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1.
Animal wastewater lagoons nearby concentrated animal feeding operations (CAFOs) represent the latest tendency in global animal farming, severely impacting the magnitude of greenhouse gas emissions, including nitrous oxide (N 2O). We hypothesized that lagoon wastewater could be supersaturated with N 2O as part of incomplete microbial nitrification/denitrification processes, thereby regulating the N 2O partitioning in the gaseous phase. The objectives of this study were: (i) to investigate the magnitude of dissolved N 2O concentrations in the lagoon; and (ii) to determine the extent to which supersaturation of N 2O occurs in wastewater lagoons. Dissolved N 2O concentrations in the wastewater samples were high, ranging from 0.4 to 40.5 μg N 2O mL −1. Calculated dissolved N 2O concentrations from the experimentally measured partition coefficients were much greater than those typically expected in aquatic systems (<∼0.6 μg N 2O mL −1). Knowledge of the factors controlling the magnitude of N 2O supersaturation could potentially bridge mass balance differences between in situ measurements and global N 2O models. 相似文献
2.
The land disposal of waste and wastewater is a major source of N2O emission. This is due to the presence of high concentrations of nitrogen (N) and carbon in the waste. Abattoir wastewater contains 186 mg/L of N and 30.4 mg/L of P. The equivalent of 3 kg of abattoir wastewater-irrigated soil was sieved and taken in a 4-L plastic container. Abattoir wastewater was used for irrigating the plants at the rates of 50 and 100 % field capacity (FC). Four crop species were used with no crop serving as a control. Nitrous oxide emission was monitored using a closed chamber technique. The chamber was placed inside the plastic container, and N2O emission was measured for 7 days after the planting. A syringe and pre-evacuated vial were used for collecting the gas samples; a fresh and clean syringe was used each time to avoid cross-contamination. The collected gas samples were injected into a gas chromatography device immediately after each sampling to analyse the concentration of N2O from different treatments. The overall N2O emission was compared for all the crops under two different abattoir wastewater treatment rates (50 and 100 % FC). Under 100 % FC (wastewater irrigation), among the four species grown in the abattoir wastewater-irrigated soil, Medicago sativa (23 mg/pot), Sinapis alba (21 mg/pot), Zea mays (20 mg/pot) and Helianthus annuus (20 mg/pot) showed higher N2O emission compared to the 50 % treatments—M. sativa (17 mg/pot), S. alba (17 mg/pot), Z. mays (18 mg/pot) and H. annuus (18 mg/pot). Similarly, pots with plants have shown 15 % less emission than the pots without plants. Similar trends of N2O emission flux were observed between the irrigation period (4-week period) for 50 % FC and 100 % FC. Under the 100 % FC loading rate treatments, the highest N2O emission was in the following order: week 1 > week 4 > week 3 > week 2. On the other hand, under the 50 % FC loading rate treatments, the highest N2O emission was recorded in the first few weeks and in the following order: week 1 > week 2 > week 3 > week > 4. Since N2O is a greenhouse gas with high global warming potential, its emission from wastewater irrigation is likely to impact global climate change. Therefore, it is important to examine the effects of abattoir wastewater irrigation on soil for N2O emission potential. 相似文献
3.
The problem of producing strong greenhouse gas of nitrous oxide (N2O) from biological nitrogen removal (BNR) process in wastewater treatment plants (WWTP) has elicited great concern from various sectors. In this study, three laboratory-scale wastewater treatment systems, with influent C/N ratios of 3.4, 5.4, and 7.5, were set up to study the effect of influent C/N ratio on N2O generation in anaerobic/anoxic/oxic (A2O) process. Results showed, with the increased influent C/N ratio, N2O generation from both nitrification and denitrification process was decreased, and the N2O-N conversion ratio of the process was obviously reduced from 2.23 to 0.05%. Nitrification rate in oxic section was reduced, while denitrification rate in anaerobic and anoxic section was elevated and the removal efficiency of COD, NH4
+-N, TN, and TP was enhanced in different extent. As the C/N ratio increased from 3.4 to 7.5, activities of three key denitrifying enzymes of nitrate reductase, nitrite reductase, and nitrous oxide reductase were increased. Moreover, microorganism analysis indicated that the relative abundance of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were positively correlated with N2O generation, which was reduced from (8.42 ± 3.65) to (3.61 ± 1.66)% and (10.38 ± 4.12) to (4.67 ± 1.62)%, respectively. NosZ gene copy numbers of the A2O system were increased from (1.19 ± 0.49) × 107 to (2.84 ± 0.54) × 108 copies/g MLSS with the influent C/N ratio elevated from 3.4 to 7.5. Hence, appropriate influent C/N condition of A2O process could optimize the microbial community structure that simultaneously improve treatment efficiency and decrease the N2O generation. 相似文献
4.
