水样pH对不同碱度含藻水混凝性能的影响

为探明碱度对混凝去除藻细胞及其分泌有机物的影响,保证饮用水水质。以铜绿微囊藻为研究对象,选用氯化铝(AlCl3·6H2O)作为混凝剂进行混凝实验,考察了不同碱度的含藻水样在pH为6.0~9.0条件下的混凝性能、絮体特性和出水余铝。结果表明：当水样pH=6.0时,相对于低碱度(95、175和245 mg·L−1)水样,碱度较高(330 mg·L−1和415 mg·L−1)的水样Zeta电位趋近于0,可有效降低颗粒间的排斥力,藻细胞的去除率达到74.45%以上(低碱度水样藻细胞去除率在31.64%以下),出水余铝最低为0.003 6 mg·L−1(低碱度时为0.088 9 mg·L−1);当水样pH≥6.5时,碱度较低的水样依靠吸附架桥和网捕卷扫协同作用,使得藻细胞去除率最高达到94.31%,出水余铝可降低至0.035 3 mg·L−1;随着碱度的增加,铝盐水解生成的Al(OH)3胶状沉淀逐渐转变为${{\rm{Al}}\left( {{\rm{OH}}} \right)_4^ -} $,使得网捕卷扫作用减弱,藻细胞去除率有所下降;当水样pH=7.5时,随着碱度增加,平衡时絮体粒径从811.02 μm降低至540.62 μm,絮体强度因子从35.97%降低至24.79%,恢复因子从35.31%增加至47.88%,分形维数从1.586减小到1.372。通过调节水样pH,可有效缓解碱度对含藻水混凝过程的影响,提高藻细胞的去除率。     

污泥颗粒化快速启动厌氧氨氧化反应器的探讨

厌氧氨氧化工艺处理成本低,被认为是有应用前景的废水脱氮技术.但是,厌氧氨氧化菌生长缓慢,厌氧氨氧化反应器启动困难.探讨了几种快速启动厌氧氨氧化反应器的方法,包括投加颗粒污泥、惰性载体、絮凝剂及多价阳离子等,并对其作用机理进行了分析.     

静态环境下阿特拉津的生物降解研究

从农药厂阿特拉津生产车间污泥中分离出菌种AT菌,进行了系列降解实验.不同温度的降解实验表明,在4～20℃的实验温度范围内,AT菌能够降解代谢污染质,并随温度的升高,降解能力增强.20℃时降解率为38.84%;AT菌在外加氮源、碳源及以阿特拉津为惟一碳源和氮源等条件时对农药污染质阿特拉津均具有降解能力,且在以阿特拉津为惟一氮源(外加碳源)条件下的降解效果最好,此时的降解率为30.39%.     

利用生态混凝土控制城市坡面暴雨径流污染试验研究

利用生态混凝土作为护坡材料,研究暴雨条件下生态混凝土控制山坡降雨径流污染的机理,以期对生态混凝土在城市护坡和护岸中的应用提供理论依据.研究结果表明,生态混凝土改变了雨水在坡面上的水文过程,阻延径流作用十分明显,有效地降低了污染物的负荷输出.生态混凝土试验小区(T2)与裸地(CK)和改良土壤小区(T1)相比,径流量分别减少了48%和24%,TN年度污染负荷(UPLRs)分别减少了53%和45%,溶解态氮(DN)减少了26%和28%,TP减少了57%和30%,溶解态磷(DP)降低了80%和33%,COD降低了62%和40%,TSS降低了56%和43%,产流时间和流量峰均明显滞后.另外,同植被覆盖良好的小区(T3)相比,生态混凝土对各种污染指标的控制效果没有明显差异,但其抗冲刷能力较强,更能适应城市护坡和护岸的需要.     

