Influence of root-exudates concentration on pyrene degradation and soil microbial characteristics in pyrene contaminated soil

The effect of ryegrass (Lolium perenne L.) root-exudates concentration on pyrene degradation and the microbial ecological characteristics in the pyrene contaminated soil was investigated by simulating a gradually reducing concentration of root exudates with the distance away from root surface in the rhizosphere. Results showed that, after the root-exudates were added 15 d, the pyrene residue in contaminated soil responded nonlinearly in the soils with the same pyrene contaminated level as the added root-exudates concentration increased, which decreased first and increased latter with the increase of the added root-exudates concentration. The lowest pyrene concentration appeared when the root exudates concentration of 32.75 mg kg(-1) total organic carbon (TOC) was added. At the same time, changes of microbial biomass carbon (MBC, C(mic)) and microbial quotient (C(mic)/C(org)) were opposite to the trend of pyrene degradation as the added root-exudates concentration increased. Phospholipid fatty acid (PLFA) analysis revealed that bacteria was the dominating microbial community in pyrene contaminated soil, and the changing trends of pyrene degradation and bacteria number were the same. The changing trend of endoenzyme-dehydrogenase activity was in accordance with that of soil microbe, indicating which could reflect the quantitative characteristic of detoxification to pyrene by soil microbe. The changes in the soils microbial community and corresponding microbial biochemistry characteristics were the ecological mechanism influencing pyrene degradation with increasing concentration of the added root-exudates in the pyrene contaminated soil.     

Biofilm formation and microbial community analysis of the simulated river bioreactor for contaminated source water remediation

Background, aim, and scope

The start-up pattern of biofilm remediation system affects the biofilm characteristics and operating performances. The objective of this study was to evaluate the performances of the contaminated source water remediation systems with different start-up patterns in view of the pollutants removal performances and microbial community succession.

Methods

The operating performances of four lab-scale simulated river biofilm reactors were examined which employed different start-up methods (natural enrichment and artificial enhancement viadischarging sediment with influent velocity gradient increase) and different bio-fillers (Elastic filler and AquaMats? ecobase). At the same time, the microbial communities of the bioreactors in different phases were analyzed by polymerase chain reaction, denaturing gradient gel electrophoresis, and sequencing.

Results and discussion

The pollutants removal performances became stable in the four reactors after 2 months?? operation, with ammonia nitrogen and permanganate index (COD_Mn) removal efficiencies of 84.41?C94.21% and 69.66?C76.60%, respectively. The biomass of mature biofilm was higher in the bioreactors by artificial enhancement than that by natural enrichment. Microbial community analysis indicated that elastic filler could enrich mature biofilm faster than AquaMats?. The heterotrophic bacteria diversity of biofilm decreased by artificial enhancement, which favored the ammonia-oxidizing bacteria (AOB) developing on the bio-fillers. Furthermore, Nitrosomonas- and Nitrosospira-like AOB coexisted in the biofilm, and Pseudomonas sp., Sphaerotilus sp., Janthinobacterium sp., Corynebacterium aurimucosum were dominant in the oligotrophic niche.

Conclusion

Artificial enhancement via the combination of sediment discharging and influent velocity gradient increasing could enhance the biofilm formation and autotrophic AOB enrichment in oligotrophic niche.     

Heterogeneous photocatalytic degradation of methyl orange in schwertmannite/oxalate suspension under UV irradiation

Introduction

Schwertmannite was synthesized through an oxidation of FeSO₄ by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH?2.5 and 28°C for 3?days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The schwertmannite photocatalytic degradation of methyl orange (MO) by oxalate was investigated at different initial pH values, concentrations of schwertmannite, oxalate, and MO.

Results

The results demonstrated that photodegradation of MO in the presence of schwertmannite or oxalate alone was very weak. However, the removal of MO was significantly enhanced when schwertmannite and oxalate coexisted in the reaction system. Low pH (4 or less) was beneficial to the degradation of MO. The optimal doses of schwertmannite and oxalate were 0.2?g?L^?1 and 2?mM, respectively. Hydroxyl radicals (·OH) and Fe(II), the intermediate products, were also examined during the reaction to explore their correlation with the degradation of MO.

