Results 1 - 10 of 12
Results 1 - 10 of 12. Search took: 0.018 seconds
|Sort by: date | relevance|
[en] Antibiotic resistance is a worsening global concern, and the environmental behaviors and migration patterns of antibiotic resistance genes (ARGs) have attracted considerable interest. Understanding the long-range transport of ARG pollution is crucial. In this study, we characterized the dynamics of ARG changes after their release into aquatic environments and demonstrated the importance of traditional chemical contaminants in the transmission mechanisms of ARGs. We hypothesized that the main route of ARG proliferation switches from active transmission to passive transmission. This antibiotic-dominated switch is motivated and affected by non-corresponding contaminants. The effect of anthropogenic activities gradually weakens from inland aquatic environments to ocean environments; however, the effect of changes in environmental conditions is enhanced along this gradient. The insights discussed in this study will help to improve the understanding of the distribution and migration of ARG pollution in various aquatic environments, and provide a modern perspective to reveal the effect of corresponding contaminants and non-corresponding contaminants in the process of antibiotic resistance proliferation. - Highlights: • Process of ARGs flow through WWTPs, rivers, estuaries and ocean to implement global proliferation and commutation. • The diversity and concentrations of ARGs progressively decrease during dynamic long-range migration processes. • The main route of ARG proliferation switches from active transmission to passive transmission from inland to ocean. - The diversity and concentrations of antibiotic resistance genes progressively decrease during dynamic long-range migration processes.
[en] Highlights: • Comparison of production-based and consumption-based accounting of CO2 emissions. • Longitudinal analysis of the newest data for 110 countries for the last 15 years. • Results show only small differences between PBA and CBA. • Countries with large imports have higher CBA/PBA ratios. • The CBA/PBA ratio is positive for countries with high energy efficiency. - Abstract: Lately, a controversial debate has evolved regarding consumption-based accounting (CBA) versus production-based accounting (PBA) of CO2 emissions. So far, the debate has been predominately theoretical and has inspired only a few empirical studies. In this article, we compare production-based versus consumption-based emissions, and for the first time analyze reasons for the differences. In particular, we focus on whether there is evidence for carbon leakage from developed to developing countries. We use the newest available data for 110 countries and analyze whether there are differences between OECD and non-OECD members. Furthermore, we compare the within-country differences for the time span of 1997 to 2011 via fixed effects panel regression models in order to investigate whether increases in GDP per capita result in higher imported emissions. The results suggest that for most countries the differences depending on accounting schemes are small. Furthermore, we find no evidence for carbon leakages. In particular, the ratio of CBA to PBA is not driven by OECD membership or GDP per capita. Instead, the ratio is greater for countries with high energy efficiency and high import rates. Given the small differences between PBA and CBA, we suggest keeping the production-based accounting of CO2 emissions.
[en] Here, the Arctic is warming at an alarming rate, yet the processes that contribute to the enhanced warming are not well understood. Arctic aerosols have been targeted in studies for decades due to their consequential impacts on the energy budget, both directly and indirectly through their ability to modulate cloud microphysics. Even with the breadth of knowledge afforded from these previous studies, aerosols and their effects remain poorly quantified, especially in the rapidly changing Arctic. Additionally, many previous studies involved use of ground-based measurements, and due to the frequent stratified nature of the Arctic atmosphere, brings into question the representativeness of these datasets aloft. Here, we report on airborne observations from the US Department of Energy Atmospheric Radiation Measurement (ARM) program's Fifth Airborne Carbon Measurements (ACME-V) field campaign along the North Slope of Alaska during the summer of 2015. Contrary to previous evidence that the Alaskan Arctic summertime air is relatively pristine, we show how local oil extraction activities, 2015's central Alaskan wildfires, and, to a lesser extent, long-range transport introduce aerosols and trace gases higher in concentration than previously reported in Arctic haze measurements to the North Slope. Although these sources were either episodic or localized, they serve as abundant aerosol sources that have the potential to impact a larger spatial scale after emission.
[en] Highlights: • Convergence in CO2 emissions per capita is studied in a global sample of countries during 1970– 2014. • A Spatial Green Solow model is developed to accommodate spatial dependence in emissions data. • A convergence equation which has the form of a Dynamic Spatial Durbin model is estimated. • Spatial multi-regime panel data models are developed to study heterogeneous convergence dynamics • Spatial non-parametric techniques are used to analyze convergence dynamics across clubs. - Abstract: This research analyzes the evolution of CO2 emissions per capita in a sample of 141 countries during the period 1970–2014. The study develops a spatially augmented Green Solow model by taking into consideration technological externalities and interdependence in the process of production, which ultimately implies that CO2 emissions in an economy are affected by the economic characteristics in neighboring countries. The empirical model predicts convergence in CO2 emissions among countries which is examined by means of modern dynamic spatial panel econometric techniques. The multimodal distribution of the CO2 emissions is consistent with the existence of three spatial clubs. The space-time dynamics of the three clubs are analyzed by means of the Local Directional Moran Scatterplot and spatial panel model with heterogeneous parameters. Our analysis reveals the hypothesis of spatial convergence clubs is more consistent with the data than the hypothesis of conditional convergence.
