塔里木盆地北缘绿洲不同连作年限棉田土壤有机碳、无机碳含量与环境因子的相关性

农田土壤碳库是土壤碳库的重要组成部分,易受人类活动调节且固碳减排潜力巨大,研究土壤有机碳、无机碳含量特征及其与环境因子的关系有助于深入理解土壤生态过程,为全球碳收支平衡研究提供理论支持.本文以塔里木盆地北缘绿洲为靶区,分析土壤碳库特征,结合冗余分析、通径分析,探究土壤有机碳、无机碳含量及其与环境因子的相关关系.结果表明:(1)同一土层不同连作年限棉田土壤有机碳、无机碳含量存在显著差异(P0.05),随连作年限增加,有机碳含量呈先增加后减少趋势,而无机碳含量呈先减少后增加趋势;同一连作年限棉田不同土层土壤有机碳、无机碳含量存在显著差异(P0.05),有机碳含量均在0~20 cm层达到最大值,而无机碳含量均在20~50 cm层达到最大值.(2)通过冗余分析得出环境因子对土壤碳库特征影响的重要性排序为:磷酸酶活性p H值蔗糖酶活性过氧化氢酶活性全氮速效磷速效钾土壤含水量脲酶活性电导率;磷酸酶活性、p H值、蔗糖酶活性、过氧化氢酶活性、全氮、速效磷、速效钾与土壤有机碳、无机碳含量呈极显著相关关系(P0.01);土壤含水量、脲酶活性与土壤有机碳、无机碳含量表现为显著相关(P0.05).(3)通径分析表明,速效钾对有机碳含量直接作用显著,是影响有机碳含量的主要因素,而脲酶活性对无机碳含量直接作用显著,是影响无机碳含量的主要因素.干旱半干旱区土壤有机碳、无机碳含量研究是评价农田生态系统土壤碳的"源/汇"效应的基础数据,对研究全球碳收支平衡和陆地碳循环机制具有重要意义.     

南京冬季气溶胶光学特性及黑碳光吸收增强效应

2016年1月1~19日在南京北郊利用三波长光声黑碳光度仪(PASS-3)对气溶胶的光学性质进行了实时在线观测,同时结合气溶胶化学组成分析了黑碳气溶胶的光吸收增强效应.结果表明,观测期间气溶胶在532 nm下的吸收系数、散射系数、单散射反照率的平均值为(64.19±35.28)Mm-1、(454.68±238.71)Mm-1、0.87±0.03,受边界层高度及颗粒物浓度的影响,呈现出明显的日变化特征.黑碳气溶胶的质量吸收截面(MAC)在观测期间的变化趋势为前期低,后期高,与非EC组分相对EC比值的变化趋势一致,受不同污染条件下二次物质的占比及覆盖物厚度变化的影响.基于MAC计算得到的405、532、781nm下的光吸收增强(EMAC)平均值分别为1.53±0.56、1.34±0.47、1.14±0.40,随着波长增加而降低,存在棕色碳(Br C)的贡献.各非EC组分相对EC的比值与EMAC均有一定相关性,其中OC/EC与EMAC相关性最高,说明有机物的积累是导致黑碳光吸收增强的主要原因.K+/EC与EMAC的高相关性表明生物质燃烧过程对光吸收增强也有一定影响.     

钙法解吸并固定乙醇胺富液中CO2

针对醇胺类吸收剂富液中CO_2的解吸及后续处置所存在的不足,提出一种新型解吸方案——钙法.通过CO_2负荷试验和Ca(OH)_2投加量试验确定了该法理想处理负荷为0.84 mol·L-1,理想投加比例为C∶Ca=1∶1(摩尔比),此条件下反应15 min和30 min的解吸率达到52.17%和55.02%,这表明钙法矿化解吸乙醇胺富液中CO_2是可行的.在此基础上,进一步研究了pH、温度和搅拌强度对CO_2解吸固定效果的影响.试验结果表明,CO_2解吸率随着pH和搅拌强度的增加而增大,但当pH和搅拌强度增大到一定程度后,解吸率增长放缓甚至出现下降.较高的解吸温度尽管解吸率更大,但高温条件下无法达到矿化固定CO_2的目的.CO_2二次吸收负荷试验表明经钙法解吸后的MEA再生液具有良好的可重复使用性.     

Simultaneous removal of ammonia and N-nitrosamine precursors from high ammonia water by zeolite and powdered activated carbon

