Minimizing opportunity costs to aquatic connectivity restoration while controlling an invasive species

Controlling invasive species is critical for conservation but can have unintended consequences for native species and divert resources away from other efforts. This dilemma occurs on a grand scale in the North American Great Lakes, where dams and culverts block tributary access to habitat of desirable fish species and are a lynchpin of long‐standing efforts to limit ecological damage inflicted by the invasive, parasitic sea lamprey (Petromyzon marinus). Habitat restoration and sea‐lamprey control create conflicting goals for managing aging infrastructure. We used optimization to minimize opportunity costs of habitat gains for 37 desirable migratory fishes that arose from restricting sea lamprey access (0–25% increase) when selecting barriers for removal under a limited budget (US$1–105 million). Imposing limits on sea lamprey habitat reduced gains in tributary access for desirable species by 15–50% relative to an unconstrained scenario. Additional investment to offset the effect of limiting sea‐lamprey access resulted in high opportunity costs for 30 of 37 species (e.g., an additional US$20–80 million for lake sturgeon [Acipenser fulvescens]) and often required ≥5% increase in sea‐lamprey access to identify barrier‐removal solutions adhering to the budget and limiting access. Narrowly distributed species exhibited the highest opportunity costs but benefited more at less cost when small increases in sea‐lamprey access were allowed. Our results illustrate the value of optimization in limiting opportunity costs when balancing invasion control against restoration benefits for diverse desirable species. Such trade‐off analyses are essential to the restoration of connectivity within fragmented rivers without unleashing invaders.     

Evaluation of methylene blue and riboflavin for the photosensitized degradation of ethylene glycol

Degradation rates ranging from 0.22 ± 0.11 to 1.52 ± 0.50 mg/L-h were measured for ethylene glycol in riboflavin solutions exposed to natural sunlight. Significant degradation rates were noted in systems using 6 and 10 mg/L riboflavin at pH values of 4, 7, and 10. No significant degradation was found in systems using methylene blue as the photosensitizing agent. Possible mechanisms for ethylene glycol degradation include a combination hydrogen or electron abstraction by an excited photosensitizer and reaction with singlet oxygen or reaction with superoxide radicals.     

Application of an improved method for the analysis of pesticides and their metabolites in the urine of farmer applicators and their families

As the annual use of pesticides in the United States has escalated, public health agencies have become increasingly concerned about chronic pesticide exposure. However, without reliable, accurate analytical methods for biological monitoring, low-level chronic exposures are often difficult to assess. A method for measuring simultaneously the urinary residues of as many as 20 pesticides has been significantly improved. The method uses a sample preparation which includes enzyme digestion, extraction, and chemical derivatization of the analytes. The derivatized analytes are measured by using gas chromatography coupled with isotope-dilution tandem mass spectrometry. The limits of detection of the modified method are in the high pg/L - low μg/L range, and the average coefficient of variation (CV) of the method was below 20% for most analytes, with approximately 100% accuracy in quantification. This method was used to measure the internal doses of pesticides among selected farmer applicators and their families. Definite exposure and elimination patterns (i.e., an increase in urinary analyte levels following application and then a gradual decrease to background levels) were observed among the farmer applicators and many of the family members whose crops were treated with carbaryl, dicamba, and 2,4-D esters and amines. Although the spouses of farm workers sometimes exhibited the same elimination pattern, the levels of the targeted pesticides or metabolites found in their urine were not outside the ranges found in the general U.S. population (reference range). The farmer applicators who applied the pesticides and some of their children appeared to have higher pesticide or metabolite levels in their urine than those found in the general U.S. population, but their levels were generally comparable to or lower than reported levels in other occupationally exposed individuals. These results, however, were obtained from a nonrandom sampling of farm residents specifically targeted to particular exposures who may have altered their practices because they were being observed; therefore, further study is required to determine if these results are representative of pesticide levels among residents on all farms where these pesticides are applied using the same application techniques. Using this method to measure exposure in a small nonrandom farm population allowed differentiation between overt and background exposure. In addition, the important role of reference-range information in distinguishing between various levels of environmental exposure was reaffirmed.     

Cadmium—Towards a rational use of a toxic element

Because of its toxicity, cadmium creates an environmental problem as well as a health hazard for exposed workers. Most cadmium emissions arise from the intentional use of the element. It is therefore mandatory to reduce cadmium consumption to the lowest possible level. Cadmium pigments, mainly used in plastic processing, can be replaced in all applications where the processing temperature does not exceed 300°C. Newly developed polyvinyl chloride stabilizers promise to be an excellent substitute for cadmium stabilizers in even the most demanding applications. Cadmium plating, still extensively used in the United States and the West Germany, has been virtually abandoned in Japan. Improved lead acid batteries are replacing vented nickel cadmium batteries because of their cost effectiveness. While in these applications cadmium use is declining, more and more cadmium is needed for the manufacturing of sealed nickel cadmium batteries. These relatively small electrochemical cells are used mainly by individual consumers. Here cadmium can only be replaced in some marginal applications. The high cadmium content of these batteries (up to 22%) makes them a good candidate for recycling of the heavy metal.