Immobilizing a light,nonaqueous phase liquid

A new technique has been developed to immobilize organic chemicals at a Superfund site. In the course of predesign studies in preparing the Remedial Design for the Pioneer Sand Superfund site in Pensacola, Florida, a light, nonaqueous phase liquid (LNAPL) was discovered floating on the groundwater within the on-site landfill. The liquid, with a viscosity similar to SAE 20 motor oil, was made up of heavy organic chemicals and volatile organic chemicals (VOCs), but no pesticides or polychlorinated biphenyls (PCBs). The volatiles present included toluene, ethylbenzene, and xylenes. Regulatory agencies expressed concern over the possibility of LNAPL migration and asked that a method of LNAPL immobilization be devised.     

An inventory of wetland impoundments in the coastal zone of Louisiana,USA: Historical trends

We inventoried wetland impoundments in the Louisiana, USA, coastal zone from the late 1900s to 1985. Historically, impoundment of wetlands for reclamation resulted in direct wetland loss after levees (dikes) failed and the impounded area was permanently flooded, reverting not to wetland, but to open-water habitat. A current management approach is to surround wetlands by levees and water control structures, a practice termed semi-impoundment marsh management. The purpose of this semi-impoundment is to retard saltwater intrusion and reduce water level fluctuations in an attempt to reduce wetland loss, which is a serious problem in coastal Louisiana. In order to quantify the total impounded area, we used historic data and high-altitude infrared photography to map coastal impoundments. Our goal was to produce a documented inventory of wetlands intentionally impounded by levees in the coastal zone of Louisiana in order to provide a benchmark for further research. We inventoried 370,658 ha within the coastal zone that had been intentionally impounded before 1985. This area is equal to about 30% of the total wetland area in the coastal zone. Of that total area, approximately 12% (43,000 ha) is no longer impounded (i.e., failed impoundments; levees no longer exist or only remnants remain). Of the 328,000 ha still impounded, about 65% (214,000 ha) is developed (agriculture, aquaculture, urban and industrial development, and contained spoil). The remaining 35% (114,000 ha) of impoundments are in an undeveloped state (wetland or openwater habitat). In December 1985, approximately 50% (78,000 ha) of the undeveloped and failed impoundments were open-water habitat. This inventory will allow researchers to monitor future change in land-water ratios that occur within impounded wetlands and thus to assess the utility of coastal wetland management using impoundments.     

Crystallization behavior of predominantly syndiotactic poly(β-hydroxybutyrate)

Predominantly syndiotactic poly(-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T _c ) of 30°C. AtT _c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent onT _c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at 50°C. This result showed little to no dependence on syn-PHB syndio-regularity andT _c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition onT _c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M _n =83,700 g/mol) and a 0.64-syn-PHB (M _n =11,900 g/mol) were 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.Guest Editor: Dr. Graham Swift, Rohm & Haas.     

Adaptation to Climate Variability and Change: Methodological Issues

The Intergovernmental Panel on Climate Change (IPCC) convened a Workshop on Adaptation to Climate Variability and Change in Costa Rica in 1998 that involved more than 200 expects and incorporated views from many research communities. This paper summarizes the recommendations from the Workshop and profiles the contributions to the advancement of methodologies for adaptation science.     

Arthropod populations,yield and damage in monocultures and polycultures of corn,beans and tomatoes

This study involved an examination of a polyculture system (corn-bean-tomato) for specific interactions that may be useful in the development of agronomic systems that are less susceptible to pest attack. The data show that the arthropods generally prefer (are found in) one cultivar more than the others, even in polycultural situations. For example Trichogramma sp. are much more active on tomatoes than on corn, while Coccinellidae are much more common on corn than on tomatoes. The data do not, for the most part, demonstrate any significant differences in insect populations, yield or damage that resulted from interplanting the various cultivars. The role of diversity in agricultural systems is also discussed.     

Adaptation and mitigation: trade-offs in substance and methods

Adaptation to climate change and mitigation of climate change are policy substitutes, as both reduce the impacts of climate change. Adaptation and mitigation should therefore be analysed together, as they indeed are, albeit in a rudimentary way, in cost-benefit analyses of emission abatement. However, adaptation and mitigation are done by different people operating at different spatial and temporal scales. This hampers analysis of the trade-offs between adaptation and mitigation. An exception is facilitative adaptation (enhancing adaptive capacity), which, like mitigation, requires long-term policies at macro level. Facilitative adaptation and mitigation not only both reduce impacts, but they also compete for resources.