[en] After performing a first multi-model exercise in 2015 a comprehensive and technically more demanding atmospheric transport modelling challenge was organized in 2016. Release data were provided by the Australian Nuclear Science and Technology Organization radiopharmaceutical facility in Sydney (Australia) for a one month period. Measured samples for the same time frame were gathered from six International Monitoring System stations in the Southern Hemisphere with distances to the source ranging between 680 (Melbourne) and about 17,000 km (Tristan da Cunha). Participants were prompted to work with unit emissions in pre-defined emission intervals (daily, half-daily, 3-hourly and hourly emission segment lengths) and in order to perform a blind test actual emission values were not provided to them. Despite the quite different settings of the two atmospheric transport modelling challenges there is common evidence that for long-range atmospheric transport using temporally highly resolved emissions and highly space-resolved meteorological input fields has no significant advantage compared to using lower resolved ones. As well an uncertainty of up to 20% in the daily stack emission data turns out to be acceptable for the purpose of a study like this. Model performance at individual stations is quite diverse depending largely on successfully capturing boundary layer processes. No single model-meteorology combination performs best for all stations. Moreover, the stations statistics do not depend on the distance between the source and the individual stations. Finally, it became more evident how future exercises need to be designed. Set-up parameters like the meteorological driver or the output grid resolution should be pre-scribed in order to enhance diversity as well as comparability among model runs.
[en] Highlights: • Lead-210 and 212Pb activity results and meteorological conditions at the Yellowknife. • A new method to calculate the mean transit time of aerosol bearing 210Pb from its origin. • The mean transit time estimated based the activity ratio of 210Po/210Pb in different seasons. • A radioanalytical method to determine 210Po in air-filter sample. - Abstract: In this study, the activity concentrations of 210Pb and 210Po on the 22 daily air filter samples, collected at CTBT Yellowknife station from September 2015 to April 2016, were analysed. To estimate the time scale of atmospheric long-range transport aerosol bearing 210Pb in the Arctic during winter, the mean transit time of aerosol bearing 210Pb from its origin was determined based on the activity ratios of 210Po/210Pb and the parent-progeny decay/ingrowth equation. The activity ratios of 210Po/210Pb varied between 0.06 and 0.21 with a median value of 0.11. The aerosol mean transit time based the activity ratio of 210Po/210Pb suggests longer mean transit time of 210Pb aerosols in winter (12 d) than in autumn (3.7 d) and spring (2.9 d). Four years 210Pb and 212Pb monitoring results and meteorological conditions at the Yellowknife station indicate that the 212Pb activity is mostly of local origin, and that 210Pb aerosol in wintertime are mainly from outside of the Arctic regions in common with other pollutants and sources contributing to the Arctic. The activity concentration ratios of 210Pb and 212Pb have a relatively constant value in summer with a significant peak observed in winter, centered in the month of February. Comparison of the 210Pb/212Pb activity ratios and the estimated mean 210Pb transit time, the mean aerosol transit times were real reflection of the atmosphere transport characteristics, which can be used as a radio-chronometer for the transport of air masses to the Arctic region.
[en] Arctic-alpine tundra habitats are very vulnerable to the input of relatively small amounts of xenobiotics, and thus their level in such areas must be carefully controlled. Therefore, we collected the terrestrial widespread moss Racomitrium lanuginosum (Hedw.) Brid. in Spitsbergen in the Arctic moss lichen tundra and, for comparison, in the Arctic-alpine tundra in the Karkonosze (SW Poland). Concentrations of the elements Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Na, Ni, Pb, V, and Zn in this species and in the parent rock material were measured. We tested the following hypothesis: R. lanuginosum from Spitsbergen contains lower metal levels than the species from the Karkonosze collected at altitudes influenced by long-range transport from former Black Triangle industry. Principal component and classification analysis (PCCA) ordination revealed that mosses of Spitsbergen were distinguished by a significantly higher Na concentration of marine spray origin and mosses of Karkonosze were distinguished by significantly higher concentrations of Cd, Cr, Cu, Fe, Hg, Li, Mn, Pb, V, and Zn probably from long-range atmospheric transport. The influence of the polar station with a waste incinerator resulted in significantly higher Co, Li, and Ni concentrations in neighbouring mosses in comparison with this species from other sites. This investigation contributes to the use of R. lanuginosum as a bioindicator for metal contamination in Arctic and alpine tundra regions characterised by severe climate habitats with a restricted number of species. This moss enables the control of pollution usually brought solely by long-range atmospheric transport in high mountains as well as in Arctic areas.
