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641.
Elena Nilsen Edward T. Furlong Robert Rosenbauer 《Journal of the American Water Resources Association》2014,50(2):291-301
One by‐product of advances in modern chemistry is the accumulation of synthetic chemicals in the natural environment. These compounds include contaminants of emerging concern (CECs), some of which are endocrine disrupting compounds (EDCs) that can have detrimental reproductive effects. The role of sediments in accumulating these types of chemicals and acting as a source of exposure for aquatic organisms is not well understood. Here we present a small‐scale reconnaissance of CECs in bed sediments of the lower Columbia River and several tributaries and urban streams. Surficial bed sediment samples were collected from the Columbia River, the Willamette River, the Tualatin River, and several small urban creeks in Oregon. Thirty‐nine compounds were detected at concentrations ranging from <1 to >1,000 ng [g sediment]?1 dry weight basis. Concentrations and frequencies of detection were higher in tributaries and small urban creeks than in the Columbia River mainstem, suggesting a higher risk of exposure to aquatic life in lower order streams. Ten known or suspected EDCs were detected during the study. At least one EDC was detected at 21 of 23 sites sampled; several EDCs were detected in sediment from most sites. This study is the first to document the occurrence of a large suite of CECs in the sediments of the Columbia River basin. A better understanding of the role of sediment in the fate and effects of emerging contaminants is needed. 相似文献
642.
Akkoyunlu Bülent O. Tayanç Mete Karaca Mehmet 《Water, Air, & Soil Pollution: Focus》2003,3(5-6):141-155
This study presents the chemical composition of bulk deposition during the period of February 1996–May 1997 and the chemical composition of sub-event wet deposition on 13 August 1997 in Gebze. Samples were analyzed for SO4
2-, NO3
-, Cl-,Ca2+, Mg2+, K+, Na+, and NH4
+ in addition to pH. The source of some ionic components in the bulk deposition such as K+ and Ca2+ were found to be the terrestrial regions, as expected. The (non-sea Cl-)/Cl- ratio of 0.05 suggests that the very large portion of Cl- in the bulkdeposition was of marine origin. The ratio of (non-sea SO4
2-)/SO4
2- varied between 0.86 and 0.99,indicating that the main source of sulfate was not the sea. It is found that the sulfate and calcium concentrations were highest in summer and lowest in fall. The analysis of bulk deposition also indicated that nearly 24% of the events were acidic (pH < 5.6). During sub-event wet deposition collectedon the same site pH decreased continually, and during the passageof cold front concentrations of Cl-, SO4
2- and NO3
- increased. 相似文献
643.
644.
Manfred Owe E. Bruce Jones Thomas J. Schmugge 《Journal of the American Water Resources Association》1982,18(6):949-954
ABSTRACT: Sail moisture data were taken during nine sampling events (1976-1978) at a test site in South Dakota as part of the ground truth used in NASA's aircraft experiments studying the microwave sensing of soil moisture. This portion of the study dealt only with the spatial variability observed with regard to the ground data. Samples were taken over three surface depths at each point, and the data reported as the mean field moisture content within each of three surface horizons. The results shed additional light on the relationship between ground sampling and remote sensing of soil moisture. First, it was found that it is best to partition data of well drained sites from poorly drained areas when attempting to characterize the surface moisture content throughout an area of varying soil and cover conditions. It was also found that the moisture coefficient of variation within a field decreased as the mean field soil moisture increased, and that the standard deviation was at a maximum in the mid-range of observed moisture conditions (15-25 percent). Within field sample variation also decreases as the sample is integrated over a greater surface depth. It was determined that a sampling intensity of 10 samples per kilometer was adequate to characterize the mean field soil moisture at all three depths along a transect in the areas of moderate to good drainage-. 相似文献
645.
