Enzyme-linked immunosorbent assay for ultratrace determination of antibiotics in aqueous samples

Two commercially available enzyme-linked immunosorbent assay (ELISA) kits that are commonly used for tylosin or tetracycline residues in meat and milk were adapted for ultratrace analysis of these antibiotics in surface and ground waters. These two antibiotics are commonly fed to swine, turkeys, and cattle at subtherapeutic doses for growth promotion purposes. Both ELISA techniques were found to be highly sensitive and selective for the respective antibiotics with detection limits of 0.10 and 0.05 microg L(-1) for tylosin and tetracycline, respectively. The recovery of both tylosin and tetracycline from spiked samples of lake waters, runoff samples, soil saturation extracts, and nanopure water was close to 100%. Tetracycline ELISA was highly specific for tetracycline and chlortetracycline but not for other forms of tetracycline (oxytetracycline, demeclocycline, and doxycycline). Analysis of a few liquid swine manure samples by liquid chromatography-mass spectrometry (LC-MS) showed lower concentrations for chlortetracycline as compared with concentrations obtained using ELISA. However, the concentrations of tylosin from ELISA were comparable with that of LC-MS. The lower concentrations of chlortetracycline obtained by LC-MS in manure samples indicate the presence of other similar or transformed compounds that were detected by ELISA but not determined by LC-MS. These results indicate that both ELISA kits can be useful tools for low-cost screening of tylosin, tetracycline, and chlortetracycline in environmental waters. Furthermore, both ELISA procedures are rapid, portable, and easily adaptable for testing of multiple samples simultaneously.     

Antibacterial activity of soil-bound antibiotics

There is some concern that antibiotic residues in land-applied manure may promote the emergence of antibiotic resistant bacteria in the environment. The goal of this study was to determine whether or not soil bound antibiotics are still active against bacteria. The procedure involved sorbing various amounts of tetracycline or tylosin on two different textured soils (Webster clay loam [fine-loamy, mixed, superactive, mesic Typic Endoaquolls] and Hubbard loamy sand [sandy, mixed, frigid Entic Hapludolls]), incubating these soils with three different bacterial cultures (an antibiotic resistant strain of Salmonella sp. [Salmonella(R)], an antibiotic sensitive strain of Salmonella sp. [Salmonella(S)], and Escherichia coli ATCC 25922), and then enumerating the number of colony forming units relative to the control. Incubation was done under both static and dynamic conditions. Soil-adsorbed antibiotics were found to retain their antimicrobial properties since both antibiotics inhibited the growth of all three bacterial species. Averaged over all other factors, soil adsorbed antimicrobial activity was higher for Hubbard loamy sand than Webster clay loam, most likely due to higher affinity (higher clay content) of the Webster soil for antibiotics. Similarly, there was a greater decline in bacterial growth with tetracycline than tylsoin, likely due to greater amounts of soil-adsorbed tetracycline and also due to lower minimum inhibitory concentration of most bacteria for tetracycline than tylosin. The antimicrobial effect of tetracycline was also greater under dynamic than static growth conditions, possibly because agitation under dynamic growth conditions helped increase tetracycline desorption and/or increase contact between soil adsorbed tetracycline and bacteria. We conclude that even though antibiotics are tightly adsorbed by clay particles, they are still biologically active and may influence the selection of antibiotic resistant bacteria in the terrestrial environment.     

Water footprint: methodologies and a case study for assessing the impacts of water use

The methodologies, approaches and indicators for assessing the impacts of freshwater usage are still evolving. The development of the water footprint concept has been an important step in this direction but the existing methodologies mainly assess the quantity of water used rather than the related impacts. Although there is a recognised need to consider the latter, particularly on a life cycle basis, the difficulty is that there are little or no reliable data on water usage in life cycle databases; furthermore, there is no agreed life cycle impact assessment method for estimating impacts related to freshwater use. However, there have been some methodological developments which propose methods for inventory modelling and impact assessment for water use in life cycle assessment. This paper reviews some of these approaches and discusses their strengths and limitations through a case study, which considers the impacts of freshwater consumption from corn-derived ethanol produced in 12 different countries. The results show a huge variation in the results between different methods and demonstrate the need for a standardised methodology for assessing the impacts of water use on a life cycle basis. Specific recommendations for further research in this field have been made accordingly.     

Emissions analysis on second generation biodiesel

This work investigates the effect of adding pentanol with biodiesel derived from cashew nut shell on its emissions characteristics is conducted in stationery diesel engine. The main purpose of this work is intended to reduce the emissions by fuelling biodiesel derived from cashew nut shell and the pentanol blends. Cashew nut shell biodiesel is prepared by transesterification process. Oxygenated additive used in the work is Pentanol. The experiment is conducted using four test fuels such as, biodiesel derived from cashew nut shell (CNSBD), a fuel containing 90% cashew nut shell biodiesel and 10% pentanol (CNSBD90P10), a fuel containing 80% cashew nut shell biodiesel and 20% pentanol (CNSBD80P20) and neat diesel. Experimental work concluded that by adding 10% of pentanol to cashew nut shell biodiesel 10.1%, 2.6%, 5.1%and 2.1%reduction in CO, HC, NO _x and Smoke emissions were observed respectively. Further by fueling with these blends, no modifications in engines were required.

