饱和持水量条件下不同氮添加对森林土壤氮素净转化的影响

为了研究在饱和持水量条件下不同氮沉降形态和水平对森林土壤氮素净转化及土壤N₂O排放的影响,选取中亚热带地带性森林红壤为研究对象,采用室内模拟试验方法,设置110%饱和持水量（WHC）的土壤水分,添加不同形态氮[（NH₄）₂SO₄、NaNO₃、NH₄NO₃]和不同含量[0 mg/kg（CK）、20.0 mg/kg（LN）、66.7 mg/kg（HN）,以干土计]的氮素,进行为期14 d的室内培养（20℃）.结果表明,与CK相比,（NH₄）₂SO₄和NaNO₃处理对土壤净氮矿化和氨化的影响不大,而（NH₄）₂SO₄处理的净硝化量在高氮水平下为负值,说明硝化很弱,但该处理的净氨化量高于其他处理,特别是NaNO₃处理的净氨化量较高,认为很可能存在NO₃--N异化还原为铵（DNRA）.NaNO₃处理能显著提高土壤净硝化量而显著降低w（SON）（SON为土壤可溶性有机氮）,NH₄NO₃处理同时降低了土壤w（NH₄+-N）和w（NO₃--N）,表现为氮固定作用,并且高氮水平的土壤w（MBN）（MBN为微生物量氮）显著高于低氮水平;NaNO₃和NH₄NO₃处理的土壤N₂O排放速率和培养周期内的累积排放量均显著高于CK,并且高氮水平显著高于低氮水平,而（NH₄）₂SO₄处理与CK相当,并且高氮水平下的N₂O累积排放量低于低氮水平.研究显示,在过饱和土壤水分条件下,混合形态氮对土壤氮素净转化格局影响较大,含NO₃-形态氮明显促进土壤N₂O的排放,尤其是高氮水平.研究结果可为评价全球气候变化下特别是降雨情况下沉降氮形态对土壤氮素转化的影响提供重要参考.      

Effect of lubricant sulfur on the morphology and elemental composition of diesel exhaust particles

This work investigates the effects of lubricant sulfur contents on the morphology, nanostructure, size distribution and elemental composition of diesel exhaust particle on a light-duty diesel engine. Three kinds of lubricant (LS-oil, MS-oil and HS-oil, all of which have different sulfur contents: 0.182%, 0.583% and 1.06%, respectively) were used in this study. The morphologies and nanostructures of exhaust particles were analyzed using high-resolution transmission electron microscopy (TEM). Size distributions of primary particles were determined through advanced image-processing software. Elemental compositions of exhaust particles were obtained through X-ray energy dispersive spectroscopy (EDS). Results show that as lubricant sulfur contents increase, the macroscopic structure of diesel exhaust particles turn from chain-like to a more complex agglomerate. The inner cores of the core-shell structure belonging to these primary particles change little; the shell thickness decreases, and the spacing of carbon layer gradually descends, and amorphous materials that attached onto outer carbon layer of primary particles increase. Size distributions of primary particles present a unimodal and normal distribution, and higher sulfur contents lead to larger size primary particles. The sulfur content in lubricants directly affects the chemical composition in the particles. The content of C (carbon) decreases as sulfur increases in the lubricants, while the contents of O (oxygen), S (sulfur) and trace elements (including S, Si (silicon), Fe (ferrum), P (phosphorus), Ca (calcium), Zn (zinc), Mg (magnesium), Cl (chlorine) and Ni (nickel)) all increase in particles.     

岩溶地区隧道施工对水环境影响评价指标体系的建立

随着人们环保意识的不断提高,交通隧道施工期对周边水环境的影响也日益受到关注。针对岩溶地区隧道的施工特点建立了隧道施工期对水环境影响的评价指标体系。该体系研究了施工中含污废水排放对地表水体污染以及地下水疏排给隧道周边水资源流失两方面进行评价;指标体系各层指标数量随施工进展与现场情况变化进行增减,以满足施工期不断变化情况对水环境影响大小的准确评估;该指标体系充分考虑到"木桶理论"的原理,明确施工过程中对水环境影响最严重环节,有助于及时采取保护措施。     

Ti/SnO_2-Sb阳极-空气阴极电催化降解染料废水

为解决电化学法处理高盐染料废水存在的能耗大、成本高等问题,分别采用溶胶-凝胶法和辊压法制备Ti/SnO_2-Sb阳极和空气阴极,构建了Ti/SnO_2-Sb阳极-空气阴极双极体系(TSSA-ADC)。甲基橙(MO)作为高盐染料废水的典型污染物,考察了电流强度、MO浓度、电解液浓度和初始p H对TSSA-ADC体系和TSSA单阳极体系降解MO的影响。结果表明:与TSSA单阳极体系相比,TSSA-ADC体系具有更好的抗有机负荷冲击、抗盐分冲击、抗酸碱波动能力,能够维护酸碱平衡防止硬度离子结垢。最佳反应条件为电流强度为0.030 A,电解液浓度为3%,MO浓度为100 mg/L,初始pH=6。以MO去除率达到98%为基准,TSSA-ADC体系比TSSA体系可节能74.26%。     

