RESEARCH: Shrub Propagation Techniques for Biological Control of Invading Tree Species

Cornus stolonifera, Salix petiolaris, and Spiraea alba clones already located within the corridor of an electrical power line. To establish the efficiency of treatments, we examined the statistical differences of growth traits between species and treatments. An analysis of the effects of layering shows, after the first growth season, differences for all growth traits in only one species, Spiraea alba. After the second growth season, we observed the development of new aerial stems. Layering favors horizontal expansion of shrubs over height development. The third year after treatment, the effect of layering is reduced except for Cornus stolonifera, which continuously increases, as shown by the significant progression of the clone issued from the layer even five years after treatments. With the cutting back technique, we expected a distinct vertical growth of the shrubs at the expense of increasing the crown diameter. This technique would be best associated with the rejuvenation of clones, followed by a layering of new shoots to allow a horizontal expansion of the shrubs. Therefore, the formation of a dense shrub community by layering should be considered a valuable approach for the biological control of undesirable trees in powerline rights-of-way.     

Exploring Chemical Variables in Ligustrum lucidum Ait. F. Tricolor (Rehd.) Rehd. in Relation to Air Pollutants and Environmental Conditions

Ligustrum lucidum Ait. f. tricolor (Rehd.) Rehd. in relation to atmospheric pollutants in Córdoba city, Argentina. The study area receives regional pollutants and was categorized taking into account traffic level, industrial density, type of industry, location of the sample point in relation to the street corner, treeless condition, and topographic level. Dried weight/fresh weight ratio (DW/FW) and specific leaf area (SLA) were calculated, and concentrations of chlorophylls, carotenoids, total sulfur, soluble proteins, malondialdehyde (MDA), and hydroperoxy conjugated dienes (HPCD) were determined in leaf samples. Sulfur content correlates positively with traffic density and SLA correlates negatively with some combinations of the categorical variables; MDA correlates positively with topographic level and total protein concentration correlates negatively with treeless condition. On the basis of our results, traffic, location of trees, type of industry, situation of a tree with respect to others, and topographic level are the environmental variables to bear in mind when selecting analogous sampling points in a passive monitoring program. An approximation to predict tree injury may be obtained by measuring DW/FW ratio, proteins, pigments, HPCD, and MDA as they are responsible for the major variability of data.     

Dynamics and Causation of Environmental Equity, Locally Unwanted Land Uses, and Neighborhood Changes

/ Why are some environmental risks distributed disproportionately in the neighborhoods of the minorities and the poor? A hypothesis was proposed in a recent study that market dynamics contributed to the current environmental inequity. That is, locally unwanted land uses (LULUs) make the host communities home to more poor people and people of color. This hypothesis was allegedly supported by a Houston case study, whereby its author analyzed the postsiting changes of the socioeconomic characteristics of the neighborhoods surrounding solid waste facilities. I argue that such an analysis of postsiting changes alone is insufficient to test the causation hypothesis. Instead, I propose a conceptual framework for analysis of environmental equity dynamics and causation. I suggest that the presiting neighborhood dynamics and the characteristics of control neighborhoods be analyzed as the first test for the causation hypothesis. Furthermore, I present theories of neighborhood change and then examine alternative hypotheses that these theories offer for explaining neighborhood changes and for the roles of LULUs in neighborhood changes. These alternative hypotheses should be examined when analyzing the relationship between LULUs and neighborhood changes in a metropolitan area. Using this framework of analysis, I revisited the Houston case. First, I found no evidence that provided support for the hypothesis that the presence of LULUs made the neighborhoods home to more blacks and poor people, contrary to the conclusion made by the previous study. Second, I examined alternative hypotheses for explaining neighborhood changes-invasion-succession, other push forces, and neighborhood life-cycle; the former two might offer better explanation.KEY WORDS: Environmental equity and justice; Locally unwanted lane uses; Siting; Market dynamics; Invasion-succession; Neighborhood changes     

