Estimation of Greenhouse Gases in the Ambient Air

BackgroundGlobally, rice systems are a major source of atmospheric CH4 and for major rice‐producing countries, such as Vietnam, CH4 as well as N2O emissions from agricultural land used for rice production may represent about one‐fourth of total national anthropogenic greenhouse gas (GHG) emissions. However, national‐scale estimates of GHG emissions from rice systems are uncertain with regard to its magnitude, spatial distribution, and seasonality.AimsHere, we used the biogeochemical model LandscapeDNDC to calculate emissions of CH4 and N2O from rice systems in Vietnam (Tier 3 IPCC approach). Our objectives were to identify hotspot regions of emissions and to assess the contribution of N2O to the total non‐CO2 (CH4+N2O) GHG balance of rice systems as well as the seasonal and interannual variability of fluxes in dependence of uncertain input data on field management .MethodsThe biogeochemical model LandscapeDNDC model was linked to publicly available information on climate, soils, and land management (fertilization, irrigation, crop rotation) for calculating a national inventory in daily time steps of CH4 and N2O emissions from rice systems at a spatial resolution of 0.083° × 0.083°. Uncertainty in management practices related to fertilization, use of harvest residues or irrigation water, and its effects on simulated CH4 and N2O fluxes was accounted for by Latin Hypercube Sampling of probability distribution functions.ResultsOur study shows that CH4 and N2O fluxes from rice systems in Vietnam are highly seasonal, with national CH4 and N2O emissions totaling to about 2600 Gg CH4 year–1 and 42 Gg N2O year–1, respectively. Highest emissions were simulated for double and triple rice cropping systems in the Mekong Delta region. Yield‐scaled emissions varied largely in a range of 300–3000 kg CO2‐eq Mg–1 year–1, with CH4 emissions during the rice season(s) dominating (>82%) the total annual non‐CO2 GHG balance of rice systems. In our study, uncertainty in field management information (nitrogen fertilization, ratio synthetic to organic fertilization, residue management, availability of irrigation water) were major drivers of uncertainty of the national CH4 and N2O emission inventory.ConclusionsOur study shows that Tier 3 approaches, that is, process‐oriented model approaches combined with GIS databases, for estimating national‐scale GHG emissions from rice systems are ready to be applied at national scale. Generally, this approach is powerful as it allows to identify regions with elevated emissions, thereby accounting not only for CH4, but as well for N2O emissions. However, our study also shows that specifically better information on land management is required to narrowing uncertainties.

CH4 and CO2 are important greenhouse gases, playing a very important role in greenhouse effect. In order to estimate the current situation of source and sink of main greenhouse gases in Baiyangdian wetland and evaluate the influences of wetland system to the greenhouse effect of North China, static closed chamber-gas chromatogram method was adopted to study the space-time variation characteristics of N2O, CH4, and CO2 emission fluxes in Baiyangdian wetland. The analysis results indicate: the lake wetland which was abundant in organic matters and nutritive salt was an important greenhouse gases emission source. During one year of observation, it was found out that the fluxes of N2O, CH4, and CO2 of Baiyangdian wetland posses a very high time variability, with the range of variation being-0.08~0.33 mg·m-2·h-1, -5.40~328.65 mg·m-2·h-1 and -814.06~2934.93 mg·m-2·h-1. The emission fluxes of N2O, CH4, and CO2 reaches to maximum in summer, respectively being 62.09%, 92.15% and 87.04% of the annual total emission flux, The lakeside was a core area of N2O, CH4 emission, with annual average emission flux respectively reaching up to 0.11 mg·m-2·h-1 and 40.86 mg·m-2·h-1. Although the main emission area of CO2 was land, the emission flux of lakeside, with annual average emission flux being 692.35 mg·m-2·h-1, was also very high, ranking only second to land, the lakeside area of Baiyangdian wetland was only 12.60% of the whole lake wetland area, but the emission loads of N2O, CH4, and CO2 were respectively 26.51%, 43.96% and 23.76% of the total emission load, which explains that the lakeside was leading the greenhouse gases emission of Baiyangdian wetland.

