Cesium and strontium sorption by selected tropical and subtropical soils around nuclear facilities

The dynamics of Cs and Sr sorption by soils, especially in the subtropics and tropics, as influenced by soil components are not fully understood. The rates and capacities of Cs and Sr sorption by selected subtropical and tropical soils in Taiwan were investigated to facilitate our understanding of the transformation and dynamics of Cs and Sr in soils developed under highly weathering intensity. The Langmuir isotherms and kinetic rates of Cs and Sr sorption on the Ap1 and Bt1 horizons of the Long-Tan (Lt) and the A and Bt1 horizons of the Kuan-Shan (Kt), Mao-Lin (Tml) and Chi-Lo (Cl) soils were selected for this study. Air-dried soil (<2 mm) samples were reacted with of 7.5 × 10⁻⁵ to 1.88 × 10⁻³ M of CsCl (pH 4.0) or 1.14 × 10⁻⁴ to 2.85 × 10⁻³ M of SrCl₂ (pH 4.0) solutions at 25 °C. The sorption maximum capacity (q_m) of Cs by the Ap1 and Bt1 horizons of the Lt soil (62.24 and 70.70 mmol Cs kg⁻¹ soil) were significantly (p < 0.05) higher than those by the A and Bt1 horizons of the Kt and Cl soils (26.46 and 27.49 mmol Cs kg⁻¹ soil in Kt soil and 34.83 and 29.96 mmol Cs kg⁻¹ soil in Cl soil, respectively), however, the sorption maximum capacity values of the Lt and Tml soils did not show significant differences. The amounts of pyrophosphate extractable Fe (Fe_p) were correlated significantly with the Cs and Sr sorption capacities (for Cs sorption, r² = 0.97, p < 1.0 × 10⁻⁴; for Sr sorption, r² = 0.82, p < 2.0 × 10⁻³). The partition coefficient of radiocesium sorbed on soil showed the following order: Cl soil ? Kt soil > Tml soil > Lt soil. It was due to clay minerals. The second-order kinetic model was applied to the Cs and Sr sorption data. The rate constant of Cs or Sr sorption on the four soils was substantiality increased with increasing temperature. This is attributable to the availability of more energy for bond breaking and bond formation brought about by the higher temperatures. The rate constant of Cs sorption at 308 K was 1.39-2.09 times higher than that at 278 K in the four soils. The activation energy of Cs and Sr sorbed by the four soils ranged from 7.2 to 16.7 kJ mol⁻¹ and from 15.2 to 22.4 kJ mol⁻¹, respectively. Therefore, the limiting step of the Cs⁺ or Sr²⁺ sorption on the soils was diffusion-controlled processes. The reactive components, which are significantly correlated with the Langmuir sorption maxima of Cs and Sr by these soils, substantially influenced their kinetic rates of Cs and Sr sorption. The data indicate that among components of the subtropical and tropical soils studied, short-range ordered sesquioxides especially Al- and Fe-oxides complexed with organics play important roles in influencing their capacity and dynamics of Cs and Sr sorption.     

环境测试舱自吸附甲醛重释放规律与影响因素研究

广泛用于板材污染物释放量测试、空气净化产品净化效果测试等实验中的环境测试舱,往往由于其内壁黏附性杂质而对目标测试物产生不可忽视的自吸附作用,自吸附污染物将作为二次释放源出现重释放,研究目标测试物的自吸附消耗量及重释放规律,探索有效控制措施,有利于对环境测试舱实验应用及室内污染控制提出指导性实际意义。分别选取0.2%甲醛溶液、大芯板作为同一自制玻璃环境测试舱2期实验(I期、Ⅱ期)的不同甲醛释放源,通过近90 d追踪测试,经不同释放源、不同控制条件下舱内壁自吸附甲醛的多次重释放实验,结合非线性拟合分析方法,总结出舱内壁自吸附甲醛重释放甲醛浓度变化符合一阶递增指数函数:y=A1×exp(-x/t1)+y0,(A1<0、t1>0)。曲线参数y0值可用于评价实验条件下测试舱内自吸附甲醛残余量;y0值与环境舱舱体材质、环境温湿度、舱外甲醛浓度及空气交换手段有关,而与释放源及其释放平衡浓度高低无明显关系。大开舱门短时间抽气式空气交换对舱内自吸附甲醛残余有适度清除效果,使y0值降低,同时有利于再次平衡状态的快速建立;而长时间的无动力空气交换,或者自来水洗及去离子水洗等处理手段对舱内壁自吸附甲醛残余无明显清除作用。     

