溶解氧对好氧颗粒污泥影响的研究进展

好氧颗粒污泥技术是一种新颖废水处理技术。溶解氧(DO)是好氧颗粒污泥形成和稳定运行的一个重要参数。好氧颗粒污泥需要的曝气量大,能耗高。高曝气量带来的高DO浓度不利于氨氮通过SND去除。当DO扩散在颗粒内部受到限制时,颗粒中心形成的厌氧层不利于颗粒污泥的长期稳定运行。本文系统分析了DO浓度对好氧颗粒污泥影响的国内外研究现状,对好氧颗粒污泥中DO浓度这一重要参数的研究进行了总结。研究在低DO浓度下保持好氧颗粒污泥的稳定性有利于降低运行成本,采取合适的方法降低颗粒内部的扩散限制有利于增强颗粒的稳定性能。     

宁波市大气可吸入颗粒物PM1o和PM2.5的源解析研究

在宁波市布设4个代表性点位,于2010年春季、夏季和冬季进行大气PM10和PM2.s的采样,同时采集了多种颗粒物源样品,建立了PM10、PM2.5和源样品的化学成分谱.采用化学质量平衡模型(CMB)对宁波市PM10、PM2.5进行源解析.结果表明,城市扬尘、煤烟尘、机动车尾气尘是宁波市PM10、PM2.5的3大污染源,...     

Investigation of heavy metal contaminations in the lower Sakarya river water and sediments

In this work, water and sediment samples were collected from three different stations located along the Sakarya river between May and September 2003. Lead, copper, chromium, zinc, nickel and cadmium concentrations were determined by using solvent extraction and flame atomic absorption spectrometric method. The results show that differences based upon sampling times, regions, sediment and water samples were observed. The mean levels of copper, nickel, chromium, lead, cadmium, zinc for sediment samples are; 4.630 μg g⁻¹, 13.520 μg g⁻¹, 8.780 μg g⁻¹, 2.550 μg g⁻¹, 9.990 μg g⁻¹ and for water samples are; 0.851 μg g⁻¹, 1.050 μg g⁻¹, 0.027 μg g⁻¹, 1.786 μg g⁻¹, 0.236 μg g⁻¹, 0.173 μg g⁻¹, respectively.     

串联四极杆质谱(GC-QqQ-MS/MS)测定土壤中的有机氯农药和多氯联苯

建立了用加速溶剂萃取仪(ASE)萃取、凝胶渗透色谱(GPC)净化、气相色谱/串联四极杆质谱多反应监测、同时测定土壤中17种有机氯农药和19种多氯联苯的方法.加标浓度在3.3μg/kg时的平均回收率在79.6%～93.2%之间,相对标准偏差在2.9%～13.0%之间,定量限在0.01～0.51μg/kg之间.在检测土壤样品中的有机氯农药和多氯联苯残留方面,Gc-QqQ-MS/MS相对于气相色谱/电子捕获检测器(GC-ECD)和GC-MS的选择离子检测(SIM)模式具有非常明显的优势,尤其是在低浓度水平的定性和定量方面.     

THE DISCHARGE OF SEDIMENT IN CHANNELIZED ALLUVIAL STREAMS1

ABSTRACT: Approximately 400 million cubic feet of channel sediments have been delivered to the Mississippi River from the Obion-Forked Deer River system in the last 20 years. The discharge of sediment from these channelized networks in West Tennessee varies systematically with the stage of channel evolution. Variations in yields over time reflect the shifting dominance of fluvial and mass-wasting processes as the networks adjust to lower energy conditions. Maximum bed-material discharges occur during the initial phases of degradation (Stage III). In contrast, yields of suspended-sediment peak during the threshold stage (Stage 1V: large-scale mass wasting) as sediments are delivered from main-channel banks and tributary beds. Suspended-sediment yields then decrease as aggradation (Stage V) becomes the dominant trend in the main channels, but remains relatively high through restabiliza-tion (Stage VI) because of continued degradation and widening in the tributaries. Bed-material discharges decrease from the degradation stage (III) to Stage V, and increase again during restabiliza-tion (Stage VI) because secondary aggradation increases gradients and incipient meandering serves to rework bed sediments. This secondary maxima in bed-material discharge is analogous to those described previously as complex, or oscillatory, response. The trends of sediment production and transport described from these rejuvenated networks are in agreement with experimental and theoretical results of earlier investigations.     

