14C and 125I Labelling of Humic Material for Use in Environmental Studies

Humic and fulvic acids are present in nearly all natural waters. These acids are known to affect the transport of environmental contaminants such as metals and hydrophobic organics through the terrestrial environment. an understanding of their role in the transport of contaminants is therefore essential and is facilitated if the acid is labelled with a suitable radioactive label. This paper reports the use of ¹⁴C-methylamine and ¹²⁵I to label humic acid with either ¹⁴C or ¹²⁵I and investigates factors which affect the yield of these reactions. the stability and mobility of the labelled humic material through sand is also reported.     

分洪区洪灾保险工作初探

本文从洪水过程的随机特点及防洪工作的实际需要等各个方面出发,阐述了在分洪区实行洪灾保险的必要性,结合国内外已有的实践经验,分析了这一工作得以顺利开展的可能性。并在此基础上,提出了二种洪灾保险费用计算方法,实例计算结果表明,这些方法是基本可行的。     

Characteristics and recent trends of sulfur dioxide at urban, rural, and background sites in North China: Effectiveness of control measures

SO₂ measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO₂ at different types of sites in Northern China. The overall average concentrations of SO₂ are (16.8 ± 13.1) ppb, (14.8 ± 9.4) ppb, and (7.5 ± 4.0) ppb at China Meteorological Administration (CMA, Beijing urban area), Gucheng (GCH, relatively polluted rural area, 110 km to the southwest of Beijing urban area), and Shangdianzi (SDZ, clean background area, 100 km to the northeast of Beijing urban area), respectively. The SO₂ levels in winter (heating season) are 4-6 folds higher than those in summer. There are highly significant correlations among the daily means of SO₂ at different sites, indicating regional characteristics of SO₂ pollution. Diurnal patterns of surface SO₂ at all sites have a common feature with a daytime peak, which is probably caused by the downward mixing and/or the advection transport of SO₂-richer air over the North China Plain. The concentrations of SO₂ at CMA and GCH show highly significant downward trends (-4.4 ppb/yr for CMA and -2.4 ppb/yr for GCH), while a less significant trend (-0.3 ppb/yr) is identified in the data from SDZ, reflecting the character of SDZ as a regional atmospheric background site in North China. The SO₂ concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games, suggesting that the SO₂ pollution control has long-term effectiveness and benefits. In the post-Olympics period, the mean concentrations of SO₂ at CMA, GCH, and SDZ are (14.3 ± 11.0) ppb, (12.1 ± 7.7) ppb, and (7.5 ± 4.0) ppb, respectively, with reductions of 26%, 36%, and 13%, respectively, compared to the levels before. Detailed analysis shows that the differences of temperature, relative humidity, wind speed, and wind direction were not the dominant factors for the significant differences of SO₂ between the pre-Olympics and post-Olympics periods. By extracting the data being more representative of local or regional characteristics, a reduction of up to 40% for SO₂ in polluted areas and a reduction of 20% for regional SO₂ are obtained for the effect of control measures implemented for the Olympic Games.     

Sewage sludge disintegration by high-pressure homogenization: A sludge disintegration model

High-pressure homogenization (HPH) technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree (DDCOD), protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid (TS) content. The maximum DDCOD of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DD_COD= kN^aP^b was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure (P) was more significant than that of homogenization cycle number (N). The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.     

Theoretical study on the reaction mechanism of ozone addition to the double bonds of keto-limonene

The reaction mechanism of ozone (O₃) addition to the double bonds of gas phase keto-limonene was investigated using ab initio methods. Two different possibilities for O₃ addition to the double bond were considered and two corresponding van derWaals complexes (Complex 1 and Complex 2) were found for 1-endo and 2-endo. The rate constants were calculated using the transition state theory at the CCSD(T)/6-31G(d) + CF//B3LYP/6-31G(d,p) level. The high-pressure limit of the total rate constant at 298 K was 3.51 × 10^-16 cm³/(molecule sec), which was in a good agreement with the experimental data.     

Three-dimensional hydrodynamic and water quality model for TMDL development of Lake Fuxian, China

Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making.     

运用三维荧光光谱解析高温厌氧产氢反应过程对温度变化的响应

为建立反应器运行状态的荧光光谱快速监测方法,应用三维荧光光谱表征了高温厌氧反应器的出水,采用平行因子分析方法分析后得到3种荧光组分——蛋白质、辅酶NADH和核黄素,并获得它们的激发发射光谱图及相对浓度.结果表明,当温度从50 ℃上升到60 ℃的过程中,3种荧光物质的相对浓度均呈现相应的变化,它们与反应器的运行参数呈现明显相关性.进一步研究表明,核黄素是高温厌氧产氢反应中的特有荧光物质,采用标准加入法和二阶校正方法可以测定其实际浓度,出水中核黄素浓度变化范围为0.04~0.13 mg·L^-1.该研究为厌氧产氢反应器的运行监控提供了理论基础.     

再生条件对钾基CO_2吸附剂吸附性能的影响

通过固定床实验研究了再生条件对钾基CO2吸附剂吸附性能的影响。深入分析了再生温度和气氛对吸附穿透时间和饱和吸附量的影响。研究发现,当再生温度为200℃,N2气氛下再生时效果最佳,在此条件下再生后钾基CO2吸附剂循环性能良好,10次循环后仍然能有很好的吸附效果;再生气氛中有H2O或CO2时会影响再生反应的进行,不利于吸附剂的再生。     

北湖流域水质改善系统动力学研究

利用系统动力学擅长研究动态、非线性复杂系统的特点,将其应用于北湖水质改善分析,构建了系统动力学-水质耦合模型,可实现长时间序列的连续模拟和水环境管理的情景分析。文章定量分析了三产比例调整、城镇化率提高与污水集中处理等因素对流域纳污控制及水质改善的影响,推演出可协调经济发展-水环境保护-污水治理资金三方矛盾的合理方案,为类似小城镇的发展提供可借鉴的思路和方法。     

养殖废水新型处理技术中试

针对畜禽养殖污染废水传统处理方法效率不高、噪声较大等缺点进行改进,采用"水解酸化池-塔式膜生物反应器-悬浮澄清池"工艺进行处理,结果表明:COD、氨氮去除率分别为97.5%和91%,出水水质可达GB 18596—2001《畜禽养殖污染物排放标准》。