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21.
J. Church H. Kannan J. An W. H. Lee S. Santra 《International Journal of Environmental Science and Technology》2017,14(3):543-552
Growing demand for point-of-use water treatment including greywater recycling as well as appropriate disinfection without formation of harmful disinfection byproducts (DBPs) calls for new methods of efficient microbial control. In recent years, antimicrobial nanomaterials (NMs) have been widely studied as a potential alternative to traditional chlorine disinfection, yet concerns over their releases to environments and subsequent impacts have limited their use on a large scale. In this work, recycled concrete aggregate (RCA) was proposed as a sustainable and environmentally friendly disinfecting substrate for water disinfection by coating with a composite of silica-quaternary ammonium compound (Fixed-Quat). Two different types (gel and particle) of Fixed-Quat were applied to RCA, and their adherence and antimicrobial activities were compared each other. When using E. Coli as a model bacterial pathogen, the Fixed-Quat gel and particle coated RCA materials showed similar and effective microbial inactivation performance with a rate of 2.0 × 10?3 (gel) and 1.82 × 10?3 (particle) log reduction cm?2 min?1. By potentially eliminating regulated DBPs formation and minimizing release of NMs into the environment, the antimicrobial coated RCA would be a promising and sustainable alternative to conventional disinfection methods in engineered aquatic systems. 相似文献
22.
Cell bioassays for detection of aryl hydrocarbon (AhR) and estrogen receptor (ER) mediated activity in environmental samples 总被引：5，自引：0，他引：5
In vitro cell bioassays are useful techniques for the determination of receptor-mediated activities in environmental samples containing complex mixtures of contaminants. The cell bioassays determine contamination by pollutants that act through specific modes of action. This article presents strategies for the evaluation of aryl hydrocarbon receptor (hereafter referred as dioxin-like) or estrogen receptor mediated activities of potential endocrine disrupting compounds in complex environmental mixtures. Extracts from various types of environmental or food matrices can be tested by this technique to evaluate their 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents or estrogenic equivalents and to identify contaminated samples that need further investigation using resource-intensive instrumental analyses. Fractionation of sample extracts exhibiting significant activities, and subsequent reanalysis with the bioassays can identify important classes of contaminants that are responsible for the observed activity. Effect-directed chemical analysis is performed only for the active fractions to determine the responsible compounds. Potency-balance estimates of all major compounds contributing to the observed effects can be calculated to determine if all of the activity has been identified, and to assess the potential for interactions such as synergism or antagonism among contaminants present in the complex mixtures. The bioassay approach is an efficient (fast and cost effective) screening system to identify the samples of interest and to provide basic information for further analysis and risk evaluation. 相似文献
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Murata S Takahashi S Agusa T Thomas NJ Kannan K Tanabe S 《Marine pollution bulletin》2008,56(4):641-649
Organotin compounds (OTs) including mono- to tri-butyltins, -phenyltins, and -octyltins were determined in the liver of adult sea otters (Enhydra lutris) found dead along the coasts of California, Washington, and Alaska in the USA and Kamchatka, Russia. Total concentrations of OTs in sea otters from California ranged from 34 to 4100ng/g on a wet weight basis. The order of concentrations of OTs in sea otters was total butyltins>total octyltins> or = total phenyltins. Elevated concentrations of butyltins (BTs) were found in some otters classified under 'infectious-disease' mortality category. Concentrations of BTs in few of these otters were close to or above the threshold levels for adverse health effects. Total butyltin concentrations decreased significantly in the livers of California sea otters since the 1990s. Based on the concentrations of organotins in sea otters collected from 1992 to 2002, the half-lives of tributyltin and total butyltins in sea otters were estimated to be approximately three years. 相似文献
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The soil water retention characteristics curve (SWRC) has been reported to be quite useful for estimation of unsaturated soil properties. However, the uniqueness of SWRC is questionable due to hysteresis associated with the drying- and wetting-path SWRCs and this poses great challenge in utilising the SWRC for reliable estimation of unsaturated soil properties. Although hysteresis associated with SWRCs has been extensively studied for coarse-grained soils, due to limited studies on wetting-path SWRC for fine-grained soils, the hysteresis for fine-grained soils is not well understood. The present work attempts to address this gap, by studying the drying- and wetting-path SWRCs for eight different fine-grained soils by employing Dew point Potentiameter (WP4C®), Environmental Chamber and Controlled Water Sprinkling method. The study employs the concept of ‘Suction Hysteresis’, ψh, for quantification of hysteresis. Further, the influence of various soil-specific properties on the variation of ψh-water content relationship (viz., slope of variation of suction hysteresis, Sψh) has also been studied and demonstrated. The findings of the study are quite encouraging and it has been realised that extensive studies on soils of different characteristics would be quite useful in quantifying the variation of SWRC during drying and wetting cycles. 相似文献
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Kannan K. R. Iyer Jeevan Joseph Bruna C. F. L. Lopes D. N. Singh Alessandro Tarantino 《Geomechanics and Geoengineering》2018,13(2):88-103
