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1.
Luo J Shukla R Adhikari A Reponen T Grinshpun SA Zhang Q LeMasters GK 《Journal of environmental monitoring : JEM》2006,8(9):955-962
A time series model was fitted to the pollen concentration data collected in the Greater Cincinnati area for the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS). A traditional time series analysis and temporal variogram approach were applied to the regularly spaced databases (collected in 2003) and irregularly spaced ones (collected in 2002), respectively. The aim was to evaluate the effect of the sampling frequency on the sampling precision in terms of inverse of standard error of the overall level of mean value across time. The presence of high autocorrelation in the data was confirmed and indicated some degree of temporal redundancy in the pollen concentration data. Therefore, it was suggested that sampling frequency could be reduced from once a day to once every several days without a major loss of sampling precision of the overall mean over time. Considering the trade-offs between sampling frequency and the possibility of sampling bias increasing with larger sampling interval, we recommend that the sampling interval should take values from 3 to 5 days for the pollen monitoring program, if the goal is to track the long-term average. 相似文献
2.
Abstact The present study was designed to evaluate indirect, non-invasive, on-line measurement of biofilm thickness using an electrical capacitance technique. Several assays were carried out and the results showed that, at a frequency of 1 kHz, electrical capacitance could be used to measure biofilm thickness indirectly (with a correlation coefficient of 0.9495). The reproducibility revealed by the assays was also highly satisfactory.However, in contrast to what was expected, there was an inverse relationship between electrical capacitance and biofilm thickness, i.e. electrical capacitance diminished with the increase in the biofilm thickness.The tests were also carried out at different frequencies (1 kHz, 10 kHz and 100 kHz) 相似文献
3.
Kumar A Baroth A Soni I Bhatnagar P John PJ 《Environmental monitoring and assessment》2006,116(1-3):1-7
Anupgarh is the most fertile area of Rajasthan state where a variety of seasonal crops are grown. The availability of three
manmade canals has enhanced the agricultural activities in this area. The farmers use huge amounts of pesticides to increase
the crop productivity. Exposure of humans to these hazardous chemicals occurs directly in the fields and indirectly due to
consumption of contaminated diet, or by inhalation or by dermal contact. The organochlorine pesticides are reported to be
lipophilic and their presence in human milk and blood has been documented in different parts of the world. Blood and milk
samples were collected from lactating women who were divided into four groups on the basis of different living standards viz
residence area, dietary habits, working conditions and addiction to tobacco. The level of total organochlorine pesticides
in blood ranged from 3.319mg/L—6.253mg/L while in milk samples it ranged from 3.209Mdash;4.608 mg/L. The results are in concurrence
with the reports from other countries. 相似文献
4.
San Vicente Bay is a coastal shallow embayment in Central Chile with multiple uses, one of which is receiving wastewater from
industrial fisheries, steel mill effluents, and domestic sewage. A simulation model was developed and applied to dissolved
oxygen consumption by organic residues released into this embayment. Three compartments were established as function of: depth,
circulation and outfall location. The model compartments had different volumes, and their oxygen saturation value was used
as baseline. The parameters: (a) BOD5 of the industrial and urban effluents, (b) oxygen demand by organic sediments, (c) respiration, (d) photosynthesis and (e)
re-aeration were included in the model. Iteration results of the model showed severe alterations in Compartment 1, with a
decrease of 65% in the oxygen below saturation. Compartment 2 showed a small decline (10%) and compartment 3 did not show
apparent changes in oxygen values. Measures recommended for remediation were to decrease the BOD5 loading by 30% in the affected sector. Iteration of the model for 200 h following recommendations derived from the preceding
results produced an increase in saturation of 60% (5 ml O2 L−1), which suggested an improvement of the environmental conditions. 相似文献
5.
A new approach to Assess Atmospheric Nitrogen Deposition by Way of Standardized Exposition of mosses
A standardized method of moss exposition for assessing variations in nitrogen deposition was tested in the western part of
Germany. Six pleurocarpous moss species were transplanted to two sites differing in their deposition rates but being comparable
as to their climatic conditions. The mosses were exposed in standardized containers over a period of 12 months; the focus
of interest was the effect of N deposition on nitrogen content and on 15N natural abundance (δ15N-values). Within the first nine months only trends could be observed. However, after one year all species tested showed significantly
higher N concentrations at the highly polluted site. Besides, more negative δ15N-values possibly reflecting the higher ammonium input were detected at this site. Surprisingly, most of the plants though
being kept in plastic containers without a favourable substratum did not show any conspicuous deficiency symptoms. The potential
advantages of a standardized moss exposition for N monitoring purposes are discussed. It is concluded that the method presented
here can yield significant results in particular if the number of testing sites is increased. 相似文献
6.
D'Affonseca FM Blum P Finkel M Melzer R Grathwohl P 《Journal of contaminant hydrology》2008,102(1-2):120-139
A coal tar contaminated site was characterized using traditional and innovative investigation methods. A careful interpretation of hydrogeological and hydrogeochemical data allowed for the conceptualization of the heterogeneous coal tar distribution in the subsurface. Past and future contaminant release from the source zone was calculated using a modeling framework consisting of a three-dimensional steady-state groundwater flow model (MODFLOW) and two hydrogeochemical models (MIN3P). Computational time of long-term simulations was reduced by simplifying the coal tar composition using 3 composite and 2 individual constituents and sequential application of a 2D centerline model (for calibration and predictions) and a 3D model (only for predictions). Predictions were carried out for a period of 1000 years. The results reveal that contaminant mass flux is governed by the geometry of zones containing residual coal tar, amount of coal tar, its composition and the physicochemical properties of the constituents. The long-term predictions made using the 2D model show that even after 1000 years, source depletion will be small with respect to phenanthrene, 89% of initial mass will be still available, and for the moderately and sparingly soluble composite constituents, 60% and 98%, respectively. 相似文献
7.
