排序方式: 共有137条查询结果,搜索用时 15 毫秒
101.
Farooq S Hashmi I Qazi IA Qaiser S Rasheed S 《Environmental monitoring and assessment》2008,140(1-3):339-347
The present study was undertaken to examine the drinking water quality of Rawal Treatment Plant, Rawalpindi and its distribution
network by collecting samples from eight different locations. The aim was to determine potential relationship between the
presence of microorganisms and chlorine residual in the distribution network. Quantification of chlorine residual, turbidity,
standard plate count (SPC), fecal and total coliforms by Most Probable Number (MPN) was performed. Three different forms of chlorine were measured at each sampling station such
as free chlorine, residual chlorine, chloramines and total chlorine residual. A critical evaluation of data presented indicated
that pH generally ranged from 7.02–7.30; turbidity varied from 0.34–2.79 NTU; conductivity fluctuated from 359–374 μS/cm;
and TDS values were found to be ranging between 180–187 mg/l. Station # 7 was found to be most contaminated. The value of total chlorine was found to be 0.86 to1.7 mg/l at Station # 3 and 6, respectively. Highest standard plate count was 62 CFU/ml at Station # 7. Total
coliforms were less than 1.1 MPN/100 ml at almost most of the stations except at Station # 3 where it was found to be greater than 23.0 MPN /100 ml. Overall aim of this study is to create awareness about contamination
of drinking water in the water distribution networks and to make recommendations to provincial agencies such as EPA, CDA and
WASA that regular monitoring should be carried out to ensure that the chlorine residual is available at consumer end. 相似文献
102.
Assessment of phenanthrene bioavailability in aged and unaged soils by mild extraction 总被引:2,自引:0,他引:2
Khan MI Cheema SA Shen C Zhang C Tang X Shi J Chen X Park J Chen Y 《Environmental monitoring and assessment》2012,184(1):549-559
It has become apparent that the threat of an organic pollutant in soil is directly related to its bioavailable fraction and
that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms
is inappropriate. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness
in determining bioavailability. To find a suitable and rapid extraction method to predict phenanthrene bioavailability, multiple
extraction techniques (i.e., mild hydroxypropyl-β-cyclodextrin (HPCD) and organic solvents extraction) were investigated in soil spiked to a range of phenanthrene levels (i.e.,
1.12, 8.52, 73, 136, and 335 μg g − 1 dry soil). The bioaccumulation of phenanthrene in earthworm (Eisenia fetida) was used as the reference system for bioavailability. Correlation results for phenanthrene suggested that mild HPCD extraction
was a better method to predict bioavailability of phenanthrene in soil compared with organic solvents extraction. Aged (i.e.,
150 days) and fresh (i.e., 0 day) soil samples were used to evaluate the extraction efficiency and the effect of soil contact
time on the availability of phenanthrene. The percentage of phenanthrene accumulated by earthworms and percent recoveries
by mild extractants changed significantly with aging time. Thus, aging significantly reduced the earthworm uptake and chemical
extractability of phenanthrene. In general, among organic extractants, methanol showed recoveries comparable to those of mild
HPCD for both aged and unaged soil matrices. Hence, this extractant can be suitable after HPCD to evaluate risk of contaminated
soils. 相似文献
103.
Removal of arsenic species from water by batch and column operations on bagasse fly ash 总被引:2,自引:0,他引:2
Imran Ali Zeid A. Al-Othman Abdulrahman Alwarthan Mohd Asim Tabrez A. Khan 《Environmental science and pollution research international》2014,21(5):3218-3229
Bagasse fly ash (BFA, a sugar industrial waste) was used as low-cost adsorbent for the uptake of arsenate and arsenite species from water. The optimum conditions for the removal of both species of arsenic were as follows: pH 7.0, concentration 50.0 μg/L, contact time 50.0 min, adsorbent dose 3.0 g/L, and temperature 20.0 °C, with 95.0 and 89.5 % removal of arsenate and arsenite, respectively. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherms were used to analyze the results. The results of these models indicated single-layer uniform adsorption on heterogeneous surface. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, were also calculated. At 20.0 to 30.0 °C, the values of ΔG° lie in the range of ?4,722.75 to ?4,878.82 and ?4,308.80 to ?4,451.73 while the values of ΔH° and ΔS° were ?149.90 and ?121.07, and 15.61 and 14.29 for arsenate and arsenite, respectively, indicating that adsorption is spontaneous and exothermic. Pseudo-first-order kinetics was followed. In column experiments, the adsorption decreased as the flow rate increased with the maximum removal of 98.9 and 95.6 % for arsenate and arsenite, respectively. The bed depth service time and Yoon and Nelson models were used to analyze the experimental data. The adsorption capacity (N o) of BFA on column was 3.65 and 2.98 mg/cm3 for arsenate and arsenite, respectively. The developed system for the removal of arsenate and arsenite species is economic, rapid, and capable of working under natural conditions. It may be used for the removal of arsenic species from any contaminated water resources. 相似文献
104.
