Influence of atmospheric stability on the mass concentration and chemical composition of atmospheric particles: a case study in Rome, Italy

PM(10) concentration and chemical composition (ions and carbon compounds) at three sampling stations in Rome and in its surroundings was determined daily during a one-month field study, carried out during December 2003. PM concentration at the traffic station was considerably higher than at the urban background and semi-rural stations; elemental carbon was detected as one of the chemical components responsible for this increase. The difference in the concentration of sulphate and ammonium was negligible, as it was expected for secondary pollutants. A negative artefact in the determination of ammonium nitrate by means of heated automatic monitors was highlighted. The dilution properties of the lower atmosphere were traced by means of a natural radioactivity monitor. This parameter has been found to play an essential role in pollution buildup. A considerable increase in PM concentration was observed to coincide with periods of atmospheric stability. The main difference in PM composition between periods of high concentration and periods of "clean" air was found to be in the increase of ammonium nitrate concentration.     

三峡小流域水体硝态氮含量变化特征及其影响因素研究

为了解三峡地区典型农业流域水体水质状况以及对流域各影响因素的响应,在2004年和2005年间,对三峡库区内长江一级支流曲溪的水体硝态氮含量进行了连续监测,利用划分子流域的方法,分析了该流域异质景观条件下溪流水硝态氮含量的变化特征.结果表明,该流域溪流水体中硝态氮含量变化在0.4～14.6 mg·L-1之间,且其含量冬季＞秋季＞夏季＞春季,年际之间也存在着一定的差异,随着农业活动对环境影响的日益加剧水体中硝态氮含量还有加大的趋势;在该流域内水体硝态氮含量与不同类型的土地利用之间存在不同程度的相关性;而且流域内地质水文特征等环境因素对水体硝态氮含量有一定的影响,说明在流域尺度上水体硝态氮含量对影响因素的响应是明显的.     

不同形态氮转化对啶虫脒在水溶液中光解的影响

模拟研究了环境中氮发生形态转化时对啶虫脒在水体中光解的影响.结果表明,啶虫脒的光解反应符合一级动力学规律.pE反映了体系的氧化还原性,环境pE值较低时,无机氮主要以NH4+形式存在,对啶虫脒光解几乎没有影响;;随着pE值的提高,无机氮逐渐由NH4+形式向NO2-和NO3-形式转化,NO2-、NO3-的存在均对啶虫脒的光解有抑制作用,它们对啶虫脒光解的抑制是由于对光辐射的竞争性吸收所引起的.多种形态无机氮共存时,其对啶虫脒光解的抑制作用不是简单的加和关系,各形态无机氮之间存在一定的拮抗作用.当环境pE值达到7.2后,无机氮主要以NO3-形式存在,其对啶虫脒光解的抑制率最高可达36.71%.     

腐殖酸缓效肥料的NO_3~--N田间淋溶及土壤残留

为探讨腐殖酸缓效肥料对地下水及土壤质量的潜在影响,分别在砂质(SS)和黏质土壤(CS)中,利用自制田间淋溶设备研究了不同肥料处理的NO3--N淋溶及土壤残留特性.结果表明,在2种不同质地土壤中,不同时间施肥处理淋溶液中的NO3--N浓度比不施氮肥处理高28.1%～222.2%,但腐殖酸缓效肥料可在一定程度上抑制NO3--N的向下淋溶,且在CS土壤中的抑制作用更有持续性.CS土壤淋溶液中NO3--N的浓度比SS土壤降低41.2%～59.1%,抑制NO3--N向下淋失的作用更强.施肥可造成NO3--N在土壤剖面中的累积,腐殖酸缓效肥料处理0～40cm土壤剖面中NO3--N所占比例显著高于尿素及复合肥处理,分别达59.8%和54.4%.SS土壤中NO3--N的总量显著低于CS土壤,HA缓施肥、尿素及复合肥处理分别降低81.7%、81.1%和47.6%.同常规施肥处理相比,腐殖酸缓效肥料处理可不同程度的提高土壤有机质、碱解氮、速效磷及阳离子交换量的含量,且在黏质土壤中水溶性盐总量比尿素及复合肥处理分别降低24.8%和22.5%.因此,施用腐殖酸缓效肥料可有效改善土壤理化性状、降低施肥对地下水等造成的潜在污染风险.     

