339 research outputs found
Chemical and ecological health of white sucker (Catostomus commersoni) in Rock Creek Park, Washington, D.C., 2003-04 / by Cherie V. Miller ... [et al.] ; prepared in copoeration with the National Park Service
Several classes of chemicals that are known or suspected contaminants were found in bed sediment in Rock Creek, including polyaromatic hydrocarbons (PAHs), phthalate esters, organochlorine pesticides, dioxins and furans, trace metals and metalloids (mercury, arsenic, cadmium, chromium, cobalt, copper, lead, nickel, silver, and zinc), and polychlorinated biphenyls (total PCBs and selected aroclors). Concentrations of many of these chemicals consistently exceeded thresholdor chronic-effects guidelines for the protection of aquatic life and often exceeded probable effects levels (PELs). Exceedance of PELs was dependent on the amount of total organic carbon in the sediments. Concurrent with the collection of sediment-quality data, white sucker (Catostomus commersoni) were evaluated for gross-external and internal-organ anomalies, whole-body burdens of chemical contaminants, and gut contents to determine prey. The histopathology of internal tissues of white sucker was compared to contaminant levels in fish tissue and bed sediment. Gut contents were examined to determine preferential prey and thus potential pathways for the bioaccumulation of chemicals from bed sediments. Male and female fish were tested separately. Lesions and other necroses were observed in all fish collected during both years of sample collection, indicating that fish in Rock Creek have experienced some form of environmental stress. No direct cause and effect was determined for chemical exposure and compromised fish health, but a substantial weight of evidence indicates that white sucker, which are bottom-eeding fish and low-order consumers in Rock Creek, are experiencing some reduction in vitality, possibly due to immunosuppression. Abnormalities observed in gonads of both sexes of white sucker and observations of abnormal behavior during spawning indicated some interruption in reproductive success
Recommended from our members
Linear Versus Web-Style Layout of Computer Tutorials for Medical Student Learning of Radiograph Interpretation
Rationale and Objective:We sought to determine which is more effective in increasing skill in radiograph interpretation: a linear (PowerPoint-style) computer tutorial that locks the student into a fixed path through the material or a branched (Web-style) version that allows random access. Materials and Methods: We prepared a computer tutorial for learning how to interpret cervical spine radiographs. The tutorial has 66 screens including radiographs or graphics on almost every page and five unknown radiographs for the student to interpret. One version (linear) presents the material in a linear sequence with the unknown radiographs heading up "chapters" detailing an important aspect of the task. In the second (branched) version, the same 66 screens were accessed through hyperlinks in a frame beside the unknown radiographs. One hundred thirty-nine medical students at two sites participated in a randomized single-blinded controlled experiment. They interpreted cervical spine images as a pretest and then completed one of the two tutorial versions. Afterward, they did the same examination as a post-test. Results:The tutorial was successful, in both layouts, in improving the subjects' ability to interpret cervical spine radiograph images (effect size 2.1; 95% confidence interval 1.7-2.5). However, the layout did not make a difference to their gain in ability. Students in the linear group completed the tutorial in 17% less time (P < .001) but were slightly less likely to rate the tutorial as "valuable." Conclusion:For these novice learners, computer tutorial layout does not affect knowledge gain. Students may be more satisfied with the linear layout, but in time-pressured situations, the Web-style layout may be preferable because it is more efficient
Recommended from our members
Linear Versus Web-Style Layout of Computer Tutorials for Medical Student Learning of Radiograph Interpretation
Rationale and Objective:We sought to determine which is more effective in increasing skill in radiograph interpretation: a linear (PowerPoint-style) computer tutorial that locks the student into a fixed path through the material or a branched (Web-style) version that allows random access. Materials and Methods: We prepared a computer tutorial for learning how to interpret cervical spine radiographs. The tutorial has 66 screens including radiographs or graphics on almost every page and five unknown radiographs for the student to interpret. One version (linear) presents the material in a linear sequence with the unknown radiographs heading up "chapters" detailing an important aspect of the task. In the second (branched) version, the same 66 screens were accessed through hyperlinks in a frame beside the unknown radiographs. One hundred thirty-nine medical students at two sites participated in a randomized single-blinded controlled experiment. They interpreted cervical spine images as a pretest and then completed one of the two tutorial versions. Afterward, they did the same examination as a post-test. Results:The tutorial was successful, in both layouts, in improving the subjects' ability to interpret cervical spine radiograph images (effect size 2.1; 95% confidence interval 1.7-2.5). However, the layout did not make a difference to their gain in ability. Students in the linear group completed the tutorial in 17% less time (P < .001) but were slightly less likely to rate the tutorial as "valuable." Conclusion:For these novice learners, computer tutorial layout does not affect knowledge gain. Students may be more satisfied with the linear layout, but in time-pressured situations, the Web-style layout may be preferable because it is more efficient
Interleukin-6 and soluble interleukin-6 receptor levels in posttraumatic stress disorder : associations with lifetime diagnostic status and psychological context.