In coastal Antarctica, freezing and thawing influence many physical, chemical and biological processes for ice-free tundra ecosystems, including the production of greenhouse gases (GHGs). In this study, penguin guanos and ornithogenic soil cores were collected from four penguin colonies and one seal colony in coastal Antarctica, and experimentally subjected to three freezing–thawing cycles (FTCs) under ambient air and under N 2. We investigated the effects of FTCs on the emissions of three GHGs including nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4). The GHG emission rates were extremely low in frozen penguin guanos or ornithogenic soils. However, there was a fast increase in the emission rates of three GHGs following thawing. During FTCs, cumulative N 2O emissions from ornithogenic soils were greatly higher than those from penguin guanos under ambient air or under N 2. The highest N 2O cumulative emission of 138.24 μg N 2O–N kg ?1 was observed from seal colony soils. Cumulative CO 2 and CH 4 emissions from penguin guanos were one to three orders of magnitude higher than those from ornithogenic soils. The highest cumulative CO 2 (433.0 mgCO 2–C kg ?1) and CH 4 (2.9 mgCH 4–C kg ?1) emissions occurred in emperor penguin guanos. Penguin guano was a stronger emitter for CH 4 and CO 2 while ornithogenic soil was a stronger emitter for N 2O during FTCs. CO 2 and CH 4 fluxes had a correlation with total organic carbon (TOC) and soil/guano moisture (M c) in penguin guanos and ornithogenic soils. The specific CO 2–C production rate (CO 2–C/TOC) indicated that the bioavailability of TOC was markedly larger in penguin guanos than in ornithogenic soils during FTCs. This study showed that FTC-released organic C and N from sea animal excreta may play a significant role in FTC-related GHG emissions, which may account for a large proportion of annual fluxes from tundra ecosystems in coastal Antarctica. 相似文献
5.
Municipal solid waste landfills are the significant anthropogenic sources of N 2O due to the cooxidation of ammonia by methane-oxidizing bacteria in cover soils. Such bacteria could be developed through CH 4 fumigation, as evidenced by both laboratory incubation and field measurement. During a 10-day incubation with leachate addition, the average N 2O fluxes in the soil samples, collected from the three selected landfill covers, were multiplied by 1.75 ( p < 0.01), 3.56 ( p < 0.01), and 2.12 ( p < 0.01) from the soil samples preincubated with 5% CH 4 for three months when compared with the control, respectively. Among the three selected landfill sites, N 2O fluxes in two landfill sites were significantly correlated with the variations of the CH 4 emissions without landfill gas recovery ( p < 0.001). N 2O fluxes were also elevated by the increase of the CH 4 emissions with landfill gas recovery in another landfill site ( p > 0.05). The annual average N 2O flux was 176 ± 566 μg N 2O–N m ?2 h ?1 ( p < 0.01) from sandy soil–covered landfill site, which was 72% ( p < 0.05) and 173% ( p < 0.01) lower than the other two clay soil covered landfill sites, respectively. The magnitude order of N 2O emissions in three landfill sites was also coincident by the results of laboratory incubation, suggesting the sandy soil cover could mitigate landfill N 2O emissions. 相似文献
6.
Tetracycline antibiotics including tetracycline (TTC), oxytetracycline (OTC) and chlorotetracycline (CTC) undergo rapid transformation to yield various products in the presence of MnO 2 at mild conditions (pH 4-9 and 22 °C). Reaction rates follow the trend of CTC > TTC > OTC, and are affected by pH and complexation of TCs with Mg 2+ or Ca 2+. Experimental results of TTC indicate that MnO 2 promotes isomerization at the C ring to form iso-TTC and oxidizes the phenolic-diketone and tricarbonylamide groups, leading to insertion of up to 2 O most likely at the C9 and C2 positions. In contrast, reactions of OTC with MnO 2 generate little iso-OTC, but occur mainly at the A ring’s dimethylamine group to yield N-demethylated products. CTC yields the most complicated products upon reactions with MnO 2, encompassing transformation patterns observed with both TTC and OTC. The identified product structures suggest lower antibacterial activity than that of the parent tetracyclines. 相似文献
7.
