https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_57-58/010025232.pdf

Production, oxidation, emission and consumption of methane by soils: A review

The purpose of this paper is to support the development of so-called good practice guidelines for the estimation of methane (CH 4) emissions from solid waste (SW) disposal for national greenhouse gas inventories. The paper reviews and discusses the emission estimation methods given in the IPCC 1996 Revised Guidelines (IPCC Guidelines), and uncertainty and quality management issues related to the emission estimation. At solid waste disposal sites (SWDS) the degradable organic carbon in waste is decomposed by bacteria under anaerobic conditions into methane (CH 4) and other compounds. The CH 4 emissions from SWDS are important contributors of global anthropogenic CH 4 emissions. The IPCC Guidelines give two methods for estimation CH 4 emissions from solid waste disposal. The IPCC default method is a simple mass balance calculation which estimates the amount of CH 4 emitted from the SWDS assuming that all CH 4 is released the same year the waste is disposed of. The other method outlined in the IPCC Guidelines is the so-called First Order Decay (FOD) method. The FOD method takes the time factors of the degradation process into account, and produces annual emission estimates that reflect this process, which can take years, even decades. The estimates on annual emissions produced by the two methods are therefore not comparable. The FOD method produces better estimates on annual emissions, whereas the IPCC default method has merits e.g. in studies comparing the potential to reduce the CH 4 emissions by alternative waste treatment methods. The use of the IPCC default method and FOD method require as input annual SW disposal data including information on the composition of the waste and on the conditions at the SWDS. The IPCC default method requires this data only for the inventory years, whereas the FOD method requires data for also the past 20-25 or more years. In addition, the rate of degradation for waste disposed at SWDS needs to be determined in the FOD method. The IPCC Guidelines contain default values for most of the data needed in the use of the default method, whereas the guidance and default values needed in the use of the FOD method are insufficient. The uncertainties in the emission estimates produced by both the IPCC method and the FOD method are large in most countries. Even few industrialised countries have good SW disposal data based on weighing of amounts disposed and frequent sampling to determine the composition …

Good practice guidance and uncertainty management in national greenhouse gas inventories

The differential environmental fates and toxicities of the various hexachlorocyclohexane (HCH) isomers including lindane and isomers in the technical mixture will be the focus of this review. HCHs are one of the most widely used and most readily detected organochlorine pesticides in environmental samples. The relatively high volatility of HCH has led to global transport, even into formerly pristine locations such as the Arctic. Certain HCHs cause central nervous system, reproductive, and endocrine damage. Because γ-HCH is rapidly metabolized, the β-HCH isomer is consistently found in higher concentrations in human fat, blood, and breast milk. In contrast, α- and γ-HCH are the most prevalent isomers in soil, water, and air samples. The ratio of the α- to γ-isomers can be used to track global transport of HCHs. A new area of HCH research focuses on the selective degradation of the two α-HCH enantiomers in various environmental matrices. These HCH issues and recommendations for future HCH research are presen...

Differential Toxicity and Environmental Fates of Hexachlorocyclohexane Isomers

Rice plants play a pivotal role in different levels of the methane (CH4) budget of rice fields. CH4 production in rice fields largely depends on plant-borne material that can be either decaying tissue or root exudates. The quantity and quality of root exudates is affected by mechanical impedance, presence of toxic elements, nutrient deficiencies, water status of growing medium, and nitrogenase activity in the rhizosphere. CH4 oxidation in rice fields is localized in the rhizosphere where the concentration gradients of CH4 and oxygen overlap. CH4 oxidation capacity is a function of the downward transport of oxygen through the aerenchyma, which, in turn, also acts as a conduit for CH4 from the soil to the atmosphere. The decisive step in the passage of CH4 through rice plant is the transition from root to stem. However, rice plants show an enormous variety of morphological and physiological properties, including differences in root exudation and gas transfer capacity. Comparative studies on different cultivars are deemed crucial for accomplishing a better understanding of the mechanisms of CH4 consumption in the rhizosphere and CH4 transport through the rice plant as well as the interaction of these processes. The results of such studies are considered tools for devising mitigation options.

The role of rice plants in regulating mechanisms of methane missions

Methane production, oxidation and mitigation: A mechanistic understanding and comprehensive evaluation of influencing factors.

In a study on CH4 emission from flooded rice fields under irrigated conditions, fields planted with rice emitted more methane than unplanted fields. The CH4 efflux in planted plots varied with the rice variety and growth stage and ranged from 4 to 26 mg h-1m-2. During the reproductive stage of the rice plants, CH4 emission was high and the oxidation power of rice roots, in terms of α-naphthylamine oxidation, was very low. The CH4 emission reached a maximum at midday and declined to minimum levels at midnight, irrespective of the rice variety. The peak CH4 emission at midday was associated with higher solar radiation and higher soil/water temperature.

Amarendra K. Rath

Papers

Methane emission from flooded rice fields under irrigated conditions

Effect of hexachlorocyclohexane on metel4ne production and emission from flooded rice soil

Effect of pesticides on microbial biomass of flooded soil