共查询到20条相似文献,搜索用时 70 毫秒
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气相分子吸收光谱法测定海水中的硝酸盐氮 总被引:1,自引:0,他引:1
采用GMA3212型气相分子吸收光谱仪测定海水中的硝酸盐氮,在常规海水中硝酸盐氮质量浓度范围内(0~4.00 mg/L)线性良好(线性相关系数0.999 9),检出限为0.004 mg/L,标准溶液平行测定的相对标准偏差小于或等于1.44%,相对误差小于或等于1.33%,实际水样加标回收率为96.0%~102%。通过与国标方法镉柱还原法的比对实验,2种方法在精密度、准确度、实样比对等方面均无显著性差异,测定结果具有良好的一致性。气相分子吸收光谱法具有操作简便、分析快速准确、试剂消耗少、适合批量测定等优点,是值得推介的先进方法。 相似文献
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Irja Helm Gerli Karina Lauri Jalukse Todd Pagano Ivo Leito 《Environmental monitoring and assessment》2018,190(5):313
A comprehensive comparative validation for two different types of dissolved oxygen (DO) analyzers, amperometric and optical, is presented on two representative commercial DO analyzers. A number of performance characteristics were evaluated including drift, intermediate precision, accuracy of temperature compensation, accuracy of reading (under different measurement conditions), linearity, flow dependence of the reading, repeatability (reading stability), and matrix effects of dissolved salts. The matrix effects on readings in real samples were evaluated by analyzing the dependence of the reading on salt concentration (at saturation concentration of DO). The analyzers were also assessed in DO measurements of a number of natural waters. The uncertainty contributions of the main influencing parameters were estimated under different experimental conditions. It was found that the uncertainties of results for both analyzers are quite similar but the contributions of the uncertainty sources are different. Our results imply that the optical analyzer might not be as robust as is commonly assumed; however, it has better reading stability, lower stirring speed dependence, and typically requires less maintenance. On the other hand, the amperometric analyzer has a faster response and wider linear range. Both analyzers seem to have issues with the accuracy of temperature compensation. The approach described in this work will be useful to practitioners carrying out DO measurements for ensuring reliability of their measurements. 相似文献
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Heavy metal binding fractions in the sediments of the Godavari estuary,East Coast of India 总被引:1,自引:0,他引:1
Sequential chemical extraction was used to study the operationally determined chemical forms of five heavy metals (Pb, Cu,
Zn, Co and Ni) and their spatial distribution in the sediments. The binding behaviour of heavy metals associating with Fe–Mn
oxides showed a good correlation towards Cu, Zn and Co, but moderate linear dependence with Ni and Pb. Among the five metals,
correlation between Fe–Mn oxide bound Cu and Fe–Mn oxides (r = 0.95) is highest. The coefficient of determination (r
2) in organically bound heavy metals versus organic matter (OM) ranges from 0.772 to 0.952, which indicates a good linear dependence.
