Mercury biomethylation assessment in the estuary of Bilbao (North of Spain)

The relationship between the microbial methylation of mercury and the microbial activities in sediments and water collected from the estuary of Bilbao (North of Spain) was studied in three different sampling points and in two different seasons. Three different cultures were prepared with a sediment slurry to distinguish between biotic and abiotic methylation pathways and the variations of the methylmercury concentration and the variations of the population of total number of bacteria (TDC), anaerobic heterotrophic bacteria (AHB), sulphate-reducing bacteria (SRB) and Desulfovibrio were measured. From this work, it can be concluded that the variation of MeHg concentrations is a result of the methylation/demethylation processes in the sediments, and that the abiotic processes have a negligible contribution to those processes. According to the statistical analysis of the results (partial least squares analysis) a significant statistical correlation was established between methylmercury and the SRB counts.     

Enhancement of the CO(2) retention capacity of X zeolites by Na- and Cs-treatments

Adsorption of carbon dioxide on alkaline modified X zeolites was investigated by temperature programmed desorption (TPD) analysis of these materials previously saturated with CO(2) at 50, 100 and 200 degrees C. Parent X zeolite (in its sodium form) was treated with different sodium and cesium aqueous solutions, using both carbonates and hydroxides as precursors. The resulting materials were characterised by nitrogen physisorption, XRD, and NH(3)-TPD, in order to determine their morphological, crystallographic and chemical properties. Slight desilication phenomena were observed using hydroxides as precursors, whereas the treatment with Cs salts lead to higher crystallinity losses. Several successive adsorption-desorption cycles were carried out in order to check the regenerability of the adsorbents. Cesium-treated zeolites present higher carbon dioxide retention capacities than the sodium treated and than the parent material. When working with these Cs-modified materials, the desorption takes place mainly at temperatures between 250 and 400 degrees C, results of great practical interest, since it allows the use these kinds of materials for adsorption-desorption cycles. The evolution of the retention capacity with temperature is also markedly more positive for Cs-treated zeolite, especially when carbonate is used as the precursor. These materials maintain high retention capacities at 100 degrees C (10mg g(-1)) and even at 200 degrees C (3mg g(-1)), temperatures at which the most of the adsorbents are inactive.     

活性焦负载MnO2对气态Hg0的吸附脱除研究

研究了活性焦(AC)及负载MnO2的活性焦(MnO2/AC)对气态Hg0的吸附脱除,发现负载MnO2到AC明显提高了其对Hg0的吸附脱除能力.考察了MnO2负载量、温度、Hg0浓度和烟气成分等对MnO2/AC吸附脱除Hg0的影响.结果表明,MnO2/AC对Hg0的吸附脱除能力随MnO2负载量的增加而增强;在120～200℃的温度范围内,随着温度升高,MnO2/AC对Hg0的吸附脱除能力增强;O2和HCl对MnO2/AC吸附脱除Hg0具有促进作用,而SO2和H2O具有抑制作用.SEM-EDX和逐级化学提取结果证实,MnO2将Hg0催化氧化为HgO并吸附在AC上,这是MnO2/AC具有较高的吸附脱除Hg0能力的原因.     

Activity maintenance of the excised branches and a case study of NO2 exchange between the atmosphere and P. nigra branches

The efficient maintenance of the activity of excised branches is the powerful guarantee to accurately determine gas exchange flux between the detached branches of tall trees and the atmosphere. In this study, the net photosynthetic rate(NPR) of the excised branches and branches in situ were measured simultaneously by using two photosynthetic instruments to characterize the activity of the excised branches of Phyllostachys nigra. The ratio of normalized NPR of excised branches to NPR in situ was used to assess the photosynthetic activity of detached branches. Based on photosynthetic activity, an optimal hydroponics protocol for maintaining activity of excised P. nigra branches was presented:1/8 times the concentration of Gamborg B5 vitamin mixture with p H = 6. Under the best cultivation protocol, photosynthetic activity of excised P. nigra branches could be maintained more than 90% within 6 hr in the light intensity range of 200–2000 μmol/(m2·sec) and temperature range of 13.4–28.7°C. The nitrogen dioxide(NO2) flux differences between in situ and in vitro branches and the atmosphere were compared using double dynamic chambers.Based on the maintenance method of excised branches, the NO2 exchange flux between the excised P. nigra branches and the atmosphere(from-1.01 to-2.72 nmol/(m2·sec) was basically consistent with between the branches in situ and the atmosphere(from-1.12 to-3.16 nmol/(m2 sec)) within 6 hr. Therefore, this study provided a feasible protocol for in vitro measurement of gas exchange between tall trees and the atmosphere for a period of time.     

