediterranean was assessed by collecting and analyzing wet and dry deposition samples and size segregated aerosols during a one year period (2006). In rain water volume weighted mean (VWM) concentration of urea was found equal to 5.5 μM. In atmospheric particles the average concentration of urea in coarse and fine mode was 0.9 ± 1.9 nmol N m− 3 (median 0.0 nmol N m− 3) and 2.2 ± 3.0 nmol N m− 3 (median 1.1 nmol N m− 3), respectively. The percentage contribution of urea to WSON fraction was 0% and 20% in coarse and fine particles respectively. On an annual basis 0.81 mmol m− 2 and 1.78 mmol m− 2 of urea were deposited via wet and dry deposition, contributing to WSON by 10% and 11% respectively. Regression analysis of urea with the main ions and trace metals measured in parallel suggest that soil and anthropogenic activities significantly contribute to atmospheric urea. Comparison of dry deposition of urea using size segregated deposition velocities with urea collected on a glass bead collector suggested the existence of significant fraction of urea in the gas phase. 相似文献
16.
Fred Worrall Martin G. Evans Mark S. Reed Joseph Holden 《The Science of the total environment》2009,408(1):26-36
Upland peat soils represent a large terrestrial carbon store and as such have the potential to be either an ongoing net sink of carbon or a significant net source of carbon. In the UK many upland peats are managed for a range of purposes but these purposes have rarely included carbon stewardship. However, there is now an opportunity to consider whether management practices could be altered to enhance storage of carbon in upland peats. Further, there are now voluntary and regulated carbon trading schemes operational throughout Europe that mean stored carbon, if verified, could have an economic and tradeable value. This means that new income streams could become available for upland management. The ‘Sustainable Uplands’ RELU project has developed a model for calculating carbon fluxes from peat soils that covers all carbon uptake and release pathways (e.g. fluvial and gaseous pathways). The model has been developed so that the impact of common management options within UK upland peats can be considered. The model was run for a decade from 1997-2006 and applied to an area of 550 km2 of upland peat soils in the Peak District. The study estimates that the region is presently a net sink of − 62 ktonnes CO2 equivalent at an average export of − 136 tonnes CO2 equivalent/km2/yr. If management interventions were targeted across the area the total sink could increase to − 160 ktonnes CO2/yr at an average export of − 219 tonnes CO2 equivalent/km2/yr. However, not all interventions resulted in a benefit; some resulted in increased losses of CO2 equivalents. Given present costs of peatland restoration and value of carbon offsets, the study suggests that 51% of those areas, where a carbon benefit was estimated by modelling for targeted action of management interventions, would show a profit from carbon offsetting within 30 years. However, this percentage is very dependent upon the price of carbon used. 相似文献
17.
Desloover J De Clippeleir H Boeckx P Du Laing G Colsen J Verstraete W Vlaeminck SE 《Water research》2011,45(9):2811-2821
New Activated Sludge (NAS®) is a hybrid, floc-based nitrogen removal process without carbon addition, based on the control of sludge retention times (SRT) and dissolved oxygen (DO) levels. The aim of this study was to examine the performance of a retrofitted four-stage NAS® plant, including on-line measurements of greenhouse gas emissions (N2O and CH4). The plant treated anaerobically digested industrial wastewater, containing 264 mg N L−1, 1154 mg chemical oxygen demand (COD) L−1 and an inorganic carbon alkalinity of 34 meq L−1. The batch-fed partial nitritation step received an overall nitrogen loading rate of 0.18-0.22 kg N m−3 d−1, thereby oxidized nitrogen to nitrite (45-47%) and some nitrate (13-15%), but also to N2O (5.1-6.6%). This was achieved at a SRT of 1.7 d and DO around 1.0 mg O2 L−1. Subsequently, anammox, denitrification and nitrification compartments were followed by a final settler, at an overall SRT of 46 d. None of the latter three reactors emitted N2O. In the anammox step, 0.26 kg N m−3 d−1 was removed, with an estimated contribution of 71% by the genus Kuenenia, which constituted 3.1% of the biomass. Overall, a nitrogen removal efficiency of 95% was obtained, yielding a dischargeable effluent. Retrofitting floc-based nitrification/denitrification with carbon addition to NAS® allowed to save 40% of the operational wastewater treatment costs. Yet, a decrease of the N2O emissions by about 50% is necessary in order to obtain a CO2 neutral footprint. The impact of emitted CH4 was 20 times lower. 相似文献
18.