This study correlated lifetime PTSD diagnostic status with interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) levels, and tested whether these correlations are sensitive to psychological context. Midlife women attended two research visits where blood was drawn (beginning of visits) and saliva and oral mucosal transudate were collected (beginning and end of visits) to measure IL-6 and sIL-6R. Women were classified as PTSD−/− (past and current symptoms below subsyndromal levels), PTSD+/− (past symptoms at or above subsyndromal levels), or PTSD +/+ (past and current symptoms at or above subsyndromal levels). PTSD+/+ women, compared to the other women, showed more negative emotion at the beginning of the visits, higher salivary IL-6 levels at the beginning versus end of visits, and positive correlations between negative emotion, salivary IL-6, and plasma sIL-6R. Their plasma sIL-6R levels exceeded those of the PTSD+/− women. Overall, IL-6 sensitivity to anticipation and to negative emotions, and higher sIL-6R levels, differentiated persistent versus remitted PTSD
Chapter 4- Human Dimensions of Water for Food Production
Feeding 9 Billion and Maintaining the Planet: Meeting the Challenge of 2050
Environmental concerns, which fall outside normal market powers, require special incentives and consideration in water resource decisions, Marty Matlock said.
Given that the world’s population now consumes past the point of sustainability, should sustainability be a market choice for consumers? “This should be pre-competitive,” Matlock said. “The consumers should have confidence that everything they buy complies with a certain threshold of humanity, of behavior, of ethics and sustainability.”
The market has the power to move materials, goods and services from areas of plenty to those of scarcity. The problem is that the market is not responding to water scarcity, in part because crops are grown where there is no water. For example, in Brazil, areas that once were rainforest now grow 2.4 crops annually for export to China. “They’re exporting de facto water to China,” Matlock said.
Another example stems from the 1 billion people who lack access to water and the 2.4 billion who don’t have basic sanitation. Every day, waterborne diseases kill 5,400 children. “That’s the cost of this failure of technology – failure of civilizations,” Matlock said. “It’s a pretty dramatic cost.”
Global climate change will increase water scarcity in already water-stressed areas. Although agriculture no longer accounts for 90 percent of global water use, as it did in 1900, agricultural water use has increased fivefold since then. Competing with other sectors for limited water affects the many other uses that are not monetized, such as biodiversity. The Colorado and Ganges rivers offer examples of dramatic decreases in water discharge due to overallocation. Peak flows have not changed, but critical base flows have dropped considerably over time. “It’s hard to have a functional, viable aquatic ecosystem without the aquatic,” Matlock said.
Rice, which accounts for 15 percent of human water use, presents another problem. But improvement is possible, Matlock said.
Human Dimensions of Water for Food Production
Anheuser-Busch InBev, for example, achieved 4.7 percent per-unit reductions in rice culture, saving 3.5 billion liters of water in five years.
Water intake is only one issue; equally important is water effluent. From an ecological standpoint, given grossly limited incentive funding, Matlock believes profitable production practices should not be incentivized. “If you already have an incentive for conserving water − reducing soil erosion − then we don’t need to give you more money to do that which you ought to be doing anyway, because the marketplace will weed you out if you don’t perform,” he said. “It’s the things that we don’t incentivize, like preservation of riparian zones, that we should perhaps be incentivizing with our limited resources.”
The Mesoamerican Barrier Reef System offers an example of the interconnectedness of agriculture effluent and environmental harm. Pollutants, particularly sediment and nutrients carried downstream from plantations to the Caribbean Sea, have the equivalent effect of a 10-degree temperature change, bleaching the coral reefs.
Impacts that are acceptable with 6.7 billion people will not be with 9 billion, Matlock concluded. If management happens only to things that are measured, and not everything can be measured, which metrics are important and how can they be incentivized? “We have to shift our thinking from maximizing any one variable or metric to optimizing several key ones.
Chapter 6- A View from Agricultural Producers
Rainfed and Irrigated Production in Argentina
Martin Pasman, an Argentine agronomist with a master’s degree in business administration, began his career as a consultant to farmers and has experience in Argentina, Uruguay, Paraguay and Brazil, where he was instrumental in helping to develop 80,000 hectares in the western part of the Cerrado area. His farming experience stems from his family’s farms, located in five areas of Argentina. Most are rainfed, but one area receives less than 500 millimeters of rain annually. Pasman also runs an irrigation business serving 80 percent of the Argentine market, giving him vast experience in developing irrigated land.
Argentina is the second-largest South American country after Brazil and is one-third the size of the U.S. One-third of Argentina receives more than 800 millimeters of rain and depends upon rainfed agriculture, while the majority receives less than 800 millimeters. Argentina cultivates 30 million hectares per year, of which 2.2 million are irrigated. Total production output is 90 million metric tons, and about 70 percent of farmers in Argentina practice no-till agriculture.