A UK inventory of the nitrous oxide (N 2O) emissions from farmed livestock was compiled to identify areas where potential abatement practices may be effective. Where possible, emission factors based on direct experimental data gathered under UK conditions were used, but published data were used when this was not feasible, together with statistical information, which included details of numbers of animals within each category of a species, animal liveweights, number of days housed, excretal rates and volumes of manures in stores. Total N 2O emissions were calculated for each component of livestock production systems, i.e. animal houses, manure stores, following application of manures to land and during grazing. Emissions were also estimated from land used for forage conservation and tillage. Total annual N 2O emissions from UK farmed livestock, based mainly on 1996 animal census data, were estimated to be 38.27 kt. The two main terms were 22.66 kt N 2O from mineral fertilisers after application to soils and 5.61 kt N 2O from stored manures (mainly in the form of farmyard manure). Within buildings, poultry were the largest contributors of N 2O, 2.97 kt, followed by cattle, 1.62 kt. Within the total emissions from stored manures, cattle were the largest contributors of N 2O, 3.58 kt, followed by poultry, 1.86 kt. Dietary manipulation and a move from solid manure based systems to slurry based systems appear to be promising abatement practices. 相似文献
8.
The wetlands play an important role in global carbon and nitrogen storage, and they are also natural sources of greenhouse gases such as methane (CH 4) and nitrous oxide (N 2O). Land-use change is an important factor affecting the exchange of greenhouse gases between wetlands and the atmosphere. However, few studies have investigated the effect of land-use change on CH 4 and N 2O emissions from freshwater marsh in China. Therefore, a field study was carried out over a year to investigate the seasonal changes of the emissions of CH 4 and N 2O at three sites ( Deyeuxia angustifolia marsh, dryland and rice field) in the Sanjiang Plain of Northeast China. Marsh was the source of CH 4 showing a distinct temporal variation. Maximum fluxes occurred in June and the highest value was 20.69 ± 2.57 mg CH 4 m ?2 h ?1. The seasonal change of N 2O fluxes from marsh was not obvious, consisted of a series of emission pulses. The marsh acted as a N 2O sink during winter, while became a N 2O source in the growing season. The results showed that gas exchange between soil/snow and the atmosphere in the winter season contributed greatly to the annual budgets. The winter season CH 4 flux was about 3.24% of the annual flux and the winter uptake of N 2O accounted for 13.70% of the growing-season emission. Conversion marsh to dryland resulted in a shift from a strong CH 4 source to a weak sink (from 199.12 ± 39.04 to ?1.37 ± 0.68 kg CH 4 ha ?1 yr ?1), while increased N 2O emissions somewhat (from 4.07 ± 1.72 to 4.90 ± 1.52 kg N 2O ha ?1 yr ?1). Conversion marsh to rice field significantly decreased CH 4 emission from 199.12 ± 39.04 to 94.82 ± 9.86 kg CH 4 ha ?1 yr ?1 and N 2O emission from 4.07 ± 1.72 to 2.09 ± 0.79 kg N 2O ha ?1 yr ?1. 相似文献
9.
A field experiment was conducted in a rice–winter wheat rotation agroecosystem to quantify the direct emission of N 2O for synthetic N fertilizer and crop residue application in the 2002–2003 annual cycle. There was an increase in N 2O emission accompanying synthetic N fertilizer application. Fertilizer-induced emission factor for N 2O (FIE) averaged 1.08% for the rice season, 1.49% for the winter wheat season and 1.26% for the whole annual rotation cycle. The annual background emission of N 2O totaled 4.81 kg N 2O–N ha −1, consisting of 1.24 kg N 2O–N ha −1 for rice, 3.11 kg N 2O–N ha −1 for wheat seasons. When crop residue and synthetic N fertilizer were both applied in the fields, crop residue-induced emission factor for N 2O (RIE) was estimated as well. When crop residue was retained at the rate of 2.25 and 4.50 t ha −1 for each season, the RIE averaged 0.64% and 0.27% for the whole annual rotation cycle, respectively. Based on available multi-year data of N 2O emissions over the whole rice–wheat rotation cycle at 3 sites in southeast China, the FIE averaged 1.02% for the rice season, 1.65% for the wheat season. On the whole annual cycle, the FIE for N 2O ranged from 1.05% to 1.45%, with an average of 1.25%. Annual background emission of N 2O averaged 4.25 kg ha −1, ranging from 3.62 to 4.87 kg ha −1. It is estimated that annual N 2O emission in paddy rice-based agroecosystem amounts to 169 Gg N 2O–N in China, accounting for 26–60% of the reported estimates of total emission from croplands in China. 相似文献
10.