Rivers play an important role in greenhouse gas emissions. Over the past decade, because of global urbanization trends, rapid land use changes have led to changes in river ecosystems that have had a stimulating effect on the greenhouse gas production and emissions. Presently, there is an urgent need for assessments of the greenhouse gas concentrations and emissions in watersheds. Therefore, this study was designed to evaluate river-based greenhouse gas emissions and their spatial-temporal features as well as possible impact factors in a rapidly urbanizing area. The specific objectives were to investigate how river greenhouse gas concentrations and emission fluxes are responding to urbanization in the Liangtan River, which is not only the largest sub-basin but also the most polluted one in Chongqing City. The thin layer diffusion model method was used to monitor year-round concentrations of pCO2, CH4, and N2O in September and December 2014, and March and June 2015. The pCO2 range was (23.38±34.89)-(1395.33±55.45) Pa, and the concentration ranges of CH4 and N2O were (65.09±28.09)-(6021.36±94.36) nmol·L-1 and (29.47±5.16)-(510.28±18.34) nmol·L-1, respectively. The emission fluxes of CO2, CH4, and N2O, which were calculated based on the method of wind speed model estimations, were -6.1-786.9, 0.31-27.62, and 0.06-1.08 mmol·(m2·d)-1, respectively. Moreover, the CO2 and CH4 emissions displayed significant spatial differences, and these were roughly consistent with the pollution load gradient. The greenhouse gas concentrations and fluxes of trunk streams increased and then decreased from upstream to downstream, and the highest value was detected at the middle reaches where the urbanization rate is higher than in other areas and the river is seriously polluted. As for branches, the greenhouse gas concentrations and fluxes increased significantly from the upstream agricultural areas to the downstream urban areas. The CO2 fluxes followed a seasonal pattern, with the highest CO2 emission values observed in autumn, then successively winter, summer, and spring. The CH4 fluxes were the highest in spring and the lowest in summer, while N2O flux seasonal patterns were not significant. Because of the high carbon and nitrogen loads in the basin, the CO2 products and emissions were not restricted by biogenic elements, but levels were found to be related to important biological metabolic factors such as the water temperature, pH, DO, and chlorophyll a. The carbon, nitrogen, and phosphorus content of the water combined with sewage input influenced the CH4 products and emissions. Meanwhile, N2O production and emissions were mainly found to be driven by urban sewage discharge with high N2O concentrations. Rapid urbanization accelerated greenhouse gas emissions from the urban rivers, so that in the urban reaches, CO2/CH4 fluxes were twice those of the non-urban reaches, and all over the basin N2O fluxes were at a high level. These findings illustrate how river basin urbanization can change aquatic environments and aggravate allochthonous pollution inputs such as carbon, nitrogen, and phosphorus, which in turn can dramatically stimulate river-based greenhouse gas production and emissions; meanwhile, spatial and temporal differences in greenhouse gas emissions in rivers can lead to the formation of emission hotspots.

