ABSTRACT
Microbial communities in wastewater treatment plants(WWTPs) are very important for water purification in the context of public drinking water safety and environmental health. Therefore, it is necessary to explore the trends in microbial community structure and diversity in sewage treatment plants and their main environmental impact factors under different climates in China. Based on high-throughput sequencing techniques, a meta-analysis was conducted to screen the 16S rRNA genes in an open database. We analyzed the trends in microbial community structure and diversity in WWTPs under three climate types(Dwa, Cfa, and Cwa) in China. We then constructed cohesion models to examine the core microbial taxa and their interactions within the communities. We also used a piecewise structural equation model(PSEM) to examine the effects of different climate types on microbial community structure. The three climate types significantly affected the structure and diversity of the microbial communities, with patterns correlated with influent pH, mixed liquid temperature, conductivity, and nitrogen concentrations(P<0.05). Based on the PSEM analysis, the ß-diversity of the microbial communities was directly correlated with latitude, while α-diversity was indirectly correlated with latitude through conductivity and water temperature. Based on the cohesion modeling, microbial community stability was the highest under Dwa climate followed by the Cfa climate. This could be explained by a small subset of highly connected taxa capable of withstanding disturbance, indicating an important stability role. In contrast, the stability of the microbial communities under the Cwa climate was low, and no species with strong negative cohesion were observed. Overall, the structure, diversity, and stability of microbial community in WWTPs were found to be sensitive to climate, and the responsive mechanisms of α-diversity and ß-diversity with respect to latitude were distinct.
Subject(s)
Microbiota , Water Purification , China , RNA, Ribosomal, 16S , Sewage , WastewaterABSTRACT
Cosmic-ray neutrons (CRNs) account for about half of the radiation dose received by airline crews and passengers at aviation altitudes. CRNs also comprise important background radiation near the ground, which should be considered in neutron counts for the purpose of nuclear safeguarding and homeland security. In this study, simulations were conducted with the Geant4 toolkit to describe the air shower of cosmic rays. The latest experimental driving models for the atmosphere, geomagnetic field, and primary galactic cosmic rays were applied in these simulations. The simulation was validated by comparing the results with those measured on the NASA ER-2 aircraft. the CRN fluxes and spectra were calculated at altitudes ranging from one to tens of kilometers. We determined the characteristics of the CRN spectra and analyzed their dependency on the altitude. To consider their impact on the local environment, the CRNs near the ground were modeled with a specific equivalent approach, which allowed the simulations to be conducted with limited computer processing power. The parameters for the incident primary CRNs near the ground were calculated by simulating the cosmic ray air shower. The modeling dimensions were considered for the air and ground, and an appropriate approximation solution was obtained. The model near the ground was used to investigate the dependences of the CRN flux and spectrum on the soil moisture.
ABSTRACT
It's vital to explore critical indicators when identifying potential pollution sources of urban rivers. However, the variations of urban river water qualities following temporal and spatial disturbances were highly local-dependent, further complicating the understanding of pollution emission laws. In order to understand the successional trajectory of water qualities of urban rivers and the underlying mechanisms controlling these dynamics at local scale, we collected daily monitoring data for 17 physical and chemical parameters from seven on-line monitoring stations in Nanfeihe River, Anhui, China, during the year 2018. The water quality at tributaries were similar, while that at main river was much different. A seasonal ''turning-back" pattern was observed in the water quality, which changed significantly from spring to summer but finally changed back in winter. This result was possibly regulated by seasonally-changed dissolved oxygen and water temperature. Linear mixed models showed that the site 2, with the highest loads of pollution, contributed the highest (ß = 0.316, P < 0.001) to the main river City Water Quality Index (CWQI) index, but site 5, the geographically nearest site to main river monitoring station, did not show significant effect. In contrast, site 5 but not site 2 contributed the highest (ß = 0.379, P < 0.001) to the main river water quality. Therefore, CWQI index was a better index than water quality to identify potential pollution sources with heavy loads of pollutants, despite temporal and spatial disturbances at local scales. These results highlight the role of aeration in water quality controlling of urban rivers, and emphasized the necessity to select proper index to accurately trace the latent pollution sources.
ABSTRACT
Tritium analysis in water is an important part of environmental radiation monitoring. At present, tritium in water is generally measured by liquid scintillation counting (LSC). To optimize the pretreatment process and improve the efficiency of tritium analysis via LSC, a pretreatment device for tritium analysis in water based on a reverse osmosis (RO) film was developed. This paper introduces the system composition and carries out the following experimental studies: First, the comprehensive performance of the device was studied by performing repeated analyses, and the pretreatment time can be reduced by approximately 77% compared with that of the traditional method; then, the device was used to process tritium samples with different concentrations to verify the negligible impact of any tritium residue in the RO film; finally, the reliability of the results is verified by comparing with the traditional atmospheric distillation pretreatment method under the same measurement conditions. The results showed the developed method has the advantages of a simple operation and a high degree of automation, which effectively improves the efficiency of tritium analysis in water.
ABSTRACT
In this paper, we present a new method to correct dynamic error (DE) in on-line gamma ray thickness measurement, which significantly improves measurement precision over traditional method, in most cases, by one order of magnitude. Theoretical analysis of DE is presented and the correction method is proposed. In order to further prove our theory, Monte Carlo simulation is taken and the performance improvement is given. The method has been successfully applied to our thickness measurement system and brought dramatic improvement to its dynamic precision.
