Institution
United States Environmental Protection Agency
Government•Washington D.C., District of Columbia, United States•
About: United States Environmental Protection Agency is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 13873 authors who have published 26902 publications receiving 1191729 citations. The organization is also known as: EPA & Environmental Protection Agency.
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TL;DR: In this paper, the reference condition for biological integrity (RC(BI) was proposed to describe the naturalness of the biota and the absence of significant human disturbance or alteration.
Abstract: An important component of the biological assessment of stream condition is an evaluation of the direct or indirect effects of human activities or disturbances. The concept of a ''reference condition'' is increasingly used to describe the standard or benchmark against which current condition is compared. Many individual nations, and the European Union as a whole, have codified the concept of reference condition in legislation aimed at protecting and improving the ecological condition of streams. However, the phrase ''reference condition'' has many meanings in a variety of contexts. One of the primary purposes of this paper is to bring some consistency to the use of the term. We argue the need for a ''reference condition'' term that is reserved for referring to the ''naturalness'' of the biota (structure and function) and that naturalness implies the absence of significant human disturbance or alteration. To avoid the confusion that arises when alternative definitions of reference condition are used, we propose that the original concept of reference condition be preserved in this modified form of the term: ''reference condition for biological integrity,'' or RC(BI). We further urge that these specific terms be used to refer to the concepts and methods used in individual bioassessments to characterize the expected condition to which current conditions are compared: ''minimally disturbed condition'' (MDC); ''historical condition'' (HC); ''least disturbed condition'' (LDC); and ''best attainable condition'' (BAC). We argue that each of these concepts can be narrowly defined, and each implies specific methods for estimating expectations. We also describe current methods by which these expectations are estimated including: the reference-site approach (condition at minimally or least-disturbed sites); best professional judgment; interpretation of historical condition; extrapolation of empirical models; and evaluation of ambient distributions. Because different assumptions about what constitutes reference condition will have important effects on the final classification of streams into condition classes, we urge that bioassessments be consistent in describing the definitions and methods used to set expectations.
907 citations
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TL;DR: In this article, the authors assess the combined impact of eutrophication and ocean acidification on acidity in the coastal ocean, using data collected in the northern Gulf of Mexico and the East China Sea.
Abstract: Human inputs of nutrients to coastal waters can lead to the excessive production of algae, a process known as eutrophication. Microbial consumption of this organic matter lowers oxygen levels in the water 1‐3 . In addition, the carbon dioxide produced during microbial respiration increases acidity. The dissolution of atmospheric carbon dioxide in ocean waters also raises acidity, a process known as ocean acidification. Here, we assess the combined impact of eutrophication and ocean acidification on acidity in the coastal ocean, using data collected in the northern Gulf of Mexico and the East China Sea—two regions heavily influenced by nutrient‐laden rivers. We show that eutrophication in these waters is associated with the development of hypoxia and the acidification of subsurface waters, as expected. Model simulations, using data collected from the northern Gulf of Mexico, however, suggest that the drop in pH since pre-industrial times is greater than that expected from eutrophication and ocean acidification alone. We attribute the additional drop in pH— of 0.05 units—to a reduction in the ability of these carbon dioxide-rich waters to buffer changes in pH. We suggest that eutrophication could increase the susceptibility of coastal
902 citations
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895 citations
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TL;DR: In healthy adults with no serologic evidence of past infection with C. parvum, a low dose of C.Parvum oocysts is sufficient to cause infection, and there were no secondary cases of diarrhea among household contacts.
Abstract: Background Small numbers of Cryptosporidium parvum oocysts can contaminate even treated drinking water, and ingestion of oocysts can cause diarrheal disease in normal as well as immunocompromised hosts. Since the number of organisms necessary to cause infection in humans is unknown, we performed a study to determine the infective dose of the parasite in healthy adults. Methods After providing informed consent, 29 healthy volunteers without evidence of previous C. parvum infection, as determined by the absence of anti-cryptosporidium–specific antibodies, were given a single dose of 30 to 1 million C. parvum oocysts obtained from a calf. They were then monitored for oocyst excretion and clinical illness for eight weeks. Household contacts were monitored for secondary spread. Results Of the 16 subjects who received an intended dose of 300 or more oocysts, 14 (88 percent) became infected. After a dose of 30 oocysts, one of five subjects (20 percent) became infected, whereas at a dose of 1000 or more oocysts, ...
884 citations
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TL;DR: In this paper, effective sample size (ESS) has been proposed to modify the nonparametric Mann-Kendall (MK) statistical test to assess the significance of trend in hydrological time series.
Abstract: The non-parametric Mann-Kendall (MK) statistical test has been popularly used to assess the significance of trend in hydrological time series The test requires sample data to be serially independent When sample data are serially correlated, the presence of serial correlation in time series will affect the ability of the test to correctly assess the significance of trend To eliminate the effect of serial correlation on the MK test, effective sample size (ESS) has been proposed to modify the MK statistic This study investigates the ability of ESS to eliminate the influence of serial correlation on the MK test by Monte Carlo simulation Simulation demonstrates that when no trend exists within time series, ESS can effectively limit the effect of serial correlation on the MK test When trend exists within time series, the existence of trend will contaminate the estimate of the magnitude of sample serial correlation, and ESS computed from the contaminated serial correlation cannot properly eliminate the effect of serial correlation on the MK test However, if ESS is computed from the sample serial correlation that is estimated from the detrended series, ESS can still effectively reduce the influence of serial correlation on the MK test
878 citations
Authors
Showing all 13926 results
Name | H-index | Papers | Citations |
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Joel Schwartz | 183 | 1149 | 109985 |
Timothy A. Springer | 167 | 669 | 122421 |
Chien-Jen Chen | 128 | 655 | 66360 |
Matthew W. Gillman | 126 | 529 | 55835 |
J. D. Hansen | 122 | 975 | 76198 |
Dionysios D. Dionysiou | 116 | 675 | 48449 |
John P. Giesy | 114 | 1162 | 62790 |
Douglas W. Dockery | 105 | 244 | 57461 |
Charles P. Gerba | 102 | 692 | 35871 |
David A. Savitz | 99 | 572 | 32947 |
Stephen Polasky | 99 | 354 | 59148 |
Judith C. Chow | 96 | 427 | 32632 |
Diane R. Gold | 95 | 443 | 30717 |
Scott L. Zeger | 95 | 377 | 78179 |
Rajender S. Varma | 95 | 672 | 37083 |