Ammonia-nitrogen flux (NH 3-N=(14/17)NH 3) was determined from six anaerobic swine waste storage and treatment lagoons (primary, secondary, and tertiary) using the dynamic chamber system. Measurements occurred during the fall of 1998 through the early spring of 1999, and each lagoon was examined for approximately one week. Analysis of flux variation was made with respect to lagoon surface water temperature (∼15 cm below the surface), lagoon water pH, total aqueous phase NH x(=NH 3+NH 4+) concentration, and total Kjeldahl nitrogen (TKN). Average lagoon temperatures (across all six lagoons) ranged from approximately 10.3 to 23.3 °C. The pH ranged in value from 6.8 to 8.1. Aqueous NH x concentration ranged from 37 to 909 mg N l −1, and TKN varied from 87 to 950 mg N l −1. Fluxes were the largest at the primary lagoon in Kenansville, NC (March 1999) with an average value of 120.3 μg N m −2 min −1, and smallest at the tertiary lagoon in Rocky Mount, NC (November 1998) at 40.7 μg N m −2 min −1. Emission rates were found to be correlated with both surface lagoon water temperature and aqueous NH x concentration. The NH 3-N flux may be modeled as ln(NH 3-N flux)=1.0788+0.0406 TL+0.0015([NH x]) ( R2=0.74), where NH 3-N flux is the ammonia flux from the lagoon surface in μg N m −2 min −1, TL is the lagoon surface water temperature in °C, and [NH x] is the total ammonia-nitrogen concentration in mg N l −1. 相似文献
11.
Greenhouse gas emissions from hydroelectric dams have recently given rise to controversies about whether hydropower still provides clean energy. China has a large number of dams used for energy supply and irrigation, but few studies have been carried out on aquatic nitrous oxide (N 2O) variation and its emissions in Chinese river-reservoir systems. In this study, N 2O spatiotemporal variations were investigated monthly in two reservoirs along the Wujiang River, Southwest China, and the emission fluxes of N 2O were estimated. N 2O production in the reservoirs tended to be dominated by nitrification, according to the correlation between N 2O and other parameters. N 2O saturation in the surface water of the Wujiangdu reservoir ranged from 214% to 662%, with an average fluctuation of 388%, while in the Hongjiadu reservoir, it ranged from 201% to 484%, with an average fluctuation of 312%. The dissolved N 2O in both reservoirs was over-saturated with respect to atmospheric equilibrium levels, suggesting that the reservoirs were net sources of N 2O emissions to the atmosphere. The averaged N 2O emission flux in the Wujiangdu reservoir was 0.64 μmol m ?2 h ?1, while it was 0.45 μmol m ?2 h ?1 in the Hongjiadu reservoir, indicating that these two reservoirs had moderate N 2O emission fluxes as compared to other lakes in the world. Downstream water of the dams had quite high levels of N 2O saturation, and the estimated annual N 2O emissions from hydropower generation were 3.60 × 10 5 and 2.15 × 10 5 mol N 2O for the Wujiangdu and the Hongjiadu reservoir, respectively. These fluxes were similar to the total N 2O emissions from the reservoir surfaces, suggesting that water released from reservoirs would be another important way for N 2O to diffuse into the atmosphere. It can be concluded that dam construction significantly changes the water environment, especially in terms of nutrient status and physicochemical conditions, which have obvious influences on the N 2O spatiotemporal variations and emissions. 相似文献
12.