全程自养颗粒污泥快速启动及混合营养型脱氮性能分析

在连续流条件下,基于颗粒污泥全程自养脱氮（CANON）工艺的快速启动和混合营养条件下高效脱氮,是CANON工程应用的重要环节.本研究在气提内循环反应器（AIR）中,以老化的CANON颗粒污泥经机械破碎至0.3 mm作为种泥,实现混合营养型单级颗粒污泥同步脱氮除碳.启动26 d,通过控制DO,系统出现稳定的部分硝化,再缩短HRT提升氨氮负荷至5.65 kg ·（m³ ·d）^-1,促进颗粒化和厌氧氨氧化;第68 d,总氮去除率达到58%之后,进水加入有机物,C/N从0提升到0.25和0.5,促进AOB、AMX和异养微生物的协同,氨氮去除率达95%,总氮去除率达85%,COD去除率达80%左右.COD浓度增加,能较好地抑制Nitrospira菌属等NOB的活性,q（NH₄⁺-N）和q（TN）稳定在0.4 g ·（g ·h）^-1和0.34 g ·（g ·h）^-1,q（NO₃^--N）约为0.02 g ·（g ·h）^-1.采用MiSeq高通量测序对微生物多样性分析,表明有机物对污泥中Nitrosomomas和Candidutus_Kuenenia丰度未产生显著影响,增加了Candidutus_Brocadia菌属以及具有反硝化功能Denitratisoma等菌属的丰度.这对于快速启动连续流CANON颗粒污泥工艺处理低C/N比废水提供思路.     

不同碳源模式下酵母菌PNY2013同步脱氮除磷的应用研究

针对首次分离得到的一株具有同步脱氮除磷新功能的热带假丝酵母（Candida tropicalis） PNY2013,通过生理及动力学特征,连续流运行操作及其在含糖类工业废水中的应用3个环节,探讨了不同碳源模式下PNY2013同步脱氮除磷的特性.结果表明：PNY2013以葡萄糖、乙醇及乙酸为唯一碳源时均生长良好,其最大比增长速率μ_max分别为0.1327、0.1252及0.1115 h^-1,其同步脱氮除磷率分别可达100%、80%、100%（NH₄⁺-N）及93%、95%、98%（PO₄^3--P）.3种碳源下PNY2013同步脱氮除磷的最佳条件基本接近为：温度30℃,pH=8.0,溶解氧0~2 mg·L^-1,C/N=200∶5左右.PNY2013同步脱氮除磷的长期连续运行条件下的实验进一步表明,以葡萄糖为碳源条件下,进水NH₄⁺-N及PO₄^3--P浓度分别达400及80 mg·L^-1时,两者去除率均接近100%.与这种超强能力相比,以乙醇及乙酸为碳源条件下,进水NH₄⁺-N及PO₄^3--P浓度分别达100及20 mg·L^-1时,两者的去除率也可达60%~80%（NH₄⁺-N）及40%（PO₄^3--P）,显示出相当的同步脱氮除磷能力.在以模拟制糖废水、淀粉加工废水、啤酒废水、味精废水这4种典型含糖工业废水为碳源条件下,除淀粉加工废水外PNY2013均能有效去除COD、NH₄⁺-N和PO₄^3--P,其中,制糖、啤酒、制药废水中的COD去除率分别可达40%、89%、96%,NH₄⁺-N去除率分别为85%、94%、76%,PO₄^3--P去除率均为90%.即使在40000 mg·L^-1（制糖）及12500 mg·L^-1（啤酒）的高COD条件下,PNY2013也均具有稳定的NH₄⁺-N和PO₄^3--P去除效果,显示出良好的同步脱氮除磷应用前景.     

河岸过滤中氨氮的削减及其浓度对细菌与氨氧化微生物的影响

通过小试滤柱模拟河岸过滤,结合荧光定量PCR和高通量测序等手段研究了河岸过滤对氨氮的削减效能和进水氨氮浓度对细菌与氨氧化微生物的影响.结果表明,低浓度（0.2 mg·L^-1）氨氮未被削减,较高浓度（1.0 mg·L^-1和2.0 mg·L^-1）氨氮的削减率可达70%.进水处细菌丰度随氨氮浓度升高而增加,细菌群落组成随氨氮浓度升高发生规律性变化.出水处氨氧化古菌（Ammonia oxidizing archaea,AOA）丰度与氨氮浓度呈负相关,氨氧化细菌（Ammonia oxidizing bacteria,AOB）丰度与氨氮浓度无显著相关关系;进水处AOA-α多样性与氨氮浓度呈正相关,但AOB-α多样性与氨氮浓度呈负相关;进水处AOA群落组成受氨氮浓度影响,而进、出水处AOB群落组成均受氨氮浓度影响.可见,进水氨氮浓度会影响河岸过滤对氨氮的削减效能,还会影响细菌、氨氧化微生物的丰度及群落结构,AOB对氨氮浓度的变化比AOA更敏感.     

