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1.
Measurements of methane emission rates and concentrations in the soil were made during four growing seasons at the International Rice Research Institute in the Philippines, on plots receiving different levels of organic input. Fluxes were measured using the automated closed chambers system (total emission) and small chambers installed between plants (water surface flux). Concentrations of methane in the soil were measured by collecting soil cores including the gas phase (soil-entrapped methane) and by sampling soil solution in situ (dissolved methane). There was much variability between seasons, but total fluxes from plots receiving high organic inputs (16–24 g CH4 m–2) always exceeded those from the low input plots (3–9 g CH4 m–2). The fraction of the total emission emerging from the surface water (presumably dominated by ebullition) was greater during the first part of the season, and greater from the high organic input plots (35–62%) than from the low input plots (15–23%). Concentrations of dissolved and entrapped methane in the low organic input plots increased gradually throughout the season; in the high input plots there was an early-season peak which was also seen in emissions. On both treatments, periods of high methane concentrations in the soil coincided with high rates of water surface flux whereas low concentrations of methane were generally associated with low flux rates.  相似文献   

2.
Methane (CH4) emissions and oxidation were measured at the Air Hitam sanitary landfill in Malaysia and were modeled using the Intergovernmental Panel on Climate Change waste model to estimate the CH4 generation rate constant, k. The emissions were measured at several locations using a fabricated static flux chamber. A combination of gas concentrations in soil profiles and surface CH4 and carbon dioxide (CO2) emissions at four monitoring locations were used to estimate the CH4 oxidation capacity. The temporal variations in CH4 and CO2 emissions were also investigated in this study. Geospatial means using point kriging and inverse distance weight (IDW), as well as arithmetic and geometric means, were used to estimate total CH4 emissions. The point kriging, IDW, and arithmetic means were almost identical and were two times higher than the geometric mean. The CH4 emission geospatial means estimated using the kriging and IDW methods were 30.81 and 30.49 g m?2 day?1, respectively. The total CH4 emissions from the studied area were 53.8 kg day?1. The mean of the CH4 oxidation capacity was 27.5 %. The estimated value of k is 0.138 year?1. Special consideration must be given to the CH4 oxidation in the wet tropical climate for enhancing CH4 emission reduction.  相似文献   

3.
Methane (CH4) is one of the most relevant greenhouse gases and it has a global warming potential 25 times greater than that of carbon dioxide (CO2), risking human health and the environment. Microbial CH4 oxidation in landfill cover soils may constitute a means of controlling CH4 emissions. The study was intended to quantify CH4 and CO2 emissions rates at the Sungai Sedu open dumping landfill during the dry season, characterize their spatial and temporal variations, and measure the CH4 oxidation associated with the landfill cover soil using a homemade static flux chamber. Concentrations of the gases were analyzed by a Micro-GC CP-4900. Two methods, kriging values and inverse distance weighting (IDW), were found almost identical. The findings of the proposed method show that the ratio of CH4 to CO2 emissions was 25.4 %, indicating higher CO2 emissions than CH4 emissions. Also, the average CH4 oxidation in the landfill cover soil was 52.5 %. The CH4 and CO2 emissions did not show fixed-pattern temporal variation based on daytime measurements. Statistically, a negative relationship was found between CH4 emissions and oxidation (R 2?=?0.46). It can be concluded that the variation in the CH4 oxidation was mainly attributed to the properties of the landfill cover soil.  相似文献   

4.
采用LGR-密闭式动态通量箱法对城市绿地生态系统温室气体(CO2、CH4)通量的日变化、季节变化特征及其影响因子等进行了较为系统的研究。城市绿地花草CO2通量有明显的日变化和季节变化特征,白天通量值为负,是CO2的净吸收汇;夜晚为正值,是CO2的净释放源;7:00左右由源转为汇,17:00左右由汇转为源,不同花卉24 h总通量有正负2种结果。冬季草坪作为源的时间延长,而作为汇的时间缩短。光强和温度是影响CO2通量日变化和季节变化的主要因素。城市绿地CH4通量较小,不足以对温室气体总量产生显著影响。从减少温室气体排放的角度对城市绿地花草的选择提出了建议。  相似文献   

5.
Air pollution in the workplace environment due to industrial operation have been found to cause serious occupational health hazard. Similarly, heat stress is still most neglected occupational hazard in the tropical and subtropical countries like India. The hot climate augments the heat exposure close to sources like furnaces. In this study an attempt is made to assess air pollution and heat exposure levels to workers in the workplace environment in glass manufacturing unit located in the State of Gujarat, India. Samples for workplace air quality were collected for SPM, SO2, NO2 and CO2 at eight locations. Results of workplace air quality showed 8-hourly average concentrations of SPM: 165–9118 μg/m3, SO2: 6–9 μg/m3 and NO2: 5–42 μg/m3, which were below the threshold limit values of workplace environment. The level of CO2 in workplace air of the plant was found to be in the range 827–2886 μg/m3, which was below TLV but much higher than the normal concentration for CO2 in the air (585 mg/m3). Indoor heat exposure was studied near the furnace and at various locations in an industrial complex for glass manufacturing. The heat exposure parameters including the air temperature, the wet bulb temperature, and the globe parameters were measured. The Wet Bulb Globe Temperature (WBGT), an indicator of heat, exceeded ACGIH TLVs limits most of the time at all the locations in workplace areas. The recommended duration of work and rest have also been estimated.  相似文献   