Tabassum Riaz Ahmad Shahid Muhammad Dumat Camille Niazi Nabeel Khan Khalid Sana Shah Noor Samad Imran Muhammad Khalid Samina 《Environmental science and pollution research international》2019,26(20):20018-20029
Environmental Science and Pollution Research - Currently, several news channels and research publications have highlighted the dilemma of arsenic (As)-contaminated groundwater in Pakistan. However,... 相似文献
105.
Han Il Yoo Keunje Kang Bo Ram No Jee Hyun Wee Gui Nam Khan Muhammad Imran Jeong Tae Young Lee Tae Kwon 《Environmental geochemistry and health》2018,40(1):451-460
Environmental Geochemistry and Health - Improper decisions concerning animal carcass disposal sites pose grave threats to environmental biosecurity. However, only a few studies have focused on the... 相似文献
106.
Bashir Arshid Malik Lateef Ahmad Ahad Sozia Manzoor Taniya Bhat Mudasir Ahmad Dar G. N. Pandith Altaf Hussain 《Environmental Chemistry Letters》2019,17(2):729-754
Environmental Chemistry Letters - Pollution due to heavy metals is currently a serious problems affecting water bodies. The removal of heavy metals is of great concern due to their toxicity at... 相似文献
107.
108.
Asim Jilani Mohd Hafiz Dzarfan Othman Mohammad Omaish Ansari Syed Zajif Hussain Ahmad Fauzi Ismail Imran Ullah Khan Inamuddin 《Environmental Chemistry Letters》2018,16(4):1301-1323
Graphene was discovered in 2004 and has attracted intensive interests because of its unique mechanical, electric, thermal, optical, and structural properties, which makes graphene a potential candidate for various applications. Graphene is being used as a composite or filler material with metals, metal oxides, and polymers for potential advanced applications in solar cells, lithium-ion batteries, photocatalysis and sensing. These applications depend upon the distinctive properties of graphene, which in turn depend on the adopted synthetic approach. This article reviews the recent developments in synthesis of graphene and related composite materials. The synthesis of graphene through exfoliation, epitaxial growth and direct growth via carbon source, and modification approaches by covalent and noncovalent methodologies are discussed. Graphene-based metal and metal oxide composites for the purification of wastewater using photolytic process are also presented. 相似文献
109.
110.
The curvature-driven secondary flow in sinuous submarine channels has been a subject of considerable interest and controversy. Here, results from numerical model studies involving saline flow in laboratory-scale channels are presented. A 3D finite volume model of density and turbidity currents is used and simulations are run with different inflow discharges and channel-axis slopes. The simulation results show strong influence of bend wave length, channel gradient, confinement and cross sectional shape on the structure of secondary flow in submarine channels. Major findings are: (i) reversal of secondary flow in submarine channels is strongly associated with a tight bend characterized by a smaller wave length to width ratio or larger wave number, (ii) for the same inflow condition and planform characteristics, a trapezoidal channel cross section is more favorable to secondary flow reversal than a rectangular cross section, (iii) lateral convection resulting from the interaction between in-channel and overbank flows leads to the reversal of secondary flow in an unconfined channel at a lower channel slope than in a confined channel with the same dimensions, (iv) flow discharge has only nominal effect on the secondary flow in submarine channels. 相似文献