Comparative assessment of coal tars obtained from 10 former manufactured gas plant sites in the eastern United States

A comparative analysis was performed on eleven coal tars obtained from former manufactured gas plant sites in the eastern United States. Bulk properties analyzed included percent ash, Karl Fisher water content, viscosity and average molecular weight. Chemical properties included monocyclic- and polycyclic-aromatic hydrocarbon (PAH) concentrations, alkylated aromatic concentrations, and concentrations of aliphatic and aromatic fractions. It was found that there was at least an order-of-magnitude variation in all properties measured between the eleven coal tars. Additionally, two coal tars obtained from the same manufactured gas plant site had very different properties, highlighting that there can be wide variations in coal tar properties from different samples obtained from the same site. Similarities were also observed between the coal tars. The relative chemical distributions were similar for all coal tars, and the coal tars predominantly consisted of PAHs, with naphthalene being the single-most prevalent compound. The C(9-22) aromatic fraction, an indicator of all PAHs up to a molecular weight of approximately 276 gmole(-1), showed a strong power-law relationship with the coal tar average molecular weight (MW (ct)). And the concentrations of individual PAHs decreased linearly as MW (ct) increased up to ca. 1000 gmole(-1), above which they remained low and variable. Implications of these properties and their variation with MW (ct) on groundwater quality are discussed. Ultimately, while these similarities do allow generalities to be made about coal tars, the wide range of coal tar bulk and chemical properties reported here highlights the complex nature of coal tars.     

Overestimations of food abundance: predator responses to prey aggregation

Understanding and predicting the consequences of trophic interactions for community processes requires knowledge of the role of food availability, which is often wrongly conflated with prey abundance. For prey animals in groups, this is not fully understood. Previous work has shown that oystercatchers more frequently attack solitary rather than aggregated limpets and are more successful in predation attempts on singletons. It has also been demonstrated that an attack on one limpet in a group alerts the entire group, all of which then clamp down and become unavailable. I show that Eurasian Oystercatchers (Haematopus ostralegus L.) attack only one limpet in a group and then move on to attack another individual limpet, and I also demonstrate that the distance they move is greater than the distance at which groups of limpets have been known to detect attacks. Thus in the oystercatcher-limpet predator-prey system on rocky shores, groups of limpets are actually one prey item independently of the number of limpets in the group. This has implications for assessment of food supply for avian predators on rocky shores, with consequences for our understanding of previously documented trophic cascades.     

Nonadditive effects of leaf litter species diversity on breakdown dynamics in a detritus-based stream

Since species loss is predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity, measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analyses of single- and mixed-species leaf packs (15 possible combinations of four dominant litter species; red maple [Acer rubrum], tulip poplar [Liriodendron tulipifera], chestnut oak [Quercus prinus], and rhododendron [Rhododendron maximum]), we tested for single-species presence/absence (additive) or species interaction (nonadditive) effects on leaf pack breakdown rates, changes in litter chemistry, and microbial and macroinvertebrate biomass. Overall, we found significant nonadditive effects of litter species diversity on leaf pack breakdown rates, which were explained both by richness and composition. Leaf packs containing higher litter species richness had faster breakdown rates, and antagonistic effects of litter species composition were observed when any two or three of the four litter species were mixed. Less-consistent results were obtained with respect to changes in litter chemistry and microbial and macroinvertebrate biomass. Our results suggest that loss of litter species diversity will decrease species interactions involved in regulating ecosystem function. To that end, loss of species such as eastern hemlock (Tsuga canadensis) accompanied by predicted changes in riparian tree species composition in the southeastern United States could have nonadditive effects on litter breakdown at the landscape scale.     

Infrared differential absorption Lidar (DIAL) measurements of hydrocarbon emissions

We report the application of an infrared (IR) differential absorption Lidar (DIAL) system (also capable of ultra violet measurements) built at the National Physical Laboratory (NPL), UK, to field measurements of total site emissions (controlled and fugitive) from petrochemical and landfill installations. The validation of the IR-DIAL was carried out via a series of controlled field experiments including comparison to GC analysis and tests against controlled methane releases from a test stack, all detailing agreements on the order of ±20%. In volatile organic compound (VOC) measurements at a UK petrochemical site it was found that the American Petroleum Institute's methodology of the time for calculating the emitted flux underestimated by a factor of 2.4. Also, in a similar field trial it was found that scaling traditional point measurements at easily accessible flanges and valves to represent all flanges and valves on a site led to an underestimation by a factor of 6. In addition to petrochemical examples we also report field measurements from a landfill site to demonstrate the advantageous of the DIAL technique for monitoring area emission sources. In this case study it was found that active (still being filled) cells resulted in significantly greater VOC emission rates (30 kg h(-1)) than closed (≤ 10 kg h(-1)).     

The potential to increase soil carbon stocks through reduced tillage or organic material additions in England and Wales: A case study

Results from the UK were reviewed to quantify the impact on climate change mitigation of soil organic carbon (SOC) stocks as a result of (1) a change from conventional to less intensive tillage and (2) addition of organic materials including farm manures, digested biosolids, cereal straw, green manure and paper crumble. The average annual increase in SOC deriving from reduced tillage was 310 kg C ± 180 kg C ha⁻¹ yr⁻¹. Even this accumulation of C is unlikely to be achieved in the UK and northwest Europe because farmers practice rotational tillage. N₂O emissions may increase under reduced tillage, counteracting increases in SOC. Addition of biosolids increased SOC (in kg C ha⁻¹ yr⁻¹ t⁻¹ dry solids added) by on average 60 ± 20 (farm manures), 180 ± 24 (digested biosolids), 50 ± 15 (cereal straw), 60 ± 10 (green compost) and an estimated 60 (paper crumble). SOC accumulation declines in long-term experiments (>50 yr) with farm manure applications as a new equilibrium is approached. Biosolids are typically already applied to soil, so increases in SOC cannot be regarded as mitigation. Large increases in SOC were deduced for paper crumble (>6 t C ha⁻¹ yr⁻¹) but outweighed by N₂O emissions deriving from additional fertiliser. Compost offers genuine potential for mitigation because application replaces disposal to landfill; it also decreases N₂O emission.     

Boundary spanners as trust ambassadors in collaborative natural resource management

Collaboration is a growing trend in agency-led natural resource management in the USA, carrying the promise of defusing conflict and incorporating a broader range of stakeholder ideas. However, concerns exist that confrontational or litigious groups may use collaborative forums to their organization's own advantage. We conducted case studies on three collaboratives to understand how these efforts have influenced the behavior of environmental groups who were previously at odds with the managing agency, the US Forest Service. Results suggest that trust between boundary spanners from historically adversarial groups can support a realignment of the accountabilities they feel. As rational, affinitive, and procedural trust developed, boundary spanners began to advocate, within their home organizations, for the collaborative's goals. Key activities driving these realignments included the development of fair and transparent procedures governing the collaborative group, structured interaction designed to build consensus, and planned informal interactions that revealed shared values among collaborative participants.     

Another look at the locus of control–organizational commitment relationship: it depends on the form of commitment

Previous studies imply that individuals with an external locus of control (LOC) are less likely to be committed to their organizations. More recent work on organizational commitment has suggested that commitment is not a unidimensional construct and can take several forms (e.g., affective and continuance). Using a sample of 232 employees of a Canadian governmental agency, we examined the relations between LOC and two different forms of organizational commitment that have been found to have different antecedents and consequences. We found that internal LOC was associated with affective commitment and external LOC was associated with continuance commitment. Implications for research and practice are discussed. Copyright © 1999 John Wiley & Sons, Ltd.