Heavy metal accumulation in Littoraria scabra along polluted and pristine mangrove areas of Tanzania
The periwinkle Littoraria scabra was collected at polluted and pristine mangrove sites along the Tanzanian coastline, including Msimbazi, Mbweni (i.e. Dar es Salaam) and Kisakasaka, Nyamanzi and Maruhubi (i.e. Zanzibar). Periwinkles were morphologically characterized, sexed and their heavy metal content was determined using ICP-MS. Analysis revealed that L. scabra from polluted areas contained higher soft tissue heavy metal levels, were significantly smaller and weighed less compared to their conspecifics from the unpolluted mangroves. The current morphological observations may be explained in terms of growth and/or mortality rate differences between the polluted and non-polluted sites. Although a variety of stressors may account for these adverse morphological patterns, our data suggest a close relationship with the soft tissue heavy metal content. Compared to soft tissue heavy metal levels that were measured in L. scabra along the same area in 1998, most metals, except for arsenic, chromium and iron have decreased dramatically. 相似文献
8.
Alonso R Elvira S Sanz MJ Gerosa G Emberson LD Bermejo V Gimeno BS 《Environmental pollution (Barking, Essex : 1987)》2008,155(3):473-480
A sensitivity analysis of a proposed parameterization of the stomatal conductance (g(s)) module of the European ozone deposition model (DO(3)SE) for Quercus ilex was performed. The performance of the model was tested against measured g(s) in the field at three sites in Spain. The best fit of the model was found for those sites, or during those periods, facing no or mild stress conditions, but a worse performance was found under severe drought or temperature stress, mostly occurring at continental sites. The best performance was obtained when both f(phen) and f(SWP) were included. A local parameterization accounting for the lower temperatures recorded in winter and the higher water shortage at the continental sites resulted in a better performance of the model. The overall results indicate that two different parameterizations of the model are needed, one for marine-influenced sites and another one for continental sites. 相似文献
9.
Valverde A Piedra L Aguilera A Boulaid M Camacho F 《Journal of environmental science and health. Part. B》2007,42(7):801-807
This paper describes the application of liquid chromatography-tandem mass spectrometry (LC/MS-MS) for analysis of residues of forchlorfenuron (CPPU), a new plant growth regulator, in watermelons, after a sample preparation step based on the buffered Quick, Easy, Cheap, Effective, Rugged and Safe extraction method. Analytical determinations were carried out in a triple quadrupole system fitted with an electrospray interphase operating in the positive ionisation mode (ESI+). Three simultaneous MS-MS transitions of the quasi-molecular ion m/z 248 (precursor ion) were monitored for data acquisition (248 > 129, 248 > 155, and 248 > 248), using the transition 248 > 129 for quantitation. Recovery studies on watermelons at levels of 1-200 microg/kg, performing five replicates at each level and using bracketing single-level calibration with matrix-matched standards for quantitation, gave forchlorfenuron mean recoveries ranging from 82 to 106% with relative standard deviations (RSD) lower than 18%. The limit of determination was established at 1 microg/kg. The method was applied to evaluate the persistence of forchlorfenuron residues in watermelons grown in plastic greenhouses, after applying an individual spray treatment to the flower ovary at the anthesis stage (45 mu g/flower and 60 mu g/flower for cv "Extazy" and cv "reina de corazones" watermelons, respectively). One month after treatment, 20 "Extazy" watermelon units (1.5-2 kg/unit) and 20 "Reina de corazones" watermelon units (4-5 kg/unit) were collected and analyzed individually. None of the samples contained forchlorfenuron residues higher than 1 microg/kg. 相似文献
10.
The ageing effect on the bioaccessibility and fractionation of arsenic in soils from China 总被引:7,自引:0,他引:7
Ingestion of contaminated soil has been recognized as an important exposure pathway of arsenic for humans, especially for children through outdoor hand-to-mouth activities. An improved sequential extraction procedure was employed in an attempt to reveal the relationship between bioaccessibility and fractionation of As in five soils from China. Arsenic bioaccessibility in acidic ( approximately pH 4.5) soils reached approximately stable levels after a sharp decline within one week of ageing. In contrast, As bioaccessibility in higher pH (>6.0) soils was found to be significantly higher and took two weeks of ageing to reach stable levels. The artificially added As was more labile than indigenous As. The main proportions of added As were found in the specifically sorbed and amorphous and poorly-crystalline hydrous Fe/Al oxide-bound fractions. Correlation analysis shows that the non-specifically and specifically sorbed As are likely to constitute the main proportion of bioaccessible soil As. The soil content of amorphous and crystalline Fe/Al oxides and soil pH appear to be the key factors controlling, not only the time needed to reach a steady state, but also the magnitude of the bioaccessibility of As added to the soils. 相似文献