Pasman’s family came to Argentina from the U.S. around 1825, when it was primarily cattle country. His family brought the first Aberdeen Angus bull to Argentina and also helped develop agriculture. In the 1970s, the family farmed 6,000 hectares, of which only 500 were used for crops, yielding 3.5 tons of corn per hectare and 1.5 tons of wheat per hectare. They plowed the land and used few herbicides and no fertilizers. The majority of the land was used to raise 3,000 head of cattle, which were finished in natural pastures.
Today, the family’s farm operation has expanded to 20,000 hectares, 15,000 of them used for agriculture. In the low-productivity land, they also manage 9,000 head of cattle in cow-calf operations, finishing the animals in American style feedlots. In rainfed fields, the Pasmans produce 8 tons of corn per hectare and 3 tons of wheat; under irrigation, they get 12 tons of corn and 6 tons of wheat. The most important crop, however, is soybeans. They also grow potatoes, corn and sunflower seeds for Monsanto Company. The farm uses 42 pivots to irrigate 4,000 hectares, and about 80 percent of the farm is double-cropped: wheat plus soybeans, seed corn plus soybeans, potato plus corn. Argentina uses a huge amount of herbicides and genetically modified crops, Pasman said, adding that his farm was one of the first to produce Roundup Ready® soybean seeds in 1994.
A View from Agricultural Producers
“The cornerstone of our production technology is no-till,” Pasman said, a technique used on the entire farm except the potato fields, which follow a rotation of one year of potatoes followed by three years of no-till. A corn crop follows the potato harvest in the same year.
No-till improves water infiltration and water retention and reduces evaporation because the previous crops’ residue minimizes runoff and allows the soil to retain more water. No-till also reduces erosion risk and increases organic matter, improving oxidation and carbon circulation in the soil. It improves soil fertility, increases productivity and sustainability, and allows farming in difficult soils, particularly shallow soils of 3 inches.
No-till uses less than half the water and less labor compared to conventional tillage, reducing production costs by 30 percent, Pasman concluded. “It is very important, the mix of no tillage with center pivot (irrigation) against traditional management.
Appendix- Water for Food conference proceedings
Poster Competition, Conference Participants, and Photos
Technologies and Advances in Water Management
Human Dimensions of Water for Food Production
Genetics and Physiology of Crop Water
Other
Conference Participants (148-153)
Photos (154-160
Chapter 4- Human Dimensions of Water for Food Production
Feeding 9 Billion and Maintaining the Planet: Meeting the Challenge of 2050
Environmental concerns, which fall outside normal market powers, require special incentives and consideration in water resource decisions, Marty Matlock said.
Given that the world’s population now consumes past the point of sustainability, should sustainability be a market choice for consumers? “This should be pre-competitive,” Matlock said. “The consumers should have confidence that everything they buy complies with a certain threshold of humanity, of behavior, of ethics and sustainability.”
The market has the power to move materials, goods and services from areas of plenty to those of scarcity. The problem is that the market is not responding to water scarcity, in part because crops are grown where there is no water. For example, in Brazil, areas that once were rainforest now grow 2.4 crops annually for export to China. “They’re exporting de facto water to China,” Matlock said.
Another example stems from the 1 billion people who lack access to water and the 2.4 billion who don’t have basic sanitation. Every day, waterborne diseases kill 5,400 children. “That’s the cost of this failure of technology – failure of civilizations,” Matlock said. “It’s a pretty dramatic cost.”
Global climate change will increase water scarcity in already water-stressed areas. Although agriculture no longer accounts for 90 percent of global water use, as it did in 1900, agricultural water use has increased fivefold since then. Competing with other sectors for limited water affects the many other uses that are not monetized, such as biodiversity. The Colorado and Ganges rivers offer examples of dramatic decreases in water discharge due to overallocation. Peak flows have not changed, but critical base flows have dropped considerably over time. “It’s hard to have a functional, viable aquatic ecosystem without the aquatic,” Matlock said.
Rice, which accounts for 15 percent of human water use, presents another problem. But improvement is possible, Matlock said.
Human Dimensions of Water for Food Production
Anheuser-Busch InBev, for example, achieved 4.7 percent per-unit reductions in rice culture, saving 3.5 billion liters of water in five years.
Water intake is only one issue; equally important is water effluent. From an ecological standpoint, given grossly limited incentive funding, Matlock believes profitable production practices should not be incentivized. “If you already have an incentive for conserving water − reducing soil erosion − then we don’t need to give you more money to do that which you ought to be doing anyway, because the marketplace will weed you out if you don’t perform,” he said. “It’s the things that we don’t incentivize, like preservation of riparian zones, that we should perhaps be incentivizing with our limited resources.”
The Mesoamerican Barrier Reef System offers an example of the interconnectedness of agriculture effluent and environmental harm. Pollutants, particularly sediment and nutrients carried downstream from plantations to the Caribbean Sea, have the equivalent effect of a 10-degree temperature change, bleaching the coral reefs.
Impacts that are acceptable with 6.7 billion people will not be with 9 billion, Matlock concluded. If management happens only to things that are measured, and not everything can be measured, which metrics are important and how can they be incentivized? “We have to shift our thinking from maximizing any one variable or metric to optimizing several key ones.
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