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831.
832.
乌鲁木齐市蔬菜基地土壤有效态镍的空间变异特征 总被引:2,自引:0,他引:2
以乌鲁木齐市北郊蔬菜基地为典型区甜干旱区绿洲城市郊区土壤有效态镍含量的结构特征进行分析,得出该区有效态镍的空间分布格局并揭示了引起这种分布格局的成因,结果表明:乌鲁木齐市北郊蔬菜基地有效态镍属中等变异。半方差函数模型拟合表明有效态镍含量可以用球状函数拟合,具有高度的空间自相性,有效态Ni主要受内在因子(土壤形成因子,如气候、地形、土壤类型等)控制。采用Kriging最优内插法得到了有效态镍含量的空间分布格局,呈现明显的北高南低分布规律。 相似文献
833.
The occurrence, removal efficiency and seasonal variation of 22 antibiotics, including eight fluoroquinolones, nine sulfonamides and five macrolides, were investigated in eight sewage treatment plants (STPs) in Beijing, China. A total of 14 antibiotics were detected in wastewater samples, with the maximum concentration being 3.1 μg L−1 in the influent samples and 1.2 μg L−1 in the effluent samples. The most frequently detected antibiotics were ofloxacin, norfloxacin, sulfadiazine, sulfamethoxazole, erythromycin and roxithromycin; of these, the concentration of ofloxacin was the highest in most of the influent and effluent samples. Eighteen antibiotics were detected in the sludge samples, with concentrations ranging from 1.0 × 10−1 to 2.1 × 104 μg kg−1. The dominant antibiotics found in the sludge samples were the fluoroquinolones, with ofloxacin having the highest concentration in all the sludge samples. The antibiotics could not be removed completely by the STPs, and the mean removal efficiency ranged from −34 to 72%. Of all the antibiotics, the fluoroquinolones were removed comparatively more efficiently, probably due to their adsorption to sludge. Seasonal variation of the antibiotics in the sludge samples was also studied. The concentrations of antibiotics in winter were higher than in spring and autumn. Since the total levels of the fluoroquinolones detected in the influent samples were lower than the predicted no-effect concentration (PNEC) of 8.0 μg L−1, the residues of these antibiotics would be unlikely to have adverse effects on microorganisms involved in sewage treatment processes. 相似文献
834.
城市污水管网中水质变化特性 总被引:3,自引:0,他引:3
以管网中城市污水为研究对象,通过模拟管道的循环流动研究了水质变化特性。结果表明,在水力流动6 h的条件下,因管道沉积和管内微生物作用,城市污水中的TCOD(总有机物)去除率为10.79%,其中,沉积和生物降解作用对TCOD去除的贡献率分别为68.85%和31.15%。而管道中的氮类污染物的去除率为11.15%,管道沉积与生物降解作用各占约50%,其中生物降解引起的氮类污染物的变化主要是水中有机氮转化为NH3-N(NH3-N由35.51 mg/L升至38.38mg/L),以及反硝化作用造成的NO3-N转变(NO3-N由2.36 mg/L降至0.84 mg/L)。总磷的变化相对较小,与管道内相对稳定的缺氧环境有关。 相似文献
835.
为了研究大气中PM25污染特征以及其随时间变化规律,基于西安市2013年1月-2014年4月间SO2、NO2、CO、03、日最高温度(Tmax)、日最低温度(Tmin)、PM2.5、PM10等因素的监测数据.运用统计学原理和多元回归分析方法,分析了PM25的污染特征及相关因素对其产生的贡献度,进一步建立了四季的最优多元回归模型.研究结果表明,西安市年平均质量浓度124.9 μg/m3,四季的平均污染浓度从大到小依次为冬、春、秋、夏;春夏两季贡献较大的为SO2、CO;秋冬两季贡献较大的为NO2、CO;最终建立的模型的相关系数较高,模型很好地拟合了冬春两季PM2.5变化趋势,能较准确地反映了西安市PM2.5的污染特征,具有一定的理论和实用价值. 相似文献
836.
