Transformation of Tetracycline Antibiotics and Fe(II) and Fe(III) Species Induced by Their Complexation

Tetracycline antibiotics (TCs) are frequently detected micropollutants and are known to have a strong tendency to complex with metal ions such as Fe­(II) and Fe­(III) in aquatic environments. Experiments with Fe­(II) and TCs showed that the complexation of Fe­(II) with tetracycline (TTC), oxytetracycline (OTC), or chlorotetracycline (CTC) could lead to the accelerated oxidation of Fe­(II) and the promoted degradation of TCs simultaneously. The reaction started with complexation of Fe­(II) with TC followed by oxidation of the Fe­(II)–TC complex by dissolved oxygen to generate a Fe­(III)–TC complex and reactive oxygen species (ROS). The ROS (primarily ·OH) then degraded TC. The oxidation rate constants of Fe­(II) in the Fe^II–H₂L and Fe^II–HL complexes were 0.269 and 1.511 min^–1, respectively, at ambient conditions (pH 7, 22 °C, and <i>P</i>_O₂ of 0.21 atm), which were about 60 and 350 times of the oxidation rate of uncomplexed Fe­(II). Humic acids (HA) compete with TCs for Fe­(II), but the effect was negligible at moderate HA concentrations (≤10 mg·L^–1). Experiments with Fe­(III) and TCs showed that the complexation of Fe­(III) with TC could generate oxidized TC and Fe­(II) without the need of oxygen at a relatively slower rate compared to the reaction involving Fe­(II), O₂, and TCs. These findings indicate the mutually influenced environmental transformation of TCs and Fe­(II) and Fe­(III) induced by their complexation. These newly identified reactions could play an important role in affecting the environmental fate of TCs and cycling of Fe­(II) and Fe­(III) in TCs-contaminated water and soil systems

The vocal repertoire of infant giant pandas (<i>Ailuropoda melanoleuca</i>)

<p>Infant giant pandas (<i>Ailuropoda melanoleuca</i>) are highly vocal during the first few weeks of their life. Despite this, no previous studies have attempted to systematically categorize infant giant panda vocalizations into different call types. In this study, we used acoustic and video analyses to split infant giant panda vocalizations into three distinct call types based on their acoustic structure as well as their use in different behavioural contexts. A discriminant functions analysis on the acoustic variables confirmed our initial subjective classification of 281 vocalizations into three call types: the harsh sounding “squawk”, the high-pitched “squall” and the pulsed “croak”. Based on the observed spectral acoustic characteristics, none of these three infant call types appears to be a precursor of an adult giant panda vocalization. In addition, individual call types could not be assigned to specific recording contexts. These findings suggest that infant giant panda vocalizations convey information about a cub's distress and need, rather than being tied to specific contexts of emission. Our objective demonstration that infant giant pandas have three basic call types provides a foundation for future studies of vocal ontogeny in this highly endangered species.</p

Workshop scene.

With the increasing market demand for high-quality aquatic products, the application of industrialized aquaculture facilities may get more attention. In order to improve the poor performance of thermal insulation, the accuracy of the numerical model was verified in this study through actual measured data. The model verification results shown that the average relative errors of the measured and calculated values of indoor air temperature, water temperature and roof inner surface temperature in the industrialized aquaculture workshop is within 2.5%, it suggested that the numerical calculation results are accurate. Furthermore, the thermal environment and thermal insulation performance of industrialized aquaculture facilities in winter were conducted based on the numerical calculations. After optimized the thermophysical parameters of the workshop enclosure structure, we found that the water body temperature could reach 21°C (which was close to the breeding temperature of grouper (Epinephelinae). Therefore, the numerical calculation method was further used to analyze the energy consumption of aquaculture water in January of a typical year in this area by heating to three constant temperatures (22, 25, and 28°C). When the aquaculture water was heated to the three constant temperature states, it needed to consume 8.56×105, 1.02×106 and 1.22×106 MJ of energy respectively, which were equal to the amount of energy released by the complete combustion of 29.3, 35.1 and 41.8 t standard coal. Moreover, it is concluded that the artificial temperature increase in winter maintains the temperature in the range of 22~25°C to provide the highest heating efficiency. This conclusion can provide theoretical basis and application reference for industrialized aquaculture in winter.</div

Measured and calculated values of water temperature in the workshop.