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Antibiotic uptake by plants from soil fertilized with animal manure

Antibiotics are commonly added to animal feed as supplements to promote growth of food animals. However, absorption of antibiotics in the animal gut is not complete and as a result substantial amounts of antibiotics are excreted in urine and feces that end up in manure. Manure is used worldwide not only as a source of plant nutrients but also as a source of organic matter to improve soil quality especially in organic and sustainable agriculture. Greenhouse studies were conducted to determine whether or not plants grown in manure-applied soil absorb antibiotics present in manure. The test crops were corn (Zea mays L.), green onion (Allium cepa L.), and cabbage (Brassica oleracea L. Capitata group). All three crops absorbed chlortetracycline but not tylosin. The concentrations of chlortetracycline in plant tissues were small (2-17 ng g(-1) fresh weight), but these concentrations increased with increasing amount of antibiotics present in the manure. This study points out the potential human health risks associated with consumption of fresh vegetables grown in soil amended with antibiotic laden manures. The risks may be higher for people who are allergic to antibiotics and there is also the possibility of enhanced antimicrobial resistance as a result of human consumption of these vegetables.     

Hyperspectral reflectance response of freshwater macrophytes to salinity in a brackish subtropical marsh

Coastal freshwater wetlands are threatened by increased salinity due to relative sea level rise and reduced freshwater inputs. Remote radiometric measurement of freshwater marsh canopies to detect small shifts in water column salinity would be useful for assessing salinity encroachment. We measured leaf hyperspectral (300-1100 nm) reflectance of freshwater macrophytes (cattail, Typha latifolia and sea oxeye, Borrichia frutescens) in a field study in a subtropical brackish (2.5-4.5 parts per thousand salinity, per thousand) marsh to determine salinity effects on visible and near-infrared spectral band reflectance and to identify reflectance indices sensitive to small (1 per thousand) changes in wetland salinity. For sea oxeye, floating-position water band index [fWBI = R(900)/minimum(R(930) - R(980)), where R(lambda) = reflectance at band lambda], normalized difference vegetation index [NDVI = (R(774) - R(681))/(R(774) + R(681))], and a proposed wetland salinity reflectance ratio (WSRR = R(990)/R(933)) were sensitive to salinity with R2 of 40, 35, and 65%, respectively (p < 0.01). For cattail, NDVI and photochemical reflectance index [PRI = (R(531) - R(570))/(R(570) + R(531))] were sensitive to salinity with R2 of 29 and 33%, respectively (p 相似文献   

Analysis of urban heat island effect in Visakhapatnam,India, using multi-temporal satellite imagery: causes and possible remedies

The thermal data sets of Landsat for the years 2014 and 2019 are used to assess the transients of land surface temperature (LST) in Visakhapatnam, India. The variation in estimated temperature fields is compared with the land use pattern to validate temperature with reference to land use land cover (LULC). During the considered period, the built-up area in the study region increased by 63%. The aerial extent of water bodies has come down by 12.5%, and there is a significant drop in vegetation cover. The LST of the regions with the densely built-up area is high compared to the other types of land use. A mean rise of 4.8 °C in the LST has been noticed over the study area during this period. Few monitoring points representing rural areas within the proximity of the study region have been established, and the LST is monitored explicitly. As a result, it has been observed that the temperature in rural areas is relatively lower than the city region, which confirms the urban heat island effect. A micro-level study has been conducted by dividing the study area into four zones as per administrative boundaries. Statistical analysis using the zonal attributes affirms a positive correlation of 0.55 between LST and the built-up area. In contrast, a negative correlation of 0.52 between LST and vegetation cover is observed. The LULC results are validated using Google Earth Images captured at a finer resolution. Being selected as one of the cities under the smart city mission by the Urban Development Ministry of Govt. of India, it is expected that the land use pattern in Visakhapatnam will change drastically in the coming years. The findings of this study foster the relationship between LST and LULC, and the conclusions thus drawn would help planners for the sustainable development of Visakhapatnam.

     

Quantification of self pollution from two diesel school buses using three independent methods

We monitored two Seattle school buses to quantify the buses’ self pollution using the dual tracers (DT), lead vehicle (LV), and chemical mass balance (CMB) methods. Each bus drove along a residential route simulating stops, with windows closed or open. Particulate matter (PM) and its constituents were monitored in the bus and from a LV. We collected source samples from the tailpipe and crankcase emissions using an on-board dilution tunnel. Concentrations of PM₁, ultrafine particle counts, elemental and organic carbon (EC/OC) were higher on the bus than the LV. The DT method estimated that the tailpipe and the crankcase emissions contributed 1.1 and 6.8 μg m^?3 of PM_2.5 inside the bus, respectively, with significantly higher crankcase self pollution (SP) when windows were closed. Approximately two-thirds of in-cabin PM_2.5 originated from background sources. Using the LV approach, SP estimates from the EC and the active personal DataRAM (pDR) measurements correlated well with the DT estimates for tailpipe and crankcase emissions, respectively, although both measurements need further calibration for accurate quantification. CMB results overestimated SP from the DT method but confirmed crankcase emissions as the major SP source. We confirmed buses’ SP using three independent methods and quantified crankcase emissions as the dominant contributor.     

Assessment of indoor air quality and housing,household and health characteristics in densely populated urban slums

Environment, Development and Sustainability - This study provides the first quantitative assessment of seasonal variation in indoor PM2.5 in the high-air pollution risk and densely populated slums...