Simplification of the pretreatment method for phosphate oxygen isotope measurement in phosphogypsum leachate.

The stacking of phosphogypsum has caused considerable phosphorus pollution in water bodies near phosphogypsum yards through surface runoff and underground infiltration. The phosphate oxygen isotope (δ18Op) tracing method has served as a valuable tool for tracing phosphorus pollution in water. However, the existing δ18Op enrichment and purification methods are complex, costly, and inefficient for phosphate recovery, particularly for phosphogypsum leachate with complex compositions. Herein, a simplified and optimized pretreatment method for δ18Op measurement in phosphogypsum leachate was developed. Zirconium/polyvinyl alcohol (Zr/PVA) gel beads showed good selectivity for phosphate enrichment from water at different initial phosphate concentrations with appropriate Zr/PVA dosage. The optimal enrichment pH value was <7, and the concentrated phosphate on the Zr/PVA gel beads could be effectively eluted in an alkaline environment. Compared with the traditional Fe or Mg coprecipitation enrichment methods, impurities in the solution showed no obvious adverse effects on the phosphate enrichment process. Further, the phosphate solution eluted from the Zr/PVA gel beads was purified by a simple adjustment of the pH instead of cation exchange in the traditional purification process. Magnesium ions in the solution could be completely removed when the pH ranged from 3.17 to 6.15, and the phosphate recovery rate could reach 98.66% when the eluent pH was 5.02. Fourier-transform infrared spectroscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy revealed that similar to traditional pretreatment method, the proposed method can obtain high-purity Ag3PO4 solids for δ18OP measurement and no isotope fractionation of δ18OP was observed. Therefore, this study provides a promising and reliable pretreatment method for δ18OP measurement, especially in complex phosphogypsum leachate.

Magnetite-boosted syntrophic conversion of acetate to methane during thermophilic anaerobic digestion.

Using a batch thermophilic anaerobic system established with 60 mL serum bottles, the mechanism on how microbial enrichments obtained from magnetite-amended paddy soil via repeated batch cultivation affected methane production from acetate was investigated. Magnetite-amended enrichments (MAEs) can improve the methane production rate rather than the methane yield. Compared with magnetite-unamended enrichments, the methane production rate in MAE was improved by 50%, concomitant with the pronounced electrochemical response, high electron transfer capacity, and fast acetate degradation. The promoting effects might be ascribed to direct interspecies electron transfer facilitated by magnetite, where magnetite might function as electron conduits to link the acetate oxidizers (Anaerolineaceae and Peptococcaceae) with methanogens (Methanosarcinaceae). The findings demonstrated the potential application of MAE for boosting methanogenic performance during thermophilic anaerobic digestion.

Occurrence and Fluxes of Polycyclic Aromatic Hydrocarbons in the Third Largest Fresh Water Lake (Lake Taihu) in China.

Polycyclic aromatic hydrocarbons (PAHs) pose great risks to lake ecosystem and human health. Comprehensive knowledge on PAHs in lakes is critical for their risk control. 118 samples were collected from different environmental medium to study the occurrence and fluxes of 16 PAH in Lake Taihu. The average ∑PAH16 in air, water, phytoplankton, zooplankton, suspended particle matter, and surface sediments were 122 ng m-3, 61.3 ng L-1, 6500 ng g-1, 4940 ng g-1, 27,900 ng g-1, and 522 ng g-1, respectively. Sediments were contaminated by PAHs from pyrogenic sources. The average fluxes of air-water, dry deposition, and sinking of the 16 individual PAHs were 2900, 300, and 251 ng m-2 d-1. In the air-water column-surface sediments system, air-water exchange was the main transport pathway. In order to ensure safety of drinking water resources for local residence, the governments are suggested to work together to reduce PAHs emission and implement new energy policy.

Associations between feelings/behaviors during COVID-19 pandemic lockdown and depression/anxiety after lockdown in a sample of Chinese children and adolescents.

BACKGROUND: Children and adolescents may be more susceptible to mental disorders due to COVID-19 pandemic than adults. This study aimed to identify correlated factors for depression/anxiety among children and adolescents after COVID-19 pandemic lockdown. METHODS: An online survey by cluster sampling was conducted after lockdown in 5175 Chinese children and adolescents with informed consents from their parents. The 9-item Patient Health Questionnaire and the 7-item Generalized Anxiety Disorder scales with 10-point cutoff were used to measure depression and anxiety, separately. Stepwise logistic regression was conducted. Stata 15.1 Version was used. RESULTS: 12.33% and 6.26% of all participants reported depression and anxiety after lockdown, separately. Suicidal ideation, quarreling with parents, insomnia, difficulty in concentrating during online learning, and anxious and depressed mood during lockdown were positively associated with depression and anxiety after lockdown. Missing teachers was negatively associated with both depression and anxiety. Living in urban and not living with parents were positively associated with depression. LIMITATIONS: The past history and familial history of mental disorders have not been collected. The recall biases for collecting self-reporting information might exist, and the causal inferences cannot be drawn. CONCLUSIONS: The prevalence of depression and anxiety in children and adolescents might decline a bit after lockdown but is still at a high level after lockdown. Gatekeepers should pay more attention to modifiable factors of psychological well-being in children and adolescents, including family and school contexts and even feelings and behaviors during COVID-19 pandemic lockdown.

Climate change has weakened the ability of Chinese lakes to bury polycyclic aromatic hydrocarbons.

Burial in sediments is a crucial way to reduce mobilization and risks of hydrophobic organic contaminants (HOCs), but ability of sediments to bury HOCs may be altered if the environment is changed. Whether the ability of sediments to bury HOCs has been affected by climate change remains largely unclear. We excluded the impacts of anthropogenic emissions and eutrophication from that of climate change, and for the first time found that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation had weakened the ability of Chinese lakes to bury 16 polycyclic aromatic hydrocarbon (PAHs) by 69.2% ±â€¯9.4%-85.7% ±â€¯3.6% from 1951 to 2017. The relative contributions of the climatic variables to the reduced burial ability depended on the properties of the PAHs, and lakes. Burial ability of the PAHs responded differently to climate change, and was correlated to their volatilization and aqueous solubility, and lake area, catchment area/lake area ratio, and water depth. Our study suggests that not only the rising surface air temperature but also the declining wind speed and the reducing days with precipitation can undermine global efforts to reduce environmental and human exposure to PAHs.