排序方式: 共有15条查询结果,搜索用时 0 毫秒
11.
Jack Fishman John K. Creilson Peter A. Parker Elizabeth A. Ainsworth G. Geoffrey Vining John Szarka Fitzgerald L. Booker Xiaojing Xu 《Atmospheric environment (Oxford, England : 1994)》2010,44(18):2248-2256
Elevated concentrations of ground-level ozone (O3) are frequently measured over farmland regions in many parts of the world. While numerous experimental studies show that O3 can significantly decrease crop productivity, independent verifications of yield losses at current ambient O3 concentrations in rural locations are sparse. In this study, soybean crop yield data during a 5-year period over the Midwest of the United States were combined with ground and satellite O3 measurements to provide evidence that yield losses on the order of 10% could be estimated through the use of a multiple linear regression model. Yield loss trends based on both conventional ground-based instrumentation and satellite-derived tropospheric O3 measurements were statistically significant and were consistent with results obtained from open-top chamber experiments and an open-air experimental facility (SoyFACE, Soybean Free Air Concentration Enrichment) in central Illinois. Our analysis suggests that such losses are a relatively new phenomenon due to the increase in background tropospheric O3 levels over recent decades. Extrapolation of these findings supports previous studies that estimate the global economic loss to the farming community of more than $10 billion annually. 相似文献
12.
Inorganic pollution comprises both major and minor constituents, although only 12 chemical elements may be considered major components. Twenty‐eight elements constitute a group of common minor elements and an additional 13 elements comprise a group of less common minor constituents. Reliable quantitative data are required on the occurrence of these substances in a wide variety of water types, usually at extremely low concentrations. The analysis of standard reference water samples provides information on the overall reliability of water‐quality data. Although most major constituents may be determined with acceptable reliability, determinations of certain minor constituents lack comparable precision; for example, determinations of boron, nickel, and chromium. Few precision data are available on the determination of the less common trace elements. Several comparatively new analytical techniques, such as flameless atomic absorption spectrophotometry, voltammetry, and emission spectroscopy with plasma excitation, appear capable of providing improved sensitivity. 相似文献
13.
D. Wilson Freshwater Andrew Hines Seth Parham Ami Wilbur Michelle Sabaoun Jennifer Woodhead Lad Akins Bruce Purdy Paula E. Whitfield Claire B. Paris 《Marine Biology》2009,156(6):1213-1221
Lionfish are popular aquarium fish from the Indo-Pacific that have invaded the western Atlantic. Two species, Pterois volitans and P. miles, were well established along the United States east coast before the first lionfish were reported from the Bahamas in 2004,
where they quickly dispersed throughout the archipelago by 2007. The source of the Bahamian lionfish invasion has been in
question because of the hypothesized low connectivity between Florida and Bahamas reef species as well as the temporal lag
in their arrival in the Bahamas. Mitochondrial control region haplotypes (680 bp) were determined and analyzed for lionfish
specimens from the Bahamas, North Carolina, and two sites within their native range (Indonesia and the Philippines). Exact
tests, pairwise F
st and AMOVA analyses all showed no significant differentiation between the Bahamas and North Carolina specimens. The similarity
between the Bahamas and North Carolina lionfish was also reflected in a minimum spanning network and neighbor-joining distance
tree generated from the data. Sequence analyses also revealed the presence of only Pterois volitans, as no P. miles were detected in the Bahamian sample. These results indicate that the source of the Bahamian lionfish is egg and larval dispersal
from the United States east coast population, and support previous models of reef fish dispersal that suggest a low level
of connectivity between the Bahamas and east coast of Florida. 相似文献
14.
15.