Concentrations of cadmium and lead heavy metals in Dardanelles seawater

Cadmium and lead were determined simultaneously in seawater by differential pulse stripping voltammetry (DPSV) preceded by adsoptive collection of complexes with 8-hydroxyquinoline (oxine) on to a hanging mercury drop electrode (HMDE). In preliminary experiments the optimal analytical condition for oxine concentration was found to be 2.10⁻⁵ M, at pH 7.7, the accumulation potential was −1.1 V, and the initial scannig potential was −0.8 V. The peak potentials were found −0.652 V for Cd and −0.463 V for Pb At the 60 s accumalation time. The limit of detection (LOD) and limit of quantitatification (LOQ) were found to be by voltammetry as 0.588 and 1.959 μg l⁻¹ (RSD, 5.50%) for Cd and 0.931 and 3.104 μg l⁻¹ (RSD, 4.10%) for Pb at 60 s stirred accumulation time respectively. In these conditions the most of the seawater samples are amenable for direct voltammetric determination of cadmium and lead using a HMDE. An adsorptive stripping mechanism of the electrode reaction was proposed. For the comparison, seawater samples were also analysed by ICP-atomic emission spectrometry method (ICP-AES). The applied voltammetric technique was validated and good recoveries were obtained.     

Ambient Aerosol and its Carbon Content in Gainesville, a Mid-Scale City in Florida

Ambient aerosols were collected during 2000–2001 in Gainesville, Florida, using a micro-orifice uniform deposit impactor (MOUDI) to study mass size distribution and carbon composition. A bimodal mass distribution was found in every sample with major peaks for aerosols ranging from 0.32 to 0.56 μm, and 3.2 to 5.6 μm in diameter. The two distributions represent the fine mode (<2.5 μm) and the coarse mode (>2.5 μm) of particle size. Averaged over all sites and seasons, coarse particles consisted of 15% carbon while fine particles consisted of 22% carbon. Considerable variation was noted between winter and summer seasons. Smoke from fireplaces in winter appeared to be an important factor for the carbon, especially the elemental carbon contribution. In summer, organic carbon was more abundant. The maximum secondary organic carbon was also found in this season (7.0 μg m⁻³), and the concentration is between those observed in urban areas (15–20 μg m⁻³) and in rural areas (4–5 μg m⁻³). However, unlike in large cities where photochemical activity of anthropogenic emissions are determinants of carbon composition, biogenic sources were likely the key factor in Gainesville. Other critical factors that affect the distribution, shape and concentration were precipitation, brushfire and wind.     

226Ra, 232Th and 40K analysis in soil samples from some areas of Malwa region, Punjab, India using gamma ray spectrometry

The activity concentrations of soil samples collected from thirty different locations of Malwa region of Punjab were determined by using HPGe detector based on high-resolution gamma spectrometry system. The range of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the soil from the studied areas varies from 18.37 Bq kg⁻¹ (Sangrur) to 53.11 Bq kg⁻¹ (Sitoguno), 57.28 Bq kg⁻¹ (Dhanola) to 148.28 Bq kg⁻¹ (Sitoguno) and 211.13 Bq kg⁻¹ (Sunam) to 413.27 Bq kg⁻¹ (Virk Khera) with overall mean values of 35 Bq kg⁻¹, 80 Bq kg⁻¹and 317 Bq kg⁻¹ respectively. The absorbed dose rate calculated from activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K ranges between 8.47 and 24.48, 35.68 and 92.38, and 8.74 and 17.11 nGy h⁻¹, respectively. The total absorbed dose in the study area ranges from 58.08 nGy h⁻¹ to 130.85 nGy h⁻¹ with an average value of 79.11 nGy h⁻¹. The calculated values of external hazard index (H_ex) for the soil samples of the study area range from 0.35 to 0.79. Since these values are lower than unity, therefore, according to the Radiation Protection 112 (European Commission. Radiation Protection 112 1999) report, soil from these regions is safe and can be used as a construction material without posing any significant radiological threat to population.     

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 10⁴ cm^-3. nm^-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO₂ concentration, followed by NO₂, O₃ is hardly affected. The impact of crop residual burning on fine particles (< 2.1 μm) is larger than on coarse particles (> 2.1 μm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K⁺, Cl^-, Na⁺, and F^- and has a weak impact on the size distributions of NH₄⁺, Ca²⁺, NO₃^- and SO₄^2-.     

改进测定水中氨氮分子吸收光谱法的试验研究

水中氨氮含量是反应水质状况的重要指标。文章对测定水中氨氮气相分子吸收光谱法(标准号HJ/T195-2005)进行了改进试验研究。第一,对氧化剂的配比进行了改进,使氨氮的测定范围扩展至100μg。第二,对标准HJ/T195-2005中直接使用亚硝酸钠标准溶液做标准曲线的处理方式也做了探讨。通过一系列对比实验认为,应用硫酸铵标准溶液做工作曲线更加准确合理。最后应用改进后的气相分子吸收光谱法和纳氏比色法或滴定法对多种实际废水样品进行同时测定。结果表明,改进后的气相分子吸收光谱法测定氨氮的范围更宽,灵敏度更高和准确度更好。