Conclusion

A possible mechanism for the photocatalytic decomposition of MO in the study was proposed. The formation of Fe(III)-oxalate complexes on the surface of schwertmannite was a precursor of H₂O₂ and Fe(II) production, further leading to the yield of ·OH responsible for the decomposition of MO.     

百色市右江区大气PM10中水溶性无机离子的化学特征与来源

2010年10月至2011年9月采集百色市右江区大气PM10样品,分析PM10及其水溶性无机离子的化学特征与来源。结果表明:(1)百色市右江区大气PM10为13.89～319.44μg/m3,年均117.48μg/m3,年均值超过《环境空气质量标准》(GB 3095-2012)二级标准(100μg/m3)。百色市右江区大气可吸入颗粒物的污染主要出现在春冬季节。(2)水溶性无机离子浓度年均值依次为SO24->NO3->Cl->NH4+>K+>Na+>Mg2+>F-,SO24-、NO3-和Cl-浓度最高,分别占水溶性无机离子的57.7%、14.9%和14.5%。(3)百色市右江区大气PM10呈较强的酸性,高浓度的SO42-可能是导致百色市右江区大气PM10呈较强酸性的主要原因。(4)PM10的季节变化受气温和风速的影响极显著;气象因素对SO42-、NO3-、F-的影响不显著。(5)主因子分析表明,PM10中水溶性无机离子可能来自3个方面,Cl-和NO3-主要来自于当地低烟卤煤燃烧排放的烟气;Mg2+、K+和Na+主要来自于自然源;F-、SO24-和NH4+主要来自于混合源。     

三垟湿地沉积物-间隙水-上覆水界面磷形态研究

沉积物与上覆水间营养物质交换,成为导致水体发生富营养化的首要化学变迁过程.分别在三垟湿地的柑橘林(S1)、景观用地(S2)和生活用地(S3)取样,研究了沉积物-间隙水-上覆水界面磷形态以及相互关系.结果表明:(1)沉积物TP增加时,间隙水PO3-4和可溶性总磷(TDP)也增加.要削减磷在上覆水中的含量,控制间隙水PO3-4或TDP是一良策.(2)随着沉积物铁磷、铝磷的增加,间隙水PO3-4也增加.在三垟湿地沉积物中,铁磷和铝磷含量都可作为间隙水PO34-含量的指示.(3)S1、S2和S3的沉积物活性磷、间隙水TDP和上覆水TDP存在明显的浓度梯度,沉积物活性磷＞间隙水TDP＞上覆水TDP.说明在三垟湿地中,沉积物活性磷是磷释放的关键因子,而沉积物-间隙水界面则是磷释放的关键界面.     

三氯乙烯在苯酚菌中的共代谢降解性能研究

通过生物降解实验考察三氯乙烯(TCE)在苯酚驯化微生物中的共代谢降解性能,并进行动力学分析。结果表明,苯酚是TCE-苯酚共代谢过程必不可少的共代谢基质;TCE的共代谢降解与苯酚和TCE初始浓度有关。TCE在降解初期会出现一个短暂的迟滞期,TCE的大量降解要在苯酚被利用后才发生;高质量浓度TCE(>9mg/L)对共代谢降解有抑制作用。苯酚/TCE(质量比)在10～15以上时,苯酚菌对TCE的去除率较大。Haldane模型能够很好地拟合苯酚和TCE的比降解速率。动力学分析表明,微生物对苯酚的亲和力要大于TCE,苯酚对TCE共降解具有竞争性抑制作用,TCE对微生物存在毒性抑制作用;结果证实了生物降解实验的结论。     