The OM fraction in the sediments is more accessible to heavy metals and is the major ligand available for complexation. In
particular, Zn and Cu are preferentially bound to OM. In general, Zn co-precipitation with carbonates is the dominant chemical
form when Fe–Mn oxide and OM are less abundant. In this study, however, carbonates were less abundant, hence Zn bound to carbonates
was less pronounced. Based on the results, even if the excessive binding sites are contained in the sediments, competition
of various complexation reactions between sediment phases and heavy metals could dominate metal association. 相似文献
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R. A. Almbauer M. Piringer K. Baumann D. Oettl P. J. Sturm 《Environmental monitoring and assessment》2000,65(1-2):79-87
Measured air pollution concentrations in a city reflect the influence of different kinds of sources as well as varying meteorological conditions. In the city of Graz in southern Austria, frequent stagnant meteorological conditions can cause elevated levels of air pollution although emission levels are not exceptionally high. With the aid of a detailed emission inventory and an array of sodars and tethersondes as well as lidar systems supplementing the routine meteorological and air chemistry network during a field experiment in January 1998, the daily variations of air pollution concentrations of selected components within the complex topography of the city of Graz are explained. Main results show the almost linear dependence of the morning maximum concentrations on the predicted emission rates. Throughout the day the rising of the well mixed layer reduces concentrations considerably. Concerning NOX the fast reaction from NO to NO2 is important due to the down-mixing of O3 from the residual layer. The maximum in the afternoon is influenced by emission rates and pollution transport due to the mountain wind. 相似文献
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Gaga EO Ari A Döğeroğlu T Çakırca EE Machin NE 《Journal of environmental monitoring : JEM》2012,14(8):2219-2229
Ambient gas and particle phase samples were collected during two sampling periods from a residential area of an industrialized city, Kocaeli, Turkey. The sampling occurred during winter months when structures were being heated, and summer months when structures were not being heated. Σ(13)PAH (gas + particle) concentrations ranged between 6.2 ng m(-3) (DahA) and 98.6 ng m(-3) (Phe) in the heating (winter) period and 3.0 ng m(-3) (BaA) and 35.1 ng m(-3) (Phe) in the non-heating (summer) period. Phe, Flt and Pyr were found to be at high concentrations in both sampling periods. Winter time to summer time concentration ratios for individual ambient PAH concentration ratios ranged between 1.2 (DahA) and 17.5 (Flu), indicating the effect of the emissions from residential heating on measured concentrations of PAHs, but great industrial plants and the only incinerator facility of Turkey are other important pollution sources around the city. Temperature dependence of gas phase PAHs was investigated using the Clausius-Clapeyron equation. A high slope obtained (5069.7) indicated the effect of the local sources on measured gas phase PAHs. Correlation of the supercooled vapor pressure (P) with the gas particle partitioning coefficient (K(p)) and particle phase fraction was also evaluated. The relationship between the meteorological parameters and individual PAH (gas + particle) concentrations was investigated further by multiple linear regression analysis. It was found that the temperature had a significant effect on all of the measured PAH concentrations, while the effects of the wind speed and direction were not significant on the individual PAHs. On the other hand, PAH concentrations showed a strong linear relationship with the ventilation coefficient (VC) which showed the influence of local sources on measured PAHs. Benzo[a]pyrene toxic equivalent (BaP(eq.)) concentrations were used for health risk assessment purposes. The winter period risk level (2.92 × 10(-3)) due to the respiratory exposure to PAHs was found to be almost 3 times higher than in the summer period (1.15 × 10(-3)). 相似文献
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García del Barrio JM Ortega M Vázquez De la Cueva A Elena-Rosselló R 《Environmental monitoring and assessment》2006,119(1-3):137-159
This paper mainly aims to study the linear element influence on the estimation of vascular plant species diversity in five Mediterranean landscapes modeled as land cover patch mosaics. These landscapes have several core habitats and a different set of linear elements -habitat edges or ecotones, roads or railways, rivers, streams and hedgerows on farm land- whose plant composition were examined. Secondly, it aims to check plant diversity estimation in Mediterranean landscapes using parametric and non-parametric procedures, with two indices: Species richness and Shannon index.Land cover types and landscape linear elements were identified from aerial photographs. Their spatial information was processed using GIS techniques. Field plots were selected using a stratified sampling design according to relieve and tree density of each habitat type. A 50×20 m2 multi-scale sampling plot was designed for the core habitats and across the main landscape linear elements. Richness and diversity of plant species were estimated by comparing the observed field data to ICE (Incidence-based Coverage Estimator) and ACE (Abundance-based Coverage Estimator) non-parametric estimators.The species density, percentage of unique species, and alpha diversity per plot were significantly higher (p < 0.05) in linear elements than in core habitats. ICE estimate of number of species was 32% higher than of ACE estimate, which did not differ significantly from the observed values. Accumulated species richness in core habitats together with linear elements, were significantly higher than those recorded only in the core habitats in all the landscapes. Conversely, Shannon diversity index did not show significant differences. 相似文献