When adding sufficient chlorine to achieve breakpoint chlorination to source water containing high concentration of ammonia during drinking water treatment, high concentrations of disinfection by-products(DBPs) may form. If N-nitrosamine precursors are present, highly toxic N-nitrosamines, primarily N-nitrosodimethylamine(NDMA), may also form. Removing their precursors before disinfection should be a more effective way to minimize these DBPs formation. In this study, zeolites and activated carbon were examined for ammonia and N-nitrosamine precursor removal when incorporated into drinking water treatment processes.The test results indicate that Mordenite zeolite can remove ammonia and five of seven N-nitrosamine precursors efficiently by single step adsorption test. The practical applicability was evaluated by simulation of typical drinking water treatment processes using six-gang stirring system. The Mordenite zeolite was applied at the steps of lime softening, alum coagulation, and alum coagulation with powdered activated carbon(PAC) sorption. While the lime softening process resulted in poor zeolite performance, alum coagulation did not impact ammonia and N-nitrosamine precursor removal. During alum coagulation, more than67% ammonia and 70%–100% N-nitrosamine precursors were removed by Mordenite zeolite(except 3-(dimethylaminomethyl)indole(DMAI) and 4-dimethylaminoantipyrine(DMAP)). PAC effectively removed DMAI and DMAP when added during alum coagulation. A combination of the zeolite and PAC selected efficiently removed ammonia and all tested seven N-nitrosamine precursors(dimethylamine(DMA), ethylmethylamine(EMA), diethylamine(DEA), dipropylamine(DPA), trimethylamine(TMA), DMAP, and DMAI) during the alum coagulation process.     

生物质基活性炭负载金属催化还原NOx

为研究生物质材料的脱硝性能,利用木质素与纤维素2种生物质基活性炭作为还原剂,用碱金属与过渡金属作为催化活性相,制备了一系列生物质基活性炭负载金属催化剂用于富氧环境中催化还原NO_x,考察了生物质原料种类、炭化温度以及催化剂组分对脱硝效率的影响.结果表明:①当反应温度低于250℃时,炭表面主要是NO_x的吸附过程;而当反应温度高于250℃时,炭还原NO_x行为占主导,并伴随N₂、CO₂与CO的生成.炭化温度对炭反应活性的影响主要依赖于炭化温度对炭材料表面含氧官能团、比表面积以及炭表面金属还原性的影响.②研究中考察的金属（K、Cu、Fe、Ni）均对还原NO_x与O₂有催化作用,其中,K对C-NO_x反应具有明显促进作用,但对C-O₂反应并无明显促进作用,所有样品中SAC-K的选择性因子为0.56,对还原NO_x的选择性最高,且恒温反应过程NO_x还原量（以C计）达到了1 293 μmol/g.③与传统煤基活性炭催化剂相比,木屑基活性炭负载钾催化剂表现出了优良的NO_x还原选择性;X-射线光电子表征结果显示,木屑基活性炭负载钾催化剂优良的性能与其表面钾活性相的高度分散有关.研究显示,相比于煤基炭材料,生物质基炭材料具有更加优异的选择性还原NO_x性能.      

天津市区夏季碳气溶胶特征及改进的二次有机碳估算方法

为更加准确地估算环境受体PM_2.5中SOC（二次有机碳）的质量浓度,于2015年6-8月利用在线监测仪器同步采集小时分辨率的PM_2.5及OC（有机碳）和EC（元素碳）样品数据,分析碳气溶胶的变化特征,并尝试运用改进的EC示踪法估算ρ（SOC）.结果表明:天津市区夏季ρ（PM_2.5）为（70.9±46.0）μg/m3,ρ（OC）和ρ（EC）分别为（7.6±3.1）（2.2±1.5）μg/m3,占ρ（PM_2.5）的11.8%±4.6%和3.1%±1.4%,OC/EC（质量浓度之比,下同）的平均值为4.0±2.0.ρ（OC）与ρ（EC）之间的Pearson相关系数（R）仅为0.66,说明OC和EC的来源较为复杂,SOC的产生可能是重要影响因素.ρ（NO₂）与OC/EC呈显著负相关（R=-0.47,P < 0.01）,并且OC/EC（4.0）相对较低,说明天津市区机动车可能对碳气溶胶具有重要影响.ρ（SO₂）与ρ（OC）、ρ（EC）的相关性较低（R均为0.33,P均小于0.01）,说明天津市区碳气溶胶可能受燃煤源的影响较低.改进的EC示踪法主要是利用O₃和CO、EC作为光化学反应和一次源排放的指标,并结合ρ（OC）、ρ（EC）和OC/EC的变化特征,逐步筛选一次排放源主导的时间段的ρ（OC）和ρ（EC）数据,然后利用最小二乘法拟合获得ρ（OC）和ρ（EC）的线性方程,最后进行ρ（SOC）和ρ（POC）（POC为一次有机碳）的估算.天津市区夏季ρ（SOC）的平均值为（2.5±2.0）μg/m3,分别占ρ（OC）和ρ（PM_2.5）的28.8%±15.0%和3.7%±3.6%;ρ（POC）的平均值为（5.2±1.7）μg/m3,分别占ρ（OC）和ρ（PM_2.5）的71.2%±15.0%和8.1%±5.2%,说明天津市区夏季有机碳的主要来源是一次排放源.研究显示,相比于EC示踪法,改进的EC示踪法估算的ρ（SOC）明显降低,ρ（POC）明显升高.AT（大气温度）对ρ（SOC）的影响较为显著,而WS（风速）对ρ（POC）的影响较为显著.      