煤制烯烃废水处理与回用技术解析

针对煤制烯烃项目废水的来源及水质特点,从生化处理技术与回用处理技术方面阐述了煤制烯烃废水处理现状及存在问题,展望了煤制烯烃废水处理与回用技术未来发展方向,指出了新型脱氮工艺、膜集成工艺及分质结晶技术在煤制烯烃废水处理中的可行性,为煤化工废水处理与资源化利用提供理论参考。     

蚯蚓-微生物协同作用过程中的微生物特性

在环境污染治理领域,被誉为"生态型工程师"的蚯蚓在污水/污泥资源化处理与处置,以及土壤的生态修复中备受关注。蚯蚓通过掘洞、摄食、分泌黏液和排泄蚓粪等方式调控系统中微生物的数量、活性及群落结构,与微生物协同互作强化了生物系统中物质转化与能量流动关系。蚯蚓-微生物协同共生的相互依存关系是此类技术展现低耗高效和生态友好特点的关键。通过综述经人工强化的蚯蚓-微生物互作生态系统中,蚯蚓对微生物的量、活性、群落结构以及食物网的影响,探讨了该生态系统中物质转化和能量流动的特点,并展望了蚯蚓-微生物互作技术研究及应用的发展方向。     

城市大气中臭氧浓度控制的困难与挑战——以成都市为例

研究城市化、工业化和区域经济一体化进程的不断加快,对城市大气环境的影响是当前大气环境领域研究的热点问题。在此过程中,利用空气质量模型模拟系统研究大气环境污染问题成为大气环境研究中不可缺少的组成部分。在当前空气污染复杂的形势下,针对城市大气环境中臭氧的浓度尚未有效的控制措施。研究主要利用Models-3/CMAQ空气质量模式对成都市臭氧浓度数值通过不同的控制情景进行模拟,揭示城市大气中臭氧浓度控制的困难与挑战,并尝试性提出今后的研究方向,以期为控制城市大气中臭氧浓度提供建议。     

碳酸钙改性硅藻土处理电解锌漂洗废水实验研究

铅锌矿在我国储存量大,电解法生产锌过程中可产生含Zn~(2+)、Pb~(2+)、Cd~(2+)、As5+和Cu~(2+)等重金属离子的漂洗废水。以硅藻土精土为基体,用碳酸钙作为改性剂制备改性硅藻土,对电解锌漂洗废水进行吸附实验研究。结果表明:在反应时间为150 min,碳酸钙改性硅藻土用量为3 g/L,pH为5.46,温度为25℃条件下,对废水进行吸附实验,吸附后废水中的Cu~(2+)和As5+离子浓度低于仪器检测线(0.01 mg/L和0.09 mg/L),Pb~(2+)浓度为0.16 mg/L,吸附后废水中Cu~(2+)、As5+和Pb~(2+)离子浓度均满足GB 25466—2010《铅锌工业污染物排放标准》的排放要求。同时,采用SEM、FTIR、XRD等对碳酸钙改性硅藻土进行表征,进一步探讨了碳酸钙改性硅藻土对重金属的吸附机理。     

一种简便高效的土壤石油烃提取方法的建立

通过开展单因子实验与正交实验,考察不同参数下超声萃取法对土壤中总石油烃(TPH)的提取效率,并对比了超声萃取法、超声-索氏萃取法及传统索氏萃取法对不同原油污染土壤的提取效果。结果表明:超声萃取法的最优工作参数为20 m L二氯甲烷,超声10 min,4000 r/min离心10 min,萃取4次。3种提取方法中,超声萃取法对石油烃平均回收率最高,为100.95%,而传统的索氏萃取法最低,仅为94.54%。可见,超声萃取法操作简单,效率高,可广泛用于土壤中总石油烃含量的提取测定。     

On the effect of Fe(III) on proliferation of Microcystis aeruginosa at high nitrate and low chlorophyll condition

The impact of Fe concentrations on the growth of Microcystisaeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density, total and cell chlorophyll-a intracellular Fe content and organic elemental composition of M. aeruginosa to different concentration gradients of Fe(III) in the solutions were analysed. The results showed that the proliferation speeds of M. aeruginosa were: (1) decelerated when the Fe(III) concentration was lower than 50 μg/L in the solutions, (2) promoted and positively related to the increase of Fe(III) concentration from 100 to 500 μg/L in the solutions over the experimental period, and (3) promoted in the early stage but decelerated in later stages by excess adsorption of Fe by cells when the Fe(III) concentration was higher than 500 μg/L in the solutions. The maximum cell density, total and cell chlorophyll-a were all observed at 500 μg Fe(III)/L concentration. The organic elemental composition of M. aeruginosa was also affected by the concentration of Fe(III) in the solutions, and the molecular formula of M. aeruginosa should be expressed as C_7–7.5H₁₄O_0.8–1.3N_3.5–5 according to the functions for different Fe(III) concentrations. Cell carbon and oxygen content appeared to increase slightly, while cell nitrogen content appeared to decrease as Fe(III) concentrations increased from 100 to 500 μg/L in the solutions. This was attributed to the competition of photosynthesis and nitrogen adsorption under varying cell Fe content.