Dr Ingo Kennerknecht Sabine Krämer Dieter Grab Rainer Terinde Walther Vogel 《黑龙江环境通报》1993,13(4):257-269
Data in the literature suggest that confined placental mosaicism might be associated with intrauterine growth retardation. However, this association may be coincidental and due to bias of ascertainment. We therefore started a prospective study based on the cytogenetic evaluation of placentae derived from growth-retarded newborns. We further minimized possible bias by excluding those small-for-date infants displaying findings which already could explain intrauterine growth retardation (mothers who are smokers, multiple pregnancies, gestosis, dysmorphic infants). In a collection of 71 small-for-gestational age newborns, we did not see a single case of true confined placental mosaicism. 相似文献
646.
This note describes a technique for cutting undisturbed brittleblock samples into smaller specimens for further geotechnical testing. This technique revealed very useful in dealing with collapsible soils, where the sampling is recommended to be donewith block soil samples. A further use of this technique as an efficient way for sampling collapsible soils is proposed. 相似文献
647.
The results of a co-ordinated monitoring programme for pesticide residues in the European Union and Norway carried out in 1996 and 1997 are presented. The aim of this programme is to work towards a system, which makes it possible to estimate actual dietary pesticide intake for the population of the European Union. Based on a statistically dérived sampling plan and within the limited number of pesticides/commodities analysed, the most critical pesticides (benomyl group and dithiocarbamates) and commodities (mandarine and lettuce) were identified. In case of detected non-compliances, repeated sampling and, if necessary, enforcement actions are to be taken by national authorities. The programme will be continued in the next years. 相似文献
648.
Nemitz E. Flynn M. Williams P. I. Milford C. Theobald M. R. Blatter A. Gallagher M. W. Sutton M. A. 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):189-202
A continuous relaxed eddy accumulation system ispresented for the automated measurement of surface/atmosphere exchange fluxes of atmospheric ammonia (NH3) at a single height. The new system features sampling by parallel plate denuder inlets, online chemical analysis using the conductivity cell of a commercially available NH3 analyzer and online flux calculation. The effective detection limit of the system for air concentrations is 0.2 g m-3 and it is estimated to resolve fluxes > ± 20 ng m-2 s-1, depending on the NH3 concentration and turbulence. The performance of the system was tested in two measurement campaigns above agricultural grassland, in which it was compared with a 3-point continuous gradient system. During the first campaign, after urea application of 47 kg N ha-1 in autumn, the REA system derived fluxes which were on average twice as large as the gradient fluxes, while concentrations agreed closely (on average within 4%). Possible reasons include differences in the footprint and an over-correction of the gradient flux in stable conditions. Due to wet and cold conditions, only 0.3% of the fertilizer N was volatilized as NH3 during the first week. Results from the deployment of an improved system are presented for a summer day, 6 days after fertilization with calcium ammonium nitrate. The agreement of both concentrations (on average within 13%) and fluxes (26%) was very encouraging and similar to the agreement found between two state-of-the-art gradient systems with online analysis. 相似文献
649.
ABSTRACT: Catch in standard (unshielded) rain gages exposed 3 feet above the land surface was compared with catch in pit (buried) gages exposed 1 inch above the land surface. These tests confirmed that catch in standard gages under estimates point rainfall in forest openings, as well as in conventional weather stations. Pit gages caught significantly (P=0.05) more rain than did standard gages at each of four locations tested. Catch increases ranged from 2.3 to 3.4 percent. 相似文献
650.
A technique for sampling pure fetal blood in twin pregnancies using a single uterine entry with a fetoscope is described. The fetoscope was inserted into one sac and after blood had been obtained from that, twin, the fetus in the other sac was sampled by trans-septal passage of the blood-sampling needle. This was done in six out of seven patients, the first in the series having two separate insertions of the fetoscope, one into each sac. Pure fetal blood was taken from all 14 fetuses, either from the placental insertion of the umbilical cord or the umbilicus, and the volume of the samples ranged from 200 μl to 1200 μl. In six patients the fetuses were at risk of β-thalassaemia and in one of haemophilia A. Some observations are made relating zygosity to the ultrasonic and fetoscopic appearance of the septum between the sacs. 相似文献