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21.
Syam?S.?Andra Konstantinos?C.?MakrisEmail author Pantelis?Charisiadis Costas?N.?Costa 《Environmental monitoring and assessment》2014,186(11):7307-7320
Potable water samples (N?=?74) from 19 zip code locations in a region of Greece were profiled for 13 trace elements composition using inductively coupled plasma mass spectrometry. The primary objective was to monitor the drinking water quality, while the primary focus was to find novel associations in trace elements occurrence that may further shed light on common links in their occurrence and fate in the pipe scales and corrosion products observed in urban drinking water distribution systems. Except for arsenic at two locations and in six samples, rest of the analyzed elements was below maximum contaminant levels, for which regulatory values are available. Further, we attempted to hierarchically cluster trace elements based on their covariances resulting in two groups; one with arsenic, antimony, zinc, cadmium, and copper and the second with the rest of the elements. The grouping trends were partially explained by elements’ similar chemical activities in water, underscoring their potential for co-accumulation and co-mobilization phenomena from pipe scales into finished water. Profiling patterns of trace elements in finished water could be indicative of their load on pipe scales and corrosion products, with a corresponding risk of episodic contaminant release. Speculation was made on the role of disinfectants and disinfection byproducts in mobilizing chemically similar trace elements of human health interest from pipe scales to tap water. It is warranted that further studies may eventually prove useful to water regulators from incorporating the acquired knowledge in the drinking water safety plans. 相似文献
22.
Polycyclic aromatic hydrocarbons in the San Francisco Estuary water column: sources, spatial distributions, and temporal trends (1993-2001) 总被引:3,自引:0,他引:3
The composition of PAH in surface waters was examined over a range of spatial and temporal scales to determine distributions, trends, and possible sources. Water samples were collected from 1993 to 2001. PAH in organic extracts were analyzed by gas chromatography-mass spectrometry (GC-MS) and 25 individual target PAH summed to get the total PAH concentration in each water sample. The distribution of median total PAH concentration by estuary segments was Extreme South Bay (120 ng l(-1)) > South Bay (49 ng l(-1)) > North Estuary (29 ng l(-1)) > Central Bay (12 ng l(-1)) > Delta (7 ng l(-1)). Overall, total PAH concentrations were significantly higher in the Extreme South Bay compared to all other segments, and the Central Bay and Delta were significantly lower than all other segments (Kruskal-Wallis, H = 157.27, df = 4, p < 0.0005). This distribution reflects the large urbanized and industrialized areas that border the southern portions of the estuary and the less populated and rural areas that surround the Delta. Temporal trend analysis showed a statistically significant temporal trend in total PAH concentration at only one of the 18 sampling stations situated throughout the estuary (San Jose, significant decrease, p = 0.031, r(2) = 0.386, n = 12). PAH isomer pair ratio analysis showed that PAH in estuary waters were derived primarily from combustion of fossil fuels/petroleum (possible PAH source contributors include coal, gasoline, kerosene, diesel, No. 2 fuel oil, and crude oil) and biomass (possible contributors include wood and grasses), with lesser amounts of PAH contributed from direct petroleum input. 相似文献
23.
Yin-Quan Liu Carlos Bernstein Andra Thiel 《Behavioral ecology and sociobiology》2009,63(10):1459-1469
Foraging animals usually keep track of how costly it is to reach new resource patches and adjust patch residence time and
exploitation rate accordingly. There are at least two potential factors, which are not necessarily closely linked, that animals
could measure to estimate costs of traveling: the time the forager needs to reach the next patch and the amount of energy
it has to invest until arrival. In the parasitoid wasp Venturia canescens, females forage for hosts from which their offspring can develop. Two different types of this parasitoid exist. The thelytokous
type lives in anthropogenic habitats where flight is not necessarily linked with foraging. The arrhenotokous type lives under
field conditions and shows frequent flight activity. We tested whether the wasps would use time or energy needed to assess
patch availability, by either confining them into vials or letting them travel actively in a flight mill between patch visits.
Our results show that in thelytokous lines, time is a sufficient cue influencing patch exploitation and an additional effect
of the energy needed was not visible. In the arrhenotokous wasps, however, only the number of rounds flown in the mill influenced
subsequent behavior, while mere time spent traveling did not.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献