Net carbon flux from agricultural ecosystems: methodology for full carbon cycle analyses

Agricultural ecosystems have the potential to sequester carbon in soils by altering agricultural management practices (i.e. tillage practice, cover crops, and crop rotation) and using agricultural inputs (i.e. fertilizers and irrigation) more efficiently. Changes in agricultural practices can also cause changes in CO2 emissions associated with these practices. In order to account for changes in net CO2 emissions, and thereby estimate the overall impact of carbon sequestration initiatives on the atmospheric CO2 pool, we use a methodology for full carbon cycle analysis of agricultural ecosystems. The analysis accounts for changes in carbon sequestration and emission rates with time, and results in values representing a change in net carbon flux. Comparison among values of net carbon flux for two or more systems, using the initial system as a baseline value, results in a value for relative net carbon flux. Some results from using the full carbon cycle methodology, along with US national average values for agricultural inputs, indicate that the net carbon flux averaged over all crops following conversion from conventional tillage to no-till is -189 kg C ha(-1) year(-1) (a negative value indicates net transfer of carbon from the atmosphere). The relative net carbon flux, using conventional tillage as the baseline, is -371 kg C ha(-1) year(-1), which represents the total atmospheric CO2 reduction caused by changing tillage practices. The methodology used here illustrates the importance of (1) delineating system boundaries, (2) including CO2 emissions associated with sequestration initiatives in the accounting process, and (3) comparing the new management practices associated with sequestration initiatives with the original management practices to obtain the true impact of sequestration projects on the atmospheric CO2 pool.     

Acute toxicity of aromatic and non-aromatic fractions of naphthenic acids extracted from oil sands process-affected water to larval zebrafish

The toxicity of oil sands process-affected water (OSPW) has regularly been attributed to naphthenic acids, which exist in complex mixtures. If on remediation treatment (e.g., ozonation) or on entering the environment, the mixtures of these acids all behave in the same way, then they can be studied as a whole. If, however, some acids are resistant to change, whilst others are not, or are less resistant, it is important to establish which sub-classes of acids are the most toxic.     

Influence of hydrogeochemical processes on zero-valent iron reactive barrier performance: a field investigation

Geochemical and mineralogical changes were evaluated at a field Fe0-PRB at the Oak Ridge Y-12 site concerning operation performance during the treatment of U in high NO3- groundwater. In the 5-yr study period, the Fe0 remained reactive as shown in pore water monitoring data, where increases in pH and the removal of certain ionic species persisted. However, coring revealed varying degrees of cementation. After 3.8-yr treatment, porosity reduction of up to 41.7% was obtained from mineralogical analysis on core samples collected at the upgradient gravel-Fe0 interface. Elsewhere, Fe0 filings were loose with some cementation. Fe0 corrosion and pore volume reduction at this site are more severe due to the presence of NO3- at a high level. Tracer tests indicate that hydraulic performance deteriorated: the flow distribution was heterogeneous and under the influence of interfacial cementation a large portion of water was diverted around the Fe0 and transported outside the PRB. Based on the equilibrium reductions of NO3- and SO4(2-) by Fe0 and mineral precipitation, geochemical modeling predicted a maximum of 49% porosity loss for 5 yr of operation. Additionally, modeling showed a spatial distribution of mineral precipitate volumes, with the maximum advancing from the interface toward downgradient with time. This study suggests that water quality monitoring, coupled with hydraulic monitoring and geochemical modeling, can provide a low-cost method for assessing PRB performance.     

Influence of hydrogeochemical processes on zero-valent iron reactive barrier performance: a field investigation

Geochemical and mineralogical changes were evaluated at a field Fe0-PRB at the Oak Ridge Y-12 site concerning operation performance during the treatment of U in high NO3- groundwater. In the 5-year study period, the Fe0 remained reactive as shown in pore-water monitoring data, where increases in pH and the removal of certain ionic species persisted. However, coring revealed varying degrees of cementation. After 3.8-year treatment, porosity reduction of up to 41.7% was obtained from mineralogical analysis on core samples collected at the upgradient gravel-Fe0 interface. Elsewhere, Fe0 filings were loose with some cementation. Fe0 corrosion and pore volume reduction at this site are more severe due to the presence of NO3- at a high level. Tracer tests indicate that hydraulic performance deteriorated: the flow distribution was heterogeneous and under the influence of interfacial cementation a large portion of water was diverted around the Fe0 and transported outside the PRB. Based on the equilibrium reductions of NO3- and SO4(2-) by Fe0 and mineral precipitation, geochemical modeling predicted a maximum of 49% porosity loss for 5 years of operation. Additionally, modeling showed a spatial distribution of mineral precipitate volumes, with the maximum advancing from the interface toward downgradient with time. This study suggests that water quality monitoring, coupled with hydraulic monitoring and geochemical modeling, can provide a low-cost method for assessing PRB performance.     

