Mitigating Greenhouse Gas Emissions from Tropical Agriculture: Scope and Research Priorities

The scope of mitigation options in tropical agriculture is discussed for three different activities (a) agroforestry, (b) rice-based production systems and (c) pasture/animal husbandry. The prevention of deforestation - and the re-forestation of degraded land - could become a key elements to national climate protection programs of some developing countries. Agroforestry may offer economically viable windows of opportunity for sustainable use of tropical forests whereas additional funds (e.g. through “Clean Development Mechanism”) will be required to make re-forestation programs profitable. Alternative management practices in rice-based systems may offer win-win options to reduce emissions and - at the same time - to obtain another improvement in the production system, namely through optimized timing of nitrogen fertilizer, temporary drainage in irrigated rice fields and integrated residue management. Introducing pasture in degraded land can sequester substantial amounts of carbon (similar to re-forestation). Future research has to include participation of stakeholders from all conceivable levels, i.e. farmers' cooperatives, non-governmental organizations, national agricultural research centers and extension services, to devise simple and financially interesting incentives for reducing emissions. The feasibility of environmentally friendly production techniques has to be disseminated to the public through ‘success stories’ (documented in public media) and demonstration farms.     

Stakeholder attitudes on Carbon Capture and Storage—An international comparison

This paper presents results from a survey of stakeholder attitudes towards Carbon Capture and Storage (CCS). The survey is the first to make a global comparison across three major regions: North America, Japan, and Europe. It is based on a 30-question survey which targeted individuals working at stakeholder organizations that seek to shape, and will need to respond to, policy on CCS, including electric utilities, oil and gas companies, CO₂-intensive industries and non-governmental organizations (NGOs). The paper reports results from the original survey carried out in 2006 and from a recent follow up on key CCS questions (April 2009).The results show generally small differences across the regions and between the different groups of stakeholders. All believed that the challenge of significant reductions in emissions using only current technologies was severe. There was a widespread belief that CCS as well as renewable technologies such as solar power will achieve major market entry into the electricity sector within the next 10–20 years, whereas there is more scepticism about the role of hydrogen and especially nuclear fusion in the next 50 years. All groups were generally positive towards renewable energy. Yet, there were some notable areas of disagreement in the responses, for example, as expected, NGOs considered the threat of climate change to be more serious than the other groups. North American respondents were more likely to downplay the threat compared to those of the other regions. The Japanese were more concerned about the burden that would be placed on industry in the coming decade as a result of emissions constraints and NGOs were more likely to believe that the burden imposed would be light or very light. NGO respondents also believed CCS to be far more attractive than nuclear power (fission) but much less than renewables. As expected, the risk for leakage from reservoirs was ranked number one of the risk options given. The follow-up study generally confirmed the results of the original study with a few notable differences. As expected, the results of the follow-up shows that respondents consider CCS to play an increased role in the national climate debate. In Japan, there was an increased fraction of respondents who claimed that their organization has a clear position on CCS.     

Analysis of mixed halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/PXDFs) in soil by gas chromatography tandem mass spectrometry (GC-MS/MS)

Mixed halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/PXDFs, X = Br, Cl) are formed through combustion processes, and may be more toxic than their corresponding chlorinated and brominated analogues. With 4600 potential congeners, limited analytical standards, and complex environmental matrices, PXDD/PXDFs present a significant analytical challenge. Gas chromatography tandem mass spectrometry (GC-MS/MS) offers both selectivity and sensitivity through multiple reaction monitoring of unique transitions in a novel approach to PXDD/PXDF congener identification. Method validation was performed through analysis of soil samples obtained from a recycling plant fire. Of the PXDD/PXDFs examined, monobromo-dichlorodibenzofuran was the most prevalent, ranging in concentration from 8.6 ng g⁻¹ to 180 ng g⁻¹. Dibromo-dichlorodibenzo-p-dioxin, a compound of toxicological concern, ranged from 0.41 ng g⁻¹ to 10 ng g⁻¹. Concentrations of PXDD/PXDFs were between 6% and 10% that of the corresponding polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), with the exception of dibromo-dichlorodibenzo-p-dioxin concentrations, which were 36% that of tetrachlorodibenzo-p-dioxins. Higher levels of polybrominated PXDD/PXDFs may indicate a significant bromine source was present during combustion.     