I.M. Al-HelalA.M. Abdel-Ghany 《Energy and Buildings》2011,43(7):1740-1747
For a greenhouse thermal analysis, it is essential to know the energy partition and the amount of solar and thermal radiation converted into sensible and latent heat in the greenhouse. Factors that are frequently needed are: efficiency of utilization of incident solar radiation (π), and sensible and latent heat factors (η and δ). Previous studies considered these factors as constant parameters. However, they depend on the environmental conditions inside and outside the greenhouse, plants and soil characteristics, and structure, orientation and location of the greenhouse. Moreover, these factors have not yet been evaluated under the arid climatic conditions of the Arabian Peninsula.In this study, simple energy balance equations were applied to investigate π, η and δ; energy partitioning among the greenhouse components; and conversion of solar and thermal radiation into sensible and latent heat. For this study, we used an evaporatively cooled, planted greenhouse with a floor area of 48 m2. The parameters required for the analysis were measured on a sunny, hot summer day. The results showed that value of π was almost constant (≅0.75); whereas the values of η and δ strongly depended on the net radiation over the canopy (Rna); and could be represented by exponential decay functions of Rna.At a plant density corresponding to a leaf area index (LAI) of 3 and an integrated incident solar energy of 27.7 MJ m−2 d−1, the solar and thermal radiation utilized by the greenhouse components were 20.7 MJ m−2 d−1 and 3.74 MJ m−2 d−1, respectively. About 71% of the utilized radiation was converted to sensible heat and 29% was converted to latent heat absorbed by the inside air. Contributions of the floor, cover and plant surfaces on the sensible heat of the inside air were 38.6%, 48.2% and 13.2%, respectively. 相似文献
19.
Anniet M. Laverman Josette A. Garnier Emmanuelle M. Mounier Céline L. Roose-Amsaleg 《Water research》2010,44(6):1753-1764
A significant amount of nitrogen entering river basins is denitrified in riparian zones. The aim of this study was to evaluate the influence of nitrate and carbon concentrations on the kinetic parameters of nitrate reduction as well as nitrous oxide emissions in river sediments in a tributary of the Marne (the Seine basin, France). In order to determine these rates, we used flow-through reactors (FTRs) and slurry incubations; flow-through reactors allow determination of rates on intact sediment slices under controlled conditions compared to sediment homogenization in the often used slurry technique. Maximum nitrate reduction rates (Rm) ranged between 3.0 and 7.1 μg N g−1 h−1, and affinity constant (Km) ranged from 7.4 to 30.7 mg N-NO3− L−1. These values were higher in slurry incubations with an Rm of 37.9 μg N g−1 h−1 and a Km of 104 mg N-NO3− L−1. Nitrous oxide production rates did not follow Michaelis-Menten kinetics, and we deduced a rate constant with an average of 0.7 and 5.4 ng N g−1 h−1 for FTR and slurry experiments respectively. The addition of carbon (as acetate) showed that carbon was not limiting nitrate reduction rates in these sediments. Similar rates were obtained for FTR and slurries with carbon addition, confirming the hypothesis that homogenization increases rates due to release of and increasing access to carbon in slurries. Nitrous oxide production rates in FTR with carbon additions were low and represented less than 0.01% of the nitrate reduction rates and were even negligible in slurries. Maximum nitrate reduction rates revealed seasonality with high potential rates in fall and winter and low rates in late spring and summer. Under optimal conditions (anoxia, non-limiting nitrate and carbon), nitrous oxide emission rates were low, but significant (0.01% of the nitrate reduction rates). 相似文献
20.
Temporal variation of nitro-polycyclic aromatic hydrocarbons in PM10 and PM2.5 collected in Northern Mexico City 总被引:1,自引:0,他引:1
B.L. Valle-Hernández V. Mugica-Álvarez E. Salinas-Talavera M.A. Murillo-Tovar R. Villalobos-Pietrini 《The Science of the total environment》2010,408(22):5429-59
With the aim to determine the presence of individual nitro-PAH contained in particles in the atmosphere of Mexico City, a monitoring campaign for particulate matter (PM10 and PM2.5) was carried out in Northern Mexico City, from April 2006 to February 2007. The PM10 annual median concentration was 65.2 μg m− 3 associated to 7.6 μg m− 3 of solvent-extractable organic matter (SEOM) corresponding to 11.4% of the PM10 concentration and 38.6 μg m− 3 with 5.9 μg m− 3 SEOM corresponding to 15.2% for PM2.5. PM concentration and SEOM varied with the season and the particle size. The quantification of nitro-polycyclic aromatic hydrocarbons (nitro-PAH) was developed through the standards addition method under two schemes: reference standard with and without matrix, the former giving the best results. The recovery percentages varied with the extraction method within the 52 to 97% range depending on each nitro-PAH. The determination of the latter was effected with and without sample purification, also termed fractioning, giving similar results. 8 nitro-PAH were quantified, and their sum ranged from 111 to 819 pg m− 3 for PM10 and from 58 to 383 pg m− 3 for PM2.5, depending on the season. The greatest concentration was for 9-Nitroanthracene in PM10 and PM2.5, detected during the cold-dry season, with a median (10th-90th percentiles) concentration in 235 pg m− 3 (66-449 pg m− 3) for PM10 and 73 pg m− 3 (18-117 pg m− 3) for PM2.5. The correlation among mass concentrations of the nitro-PAH and criteria pollutants was statistically significant for some nitro-PAH with PM10, SEOM in PM10, SEOM in PM2.5, NOX, NO2 and CO, suggesting either sources, primary or secondary origin. The measured concentrations of nitro-PAH were higher than those reported in other countries, but lower than those from Chinese cities. Knowledge of nitro-PAH atmospheric concentrations can aid during the surveillance of diseases (cardiovascular and cancer risk) associated with these exposures. 相似文献