Degradation Adaptability Assessment of Semisolid Powder Molded Mg-Zn-Mn Alloys for Orthopedic Applications.

Semisolid powder molding was used to prepare the medical Mg-6Zn alloy; in order to further improve its degradation adaptability, 0.5 and 1 wt % Mn were added. Then, the effect of the forming temperature (540, 560, 580, and 600 °C) on the in vitro degradation behavior of the prepared Mg-6Zn-xMn (x = 0.5, 1 wt %) was analyzed, and the optimized alloy was obtained. Finally, the biocompatibility and in vivo degradation performance of the optimized and Mn-free alloys were evaluated. Importantly, single-photon emission tomographic imaging (SPECT/CT) was first applied to monitor the in vivo degradation process. The results show that the corrosion mechanism of the Mn-free alloy is microgalvanic corrosion control with corrosive pitting. After adding Mn, the in vitro degradation rate decreases by half (0.17 ± 0.01 mm/year) as the forming temperature increases to 600 °C, and Mg-6Zn-1Mn prepared at 600 °C is the optimized alloy. Mn addition improves the corrosion product film protection and discontinuous secondary phases, and thus, the corrosion mechanism is changed to corrosive pitting control. Additionally, semisolid powder molding is an easy method to prepare alloys with low average pore interconnectivity (<10%), which is helpful for slowing down the degradation rate. The Mn-containing alloy has better biocompatibility, with a cytotoxicity of grade 0-1, due to its lower degradation rate. The in vivo corrosion rate of the Mn-free alloy is 0.19 mm/year after 28 days of implantation, which was precisely detected by SPECT/CT in real-time. The long-term in vivo degradation adaptability of Mn-free and Mn-containing alloys was not correctly presented, which may be due to the unreasonable bone defect model causing implant displacement. However, both of these alloys cause no obvious inflammation and show good healing. In summary, semisolid powder molding is a potentially promising technique to prepare medical Mg alloys, and nuclear imaging is an effective in vivo degradation evaluation method.

Phytoplankton in headwater streams: spatiotemporal patterns and underlying mechanisms.

Phytoplankton are key members of river ecosystems wherein they influence and regulate the health of the local environment. Headwater streams are subject to minimal human activity and serve as the sources of rivers, generally exhibiting minimal pollution and strong hydrodynamic forces. To date, the characteristics of phytoplankton communities in headwater streams have remained poorly understood. This study aims to address this knowledge gap by comparing phytoplankton communities in headwater streams with those in plain rivers. The results demonstrated that within similar watershed sizes, lower levels of spatiotemporal variability were observed with respect to phytoplankton community as compared to plain rivers. Lower nutrient levels and strong hydrodynamics contribute to phytoplankton growth limitation in these streams, thereby reducing the levels of spatiotemporal variation. However, these conditions additionally contribute to greater phytoplankton diversity and consequent succession towards Cyanophyta. Overall, these results provide new insights into the dynamics of headwater stream ecosystems and support efforts for their ecological conservation.

Source Apportionment, Hydrodynamic Influence, and Environmental Stress of Pharmaceuticals in a Microtidal Estuary with Multiple Outlets in South China.

Pharmaceutical residues in the environment are of great concern as ubiquitous emerging contaminants. This study investigated the presence of 40 pharmaceuticals in water and sediment of the Pearl River Estuary (PRE) in the wet season of 2020. Among psychiatric drugs, only diazepam was found in water samples while six of them were detected in the sediment. The Σantibiotics levels ranged from 6.18 to 35.9 ng/L and 2.63 to 140 ng/g dry weight in water and sediment samples, respectively. Fluoroquinolones and tetracyclines were found well settling in the outlet sediment, while sulfonamides could be released from disturbed sediment under stronger tidal wash-out conditions. After entering the marine waters, pharmaceuticals tended to deposit at the PRE mouth by the influence of the plume bulge and onshore invasion of deep shelf waters. Low ecological risks to the aquatic organisms and of causing antimicrobial resistance were identified. Likewise, hydrological modeling results revealed insignificant risks: erythromycin-H2O and sulfamethoxazole discharged through the outlets constituted 30.8% and 6.74% of their environmental capacity, respectively. Source apportionment revealed that pharmaceutical discharges through the Humen and Yamen outlets were predominantly of animal origin. Overall, our findings provide strategic insights on environmental regulations to further minimize the environmental stress of pharmaceuticals in the PRE.

A projects portfolio selection for water security addressing future increasing water demand and salinity intrusion in Zhuhai City, coastal China.