Modelling the biphasic sorption of simazine,imidacloprid, and boscalid in water/soil systems

The sorption kinetics of simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine), imidacloprid (1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine), and boscalid (2-chloro-N-(4′-chlorobiphenyl-2-yl)nicotinamide), three pesticides of wide use in agriculture, was determined in five different water/soil systems over a time interval from the initial few seconds to about 1 month. In all the experiments, sorption kinetics showed a biphasic pattern characterized by an initial, relatively short phase with a high sorption rate and a later phase with much a lower sorption rate. Initial sorption capacity increased with soil organic carbon content and with sorbate hydrophobicity. We postulate that the first phase of the process involves a fast second-order sorption reaction on superficial sites of soil particles, whereas the second phase depends on diffusion-controlled migration to internal binding sites. A kinetic equation based on this hybrid model accurately fitted all data sets. Less satisfactory results were obtained employing the pseudo-first order, pseudo-second order, Elovich, two site non-equilibrium, or Weber-Morris equation. The superior performance of the hybrid model for describing boscalid sorption probably reflects the high hydrophobic character and consequent low diffusion rates of this compound. The accuracy of modelling was in any case strongly dependent on the time interval considered.     

Persistence and Dissipation Kinetics of Spiromesifen in Chili and Cotton

In a field study carried out at three different locations, the dissipation of spiromesifen on cotton and chili was studied and its DT₅₀, and DT₉₉ were estimated at each location. Spiromesifen was sprayed on chili at 96 and 192 g a.i. ha⁻¹ and cotton at 120 and 240 g a.i. ha⁻¹. Samples of chili fruits were drawn at 0, 1, 3, 5, 7, 10, 15, 21, 30 days after treatment and that of cotton seed and lint at first picking and harvest. Soil samples were drawn 30 days after treatment from 0 to 15 and 15 to 30 cm layer. Quantification of residues was done on GC–MS in Selected Ion Monitoring (SIM) mode in mass range 271–274 m/z. The LOQ of this method was found 0.033 μg g⁻¹, LOD being 0.01 μg g⁻¹. The DT₅₀ of spiromesifen when applied at recommended doses in chili fruits was found to be 2.18–2.40 days. Ninety-nine percent degradation was found to occur within 14.5–16.3 days after application. Residues of spiromesifen were not detected in cotton seed and lint samples at the first picking. In soil, no residues of spiromesifen were detectable 15 days after treatment.     

校园安全灰色关联评价模型及应用

通过对影响校园安全的因素分析和灰色关联理论在校园安全评价中的适用性分析,得出校园安全存在与灰色系统理论相耦合的特征。应用灰色关联理论建立校园安全灰色关联评价模型,合理确定标准数据序列,对非线性、离散以及动态的校园安全数据进行量化分析和评价,根据关联度大小来判断校园的相对安全性程度,并结合湘潭市5所学校的校园安全状况进行实例验证。其评价结果与实际情况相一致,该模型能有效地解决校园安全影响因素中的非线性关系和不确定性问题,可作为校园安全相对安全等级划分的重要理论依据,具有可操作性和可行性。     

Effective rates of heavy metal release from alkaline wastes--quantified by column outflow experiments and inverse simulations