高铁酸钾制备影响因素的实验研究

文章介绍了湿法制备高铁酸钾的工艺,研究了次氯酸盐浓度、氧化反应温度、铁盐原料选择、洗涤所用溶剂种类等对高铁酸钾纯度和产率的影响。实验表明在制备次氯酸盐溶液时用冰水浴反应温度控制为20℃,选用37.5%的KOH溶液,可制得ClO-质量分数为123.5 g/L的饱和次氯酸钾溶液。实验还表明制备高铁酸钾的最佳反应时间为45 min,硝酸铁投加量为化学计量的80%时,可得到纯度为80%～90%、产率为71%的高铁酸钾固体产物。通过实验提出在0℃饱和的氢氧化钾溶液中不断搅拌,高铁酸钾晶体可以充分析出。     

利用可生物降解聚合物为碳源和生物膜载体脱氮及其动力学特性研究

以闭合循环养殖系统去除硝酸盐为目的,研究了以一种非水溶性可生物降解多聚物材料(BDPs)PBS颗粒作为反硝化碳源和生物膜载体的填料床反应器对于废水中硝酸盐的去除效果及动力学特征.结果表明,在温度为(29±1)℃,进水NO 3--N浓度为25～334 mg/L的条件下,进水NO 3--N负荷0.107～1.098 kg/(m3.d)为最适进水负荷.当进水负荷为1.098 kg/(m3.d)时,可达到最大NO 3--N体积去除负荷0.577 kg/(m3.d).进一步增加进水NO 3--N负荷则NO 3--N体积去除负荷开始下降.动力学研究结果表明,以PBS作为碳源和生物膜载体的反硝化速率遵循一级反应动力学.用Eckenfelder模型拟合,并求出常数n值和K值,建立的动力学模型采用该参数可以预测出水NO 3--N浓度.对模型的预测值与实际值采用统计软件SPSS16.0做方差分析表明,p0.05,分别为p=0.5530.05和p=0.6320.05,模型预测值与实际值无显著性差异.     

Effect of elevated tropospheric ozone on methane and nitrous oxide emission from rice soil in north India

Physiological changes in crop plants in response to the elevated tropospheric ozone (O₃) may alter N and C cycles in soil. This may also affect the atmosphere-biosphere exchange of radiatively important greenhouse gases (GHGs), e.g. methane (CH₄) and nitrous oxide (N₂O) from soil. A study was carried out during July to November of 2007 and 2008 in the experimental farm of Indian Agricultural Research Institute, New Delhi to assess the effects of elevated tropospheric ozone on methane and nitrous oxide emissions from rice (Oryza sativa L.) soil. Rice crop was grown in open top chambers (OTC) under elevated ozone (EO), non-filtered air (NF), charcoal filtered air (CF) and ambient air (AA). Seasonal mean concentrations of O₃ were 4.3 ± 0.9, 26.2 ± 1.9, 59.1 ± 4.2 and 27.5 ± 2.3 ppb during year 2007 and 5.9 ± 1.1, 37.2 ± 2.5, 69.7 ± 3.9 and 39.2 ± 1.8 ppb during year 2008 for treatments CF, NF, EO and AA, respectively. Cumulative seasonal CH₄ emission reduced by 29.7% and 40.4% under the elevated ozone (EO) compared to the non-filtered air (NF), whereas the emission increased by 21.5% and 16.7% in the charcoal filtered air (CF) in 2007 and 2008, respectively. Cumulative seasonal emission of N₂O ranged from 47.8 mg m⁻² in elevated ozone to 54.6 mg m⁻² in charcoal filtered air in 2007 and from 46.4 to 62.1 mg m⁻² in 2008. Elevated ozone reduced grain yield by 11.3% and 12.4% in 2007 and 2008, respectively. Global warming potential (GWP) per unit of rice yield was the least under elevated ozone levels. Dissolved organic C content of soil was lowest under the elevated ozone treatment. Decrease in availability of substrate i.e., dissolved organic C under elevated ozone resulted in a decline in GHG emissions. Filtration of ozone from ambient air increased grain yield and growth parameters of rice and emission of GHGs.     

微生物铁氧化作用对砷迁移转化的影响

采用厌氧培养的方法,从砷污染的水稻上中富集依赖硝酸盐的铁氧化菌群,通过监测培养体系中Fe和A$的形态变化模拟水稻厌氧条件下微生物铁氧化过程对As迁移转化的影响.结果表明,约96%外源添加的Fe(Ⅱ)可在10d内氧化成Fe(Ⅲ),As(Ⅲ)对Fe(Ⅱ)的初期氧化速率具有一定的抑制作用;在微生物铁氧化过程中,As(Ⅲ)被氧...     

Pd/TiO2-SnO2催化还原硝酸盐效能及反应调控

采用共沉淀法制备了掺杂TiO2的复合载体TiO2-SnO2;浸渍法制备了单金属负载型催化剂Pd/TiO2-SnO2.用X射线衍射（XRD）、X射线光电子能谱（XPS）、比表面仪（BET）和透射电镜（TEM）表征表明Pd和TiO2在SnO2上成单层或亚单层分散,增加了反应活性位.催化剂分散性良好,比表面积为100.8m....     

Autotrophic denitrification for nitrate and nitrite removal using sulfur-limestone

In the study, both nitrate and nitrite could be removed effectively using sulfur-limestone, and the bacteria involved in sulfur-based denitrification for nitrate and nitrite removal were of the same species.