PDF HTML阅读 XML下载 导出引用 引用提醒 博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O排放通量 DOI: 10.5846/stxb201610302213 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 新疆维吾尔自治区重点实验室专项基金项目（XJDX0909-2014-05）；新疆师范大学硕士研究生科技创新项目（XSY201602002） Emission fluxes of CO2, CH4, and N2O from artificial and natural reed wetlands in Bosten Lake, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究干旱区淡水湖泊人工、天然芦苇湿地土壤温室气体源汇强度及其影响因素，采用静态箱-气相色谱法，于2015年1月-12月对博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O通量进行全年观测。结果表明，人工芦苇湿地土壤CO2、CH4和N2O排放通量变化范围分别为：10.1-588.4mg m-2 h-1、2.9-82.4μg m-2 h-1和1.32-29.7μg m-2 h-1，天然芦苇湿地土壤CO2、CH4和N2O排放通量变化范围分别为10.3-469.6mg m-2 h-1、3.1-64.8μg m-2 h-1和1.9-14.3μg m-2 h-1。人工和天然芦苇湿地夏季土壤CO2排放通量均明显高于其他季节，而土壤CH4和N2O排放通量较大值多集中在春末夏初。全年观测期间，人工芦苇湿地土壤CO2、CH4和N2O排放通量高于天然芦苇湿地（P>0.05）；温度是影响人工、天然芦苇湿地土壤CO2和N2O排放通量的关键因素，近地面温度和5cm土壤温度与CO2和N2O排放通量呈现极显著的正相关关系（P<0.01）。土壤CH4排放通量是温度和水分二者共同影响的，由近地表温度、5cm土壤温度和土壤含水量共同拟合的方程可以分别解释人工、天然芦苇湿地土壤CH4排放通量的71%、74.5%；土壤有机碳、pH、盐分、NH4+-N、NO3--N也是人工、天然芦苇湿地土壤CO2、CH4和N2O排放通量的影响因素；人工和天然芦苇湿地土壤均是CO2、CH4和N2O的"源"。基于100年尺度，由3种温室气体计算全球增温潜势得出，人工芦苇湿地全球增温潜势大于天然芦苇湿地（15150.18kg/hm2 > 12484.21kg/hm2）。 Abstract:CO2, CH4, and N2O, have strong warming potentials and are considered to be the primary greenhouse gases in the atmosphere. Global warming caused by the increasing concentrations of atmospheric CO2, CH4, and N2O is one of the hotspots in global change field. Greenhouse gas (GHG) fluxes in reed wetlands are critical in evaluating the source/sink strength of GHG in arid area. We studied the dynamics of soil CO2, CH4, and N2O fluxes using static chamber-based on gas chromatography in two reed wetlands of the freshwater Bosten Lake, located in an arid area of Northwestern China. During a full year of monitoring, environmental variables (including soil moisture, soil temperature, air temperature, pH and salinity) were measured to determine the effects of abiotic factors on soil CO2, CH4, and N2O fluxes in artificial and natural reed wetlands. SPSS 19.0 for Windows was used to analyze the relationships between environmental factors and soil CO2, CH4, and N2O fluxes. The results showed that soil CO2, CH4, and N2O fluxes in the artificial reed wetland were 10.1-588.4mg m-2 h-1, 1.32-29.7μg m-2 h-1 and 3.1-64.8μg m-2 h-1, respectively, which was comparable with the values from the natural reed wetland. Higher soil CO2 emissions occurred in summer, whereas CH4 and N2O emissions mainly occurred in late spring and early summer. Temperature was the main factor controlling soil CO2 and N2O fluxes in both reed wetlands (P < 0.01). Soil CH4 emission flux was affected by both temperature and moisture. According to regression analysis, the combination of near-surface temperature, top 5cm soil temperature, and soil water content could explain 71% and 74.5% of soil CH4 flux in artificial and natural reed wetlands, respectively. Soil organic carbon, pH, salinity, NH4+-N, and NO3--N are also influencing factors of CO2, CH4, and N2O fluxes in artificial and natural reed wetlands. However, the differences in CO2, CH4, and N2O emissions from soils of artificial and natural reed wetlands were caused by differences in soil organic carbon, soluble nitrogen, and biomass. Based on the centennial scale, the soils of artificial and natural reed wetland were "sources" of GHG, and the global warming potential from artificial reed wetland was higher than that from natural reed wetland. 参考文献 相似文献 引证文献

Effects of substrate type on enhancing pollutant removal performance and reducing greenhouse gas emission in vertical subsurface flow constructed wetland

A review on the main affecting factors of greenhouse gases emission in constructed wetlands