The relevance of indirect N 2O emission is a controversial topic which is subject to much uncertainty. Only a small number of studies measure the indirect N 2O emission at the interface from soil to stream. In addition, the majority of studies undertaken only cover a short-term period (<1 year). Therefore, limited information is available regarding the influence of seasonal or event effects, nor is there much information as to whether indirect N 2O emissions are reflected by N 2O in soil solutions. The present study aimed at clarifying these two questions along with the general relevance of dissolved nitrous oxide. A wetness gradient involving soil solutions of different soil types and surface waters within an N-saturated forest catchment (3.2 ha) was monitored over a period of 1 year. N 2O concentrations in soil solutions (0.09–16.6 μg N l −1) were affected by events such as dry–wet cycles but did not reflect to the actual, indirect N 2O emission at the soil-stream interface. It was assumed that N 2O emission was due to N transformation processes. The N 2O concentration at the spring was three times higher than the N 2O concentrations in the soil solutions. Nevertheless, indirect N 2O emission was still subordinate (<1%) to the direct emission of N 2O. The weekly amount of indirect N 2O emissions depended only on the stream flow rate (62% of the total annual amount). For this reason it was necessary to measure indirect N 2O emission at short intervals and at the interface between soil and stream over a longer time period. Our results and the results of the reviewed studies show that the default IPCC emission factor (EF5-g=1.5%) overestimates the indirect N 2O emission from ecosystems. The emission factor should therefore be lowered to about 0.1–0.3%. In addition, the results indicate that indirect N 2O emission is an insignificant pathway in the N cycle of most ecosystems. However, final judgement will depend on long-term studies. 相似文献
13.
ABSTRACT In the literature, different values of the distribution coefficient K H for HgCl 2 between water and air are present in a range that spans more than 3 orders of magnitude. In order to determine if a waste incineration scrubber solution could become saturated with regard to HgCl 2, an accurate experimental determination of the distribution constant of HgCl 2 at elevated temperatures is needed. In this work, the coefficient has been determined at four different temperatures between 10 and 50 °C. The Arrhenius expression obtained is 5.5 x 10 5 x exp[-(8060 ± 2200)/7] with a corresponding enthalpy for the process HgCl 2(aq)<» HgCl 2(g) of 67 ± 20 kJ/mole. KH at 293 K was found to be ~5 x 10 -7 atm M -1, which is in almost perfect agreement with an earlier study. Applying the obtained KH values to waste incineration scrubber conditions shows that no major saturation effect will occur. 相似文献
14.
There is increasing concern that agricultural intensification in China has greatly increased N 2O emissions due to rapidly increased fertilizer use. By linking a spatial database of precipitation, synthetic fertilizer N input, cropping rotation and area via GIS, a precipitation-rectified emission factor of N 2O for upland croplands and water regime-specific emission factors for irrigated rice paddies were adopted to estimate annual synthetic fertilizer N-induced direct N 2O emissions (FIE-N 2O) from Chinese croplands during 1980-2000. Annual FIE-N 2O was estimated to be 115.7 Gg N 2O-N year −1 in the 1980s and 210.5 Gg N 2O-N year −1 in the 1990s, with an annual increasing rate of 9.14 Gg N 2O-N year −1 over the period 1980-2000. Upland croplands contributed most to the national total of FIE-N 2O, accounting for 79% in 1980 and 92% in 2000. Approximately 65% of the FIE-N 2O emitted in eastern and southern central China. 相似文献
15.
Nitrous oxide (N 2O) has gained considerable attention as a contributor to global warming and depilation of stratospheric ozone layer. Landfill is one of the high emitters of greenhouse gas such as methane and N 2O during the biodegradation of solid waste. Landfill aeration has been attracted increasing attention worldwide for fast, controlled and sustainable conversion of landfills into a biological stabilized condition, however landfill aeration impel N 2O emission with ammonia removal. N 2O originates from the biodegradation, or the combustion of nitrogen-containing solid waste during the microbial process of nitrification and denitrification. During these two processes, formation of N 2O as a by-product from nitrification, or as an intermediate product of denitrification. In this study, air was injected into a closed landfill site and investigated the major N 2O production factors and correlations established between them. The in-situ aeration experiment was carried out by three sets of gas collection pipes along with temperature probes were installed at three different distances of one, two and three meter away from the aeration point; named points A-C, respectively. Each set of pipes consisted of three different pipes at three different depths of 0.0, 0.75 and 1.5 m from the bottom of the cover soil. Landfill gases composition was monitored weekly and gas samples were collected for analysis of nitrous oxide concentrations. It was evaluated that temperatures within the range of 30–40°C with high oxygen content led to higher generation of nitrous oxide with high aeration rate. Lower O 2 content can infuse N 2O production during nitrification and high O 2 inhibit denitrification which would affect N 2O production. The findings provide insights concerning the production potentials of N 2O in an aerated landfill that may help to minimize with appropriate control of the operational parameters and biological reactions of N turnover. Implications: Investigation of nitrous oxide production potential during in situ aeration in an old landfill site revealed that increased temperatures and oxygen content inside the landfill site are potential factors for nitrous oxide production. Temperatures within the range of optimum nitrification process (30–40°C) induce nitrous oxide formation with high oxygen concentration as a by-product of nitrogen turnover. Decrease of oxygen content during nitrification leads increase of nitrous oxide production, while temperatures above 40°C with moderate and/or low oxygen content inhibit nitrous oxide generation. 相似文献
16.
