MEASUREMENT OF ACCUMULATION OF SEMICONDUCTOR NANOCRYSTAL QUANTUM DOTS BY PIMEPHALES PROMELAS

As the production and use of nanomaterials increases, it is important to understand their environmental and biological fate. Because their unmatched chemical, physical, and optical properties make them useful in a wide variety of applications including biomedical imaging, photo-voltaics, and light emitting diodes, the use of semiconductor nanocrystals such as quantum dots (QDs) is increasing rapidly. Although QDs hold great potential in a wide variety of industrial and consumer applications, the environmental implications of these particles is largely unexplored. The nanocrystal core of many types of QDs contains the toxic metal cadmium (Cd), so possible release of Cd from the QD core is cause for concern. Because many types of QDs are miscible in water, QD interactions with aquatic organisms and their environment require more attention. In the present study we used fluorometry to measure time and dose dependent uptake, accumulation, and post-exposure clearance of accumulated QDs in the gut tract by the aquatic vertebrate Pimephales promelas. By using fluorometry, we were able to measure accumulated QD concentrations. To our knowledge, this is the first reported attempt to quantify accumulated QDs in an organism and is an important step in understanding the interactions among QDs in aquatic organisms and environments

Tributary contribution to the Spring River, AR as determined by water quality analyses

Tributaries often play an important role in the chemical properties, productivity and species diversity in a river channel. The objective of this study was to analyze the effect of tributaries on the water quality of the Spring River, AR. The Spring River has an approximate length of 92 km and has been divided into four zones according to the water source(s) that feed that segment of river. In this study approximately 30 km of the upstream river segment were sampled, which included nine tributaries contributing to the main river channel and incorporated the upper three previously defined zones. Samples were collected from the headwaters located at Mammoth Spring, AR, as well as within the tributaries and above and below the confluence of each tributary with the Spring River. Water-quality parameters analyzed included pH, conductivity, alkalinity, total suspended solids, fecal coliforms, nutrients (orthophosphate, nitrate, nitrite), and total dissolved ions. Results of total dissolved ions indicated a slight shift in the defined zones. Seven of the nine tributaries indicated chemical contributions ranging from 3.5 to 66.7% to the main stream. Results from this study demonstrate the extent of tributary contribution to the Spring River systems

Tailwater Recovery Systems for Irrigation: Benefit/Cost Analysis and Water Resource Conservation Technique in Northeast Arkansas

Water, one of the earth\u27s most vital resources, is particularly significant in the Arkansas Delta agricultural landscape. While both surface and groundwater are extremely important, 94% of the 26.9 billion L (7.1 billion gal) of water pumped daily from the Alluvial Aquifer is used for agricultural purposes. This common property is subsequently being depleted and sustainable conservation methods are being pursued. State and federal incentive programs encourage the use of a tailwater recovery system in agricultural irrigation. With the use of a complete recovery system, benefits include not only government incentives for wetland habitat, but reduced groundwater use and decreased agricultural runoff entering receiving streams. Costs incurred to the farm manager include crop loss due to reservoir storage, additional ditch construction, and the cost of a liftpump. Use of these systems offers not only economic benefits associated with aquifer preservation but also ecological benefits including reduced nutrient and sediment loading to receiving streams concurrent with ecosystem services. The overall benefit/cost analysis ofthese systems shows that the economic benefits of using a tailwater recovery system exceed the cost. Other positive features include the ecological benefits of surface water protection and ecosystem services

Winter and Spring Water Quality of the Big Creek Watershed, Craighead County, Arkansas: Nutrients, Habitat, and Macroinvertebrates

The objective of this study was to assess the water quality of the Big Creek watershed during the winter and spring of 2002 by analyzing water physical, chemical variables, aquatic macro-invertebrates, and habitat. The Big Creek watershed, arising on Crowley\u27s Ridge in northeast Arkansas, is a small deltaic watershed and is an area of intense cultivation. Four stations, Big Creek Upper (BCU), Mud Creek (MC),Lost Creek (LC), and Big Creek Lower (BCL) were established for this study from Big Creek, Mud Creek and Lost Creek. Water samples were collected on a weekly basis for 10 weeks from January 2002 through March 2002. We analyzed these streams for temperature, pH, D.O., conductivity, TSS, chlorophyll- a, DOC, total N and P, total dissolved N and P, nitrate, ammonium, and soluble reactive phosphorus. During this time period, we also sampled aquatic macroinvertebrates and assessed stream habitat according to USEPA rapid bioassessment protocols. Overall, nutrients and TSS were high, pH fluctuated from 5.8 to 7.8, and D.O. was moderate to high, ranging from 6.75 to 13.24 mg/L. Generally, physical and chemical water variables were correlated with changes in stream discharge. For a 20-jab dip-net sample, macroinvertebrate species richness ranged from 9 to 23 taxa, while abundance ranged from 38 to 209 individuals per station. Physical habitat index scores ranged from 75 to 104 (maximum of 200) indicating marginal physical habitat. We report that this watershed has high concentrations of nutrients and suspended solids during the winter and spring wet season and that the macroinvertebrate communities are influenced by stream conditions, including marginal physical habitat

Measurement of Accumulation of Semiconductor Nanocrystal Quantum Dots by

As the production and use of nanomaterials increases, it is important to understand their environmental and biological fate. Because their unmatched chemical, physical, and optical properties make them useful in a wide variety of applications including biomedical imaging, photo-voltaics, and light emitting diodes, the use of semiconductor nanocrystals such as quantum dots (QDs) is increasing rapidly. Although QDs hold great potential in a wide variety of industrial and consumer applications, the environmental implications of these particles is largely unexplored. The nanocrystal core of many types of QDs contains the toxic metal cadmium (Cd), so possible release of Cd from the QD core is cause for concern. Because many types of QDs are miscible in water, QD interactions with aquatic organisms and their environment require more attention. In the present study we used fluorometry to measure time and dose dependent uptake, accumulation, and post-exposure clearance of accumulated QDs in the gut tract by the aquatic vertebrate Pimephales promelas . By using fluorometry, we were able to measure accumulated QD concentrations. To our knowledge, this is the first reported attempt to quantify accumulated QDs in an organism and is an important step in understanding the interactions among QDs in aquatic organisms and environments