O3浓度升高对南方城市绿化树种氮素的影响

近地层臭氧(O3)浓度升高会降低树木的光合速率,抑制Rubisco酶的活性,势必会间接影响树木N素的吸收与分配.本研究利用开顶式气室研究过滤大气(CF,<20 nL·L-1)与O3浓度升高(E-O3,约150 nL·L-1)对10种南方城市常用绿化树种幼苗N素吸收和分配的影响.结果表明,与CF相比,E-O3使枫香叶生物量和马褂木茎生物量分别显著降低了20.9%和21.4%,使枫香和马褂木的根生物量显著降低了24.2%和32.5%.O3对被测树种茎中N素含量影响显著,而对叶和根中N素含量无显著影响.O3对被测树种整株树N素吸收总量(Ntu)、叶片N素吸收量及根的N素吸收量存在显著影响,而对茎N素吸收量无显著影响.与CF相比,E-O3使马褂木与木荷的Ntu分别显著降低了28.4%与22.7%,而使舟山新木姜子Ntu显著增加了15.5%.O3浓度升高对各树种N素吸收量在各器官中的分配无显著影响.     

亚青会期间南京地区气溶胶浓度变化及其与能见度的关系

为保障2014年青奥会空气质量和制定控制措施提供科学支持,利用2013年8月南京市气溶胶的观测资料,结合气象要素,分析了南京地区气溶胶浓度变化特征,并深入研究了气溶胶质量浓度与相对湿度对能见度的影响.结果表明,观测期间PM10和PM2.5质量浓度平均值分别为67.44μg·m-3和31.92μg·m-3,0.1~10μm粒径范围内的气溶胶粒子数浓度和体积浓度的平均值分别为2466.25 cm-3和19.89μm3·cm-3;对数正态分布(log-normal)拟合平均谱分布得到两个模态的中值粒径分别为0.19μm和1.12μm;局地源强是影响南京气溶胶浓度的重要因子;PM10和PM2.5质量浓度日变化略有差异,PM10浓度日变化主要受交通和边界层活动影响,PM2.5浓度日变化则主要受交通排放和光化学反应生成的二次污染物的影响;对能见度的统计分析表明,能见度随PM2.5浓度和相对湿度的增加而降低,当相对湿度小于70%时,PM2.5浓度对能见度的影响较大,当相对湿度大于70%时,相对湿度对能见度的影响较大.     

UASBB厌氧氨氧化反应器处理污泥脱水液的影响因素研究

研究基质质量浓度、温度、pH值、HRT和C/N比对厌氧氨氧化脱氮性能的影响.试验水样采用污泥脱水液,控制进水ρ(NH+4-N)/ρ(NO-2-N)为1∶1.32,分别考察了在不同基质质量浓度、HRT、温度、pH值和C/N比的情况下,UASBB厌氧氨氧化反应器的脱氮性能.结果表明,在进水NH+4-N和NO-2-N质量浓度分别为200 mg·L-1和264 mg·L-1、HRT=24 h、温度为30～35℃、pH值为7.5～8.5、C/N比在0.5左右的条件下,厌氧氨氧化反应器的脱氮效果最佳,NH+4-N、NO-2-N和TN平均去除率分别达到75.72%、76.36%和70.19%,TN平均容积负荷可达0.464 kg·(m3·d)-1,COD平均去除率在30%左右.通过合理控制进水基质质量浓度和HRT能够有效地提高厌氧氨氧化反应器的脱氮性能.只有在适宜的温度和pH值范围内,厌氧氨氧化菌才能表现出较高的活性.当进水添加有机物时,厌氧氨氧化反应器中存在反硝化现象,且随着有机物质量浓度的升高,异养反硝化菌的竞争优势逐渐增强,对厌氧氨氧化产生明显的抑制作用.     

曝气加氢氧化钙复合技术抑制底泥磷释放及对底泥微生物多样性的影响

底泥磷释放是导致水体富营养化的主要原因之一,本文通过在样泥中分别投加0、0.01和0.02 mol·L-1Ca(OH)2溶液,同时进行微臭氧曝气(0.6 g·min-1),研究了曝气加氢氧化钙复合技术抑制底泥磷释放的效果及对底泥微生物多样性的影响.结果显示,投加0.02 mol·L-1Ca(OH)2组上覆水中总磷(TP)浓度的最终值与对照组相比,抑制率达到34%;从各形态磷的角度进一步分析发现,与对照组相比,该组底泥中可溶性磷和铁磷含量分别降低了92%和60%,其最终转化为钙磷是该技术的关键.通过聚合酶链式反应-变性梯度凝胶电泳技术(PCRDGGE)研究发现,各试验组微生物相似性在65%~85%之间;Berger-Parker优势度指数、Margalef丰富度指数、Shannon多样性指数变化不明显,表明该技术不会影响底泥微生物多样性.     