Adaptive capacity determinants in developed states: examples from the Nordic countries and Russia

Adaptive capacity in a community context has so far mainly been studied in developing countries as well as indigenous communities in the industrialised world. This article adds to that literature through reviewing studies undertaken in the Nordic countries and Russia, highlighting the ways in which general determinants of adaptive capacity play out in Northern, industrialised contexts. The paper illustrates that the determinants of adaptive capacity in industrialised states exhibit systematic differences from mixed subsistence-cash based communities such as those found in Arctic Canada. We discuss in particular the importance of economic resources in a market-based system, technological competition, and infrastructure, in determining adaptive capacity of natural resource-dependent communities in the Nordic countries and Russia. The paper also illustrates differences in adaptive capacity within the case study region, including between peripheral and central locations with regard to economic resources and diversification possibilities, and between Nordic and Russian cases with regard to infrastructure and technology access. The findings indicate that understanding of determinants of adaptive capacity in resource-dependent communities would benefit from both further contextualisation and broad comparison, across different types of political and administrative systems.     

The survey of living conditions in the Arctic (SLiCA): A comparative sustainable livelihoods assessment

The Arctic is a region of the world experiencing extremely rapid climatic and social change. Indigenous communities have faced similar challenges for millennia and have historically demonstrated remarkable resilience to socioecological perturbations. In contemporary contexts, however, it appears that the pace and extent of change is overwhelming the adaptive capacities of many indigenous communities. Scholars recently completed a survey of living conditions spanning the circumpolar Arctic to quantitatively document the impacts of social and ecological stress across regions. The database they created is called the Survey of Living Conditions in the Arctic or SLiCA. This article explores the utility of using this dataset to compare livelihood systems across three sub-regions of Alaska and four sub-regions within the Chukotka Autonomous Okrug of the Russian Federation. The results point out that livelihood systems in Chukotka have a substantially lower level of sustainability than in Northwest Alaska due to the high prevalence of vulnerable households.     

Innovations and personal change: Patterns of adjustment to relocation

The aim of the study was to test hypotheses derived from Nicholson's (1984) theory of work-role transitions within the context of job relocation. These hypotheses concern the adjustment strategies used by those changing jobs. A total of 121 U.K. employees provided data at three points in time during the process of their relocation. Measures included job characteristics, personal change, role innovation, self-esteem and subjective well-being. Data were analysed via non-recursive structural equation models using LISREL VI. Results were generally consistent with the model of work-role transitions. Individual differences in self-esteem were found to influence adjustment strategies over and above the effects of job characteristics.     

The outcomes of downward managerial mobility

Research examining the effects of unemployment among white collar workers has produced patterns of findings different to those for lower socio-economic groups. The present longitudinal questionnaire study examines the psychological impact of managerial job moves which are downward in status, and considers the effects of periods of unemployment between job changes. The results indicate that among managers the negative impact of downward status moves on psychological adjustment is greater than that of temporary role loss. These effects are associated with decrements in preceived growth and development opportunities at work. The relationship between work and non-work life for our understanding of psychological adjustment is considered.     

The fiscal pit and the federalist pendulum: Explaining differences between US States in protecting health and the environment

Summary The US federal government has deliberately shifted a great deal of responsibility for protecting public health and the environment to the 50 US States. Some States are able and willing to assume control, but many others cannot or will not. It is argued that the American federal government should be prepared to intervene in those States that do not place health and environment on their agenda.Dr. Michael Greenberg is Professor of the School of Urban and Regional Policy at Rutgers as well as being an Advisory Board member to this journal. Prof. Frank Popper chairs the Department of Urban Studies and Community Health at Rutgers University. He has written extensively about land use issues and the American Great Plains. Bernadette West is a doctoral candidate in the Department of Urban Planning and Policy Development, Rutgers University. Her thesis concerns scientific and political issues in developing cancer research centers.