基于土地利用变更调查的2010-2016年新疆尉犁县生态系统碳储量时空变化

为全面认识干旱区不同土地利用类型时空变化对区域生态系统碳储量的影响,以地处塔克拉玛干沙漠边缘生态脆弱区的新疆尉犁县为研究对象,基于详细的土地利用变更调查数据（2010-2016年）,利用ArcGIS平台和InVEST模型,分析生态系统碳储量对土地利用变化尤其是二级土地利用类型变化的响应.结果表明:①研究区内,无论是区域平均碳密度还是灌木林地、其他林地、其他草地等主要土地利用类型的碳密度均较低,而面积较少的有林地和天然牧草地碳密度相对较高,因此对这些土地利用类型应着重加强保护.②2010-2016年新疆尉犁县碳存储量净减少24.23×104 t,这主要是由于其他草地、其他园地和果园等土地利用类型被开垦为水浇地,或被建设用地、交通用地占用所导致,而同时研究区内有林地和水浇地面积增加带来了碳储量的提高.③从空间变化看,受不同区域土地利用变化方式的影响,碳储量变化特征也有显著差异,但总体上变化敏感区域集中在塔里木河周边县、乡镇及兵团所在地等人类活动聚集区,这些区域平均碳密度较高,土地利用变化也更为剧烈.④尽管由于开垦行为带来耕地面积增加,从而使得研究区耕地总碳储量增加242.77×104 t,但由于塔里木河沿岸碳密度较高的耕地被建设用地占用,新增耕地多来源于土壤碳储量较低的其他草地等土地利用类型,导致耕地平均碳密度有所下降.研究显示,建设用地占用耕地、林地、草地等地类是尉犁县碳储量减少的重要原因,而林业建设能够带来碳储量增加.因此建议:一方面,推进林、草地建设提高区域生态系统固碳能力;另一方面,重点保护塔里木河周边碳密度较高区域,严控耕地开垦或建设用地占用,同时加强耕地保护,防止通过补充碳密度较低的耕地来弥补碳密度较高区域耕地的流失.      

Characterization particulate matter from several Chinese cooking dishes and implications in health effects

Cooking fume produced by oil and food at a high temperature releases large amount of fine particulate matter(PM) which have a potential hazard to human health. This chamber study investigated particle emission characteristics originated from using four types of oil(soybean oil, olive oil, peanut oil and lard) and different kinds of food materials(meat and vegetable). The corresponding emission factors(EFs) of number, mass, surface area and volume for particles were discussed. Temporal variation of size-fractionated particle concentration showed that olive oil produced the highest number PM concentration for the entire cooking process. Multiple path particle dosimetry(MPPD) model was performed to predict deposition in the human respiratory tract. Results showed that the pulmonary airway deposition fraction was the largest. It was also found that particles produced from olive oil led to the highest deposition. We strongly recommend minimizing the moisture content of ingredients before cooking and giving priority to the use of peanut oil instead of olive oil to reduce human exposure to PM.     

Insights into the formation of secondary organic carbon in the summertime in urban Shanghai

To investigate formation mechanisms of secondary organic carbon(SOC) in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O_3 concentrations(daily peak 120 ppb) was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/(C·m~3). Diurnal variations of SOC concentration and SOC/organic carbon(OC) ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with O_x(= O_3+ NO_2) and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon(EC) particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe(III) complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity.     

埃格草(Egeria densa)对铵氮胁迫的生长和生理响应

为了解富营养水体中NH₄+-N胁迫对埃格草（Egeria densa）的影响,通过室外模拟试验,研究了埃格草在不同ρ（NH₄+-N）（0、0.5、2.0 mg/L）下的RGR（relative growth rate,相对生长率）、R/S（root/shoot ratio,根冠比）、w（SC）（SC为可溶性糖,soluble sugar）、w（淀粉）、w（蔗糖）、w（FAA）（FAA为游离氨基酸,free amino acid）、w（NH₄+-N）和w（NO₃--N）的变化.结果表明:随着外源ρ（NH₄+-N）的增加,埃格草的RGR和R/S呈降低的趋势,并且在ρ（NH₄+-N）为2.0 mg/L时显著降低（RGR为P < 0.001,R/S为P < 0.05）;埃格草中w（SC）和w（淀粉）在ρ（NH₄+-N）为0.5和2.0 mg/L下有不同程度显著降低[w（SC）为P < 0.01和P < 0.001,w（淀粉）为P < 0.001和P < 0.05],w（蔗糖）在ρ（NH₄+-N）为2.0 mg/L时显著降低（P < 0.001）;w（FAA）和w（NH₄+-N）有随外源ρ（NH₄+-N）升高而升高的趋势,并且在ρ（NH₄+-N）为2.0 mg/L时升高显著[w（FAA）为P < 0.01,w（NH₄+-N）为P < 0.05];w（NO₃--N）在ρ（NH₄+-N）为0.5和2.0 mg/L下有不同程度显著降低（P < 0.01和P < 0.001）.相关分析表明,w（SC）、w（淀粉）和w（蔗糖）之间呈显著正相关,三者与w（FAA）和w（NH₄+-N）之间均呈显著负相关,而与w（NO₃--N）呈显著正相关;w（FAA）和w（NH₄+-N）呈显著正相关,而二者与w（NO₃--N）均呈显著负相关.研究显示,NH₄+-N影响埃格草的生长,导致C-N代谢的不平衡.