基于CMAQ模型的大连市大气氮湿沉降模拟研究

为了探讨大连市大气氮氧化物湿沉降的污染特征,通过监测站采集2012年内大连市的雨水样品,分析了氮氧化物的沉降浓度及沉降规律.同时,采用CMAQ模型MM5气象模式对大连市大气氮湿沉降进行了模拟研究,并在相关模拟模型的预报因子中增加氮氧化物污染源动态变化信息进行修正.结果表明:大连市大气氮湿沉降中硝酸根离子的平均当量浓度值为71.73μeq·L-1,铵根离子为98.91μeq·L-1;大连大气中氮氧化物沉降当量浓度随季节变化明显,且不同时期波动显著.CMAQ模型的模拟结果与实测数据相比存在偏差;经修正后模型模拟的结果更加逼近观测值,充分说明利用该修正模型在一定程度上修正了源清单不确定性对模拟结果造成的影响,利用修正后模型进行模拟具有可靠的准确性与可行性,可为大连市环境影响评估及控制效益评价提供科学依据.     

Characteristics of ozone and ozone precursors (VOCs and NOx) around a petroleum refinery in Beijing, China

A field measurement campaign for ozone and ozone precursors(VOCs and NOx) was conducted in summer 2011 around a petroleum refinery in the Beijing rural region. Three observation sites were arranged, one at southwest of the refinery as the background, and two at northeast of the refinery as the downwind receptors. Monitoring data revealed the presence of serious surface O3 pollution with the characteristics of high average daily mean and maximum concentrations(64.0 and 145.4 ppbV in no-rain days, respectively) and multi-peak diurnal variation. For NOx, the average hourly concentrations of NO2 and NO were in the range of 20.5–46.1 and 1.8–6.4 ppbV, respectively. For VOC measurement, a total of 51 compounds were detected. Normally, TVOCs at the background site was only dozens of ppbC, while TVOCs at the downwind sites reached several hundreds of ppbC. By subtracting the VOC concentrations at background, chemical profiles of VOC emission from the refinery were obtained, mainly including alkanes(60.0% ± 4.3%), alkenes(21.1% ± 5.5%) and aromatics(18.9% ± 3.9%). Moreover, some differences in chemical profiles for the same measurement hours were observed between the downwind sites; the volume ratios of alkanes with low reactivity and those of alkenes with high reactivity respectively showed an increasing trend and a decreasing trend. Finally, based on temporal and spatial variations of VOC mixing ratios, their photochemical degradations and dispersion degradations were estimated to be 0.15–0.27 and 0.42–0.62, respectively, by the photochemical age calculation method, indicating stronger photochemical reactions around the refinery.     

Effect of ozone on the performance of a hybrid ceramic membrane-biological activated carbon process

Two hybrid processes including ozonation-ceramic membrane-biological activated carbon （BAC） （Process A） and ceramic membrane-BAC （Process B） were compared to treat polluted raw water. The performance of hybrid processes was evaluated with the removal efficiencies of turbidity, ammonia and organic matter. The results indicated that more than 99% of particle count was removed by both hybrid processes and ozonation had no significant effect on its removal. BAC filtration greatly improved the removal of ammonia. Increasing the dissolved oxygen to 30.0 mg/L could lead to a removal of ammonia with concentrations as high as 7.80 mg/L and 8.69 mg/L for Processes A and B, respectively. The average removal efficiencies of total organic carbon and ultraviolet absorbance at 254 nm （UV254, a parameter indicating organic matter with aromatic structure） were 49% and 52% for Process A, 51% and 48% for Process B, respectively. Some organic matter was oxidized by ozone and this resulted in reduced membrane fouling and increased membrane flux by 25%-30%. However, pre-ozonation altered the components of the raw water and affected the microorganisms in the BAC, which may impact the removals of organic matter and nitrite negatively.     