Salinity has a significant impact on the sewage treatment efficiency of constructed wetlands (CWs), as well as affecting the greenhouse gas emissions of CWs. A lab-scale CW simulation system was constructed to observe the treatment efficiency and greenhouse gas flux occurring in CWs at different influent salinities (0%, 0.5%, 1.0%, 1.5%, and 2.0%). The results show that (1) the removal rates of COD, TN, NH4+-N, NO3--N, and TP reach the highest at salinity of 0 or 0.5%. And the lowest removal rates are all at a salinity of 2.0%. (2) The emission flux of CO2, CH4, and N2O in CWs varies with an increase in salinity. The trends of CO2 and CH4 emission flux were consistent with those of COD reduction rate. However, it was opposite for N2O flux to that of TN, NH4+-N, and NO3--N removal rate. Affected by salinity, the greenhouse gas emission flux in this study is generally lower than what was reported in literature. (3) Correlation analysis showed that CO2 and CH4 emission fluxes were positively correlated with the COD reduction rate. N2O emission flux was negatively correlated with the removal rates of TN, NH4+-N, and NO3--N. The results suggest that different pollutants are inhibited by salinity to different degrees. COD is more affected by salinity than nitrogen and phosphorus, while nitrogen is more easily inhibited by salinity than phosphorus. CWs can have a high removal rate of pollutants in treating low-salinity wastewater. Although increased salinity reduces treatment efficiency of wastewater to some extent, it also inhibits the emission of CO2 and CH4.

The agricultural sector is considered one of the major sources of greenhouse gas (GHG) emissions globally. The livestock industry as a significant contributor, is accounting for about 18% of GHG emissions measured in carbon dioxide (CO2) equivalent from agricultural practices. Depending on farming practices and climatic conditions, GHGs such as methane (CH4) and nitrous oxide (N2O) emissions from livestock agriculture can vary significantly. Country-specific emission factors are, therefore, needed for a precise estimation of GHG emissions and to avoid uncertainties. This study was aimed at estimating the CH4 and N2O emission fluxes from Hanwoo (the most famous and popular Korean native cattle) manure management systems. CH4 and N2O emission fluxes from litter in the Hanwoo cattle barn and composting lot were monitored and calculated for 52 weeks using the dynamic chamber method. The calculated monthly average fluxes of CH4 and N2O from litter in the cattle barn ranged from 0.0 to 30.0 ± 13.7 and 0.896 ± 0.557 to 2.925 ± 2.853 μg/m2 s, respectively during the whole measurement period. While during the composting period, the monthly average of CH4 and N2O emission fluxes were varied from 1.449 ± 0.783 to 86.930 ± 19.092 and 0.511 ± 0.410 to 2.629 ± 1.105 μg/m2 s, respectively. The calculated emission fluxes of CH4 and N2O from manure management systems in this study were almost 5.4 and 2.1 times, respectively higher than the values reported for the Asian, South and North American countries in the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Overall, this study initiates the process along with signifies the importance of developing country-specific GHG inventories for the effective reduction of GHG emissions from the livestock sector in Korea.

Large-scale multi-stage constructed wetlands for secondary effluents treatment in northern China: Carbon dynamics.

