• Lynggaard Mueller ha publicado una actualización hace 9 horas, 23 minutos

    A theoretical approach was followed to optimize the design of a cylindrical photobioreactor for wastewater treatment based on algal culture. In particular, the problem of uneven light distribution that impairs algal growth was minimized by optimizing the area of uniform illumination distribution for a bioreactor design that can be enlarged without affecting its performance. The theoretical analysis was based on modeled simulations to determine the best configuration and illumination mode. The Monte Carlo method was used to simulate the illumination distribution inside the bioreactor, and the relationships between the width of the area with uniform illumination and related parameters were explored. Based on these theoretical considerations and predictions, an actual experimental photobioreactor was built containing a working area (where culture of Chlorella pyrenoidosa was enabled) and a catchment area for effluent. The performance of this bioreactor was tested with synthetic wastewater as a substrate. The light distribution was found to be relatively uniform inside the bioreactor, supporting excellent algal growth and resulting in maximum removal rates of 84.41% for total nitrogen, 99.73% for total phosphorus, 85.03% for NH4+-N, and 75.94% for chemical oxygen demand (COD) over a period of 32 days of operation. The presented approach provides new insights for improving the efficiency and scalability of photobioreactors and promotes their development for wastewater treatment and resource utilization.Phytoremediation potential of duckweeds (Lemna minuta, Lemna minor) to remove nutrients from simulated wastewater was analyzed. In two separate experiments, the two species were grown for 28 days in waters enriched with nitrate and phosphate to simulate nutrient concentrations of domestic wastewater. Water physical and chemical measurements (temperature, pH, conductivity, oxygen) and plant physiological and biochemical analysis (biomass, relative growth rate-RGR, nutrient and chlorophyll contents, peroxidative damage, bioconcentration factor-BCF) were made to test and compare the phytoremediation capacity of the two Lemna species. L. minuta biomass increased almost tenfold during the time-course of the treatment resulting in a doubling of the mat thickness and a RGR of 0.083 ± 0.001 g/g day. Maximum frond content of phosphate was reached by day 21 (increase over 165%) and nitrate by day 7 (10%). According to the BCF results (BCF > 1000), L. minuta was a hyperaccumulator for both nutrients. On the other hand, L. minor biomass and mat thickness decreased continuously during incubation (RGR = - 0.039 ± 0.004 g/g day). In L. minor fronds, phosphate content increased until day 14, after which there was a decrease until the end of the incubation. Frond nitrate content significantly decreased by day 7, but then remained relatively constant until the end of the experiment. L. minor proved to be hyperaccumulator for phosphates, but not for nitrates. Results indicated L. minuta has a greater potential than L. minor to remove both nutrients by bioaccumulation, especially phosphates, demonstrated also by better physiological and biochemical responses. However, during the incubation, the chlorophyll content of L. minuta mat did continuously decrease and peroxidative damage had increased until day 14, indicating that the system was under some kind of stress. Strategies to avoid this stress were discussed.Chlorine atoms initiated oxidation reactions are significant for the removal of typical volatile organic compounds (VOCs) in the atmosphere. The intrinsic mechanisms of CH2=CHCOOH + Cl reaction have been carried out at the CCSD(T)/cc-pVTZ//M06-2X/6-311++G(d,p) level. There are hydrogen abstraction and C-addition pathways on potential energy surfaces. By analyses, the addition intermediates of IM1(ClCH2CHCOOH) and IM2(CH2CHClCOOH) are found to be dominant. The secondary reactions of IM1 and IM2 have been discussed in the presence of O3, O2, NO, and NO2. And we have also investigated the degradation mechanisms of ClCH2CHO2COOH with NO, NO2, and self-reaction. Moreover, the atmospheric kinetics has been calculated by the variable reaction coordinate transition-state theory (VRC-TST). As a result, the rate constants show negative temperature and positive pressure dependence. The atmospheric lifetime and global warming potentials of acrylic acid have been calculated. Overall, the current study elucidates a new mechanism for the atmospheric reaction of chlorine atoms with acrylic acid.The interactions between microplastics (MPs) and aquatic organisms are becoming increasingly frequent due to the extensive distribution of MPs in aquatic environments. KHK-6 concentration MPs from the aquatic environment tend to accumulate and move through living organisms. Therefore, MPs can affect human health though the food chain and human consumption. In this brief review, the environmental distribution, sources, and transport of MPs are reviewed, and the potential consequences of the presence of MPs in the aquatic environment to human food are discussed. This review also summarized the toxicity effects and toxicity mechanisms of MPs based on various environmentally relevant test species and discussed the combined toxicity effects of MPs and various pollutants in aquatic ecosystems. The knowledge of the adverse effects on combined toxicity and the mechanism of MPs toxicity are very limited. Thus, a systematic assessment of the aquatic environmental risk in various species from MPs is challenging. In the end, we identify the knowledge gaps that need to be filled and provide suggestions for future research.Aiming the simultaneous determination of widely used organic plastic additives in complex marine matrices, this work proposes a fast and «green» analytical protocol based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) technology. The validation of this innovative method on real matrices (i.e., sediments, mussel, fish, and Posidonia oceanica) indicated a general good performance in all of them for phthalate esters (PAEs), with low blank levels and average method recoveries varying from 54 ± 11 to 71 ± 12%. The best method performance for organophosphate ester (OPE) flame retardants and plasticizers was in biotic matrices (recoveries 52 ± 31 to 86 ± 38%). This application represents an innovative QuEChERS sequence of two dispersive solid-phase extraction (SPE) steps enabling this approach for the determination of important families of organic plastic additives in the marine environment. Indeed, our method allowed the fast screening and simultaneous determination of OPE and PAEs in various sites and matrices subject to different anthropogenic pressure in coastal NW Mediterranean Sea for the first time.