Nicholas A. Warner Gary Kozerski Jeremy Durham Martin Koerner Reinhard Gerhards Roy Campbell Debra A. McNett 《Chemosphere》2013
Contamination and analytical variation can significantly hinder trace analysis of cyclic methyl volatile siloxanes (cVMS); potentially resulting in the report of false positives at concentrations approaching detection limits. To assess detection and variation associated with trace cVMS analysis in environmental matrices, a co-operative laboratory comparison for the analysis of octametylcyclotetrasiloxane (D4), decamethylcylcopentasiloxane (D5), and dodecametylcyclohexasiloxane (D6) in sediment and biota from the Svalbard Archipelago was conducted. Two definitions of detection limits were evaluated in this study; method detection limits (MDL, matrix defined) and limits of detection (LOD, solvent defined). D5 was the only cVMS detected above both LOD (0.08–0.81 ng g−1 ww) and MDL (0.47–2.36 ng g−1 ww) within sediment by all laboratories where concentrations ranged from 0.55 to 3.91 ng g−1 ww. The percentage of positive detects for D5 decreased by 80% when MDL was defined as the detection limit. D5 was also detected at the highest frequency among all laboratories in fish liver with concentrations ranging from 0.72 to 345 ng g−1 ww. Similar to sediment, percentage of positive detects for D5 decreased by 60% across all laboratories for fish livers when using MDL (0.68–3.49 ng g−1 ww). Similar observations were seen with both D4 and D6, indicating that sample matrix significantly contributes to analytical response variation. Despite differences in analytical methods used between laboratories, good agreement was obtained when using MDL to define detection limits. This study shows the importance of incorporating variation introduced by sample matrices into detection limit calculations to insure data accuracy of cVMS at low concentrations. 相似文献
837.
838.
Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988
to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20–30 cm
of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N
ratio). Trees growing on soils with a high pH (≥4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH
<4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with
respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency.
Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation
and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than
trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic
than on more basic soils, however defoliation dynamics of these trees over 1988–99 was not related to soil acidity. Two biotic
agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics. 相似文献
839.
Salve PR Satapathy DR Katpatal YB Wate SR 《Environmental monitoring and assessment》2007,133(1-3):87-98
Stratospheric input and photochemical ozone formation in the troposphere are the two main sources determining the ozone levels
in the surface layer of the atmosphere. Because of the importance of ozone in controlling the atmospheric chemistry and its
decisive role in the heat balance of atmosphere, leading to climate change, the examination of its formation and destruction
are of great interest. This study characterized the distribution of Ground level Ozone (GLO) in Chandrapur district is lying
between 19°25′N to 20°45′N and 78°50′E to 80°10′E. Continuous ozone analyzer was used to quantify GLO at thirteen locations
fixed by Global Positioning System (GPS) during the winter of 2005–2006. The daily GLO at all the locations ranged between
6.4 and 24.8 ppbv with an average and standard deviation of 14.9 ± 6.5 ppbv. The maximum and minimum concentration occurs
during 1300–1600 h and 0300–0500 h may be due to high solar radiation facilitating photochemical production of O3 and downward mixing from the overlying air mass and in situ destruction of ozone by deposition and/or the reaction between
O3 and NO. GIS based spatial distribution of GLO in Chandrapur district is indicates that the central core of the district and
southern sites experienced elevated levels of GLO relative to the northern and western areas. The sites near by Chandrapur
city are particularly affected by elevated GLO. The average variation of GLO with temperature shows a significant correlation
of r = 0.55 indicating a direct relationship between GLO and temperature. Similarly an attempt has been made to compare the GLO
monitored data in Chandrapur district with the reported values for other locations in Indian cities. This generated database
helps regulatory agencies to identify locations where the natural resources and human health could be at risk. 相似文献
840.
Pliura A Baliuckiene A Baliuckas V 《Environmental pollution (Barking, Essex : 1987)》2008,156(1):152-161
Phenogenetic response of silver birch populations and half-sib families to separate and combined elevated ozone (O3) concentrations and ultraviolet-B (UV-B) radiation dozes was studied at juvenile age in the climatic chambers. Significant population and family effects were found for seedling height, lamina width, and leaf damage. The exposure to UV-B radiation decreased genetic variation at the stage of seed germination. Complex exposure to UV-B and O3 caused an increase of genetic variation at the stage of intensive seedling growth: seedling height genetic variation in separate treatments increased from 23.7–38.6 to 33.7–65.7%, the increase for lamina width was from 10.2–13.9 to 13.6–31.8%. Different populations and families demonstrated differing response to elevated complex UV-B and O3 exposure. Changes of genetic intra-population variation were population-specific. Such changes in genetic variation under the impact of stressors can alter adaptation, stability, and competitive ability of regenerating populations in a hardly predictive way. 相似文献