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Mixed-integer linear programs are proposed for siting development and conservation areas in watersheds, addressing economic
objectives (development perimeter and proximity) and ecological objectives. Links between watershed hydrology and ecology
need not be well defined. Parameters for the linear programs are obtained from linearization of the SWAT hydrologic model. 相似文献
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Jenq-Tzong Shiau Reza Modarres Saralees Nadarajah 《Environmental Modeling and Assessment》2012,17(5):469-482
Drought is a multi-dimensional natural hazard with stochastic characteristics usually related to each other. Separate univariate statistical models cannot capture the important relationships among drought characteristics, that is, severity and duration. In this study, an empirical copula is employed to construct a bivariate model of droughts, where droughts are defined as continuously negative standardized precipitation index (SPI) periods with one SPI value reaching ?1 or less. Bivariate frequency analyses in terms of recurrence intervals are performed using the established empirical copula-based bivariate drought model. The inter-connection among different regions of droughts is explored by a lower tail dependence coefficient. A nonparametric estimation based on an empirical copula is employed pairwisely to calculate the lower tail dependence coefficient among stations. The proposed method is applied to six rainfall gauge stations in Iran to explore drought properties of single sites as well as the inter-connection among multi-sites. The results show that greater mean drought severity and duration are associated with the least arrival rate of drought events, which occurs at the Ahwaz station. The tail dependence analysis reveals that distance between stations is not a key parameter. Generally, the Ahwaz and Isfahan stations have the highest probability of simultaneous droughts among the six stations. 相似文献
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Brito JA McNeill FE Webber CE Wells S Richard N Carvalho ML Chettle DR 《Journal of environmental monitoring : JEM》2002,4(2):194-201
The aim of this paper was to assess the endogenous release of lead from bone to blood, in 204 exposed subjects. resuming their duties after a 10-month strike in a primary lead smelter in 1991. In vivo 109Cd K X-ray Fluorescence (109Cd K XRF) was used to measure the bone lead concentration in tibia and calcaneus in the smelter, in 1994 and five years later. The 1994 data were used to derive the post-strike bone lead concentrations retrospectively from the significant association between bone lead and the cumulative blood lead index (CBLI). When a linear model was used to predict the current blood lead upon the level of lead in bone, structural analysis of the data produced slopes for tibia (2.0, 95% CI 1.66-2.54) and calcaneus (0.19, 95% CI 0.16-0.23) that were significantly higher than those predicted by the commonly used simple linear regression method, for tibia (0.73, 95%, CI 0.58-0.88) and calcaneus (0.08, 95% CI 0.06-0.09). This suggests that more lead than previously predicted by regression is released from bone to blood. Furthermore, the structural analysis of the data produced an estimation of the contribution of the bone lead stores to the bloodstream that was more consistent with the 1999 epidemiological data than did the regression estimation. Moreover, a non-linear relationship between tibia lead and blood lead was suggested from the assumption checking procedures for regression. When a non-linear regression model was fit to the data, the method produced estimates of important parameters in human lead kinetics, namely the blood lead saturation constant, showing a good agreement with current knowledge of lead metabolism. Finally, the likelihood of a non-linear bone lead release seems to be supported by the recently described dependence of the half-life of lead in bone on age and intensity of occupational exposure. 相似文献
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In this study, the relation between sulfur dioxide (SO2) and particulate matter (PM) concentrations periodically measured in the city of Afyon’s atmosphere with meteorological factors
such as precipitation, humidity, temperature, wind velocity, and inversion were investigated. The mean values of SO2 and PM concentrations measured during the winter months of October–March 1990–1999 were correlated with the meteorological
parameters of the same period. Simple and multiple linear regression analysis were utilized to evaluate the contribution of
meteorological variables. The statistical results show that the pollutants, i.e., SO2 and PM are dependent upon humidity, temperature, and inversion at the 1% significance level; while the dependence of both
pollutants with temperature is negative when those of humidity and inversion are positive. Two models in which temperature
and inversion are dependent with multiple variables are recommended for predicting the contribution of meteorological parameters
on SO2 and PM. In addition, the relationship between humidity, temperature, and inversion with pollutants is also determined using
nonlinear (polynomial) models. 相似文献