城市污水处理厂污水处理系统中四环素类药物耐药菌的分布特性研究

采用微生物平板涂布法对2家城市污水处理厂污水处理各阶段的四环素类药物(四环素、金霉素、土霉素)耐药菌分布进行了测定,分析了污水处理的各阶段对四环素类药物耐药菌的去除效果。结果显示,2家污水处理厂污水处理系统中均能检出土霉素、四环素、金霉素耐药菌,数量分布均为土霉素耐药菌>四环素耐药菌>金霉素耐药菌。3种耐药菌的浓度均在加氯消毒出水中为最小(在0～103 cfu/mL),在外排污泥中最大(高于进水浓度,在105～107 cfu/mL)。四环素耐药菌数从进水的1.1×105～1.6×105 cfu/mL降为出水的0～5.5×102 cfu/mL,说明污水处理过程对四环素耐药菌有一定的去除效果,但四环素耐药菌占总菌数的百分比没有明显下降或上升,相比于进水的1.1%～3.4%,出水仍然保持在3.1%～4.3%左右,表明污水处理过程中没有选择性的富集或去除四环素耐药菌。     

固定化嗜麦芽寡养单胞菌的制备及其降解羽毛废弃物的初步研究

以自制壳聚糖小球为载体,采用吸附固定法制备固定化嗜麦芽寡养单胞菌(Stenotrophomonas maltophilia DHHJ),并将其用于羽毛废弃物降解。结果表明,采用3.0%(质量分数)的壳聚糖制成的壳聚糖小球的形态较好,经高压灭菌后弹性增加,呈多孔状,有很强的吸水性,有利于细菌的吸附固定和生长;在细胞稀释液中加入10%(质量分数)的壳聚糖小球,固定时间设为2d时,制得的固定化小球在发酵过程中释放的有效活菌数最多,可达7.0×106 cfu/mL;在连续10次、共计40d的序批发酵降解过程中,固定化菌的羽毛降解率和发酵液中的角蛋白酶酶活均保持在最大值的80%以上。固定化菌的发酵稳定性较强,能在较长时间内稳定、有效地降解羽毛,具有连续发酵潜力;固定化菌发酵降解羽毛的最佳工艺条件为:小球投加量50mg/mL,羽毛投加量25mg/mL,摇床转速130r/min,发酵5d。     

3种植物对Cd污染农田土壤的修复效果比较试验研究

通过盆栽试验研究了3种植物三叶鬼针草(Bidens pilosa L.)、紫茉莉(Mirabilis Jalapa)、中华景天(Sedum polytrich-oides)对上海地区2种质量浓度(1.2、12.0mg/kg)Cd污染农田土壤的修复效果,以探索其在上海地区Cd污染农田土壤修复中应用的可行性。结果表明:2种浓度下,三叶鬼针草对土壤Cd去除效果均最佳,1.2mg/kg处理下盆中土壤Cd质量浓度由原来的1.249 9mg/kg下降到0.861 7mg/kg,降低0.388 2mg/kg,Cd去除率为31.06%;12.0mg/kg处理下三叶鬼针草盆中土壤Cd质量浓度由原来的12.033 2mg/kg下降到10.020 6mg/kg,降低2.012 6mg/kg,Cd去除率为16.73%;紫茉莉和中华景天相比较而言,修复效果均较差。在2种浓度下,3种植物地上部分生物量排序均为三叶鬼针草>中华景天>紫茉莉。因此,建议将三叶鬼针草作为上海地区Cd污染农田土壤修复的优选植物。     

真空紫外线与TiO2负载催化剂处理甲苯废气研究

采用波长更短、能量更强的真空紫外线(VUV)光源,在管式反应器中以负载纳米TiO2的玻璃珠和γ-Al2O3小球为催化剂,对光催化法净化甲苯废气进行了研究。主要探讨了甲苯的入口浓度、停留时间、相对湿度等因素对其去除率的影响。结果表明,使用VUV光源可以提高甲苯的平均去除率,相对湿度在45%～60%时,甲苯平均去除率相对较高,甲苯的去除率随着其入口浓度的升高而降低,随着其停留时间的延长而升高;以γ-Al2O3小球为载体时,催化剂和VUV的协同作用使得反应体系对于甲苯入口浓度的变化有更好的适应性;VUV与TiO2负载催化剂的协同作用可有效降低光催化所产生的O3浓度,有利于尾气污染控制。