6.
The groundwater is one of the most contaminated natural resources in Patancheru industrial area due to unplanned and haphazard industrial growth and urbanization without following basic pollution control norms. The rapid industrialization initiated in early 1970 has started showing up its after effects few years later in the form of physiochemical contamination of the both surface and groundwater bodies of the area. It has resulted in local people being deprived of safe drinking water, plant and aquatic life has severely affected, and situation is deteriorating over the years in the area in spite of some preventive and remedial measures being initiated. The focus of the present study is to understand the chemical characteristics of groundwater and geochemical processes the contaminant water is undergoing which are normally imprinted in its ionic assemblages. The water samples collected in pre- and post-monsoon seasons from forty two groundwater and four surface water sources were analyzed for major constituents such as Ca2+, Mg2+, Na+, K+, CO3, HCO3, Cl, SO42−, NO3, and F, and selected samples were tested for ten important trace metals like Fe, Pb, Bi, Mn, Cr, Co, Ni, Cu, Zn, and Cd. Na+ among cations and Cl among anions dominate the water in both the seasons where as Ca2+, HCO3, and Cl show significant reduction in their ionic strength in post-monsoon. The groundwater in general is of mixed type, but most of it belong to Na+–Cl, Na+–HCO3, Ca2+–Mg2+–HCO3, and Ca2+–Mg2+–Cl facies. The Na+ and Ca2+ are in the transitional state with Na+ replacing Ca2+ and HCO3–Cl due to physiochemical changes in the aquifer system. The evaluation of hydrochemistry through various ionic indices, ratios, and plots suggest that silicate–carbonate weathering, ion exchange, dissolution, and evaporation processes are responsible for origin of the present chemical status of the groundwater which is also controlled by the contamination from extraneous sources that could have accelerated the dissolution processes. Gibbs plots authenticate that the evolution of water chemistry is influenced by interaction of percolating water with aquifer matrix apart from anthropogenic enrichment of elements which get over concentrated due to evaporation.  相似文献   

7.
对国家大气背景监测福建武夷山站2014—2018年的主要温室气体监测数据进行分析,探讨华东森林及高山背景区域大气中CO_2和CH_4浓度的变化特征。结果表明:华东森林及高山区域CO_2背景浓度为414.1×10~(-6)(摩尔分数,下同),5年间呈逐年上升趋势; CH_4背景浓度为1 977×10~(-9),2014—2016年呈逐年上升趋势,2016—2018年保持稳定;两者均具有较明显的季节和月变化特征,CO_2还具有较明显的日变化特征,但季节变化幅度、月平均浓度振幅和日变化幅度均较小,具有区域背景特征。  相似文献   

8.
A time series study was conducted to ascertain the effect of barometric pressure on the variability of CH4 and CO2 concentrations in a closed landfill site. An in situ data of methane/carbon dioxide concentrations and environmental parameters were collected by means of an in-borehole gas monitor, the GasClam (Ion Science, UK). Linear regression analysis was used to determine the strength of the correlation between ground-gas concentrations and barometric pressure. The result shows CH4 and CO2 concentrations to be variable with weak negative correlations of 0.2691 and 0.2773, respectively, with barometric pressure over the entire monitoring period. Although the R 2 was slightly improved by considering their concentration over single periods of rising and falling pressure, single periods of rising pressure and single periods of falling pressure, their correlations remained insignificant at 95 % confidence level. The result revealed that atmospheric pressure—the acclaimed major control on the variability of ground-gas concentration—is not always so. A case was made for the determination of other possible controls such as changes in temperature, soil permeability, landfill water depth, season, and geology of the borehole and also how much of control each factor would have on the variability/migration of CH4 and CO2 concentrations from the studied landfill.  相似文献   

9.
The breakdown of low digestible components present in food during passage through the human and animal gastro-intestinal (GI) tract is performed by the highly diverse microbial community present in this ecosystem. Fermentation of these substances yields, besides CO2 and volatile fatty acids, H2, which is used as a substrate by three different H2-consuming bacteria. Sulphate-reducing bacteria (SRB) use H2 to reduce SO inf4 sup2- to H2S, hydrogenotrophic methane-producing bacteria (MPB) use H2 to reduce CO2 to CH4 and reductive acetogens (RAC) use H2 to reduce CO2 to CH3COOH. A competition between these three bacterial groups exists for the common H2 substrate. This results generally in the dominance of one group above the other two.  相似文献   

10.
CO2 flux of a deciduous forest and an old-field surface, and the ecotone between these two typical southern U.S. ecological communities, was studied in July, 1989. Rates of CO2 flux were greatest in the old field and least in the forest plots. The ecotone showed the greatest variation in CO2 flux. These differences appear to be due to differences in soil surface temperature, the old field being more exposed to direct solar radiation. The ecotonal community represents a landscape property which should be considered in studies of the transfer of carbon across the soil-atmosphere boundary.  相似文献   

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