一氯苯在钒钛催化剂表面亲核取代反应的DFT计算

采用DFT计算方法对一氯苯在V2O5(001)和脱钛矿表面氧上的亲核取代反应的机理进行了分析。对不同DFT泛函在氯代芳香烃-过渡金属氧化物体系计算中的准确性进行了验证,发现采用B3LYP泛函得到的过渡态相对能量与标准值的偏差为9.63 kJ/mol,产物相对能量的偏差为8.79 kJ/mol,可以用于反应路径的推断。对亲核取代反应的机理进行了分析:首先苯环上与氯原子连接的碳原子受到表面氧的攻击,氯原子被驱离环平面;然后C—O健开始形成,同时C—Cl健断裂;最后苯酚盐结构形成,而驱离的氯原子与提供一个空轨道的过渡金属原子连接。与V2O5(001)表面及脱钛矿(100)和(101)表面相比,脱钛矿(001)表面的桥位氧是亲核取代最有可能发生的位置,吸附能为193.77 kJ/mol,吸附能垒为135.33 kJ/mol。     

Environmental biogeochemical behaviors of rare earth elements in soil–plant systems

With the continual increase in the utilization of rare earth elements (REEs) for industrial and agricultural purposes in China, the research into the environmental biogeochemical behavior of REEs has become a pressing issue. The REEs’ content in soil and various parts of wheat under different conditions in soil–plant systems were measured by INAA and ICP-MS. The results showed four aspects. (1) The mean value of total REEs in soil of China was 176.8 mg kg⁻¹. The mean ratio of ΣLREE/ΣHREE in soils was 8.0 and cerium accounts for 42% of the total REEs. The content of REEs in wheat seed ranged between 10⁻¹¹ and 10⁻⁸ g g⁻¹, 3–4 orders of magnitude lower than that in soil. (2) The REEs contents in ryegrass, especially in roots, were significantly related to that of soil. The bioavailability of REEs in soil mainly depended on the exchangeable fraction of REEs, which was strongly affected by the physico–chemical properties of the soil. (3) Long-term foliage-dressing with Changle microfertilizer of REEs did not affect the contents and distribution patterns of REEs in soil. At the maturing stage of spring wheat, the REEs content was in the order of root > leaf >stem and crust. Compared with the control, foliage-dressing has a higher accumulation of REEs in root and leaf. However, no significant difference was found in stem and crust between the two treatments. (4) There was no significant accumulation with the soil-dressing method. When comparing controls in both foliage- and soil-dressing methods, no distinct residue of REEs in grains was found.     

同分异构体喹啉和异喹啉的缺氧降解性能比较

研究了同分异构体的含氮杂环化合物喹啉和异喹啉在缺氧条件下的降解情况,发现两者表现出不同的缺氧降解特性。喹啉可以在缺氧条件下得到有效降解,其缺氧降解的最佳碳氮比为8。在最佳碳氮比条件下,喹啉的缺氧降解过程符合一级动力学规律,在其降解过程中首先以硝酸盐为电子受体,当硝酸盐氮浓度为零时,亚硝酸盐氮浓度达到最高,此后喹啉的降解主要以亚硝酸盐为电子受体,并和亚硝酸盐氮同时达到最低浓度。异喹啉对硝酸盐的利用甚微,其降解主要表现为厌氧降解特征,降解过程符合零级动力学规律。     

PAB在有机废水处理中的应用

综述了光合细菌独特的生理特性和其处理高浓度有机废水的原理,介绍了近年来国内外利用光合细菌处理有机废水的研究成果,并对光合细菌用于废水生物处理的前景及存在的问题进行了评述。     

Estimation of residue levels and dietary risk assessment of cyproconazole and azoxystrobin in cucumber after field application in China

Residue field trials in cucumber were conducted for the safe use of a commercial formulation of cyproconazole·azoxystrobin 28% suspension concentrate (SC 294 g a.i. ha^?1, three applications at a 7-day interval) in the year 2018, in China. To determine the residues of cyproconazole and azoxystrobin in cucumber, a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was developed using high-performance liquid chromatography coupled with tandem mass spectrometry. This validated method was applied to analyze cucumber samples collected from 12 specified regions. At the 3-day interval to harvest, the highest residue (HR) of azoxystrobin was 0.150 mg kg^?1, which was lower than the maximum residue limit (MRL; 0.5 mg kg^?1) permitted in China, and the HR of cyproconazole was 0.084 mg kg^?1, for which no MRL value has been set in China. The chronic risk quotient values of cyproconazole and azoxystrobin for Chinese adults at a 3-day interval to harvest were 2.56% and 13.72%, respectively. The acute risk quotient values of cyproconazole in cucumber were specified as 5.52% for children (1–6 years old) and 2.83% for the adults (>?18 years old) in China. These results indicate that cyproconazole·azoxystrobin 28% SC sprayed on cucumber at the pre-harvest interval of 3 days has no significant potential risk for Chinese consumers.