Column outflow experiments operated at steady state flow conditions do not allow the identification of rate limited release processes. This requires an alternative experimental methodology. In this study, the aim was to apply such a methodology in order to identify and quantify effective release rates of heavy metals from granular wastes. Column experiments were conducted with demolition waste and municipal waste incineration (MSWI) bottom ash using different flow velocities and multiple flow interruptions. The effluent was analyzed for heavy metals, DOC, electrical conductivity and pH. The breakthrough-curves were inversely modeled with a numerical code based on the advection–dispersion equation with first order mass-transfer and nonlinear interaction terms. Chromium, Copper, Nickel and Arsenic are usually released under non-equilibrium conditions. DOC might play a role as carrier for those trace metals. By inverse simulations, generally good model fits are derived. Although some parameters are correlated and some model deficiencies can be revealed, we are able to deduce physically reasonable release-mass-transfer time scales. Applying forward simulations, the parameter space with equifinal parameter sets was delineated. The results demonstrate that the presented experimental design is capable of identifying and quantifying non-equilibrium conditions. They show also that the possibility of rate limited release must not be neglected in release and transport studies involving inorganic contaminants.     

军用装备砂尘环境试验技术

介绍了进行砂尘环境试验的目的、适用范围及环境影响因素,并说明应根据产品使用环境、本身特点及其产品技术条件来选择试验程序和确定各试验参数.同时指出了确定试验持续时间的方法,最后对砂尘试验箱(室)提出6点设计要求,为我国自行研制军用砂尘环境试验设备提供了依据,从而提高了我国军用武器装备对环境的适应性及可靠性.     

Contribution of additives Cu to its accumulation in pig feces： study in Beijing and Fuxin of China

Massive amounts of pig manure are produced by intensive pig farm in China, and the composition of pig manure has changed much due to the use of feed additives. However, little is known about the exact Cu （copper） feed as additives or present as contaminants in pig feed and the residues in feces. One hundred and thirty-seven feeds and one hundred and forty-two fecal samples from 48 pig farms were collected in Beijing and Fuxin cities in 1999 and 2005, respectively. The concentrations of Cu were in the range of 6.86-395.19 mg/kg in the feed samples, and the mean values were in the order of weaner〉 grower-finisher〉 sow＇s feeds. The high concentrations over EU recommendations implied that excessive levels of Cu are fed on many pig farms in Beijing and Fuxin. Cu was also present in high concentrations in feces, and concentrations were highly variable. Cu concentrations in the feces from grower-finisher and weaner pigs were significantly greater than feces of sows. The super-intensive and small-scale farms had higher levels of Cu in feces than the middle farms. Cu concentrations in pig feces were approximately 5-times greater than in pig feeds. Feed management in grower-finisher pigs on super-intensive and small-scale pig farms is needed to reduce high Cu concentrations in feces and risks to soil contamination while feces are land-applied.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.     

Decolorization of Blue CL-BR dye by AOPs using bleach wastewater as source of H2O2

This research was focused on the investigation of the efficacy of advanced oxidation processes (Fenton,ozonation and UV/H_2O_2) for decolorization of reactive azo dye (Blue CL-BR) using bleach wastewater as possible source of H_2O_2.All the experiments were performed on the laboratory scale set-up.The results showed that colour removal efficiencies by UV or bleach (H_2O_2) alone were not so efficient.Fenton process with bleach wastewater was found to be the most effective at process conditions such as pH of 3 and H_2O_2/Fe~(2 ) ratio of 24:1,resulting in 64% colour removal.Almost complete colour removal,i.e.,99% and 95% were achieved by UV/H_2O_2 and UVfoleach wastewater in 30 and 60 min,respectively.Ozonation proved an efficient method for decolorization of Blue CL-BR dye at alkaline pH.It was possible to achieve 98% colour removal with 30 min of ozonation at pH 9.The colour removal of dye was found to follow first order kinetics.