From waste hot-pot oil as carbon precursor to development of recyclable attapulgite/carbon composites for wastewater treatment

The utilization of waste products as valuable materials was a technical imperative for waste management. In this study, the cost-effective attapulgite/carbon(APT/C) composite was developed for wastewater treatment using waste hot-pot oil as a carbon precursor through a facile one-step calcination process. The APT/C composite prepared at 300°C exhibited the excellent adsorption capacity and rapid equilibrium rate over a broad p H range for the removal of various pollutants. More importantly, the removal ratios of the composites toward Methyl Violet and tetracycline still remained 77.6% and 60.2% of the initial adsorption capacity after ten adsorption–regeneration cycles via a facile thermal regeneration strategy, respectively.Beyond all doubt, this research provided a feasible and economical way for the sustainable utilization of waste hot-pot oil in wastewater treatment, achieving the concept of disposal waste with waste and recycling.     

上海沙田湖养殖区及周边水体中氟喹诺酮类抗性基因的分布特征及其与环境因子关系

集约化水产养殖区常被认为是水体抗生素和抗性基因的主要潜在来源,然而对其该类水体中抗生素和抗性基因污染情况的研究仍相对匮乏.本文以上海市沙田湖养殖区及周边水体为调查对象,利用宏基因组学高通量测序技术,于2020年9月对水体中的氟喹诺酮类抗生素(fluoroquinolones,FQs)和氟喹诺酮类抗性基因(fluoroquinolones antibiotic resistance genes,FQs-ARGs)的种类和丰度进行了调查,并利用多元统计分析方法研究了水体理化因子和FQs对FQs-ARGs的影响.结果表明,沙田湖养殖区及周边水体共检测出5类耐药机制、共46种FQs-ARGs,其中各水体共有基因为44种.抗性基因mfd和patA在养殖水体和周边水体中均为优势抗性基因,抗生素抗性基因变异或突变为优势耐药机制.养殖水体和周边河湖水体、不同养殖品种水体之间FQs-ARGs的平均丰度无显著差异(P＞0.05).偏冗余分析(pRDA)表明,除了诺氟沙星和环丙沙星2种抗生素外,水体电导率(Spc)、总磷(TP)、总氮(TN)、氨氮(NH4+-N)、溶解氧(DO)、pH和叶绿素a(Chl-a)等环境因子是影响水体中FQs-ARGs组成与分布的关键性因子,且非抗生素因子的总贡献率远高于抗生素.     

外秦淮河底泥污染及疏浚效果

外秦淮河是南京市一条重要的城市景观行洪河道,多年来受工业及生活污水影响,内源污染严重.为充分了解外秦淮河底泥污染特征,为疏浚提供决策依据,对河道上、中和下游典型断面底泥界面微环境以及营养物含量进行调查,采用有机指数法和污染指数法对底泥污染状况进行评估,同时根据污染物垂向分布特征模拟清淤对底泥内源释放削减的影响.结果表明,上中下游底泥界面以上DO均值分别为4.62、 3.25和3.41mg·L^-1,且分别在4.4、 3.5和5.5 mm处消耗殆尽,是典型的城市河道污染特征体现.调查河段表层底泥的ω(TN)、ω(TP)和ω(OM)均值分别为1 734mg·kg^-1、 1 337 mg·kg^-1和4.82%,底泥TN和OM的有机污染指数均值为0.48,处于尚清洁水平,TP的单项污染指数均值为3.18,处于重度污染水平.模拟30 cm清淤深度结果表明,底泥SRP和Fe²⁺的释放速率较清淤前分别削减42%～82%和88%～96%,而NH⁺₄-N的释放速率却较清淤前有...     

Sequential removal of heavy metals ions and organic pollutants using an algal-bacterial consortium

The residual algal-bacterial biomass from photosynthetically supported, organic pollutant biodegradation processes, in enclosed photobioreactors, was tested for its ability to accumulate Cu(II), Ni(II), Cd(II), and Zn(II). Salicylate was chosen as a model contaminant. The algal-bacterial biomass combined the high adsorption capacity of microalgae with the low cost of the residual biomass, which makes it an attractive biosorbent for environmental applications. Cu(II) was preferentially taken-up from the medium when the metals were present both separately and in combination. There was no observed competition for adsorption sites, which suggested that Cu(II), Ni(II), Cd(II), and Zn(II) bind to different sites and that active Ni(II), Cd(II) and Zn(II) binding groups were present at very low concentrations. Therefore, special focus was given to Cu(II) biosorption. Cu(II) biosorption by the algal-bacterial biomass was characterized by an initial fast cell surface adsorption followed by a slower metabolically driven uptake. pH, Cu(II), and algal-bacterial concentration significantly affected the biosorption capacity for Cu(II). Maximum Cu(II) adsorption capacities of 8.5+/-0.4 mg g-1 were achieved at an initial Cu(II) concentration of 20 mg l-1 and at pH 5 for the tested algal-bacterial biomass. These are consistent with values reported for other microbial sorbents under similar conditions. The desorption of Cu(II) from saturated biomass was feasible by elution with a 0.0125 M HCl solution. Simultaneous Cu(II) and salicylate removal in a continuous stirred tank photobioreactor was not feasible due to the high toxicity of Cu(II) towards the microbial culture. The introduction of an adsorption column, packed with the algal-bacterial biomass, prior to the photobioreactor reduced Cu(II) concentration, thereby allowing the subsequent salicylate biodegradation in the photobioreactor.