水库沉积物贫营养型好氧反硝化菌(Pseudomonas sp.)分离及其对微污染水体脱氮效率分析

为探究深水水库沉积物微生物功能特征及利用价值,于2019年在实验室对小湾水库表层沉积物微生物进行了驯化分离,并分析了其中一株细菌的脱氮效率.结果表明,分离出的细菌XW731经鉴定属于假单胞菌属（Pseudomonas sp.）,是一种贫营养型好氧反硝化菌;在分别以NH₄⁺-N、NO₃^--N和NO₂^--N为唯一氮源时,该菌对NH₄⁺-N、NO₃^--N和NO₂^--N去除率分别为33.6%、68.5%和9.1%;以NH₄⁺-N和NO₃^--N为氮源时,对NH₄⁺-N和NO₃^--N去除率分别为66.4%、89.6%,同步硝化反硝化能力更强.将该菌投加到两种城市微污染水体后测试表明,该菌对城市河道水体的NH₄⁺-N和NO₃^--N去除率分别为38.3%和42.4%,对城市降雨水体的NH₄⁺-N和NO₃^--N去除率分别为22.2%和7.7%.     

Long-term effects of silver nanoparticles on performance of phosphorus removal in a laboratory-scale vertical flow constructed wetland

Silver nanoparticles(AgNPs) have been widely used in many fields,which raised concerns about potential threats to biological sewage treatment systems.In this study,the phosphorus removal performance,enzymatic activity and microbial population dynamics in constructed wetlands(CWs) were evaluated under a long-term exposure to Ag NPs(0,50,and 200 μg/L) for 450 days.Results have shown that Ag NPs inhibited the phosphorus removal efficiency in a short-term exposure,whereas caused no obviously negative effects from a long-term perspective.Moreover,in the coexisting CW system of Ag NPs and phosphorus,competition exhibited in the initial exposure phase,however,cooperation between them was observed in later phase.Enzymatic activity of acid-phosphatase at the moderate temperature(10–20°C) was visibly higher than that at the high temperature(20–30℃) and CWs with Ag NPs addition had no appreciable differences compared with the control.High-throughput sequencing results indicated that the microbial richness,diversity and composition of CWs were distinctly affected with the extension of exposure time at different Ag NPs levels.However,the phosphorus removal performance of CWs did not decline with the decrease of polyphosphate accumulating organisms(PAOs),which also confirmed that adsorption precipitation was the main way of phosphorus removal in CWs.The study suggested that Ag NPs and phosphorus could be removed synergistically in the coexistence system.This work has some reference for evaluating the influences of Ag NPs on the phosphorus removal and the interrelation between them in CWs.     

Removal and desorption of chromium in synthetic effluent by a mixed culture in a bioreactor with a magnetic field

Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0.The objective was to remove Cr(Ⅵ) and total Cr from the effluent,this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(Ⅵ) in a bioreactor with neodymium magnets that applied a magnetic field(intensity85.4 mT) to the mixed culture.The removal of Cr(Ⅵ) was approximately 100.0% for the bioreactor with a magnetic field and 93,3% for the bioreactor without a magnetic field for9 hr of recirculation of the synthetic effluent by the bioreactor.The removal of total Cr was61.6% and 48.4%,with and without a magnetic field,respectively;for 24 hr.The desorption of Cr(VI) in the synthetic effluent was 0.05 mg/L,which is below the limit established by Brazilian legislation(0.1 mg/L) for the discharge of effluent containing Cr(Ⅵ) into bodies of water.The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture.The desorption of Cr(Ⅵ) in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.     

Recent advances in catalytic decomposition of ozone

Ozone (O₃), as a harmful air pollutant, has been of wide concern. Safe, efficient, and economical O₃ removal methods urgently need to be developed. Catalytic decomposition is the most promising method for O₃ removal, especially at room temperature or even subzero temperatures. Great efforts have been made to develop high-efficiency catalysts for O₃ decomposition that can operate at low temperatures, high space velocity and high humidity. First, this review describes the general reaction mechanism of O₃ decomposition on noble metal and transition metal oxide catalysts. Then, progress on the O₃ decomposition performance of various catalysts in the past 30 years is summarized in detail. The main focus is the O₃ decomposition performance of manganese oxides, which are divided into supported manganese oxides and non-supported manganese oxides. Methods to improve the activity, stability, and humidity resistance of manganese oxide catalysts for O₃ decomposition are also summarized. The deactivation mechanisms of manganese oxides under dry and humid conditions are discussed. The O₃ decomposition performance of monolithic catalysts is also summarized from the perspective of industrial applications. Finally, the future development directions and prospects of O₃ catalytic decomposition technology are put forward.