[en] Highlights: • Radioactive charging can significantly affect the coagulation rate and atmospheric transport of radioactive aerosols. • An increase of particle concentrations remaining in the atmosphere after 5 days up to a factor of 30 was simulated for iodine, and up to a factor of 3 for cesium, when radioactive charging is accounted for. -- Abstract: Radioactive charging can significantly impact the way radioactive aerosols behave, and as a result their lifetime, but such effects are neglected in predictive model studies of radioactive plumes. The objective of this work is to determine the influence of radioactive charging on the vertical transport of radioactive aerosols in the atmosphere, through its effect on coagulation and deposition, as well as quantifying the impact of this charging on aerosol lifetime. The TwO-Moment Aerosol Sectional (TOMAS) microphysical model was extended to account for radioactive charging effects on coagulation in a computationally efficient way. The expanded model, TOMAS-RC (TOMAS with Radioactive Charging effects), was then used to simulate the microphysical evolution and deposition of radioactive aerosol (containing the isotopes 131I and 137Cs) in a number of idealized atmospheric transport experiments. Results indicate that radioactive charging can facilitate or suppress coagulation of radioactive aerosols, thus influencing the deposition patterns and total amount of radioactive aerosol mass available for long-range transport. Sensitivity simulations to uncertain parameters affirm the potential importance of radioactive charging effects. An important finding is that charging of neutral, coarse mode aerosol from background radiation can reduce coagulation rates and extend its lifetime in the atmosphere by up to a factor of 2.
[en] Highlights: • 85Kr from a fuel reprocessing plant occasionally is detected at 750 km distance. • Atmospheric transport modeling results are correlated with observations. • About 50% of the results are within a factor of two of the measurements. - Abstract: Due to its half-life, chemical inertness and low solubility in water, radioactive 85Kr is a valuable tracer for testing the performance of atmospheric dispersion models in simulating long-range transport of pollutants. This paper evaluates the capability of simulating the dispersion of radiokrypton emitted by a nuclear fuel reprocessing plant in north-west France. Three time periods during which elevated activity concentrations of 85Kr in ground level air were detected in south-west Germany are chosen. Simulations have been performed using the HYSPLIT code and the European Centre for Median-Range Weather Forecasts (ECMWF) data base. Although their results show a slight trend of underestimating the measured 85Kr concentrations, there is a significant correlation and moderate scatter between observations and simulations with about 50% of the results being within a factor of two of the measured concentrations. The simulated travel time distributions provided a valuable tool for providing additional insight into the dispersion of the tracer radionuclides and for identifying potential causes of deviations between measured and calculated concentrations.
[en] Airborne pollutant characteristics, potential sources, and variation trends of cause are investigated based on the hourly air concentrations of gaseous pollutants and particulate matter from 2013 to 2016 in Lanzhou. The mean concentration of SO2, NO2, CO, 8-hO3, PM2.5, and PM10 was 25.2 ± 16.0 μg m−3, 46.5 ± 21.1 μg m−3, 1.3 ± 0.7 mg m−3, 77.8 ± 45.5 μg m−3, 58.7 ± 32.9 μg m−3, and 131.1 ± 86.2 μg m−3, respectively. The concentrations of SO2, PM10, and PM2.5 present decreasing trends while NO2, CO, and O3 present increasing trends. PM is the most frequent major pollutants with much higher value than standard limit. However, NO2 pollution had obvious trends to reach the limit and was more serious in Lanzhou compared with other Chinese cities. Relationship between air pollutants and meteorological parameters suggested that lower primary pollutants were associated with higher wind speed from north and west. Modeled back trajectory demonstrated that the transport of air masses from the Hexi Corridor and Inner Mongolia was responsible for the high concentrations of the air pollutants in wintertime, and high PM10 level in springtime was related to long-range transport of dust from desert areas of the Sinkiang and the Central Asia. Effects of local pollutant emissions and meteorological condition were preliminary analyzed. Improvement of air quality might be related to the decreasing of pollutant emissions due to strict emissions controls, and the contribution of meteorological condition was not explicit and should be further investigated.