Ratoon rice can improve rice yield by increasing the multiple cropping index in China. However, the greenhouse gas (CH4 and N2O) emission characteristics from ratoon rice fields and the cultivation methods to reduce CH4 and N2O emissions are rarely reported. This study first conducted the analysis of genotype differences in greenhouse gas emission fluxes using five strong ratoon ability rice varieties in 2020. Second, water management methods, including alternating the wet–dry irrigation (AWD) pattern and conventional flooding irrigation (CF) during the main season, were carried out in 2021. CH4 and N2O emission flux, agronomic traits, and rice yield during both main and ratoon seasons were investigated. The results showed that the CH4 emission flux during the main and ratoon seasons was 157.05–470.73 kg·ha–1 and 31.03–84.38 kg·ha–1, respectively, and the total N2O emission flux was 0.13–0.94 kg·ha–1 in the ratoon rice system over the two seasons (RRSTS). Compared with the main season, the CH4 emission flux during the ratoon season was significantly reduced, thus decreasing the greenhouse gas global warming potential (GWP) and greenhouse gas emission intensity (GHGI) in the ratoon rice system. Cliangyouhuazhan (CLYHZ) showed a high yield, and the lowest GWP and GHGI values among the five rice varieties in RRSTS. Compared with CF, the AWD pattern reduced the CH4 emission flux during the main and ratoon seasons by 67.4–95.3 kg·ha–1 and 1.7–5.1 kg·ha–1, respectively, but increased the N2O emission flux by 0.1–0.6 kg·ha–1 during the RRSTS. Further, compared with CF, the AWD pattern had a declined GWP by 14.3–19.4% and GHGI by 30.3–34.3% during the RRSTS, which was attributed to the significant reduction in GWP and GHGI during the main season. The AWD pattern significantly increased rice yield by 21.9–22.9% during the RRSTS, especially for YX203. Correlation analysis showed that CH4, GWP, and GHGI exhibited significant negative correlations with spikelet number per m2 and the harvest index during the main and ratoon seasons. Collectively, selecting the high-yield, low-emission variety CLYHZ could significantly reduce greenhouse gas emissions from ratoon rice while maintaining a high yield. The AWD pattern could reduce total CH4 emission during the main season, reducing the GWP and GHGI while increasing the ratoon rice system yield. It could be concluded that a variety of CLYHZ and AWD patterns are worthy of promotion and application to decrease greenhouse gas emissions in the ratoon rice area in the upper reaches of Yangtze River, China.

Greenhouse gas emissions from constructed wetlands are mitigated by biochar substrates and distinctly affected by tidal flow and intermittent aeration modes.

Changing the order and ratio of substrate filling reduced CH4 and N2O emissions from the aerated constructed wetlands

IntroductionFarmlands are key sources of greenhouse gas (GHG) emissions, which are susceptible to changes in precipitation regimes. The soils of seasonal fallow contribute approximately half of annual GHG emissions from farmlands, but the effect of precipitation frequency on soil GHG emissions from seasonal fallow croplands remains virtually unknown.Materials and MethodsWe conducted a microcosm study to evaluate the response of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from typical paddy and upland soils to the changes in watering frequency simulating precipitation scenarios of subtropical regions during seasonal fallow. We also analyzed changes of soil properties and biotic characteristics associated with GHG emissions, including abundances of soil denitrifiers (nirK, nirS, nosZI and nosZII genes), methanotrophs (pmoA gene) and methanogens (mcrA gene) to altered watering frequency.ResultsIncreased watering frequency led to overall increases in soil N2O and CO2 fluxes compared with low frequency. Compared with low frequency, high watering frequency decreased CH4 flux from the paddy soil by 3.5 times, while enhanced CH4 flux from the upland soil by 60%. Furthermore, the increased watering frequency had positive effects on cumulative N2O and CO2 fluxes from the upland soil, whereas no similar trend was observed for the paddy soil. Hierarchical partitioning analyses showed that N2O fluxes from the paddy soil were mostly related to nitrogen availability, and mcrA gene abundance had more than 90% of relative independent effects on CH4 and CO2 fluxes from the paddy soil. For the upland soil, nosZ (60.34%), pmoA (53.18%) and nir (47.07%) gene abundances were important predictors of N2O, CH4 and CO2 fluxes, respectively.ConclusionOur results demonstrate that increased watering frequency facilitates GHG emissions by changing soil properties and functional gene abundances. These findings provide new insights into GHG fluxes from seasonal fallow croplands in response to altered precipitation patterns.

Greenhouse gas emissions in response to tillage, nitrogen fertilization, and manure application in the tropics

Blue revolution for food security under carbon neutrality: A case from the water-saving and drought-resistance rice