Water security is essential for sustainable economic and social development. To ensure water security, water engineering projects play an important role in regional developing program. The coastal city-Zhuhai City suffers a challenge from both future increasing water demand and salinity intrusion, To keep water security of the city, several alternative projects are designed. However, as the high cost of the projects and the potential adverse influence, a final projects portfolio, as well as their construction order has not be decided. To assist a proper decision of projects portfolio for local water security, this study proposed a combined method with one-vote veto and Analytic Hierarchy Process, to evaluate every projects portfolio from various perspectives. The results show: 1) to satisfy future water demand of 150 thousands m3/h, it is recommended to adopt a projects portfolio including expanding existing reservoirs and constructing new reservoirs, as its higher capacity utilization (96.87%), relatively lower construction and operation costs (8.59 billion and 57 million respectively), and lower ecological impact; 2) to satisfy future water demand of 160 thousands m3/h or more, transferring water from other cities should be an indispensable part for water security; 3) channel reservoir is not recommended as its high construction and operation costs, and high ecological impact. This study evaluated different alternative projects for cities' water security and provided a strong support for local government to decide their long-term projects portfolio and their construction order. The proposed method may be readily applied in other regions.

Monthly variation and vertical distribution of parent and alkyl polycyclic aromatic hydrocarbons in estuarine water column: Role of suspended particulate matter.

The distribution and interaction of parent and alkyl polycyclic aromatic hydrocarbons (EPA-34 PAHs) among the multiple phases were investigated in estuarine water column of Humen outlet over a 12-months period. The water column was divided into 5 vertical layers, and each layer included dissolved phase, large- and small-size suspended particular matter (SPM). Regarding to EPA-34 PAHs, alkyl homologues were abundant, especially in the dissolved phase and small-size SPM. Moreover, SPM contributed a large proportion of EPA-34 PAHs in the water column especially for the large-size SPM, which therefore play an important role for the transportation of these pollutants. The EPA-34 PAHs concentrations in water column during wet season were higher than those in the dry season due to the decreasing of KD values which were affected by TSS and salinity obviously. Generally, the EPA-34 PAHs concentrations in the water column increased with the increasing of water depth, most of the highest concentrations of EPA-34 PAHs were found in the near-bottom layer due to the rapid sinking of large-size SPM and sediment resuspension. Additionally, during the ebb-flood tide period, the EPA-34 PAHs concentrations in different phases of the water column fluctuated oppositely based on the effects of hydrodynamic conditions.

[Desorption behaviors of 4-nitrophenol on hyper-cross-linked polymer resin NDA-701].

Desorption behaviors of loaded 4-nitrophenol (4-NP) on hyper-cross-linked polymer resin NDA-701 were studied. The molar ratio of NaOH and 4-NP desorbed (M(NAOH/4-NP)) selection experiments were carried out at two different reaction temperature(303 K and 333 K). Desorption kinetics characteristic of4-NP on NDA-701 in the batch and fixed-bed mode were examined at different reaction temperature and M(NaOH/4-NP) values. The results showed that optimal M(NaOH/4-NP) values were 1.2 and 100% 4-NP could be desorbed from NDA-701 at two different temperature. When the M(NaOH/4-NP) was lower than 1.2, the desorption efficiency increases with the increase of temperature, but the function of temperature decrease with increasing of M(NaH/4-NP) values for desorption ratio. The information indicated that desorption thermodynamic characteristic of NDA-701 was controlled by M(NaOH/4-NP) values. Desorption kinetics in the alkaline system can be well described by pseudo-second-order kinetic model, and desorption rate is increased with the increase of desorption temperatures, the k2 value increase from 0.010 g x (mmol x min)(-1) to 0.035 g x (mmol x min)(-1) when desorption temperature increase from 303 K to 333 K. Nevertheless, higher M(NaOH/4-NP) values could not promote desorption rate if only M(NaOH/4-NP) value was larger than the optimal molar ratio of NaOH and 4-NP. When M(NaOH/4-NP) values increase from 1.2 to 5.0, the k2 value increase from 0.038 g x (mmol x min)(-1) to 0.044 g x (mmol x min)(-1) merely at 333 K. the results indicated that desorption kinetic characteristic of NDA-701 was controlled by temperature. NDA-701 can be completely recovered using 2 times Bed Volume of 2% NaOH solution at the temperature of 333 K, comparing with field application, implying that more energy and cost can be saved in comparison with the actual desorption process in the industry.