臭氧-混凝交互作用对混凝效果的影响

采用臭氧-混凝联用(臭氧与混凝剂同时投加)和预臭氧混凝(预臭氧后待水中臭氧浓度为0后再投加混凝剂)两种方式处理水样,分析其氧化、混凝效果和消毒副产物生成势(DBPFP)等的差异,研究臭氧-混凝交互作用对处理效果的影响.结果表明,联用和预臭氧混凝效果之间存在明显差异.联用工艺中臭氧与混凝剂间发生交互作用,导致混凝剂水解形态分布发生改变是影响混凝效果的重要原因.联用处理后水样的浊度高于预臭氧混凝,主要原因之一在于臭氧降低了混凝剂水解形态分布中Alb的含量;Cl-DBPFP低于预臭氧混凝出水,是混凝剂Al Cl3及其某些水解形态对臭氧具有催化氧化的作用,促进了消毒副产物前驱物的氧化降解所致.联用对MCAA和CF生成势的去除效果显著强于预臭氧混凝,其中MCAAFP分别为5.6μg·L-1和16.9μg·L-1,CFFP分别为12.5μg·L-1和24.1μg·L-1.臭氧与混凝剂交互作用显著影响混凝效果及消毒副产物的生成,是臭氧和混凝配合使用安全性研究中需要重点关注的内容.因而,相关科研和实际水处理工艺中必须明确预臭氧及混凝剂投加位点和相对次序.     

南京夏季城市冠层大气 CO2浓度时空分布规律的观测

城市是CO2重要排放源,直接观测城市中大气CO2浓度对于研究人类活动对大气温室气体的贡献至关重要,而在城市中多个站点、多个高度上观测大气CO2浓度则有助于认识城市CO2浓度的时空变化规律,确定其影响机制.本研究于2014年7月18日至7月25日在南京主城区东、西、南、北和中共5个方位(100 m左右高度),2014年8月3日至2014年8月9日在南京主城区中部站点的3个高度(30、65和110 m)观测CO2浓度.结果表明:1南京主城区垂直方向上CO2浓度存在明显梯度,近地面30 m处CO2浓度受人为活动影响明显,平均值达427.3×10-6(±18.2×10-6)(摩尔分数,下同),高层65m、110 m处CO2浓度混合均匀,平均值分别为411.8×10-6(±15.0×10-6)和410.9×10-6(±14.6×10-6).大气层结越稳定,CO2浓度越高,垂直梯度越大.2南京主城区CO2浓度的水平分布受风和大气稳定度的控制.观测期间盛行东北风向,导致CO2浓度分布整体呈现西南高,东北低的格局,城市主城区上下风向CO2浓度差为7.8×10-6.而且水平风速越大,越有助于将上风向的CO2传输至城市的下风向,CO2浓度差就越小.大气层结越稳定,整体CO2浓度越高.3南京主城区5个站点CO2浓度均有明显的日变化,日最高值出现在交通早高峰期间,谷值在17:00左右,在19:00左右有时会因交通晚高峰而出现次高值.     

Characterization and prediction of highway runoff constituent event mean concentration

Highway stormwater runoff quality data were collected from throughout California during 2000-2003. Samples were analyzed for conventional pollutants (pH, conductivity, hardness, and temperature); aggregates (TSS, TDS, TOC, DOC); total and dissolved metals (As, Cd, Cr, Cu, Ni, Pb, and Zn); and nutrients (NO(3)-N, TKN, total P, and ortho-P). Storm event and site characteristics for each sampling site were recorded. A statistical summary for chemical characteristics of highway runoff is provided based on statewide urban and non-urban highways. Constituent event mean concentrations (EMCs) were generally higher in urban highways than in non-urban highways. The chemical characteristics of highway runoff in California were compared with national highway runoff chemical characterization data. The results obtained in California were generally similar to those found in other states. The median EMC for Pb measured in studies conducted in previous decades was much higher than the current median Pb EMC in California. The lower Pb EMC in California compared to previous highway runoff monitoring is believed to be due to the elimination of leaded gasoline. An attempt was also made to identify surrogate constituents within a general family of water quality categories using Spearman correlations and selected pairs with Spearman coefficients greater than 0.8. The strongest correlations were observed among parameters associated with dissolved minerals (EC, TDS, and chloride); organic carbon (TOC and DOC); petroleum hydrocarbons (TPH and O & G); and particulate matter (TSS and turbidity). Within the metals category, total iron concentration was highly correlated with most total metal concentrations. The correlations between total and dissolved concentrations were all less than 0.8, even between total and dissolved concentrations of the same metals. Multiple linear regression (MLR) analyses were performed to evaluate the impact of various site and storm event variables on highway runoff constituent EMCs. Parameters found to have significant impacts on highway runoff constituent EMCs include: total event rainfall (TER); cumulative seasonal rainfall (CSR); antecedent dry period (ADP); contributing drainage area (DA); and annual average daily traffic (AADT). Surrounding land use and geographic regions were also determined to have a significant impact on runoff quality. The MLR model was also used to predict constituent EMCs. Model performance determined by comparing predicted and measured values showed good agreement for most constituents.