Nitrous oxide (N 2O) is a trace gas contributing to stratospheric ozone depletion and global warming. Although a large quantity of information exists about N 2O emissions from various ecosystems, this study was initiated to demonstrate the features of N 2O emissions from sea-based waste disposal sites in Osaka City in relation to CH 4 emissions. Average N 2O emissions at an active landfill (S-Site) were several times higher than those at a closed landfill (N Site). Average CH 4 emissions were also much greater at the S-Site. Regarding the nature of N 2O emissions, remarkable emissions often were observed with aerobic waste layers at the N-Site, suggesting almost inversely related N 2O emissions with CH 4 production at the N-Site. However, at the S-Site a few exceptionally high N 2O emissions were noted in cases of high CH 4 emissions. 相似文献
17.
An automated system for continuous measurement of N 2O fluxes on an hourly basis was employed to study N 2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N 2O emissions occurred mainly within two weeks of application of NH 4+-based fertilizer and total N 2O emissions in wheat (average 0.35 or 0.21 kg N ha −1 season −1) and maize (average 1.47 or 0.49 kg N ha −1 season −1) under conventional and optimum N fertilization (300 and 50-122 kg N ha −1, respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N 2O was produced mainly from nitrification of NH 4+-based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N 2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH 4+- to NO 3ˉ-based fertilizers. 相似文献
18.
This study investigated the effect of bulking agents on the maturity and gaseous emissions of composting kitchen waste. Three different bulking agents (cornstalks, sawdust, and spent mushroom substrate) were used to compost kitchen waste under aerobic conditions in 60-L reactors for a 28-d period. A control treatment was also studied using kitchen waste without a bulking agent. During the experiment, maturity indexes such as temperature, pH value, C/N ratio, and germination index were determined, and continuous measurements of leachate and gaseous emissions (CH 4, N 2O, and NH 3) were taken. The results showed that all of the composts with bulking agents reached the required maturity standard, and the addition of spent mushroom substrate gave the highest maturity (C/N ratio decreased from 23 to 16 and germination index increased from 53% to 111%). The bulking agents also reduced leachate production and CH 4 and N 2O emissions, but had little impact on NH 3 emissions. Composting with sawdust as a bulking agent was found to emit less total greenhouse gas (33 kg CO 2-eq t −1 dry matter) than the other treatments. 相似文献
19.
Due to the high temporal and spatial variability of N 2O fluxes, estimates of N 2O emission from temperate forest ecosystems are still highly uncertain, particularly at larger scales. Although highest N 2O emissions with up to 7.0 kg N ha −1 yr −1 were mainly reported for soils affected by stagnant water, most of the reported gas flux measurements were performed at forest sites with well-aerated soils yielding mostly to low mean annual emission rates less than 1.0 kg N ha −1 yr −1. This study compares N 2O fluxes from upland ( Cambisols) and temporally water-logged ( Gleysols, Histosols) soils of the Central Black Forest (South-West Germany) over a period of 2 yr. Mean annual N 2O fluxes from investigated soils ranged between 0.2 and 3.9 kg N ha −1 yr −1. The fluxes showed a large variability between the different soil types. Emissions could be clearly ranked in the following order: Cambisols (0.26–0.75 kg N ha −1 yr −1)< Gleysols (1.37–2.68 kg N ha −1 yr −1)< Histosol (3.66–3.95 kg N ha −1 yr −1). Although the Cambisols cover two-thirds of the investigated area, only about half of the overall N 2O is emitted from this soil type. Therefore, regional or national N 2O fluxes from temperate forest soils are underestimated if soils characterised by intermediate aeration conditions are disregarded. 相似文献
20.
High-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH 4 retention, 99.8% (CH 4 mean flux of 12 mg C m -2 h -1) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m -2 h -1) of the same landfill age. Fresh waste at the working face emitted a large fraction of N 2O, with average fluxes of 10 mg N m -2 h -2, while N 2O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH 4 emissions were elevated under high air temperatures but decreased as landfill age increased. N 2O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO 2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr -1 in CO 2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH 4 (41.9%), while the working face contributed the most N 2O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control. Implications: Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N2O, which should draw attention. High CH4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH4 retention, and therefore is a recommended cover material for GHG control. 相似文献
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