Patterns and sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in surficial sediments of Lakes Erie and Ontario

This study determines spatial trends and congener patterns of 2378-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in surficial sediments of Lakes Erie and Ontario. Sediments are enriched in 2378-PCDFs in Lake Ontario, and the PCDD/F concentrations increased from shallow near-shore sediments towards deep-water depositional zone sediments. In Lake Erie, sediments were dominated by octachlorodibenzo-p-dioxin, and the highest PCDD/F concentrations were observed in the western basin and the southern shoreline of the central basin with a decrease towards the eastern basin and the northern shoreline of the central basin. Principal components analysis revealed that chemical manufacture and disposal of chemical waste along the Niagara River has been a major PCDD/F source to Lake Ontario; while PCDD/Fs in Lake Erie are from multiple sources including industrial sources along the Detroit River, major tributaries along the southern shoreline of the lake, and atmospherically-derived material from the upper lakes and connecting channels.     

Uptake of terbuthylazine and its medium polar metabolites into maize plants

The uptake of terbuthylazine and its medium polar metabolites into maize plants under outdoor conditions is investigated. For this purpose, a dynamical fate model consisting of soil, plant and air is developed. The model calculations are compared with experimental results of outdoor lysimeter tests, carried out with¹⁴C-labelled herbicide applied to sandy agricultural soil at a single application rate of 890 g/ha. Approximately 0.3 % of the applied activity remains in all the plants after the vegetation period. The model predicts that about three times that amount is volatilized from the plants into the air. Activity uptaken from soil and volatilized from plant surface into air is predominately associated with metabolites. During the whole vegetation period the fraction of unchanged terbuthylazine in the plants is very small (less than 1 % of the extractable activity).     

Natural formation and degradation of chloroacetic acids and volatile organochlorines in forest soil--challenges to understanding

- DOI: http:/dx.doi.org/10.1065/espr2005.06.262 Goal, Scope and Background The anthropogenic environmental emissions of chloroacetic acids and volatile organochlorines have been under scrutiny in recent years because the two compound groups are suspected to contribute to forest dieback and stratospheric ozone destruction, respectively. The two organochlorine groups are linked because the atmospheric photochemical oxidation of some volatile organochlorine compounds is one source of phytotoxic chloroacetic acids in the environment. Moreover, both groups are produced in higher amounts by natural chlorination of organic matter, e.g. by soil microorganisms, marine macroalgae and salt lake bacteria, and show similar metabolism pathways. Elucidating the origin and fate of these organohalogens is necessary to implement actions to counteract environmental problems caused by these compounds. Main Features While the anthropogenic sources of chloroacetic acids and volatile organochlorines are relatively well-known and within human control, knowledge of relevant natural processes is scarce and fragmented. This article reviews current knowledge on natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soils, with particular emphasis on processes in the rhizosphere, and discusses future studies necessary to understand the role of forest soils in the formation and degradation of these compounds. Results and Discussion Reviewing the present knowledge of the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil has revealed gaps in knowledge regarding the actual mechanisms behind these processes. In particular, there remains insufficient quantification of reliable budgets and rates of formation and degradation of chloroacetic acids and volatile organochlorines in forest soil (both biotic and abiotic processes) to evaluate the strength of forest ecosystems regarding the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Conclusion It is concluded that the overall role of forest soil as a source and/or sink for chloroacetic acids and volatile organochlorines is still unclear; the available laboratory and field data reveal only bits of the puzzle. Detailed knowledge of the natural degradation and formation processes in forest soil is important to evaluate the strength of forest ecosystems for the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Recommendation and Perspective As the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil can be influenced by human activities, evaluation of the extent of this influence will help to identify what future actions are needed to reduce human influences and thus prevent further damage to the environment and to human health caused by these compounds.