Measured and calculated values of water temperature in the workshop.</p

Stable-Isotope Probing Reveals the Activity and Function of Autotrophic and Heterotrophic Denitrifiers in Nitrate Removal from Organic-Limited Wastewater

Combined heterotrophic and autotrophic denitrification (HAD) is a sustainable and practical method for removing nitrate from organic-limited wastewater. However, the active microorganisms responsible for denitrification in wastewater treatment have not been clearly identified. In this study, a combined microelectrolysis, heterotrophic, and autotrophic denitrification (CEHAD) process was established. DNA-based stable isotope probing was employed to identify the active denitrifiers in reactors fed with either ¹³C-labeled inorganic or organic carbon sources. The total nitrogen removal efficiencies reached 87.2–92.8% at a low organic carbon concentration (20 mg/L COD). Real-time polymerase chain reaction of the <i>nirS</i> gene as a function of the DNA buoyant density following the ultracentrifugation of the total DNA indicated marked ¹³C-labeling of active denitrifiers. High-throughput sequencing of the fractionated DNA in H¹³CO₃^–/¹²CH₃¹²COO^–-fed and H¹²CO₃^–/¹³CH₃¹³COO^–-fed reactors revealed that <i>Thermomonas</i>-like phylotypes were labeled by ¹³C-bicarbonate, while <i>Thauera</i>-like and <i>Comamonas</i>-like phylotypes were labeled by ¹³C-acetate. Meanwhile, <i>Arenimonas</i>-like and <i>Rubellimicrobium</i>-like phylotypes were recovered in the “heavy” DNA fractions from both reactors. These results suggest that nitrate removal in CEHAD is catalyzed by various active microorganisms, including autotrophs, heterotrophs, and mixotrophs. Our findings provide a better understanding of the mechanism of nitrogen removal from organic-limited water and wastewater and can be applied to further optimize such processes

Test instrument.

With the increasing market demand for high-quality aquatic products, the application of industrialized aquaculture facilities may get more attention. In order to improve the poor performance of thermal insulation, the accuracy of the numerical model was verified in this study through actual measured data. The model verification results shown that the average relative errors of the measured and calculated values of indoor air temperature, water temperature and roof inner surface temperature in the industrialized aquaculture workshop is within 2.5%, it suggested that the numerical calculation results are accurate. Furthermore, the thermal environment and thermal insulation performance of industrialized aquaculture facilities in winter were conducted based on the numerical calculations. After optimized the thermophysical parameters of the workshop enclosure structure, we found that the water body temperature could reach 21°C (which was close to the breeding temperature of grouper (Epinephelinae). Therefore, the numerical calculation method was further used to analyze the energy consumption of aquaculture water in January of a typical year in this area by heating to three constant temperatures (22, 25, and 28°C). When the aquaculture water was heated to the three constant temperature states, it needed to consume 8.56×105, 1.02×106 and 1.22×106 MJ of energy respectively, which were equal to the amount of energy released by the complete combustion of 29.3, 35.1 and 41.8 t standard coal. Moreover, it is concluded that the artificial temperature increase in winter maintains the temperature in the range of 22~25°C to provide the highest heating efficiency. This conclusion can provide theoretical basis and application reference for industrialized aquaculture in winter.</div

The measured and calculated values of the outer surface of the workshop roof.

The measured and calculated values of the outer surface of the workshop roof.</p

Heat loss in constant temperature aquaculture workshop (22°C).

Heat loss in constant temperature aquaculture workshop (22°C).</p

The measured and calculated values of the temperature in the workshop.

The measured and calculated values of the temperature in the workshop.</p

Heat loss in constant temperature aquaculture workshop (25°C).

Heat loss in constant temperature aquaculture workshop (25°C).</p