The soil–water retention (SWR) characteristics of the clays play an important role in controlling their engineering behaviour, particularly, in the unsaturated state. Although, researchers have attempted to understand the water retention characteristics of the clays in their reconstituted or remoulded state, such studies are rare for the clays in their intact state. In this context, it becomes important to understand the influence of initial state of compaction, which would create different pore and fabric structure (viz., microstructure), on the water retention characteristics of the clays. With this in view, SWR behaviour was experimentally determined for the swelling clays (dried from different compaction states, viz., intact, reconstituted and remoulded) by employing Dewpoint PotentiaMeter (WP4C®). The changes in the pore size distribution of the clays at different stages of drying cycle were also studied by employing the Mercury Intrusion Porosimetry. The study reveals that the SWR curves for the intact and reconstituted specimens of the clays converge beyond a certain stage of drying. Also, a critical analysis of changes in the pore structure of the swelling clay specimens, during drying, indicates that the progressively deforming pore structure plays an important role in controlling its water retention characteristics to a great extent. 相似文献
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This research paper assesses the vulnerability of landslide for the Bodi-Bodimettu Ghat section, Theni district, Tamil Nadu, India, using remotely sensed data and geographic information system (GIS). Landslide database was generated using IRS-1C satellite LISS III data and aerial photographs accompanied by field investigations using differential global positioning system to generate a landslide inventory map. Topographical, spatial, and field data were processed to construct the spatial thematic layers using image processing and GIS environment. Twelve landslide-inducing factors were used for landslide vulnerability analysis: elevation, slope, aspect, plan curvature, profile curvature, proximity to road, drainage and lineament, land use/land cover, geology, geomorphology, and run-off. The first five factors were derived from digital elevation model, and other thematic layers were prepared from spatial database. Frequency ratio of each factor was computed using the above thematic factors with past landslide locations. Landslide vulnerability map was produced using raster analysis. The landslide vulnerability map was classified into five zones: very low, low, moderate, high, and very high. The model is validated using the relative landslide density index (R-index method). The consistency of R-index indicates good performance of the vulnerability map. 相似文献
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V. Ranga Rao B. R. Subramanian R. Mohan R. Kannan T. Mageswaran T. Arumugam B. Rajan 《Natural Hazards》2013,68(2):453-465
A very severe cyclonic storm ‘Thane’ developed over the Bay of Bengal during 25–30 December 2011, crossed the Tamilnadu coast between Pondicherry and Cuddalore (southeast coast of India) in early hours of 30 December with a wind speed 120–140 km/h. The offshore tide record reveals that the surge started to generate around 1100 hours on 29 December 2011 with a height 0.4 m and later raised to 0.68 m at the time of land fall, that is, early hours (0000 hours) of 30 December 2011. Field reconnaissance survey on surge run-up and inundation distance at 15 selected locations of cyclone affected areas reveals that the vulnerability levels are highly variable along the coast. The inundation distance extended up to 30–230 m landward from the shoreline and run-up reached to 1.6–3.2 m above chart datum depending upon the cross-shore geometry of the location. In the areas (Verranampattinam, Chinamudaliyar kuppam and Silver beach) near cyclone landfall, the run-up was up to 2.5–3.2 m and the inundation distance extended up to a maximum of 230 m. However, in the areas located about 150 km north of cyclone landfall, the run-up limited from 1.6 to 1.7 m and the inundation distance extended up to only a maximum of 169 m. The inundation distance is mainly influenced by the slope of the beach. In the areas having beach slope between 1 in 135 and 1 in 220, the inundation distance was 210–230 m. However, in the areas having beach slope 1 in 17 to 1 in 34, the inundation distance is restricted between 35 and 50 m. 相似文献
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K. A. Maruya B. G. Loganathan K. Kannan S. McCumber-Kahn R. F. Lee 《Estuaries and Coasts》1997,20(4):700-709
Sediment samples from 281 estuarine sites in the Gulf of Mexico were collected in 1993–1994 and analyzed for several classes of organic and organometallic compounds as part of the Environmental Monitoring and Assessment Program of the United States Environmental Protection Agency. Polynuclear aromatic hydrocarbons (PAHs) were the contaminant class found most frequently and in the highest concentrations; the sum of 24 congeners (ΣPAHs) ranged from <5 ng g?1 to 15.500 ng g?1 (dry wt basis). A low percentage of samples (3.9%) exceeded 2000 ng g?1 ΣPAHs, and only six samples (2.1%) exceeded 4000 ng g?1, a level above which adverse biological effects may be expected to occur. Less than 4% of sediments exceeded 20 ng g?1 for the sum of 20 polychlorinated biphenyls (ΣPCBs) and only four samples (1.4%) exceeded 20 ng g?1 for the sum of several organochlorine pesticides (ΣOCPs). A sample from Freeport Harbor, Texas, contained 4230 ng g?1 ΣPAHs, 322 ng g?1 ΣPCBs, and 49.6 ng g?1 ΣOCPs. Tributyltin exceeded 100 ng g?1 in only four samples, all of which were from stations in Corpus Christi Bay or Galveston Bay in Texas. The detection of a suite of organophosphate pesticides was very rare and did not exceed 15 ng g?1. Sediments from the tidally influenced section of the Mississippi River in Louisiana contained low to moderate levels of all classes of organic compounds. The most contaminated sites were in urban estuaries (e.g., Corpus Christi, Galveston, and Pensacola (Florida bays), underscoring the need to concentrate future monitoring and assessment efforts at the regional and local level. 相似文献