不同底泥稳定剂改善富营养化水体技术研究

河道污染底泥原位处理是一种高效、经济、便捷的处理方法。本研究以河道底泥和上覆水为研究对象,对比分析底泥、底泥+硝酸钙、底泥+过氧化钙、底泥+1∶1硝酸钙和过氧化钙、底泥+EM菌剂对于河道底泥氮磷释放抑制和上覆水体改善效果。研究结果表明:与空白底泥相比,实验组在一定程度上都可以抑制底泥氮磷释放,促进上覆水体水质改善。但由于受温度、光照和底泥扰动不同,添加底泥稳定剂对于不同深度上覆水体修复情况存在差异。     

底泥再悬浮对不同营养水平上覆水中磷酸盐迁移的影响

研究了底泥再悬浮状态下,不同营养水平上覆水对磷酸盐迁移的影响.试验结果表明:以蒸馏水为上覆水时,磷酸盐由底泥向水体迁移的量明显大于以河水为上覆水时的,并且底泥再悬浮促进了底泥中磷酸盐向水体的迁移.上覆水磷酸盐浓度达到最大值后,底泥再悬浮对水体磷酸盐向底泥迁移具有促进作用.对于特定上覆水条件下,磷酸盐不同初始浓度对底泥释放磷具有显著的抑制作用.但对于不同营养水平上覆水,磷酸盐初始浓度并不是磷释放量的决定因素.底泥在蒸馏水或河水为上覆水条件下再悬浮后,底泥的释磷能力受到抑制,说明底泥再悬浮促进了磷在底泥中的固定.     

河道水体水质对底泥污染物释放的影响

底泥内源污染物的释放是河道污染的重要因素之一。本文通过模拟试验研究了河道水体水质对底泥污染物释放规律的影响。结果表明:上覆水体pH的升高可使底泥中COD_(Cr)和NH_4~+-N的释放受到抑制,但会促进底泥TN的释放,酸性或碱性条件都会促进底泥中TP的释放;上覆水体有机物浓度的增加可抑制底泥NH_4~+-N和TN的释放,促进TP的释放;溶解氧的增加对底泥COD_(cr)、NH_4~+-N和TN的释放有促进作用,但会抑制底泥中TP的释放。对比分析表明,上覆水体溶解氧(10 mg/L)对底泥COD_(Cr)、NH_4~+-N和TN的释放量影响最大,pH(4.0～10.0)对TP的释放量影响最为显著,累积释放量极差达5.89 mg/kg。     

我国城市水体底泥污染特征分析及治理方案探讨

本文研究了城市水体新生底泥对上覆水DO、ORP等水体黑臭指标的影响,及向水体释放NH₃-N和PO₄^3--P的特征规律。结果表明,长期未清淤的底泥中大量的还原性物质会造成水体厌氧环境,且会降低水体ORP,导致水体黑臭;同时新生底泥释放的NH₃-N和PO₄^3--P会引起水体富营养化风险。城市水体水质的长效保持需采取底泥定期清淤与生态修复相结合的措施,清除历史污染的同时,减少新生污染的富集。     

三种药剂对黑臭底泥原位修复效果的研究

为了解常见底泥原位修复药剂对黑臭底泥及其上覆水以及沉水植物存活情况的影响,通过模拟试验,考察了水泥、生石灰以及过氧化钙对底泥的原位修复效果,包括底泥向上覆水的氮磷释放、底泥和上覆水pH值的综合变化,以及沉水植物的存活率.结果 表明:生石灰和水泥对底泥中氨氮、总氮、总磷均有良好的抑制效果,过氧化钙对底泥中氨氮和总磷的抑制...     

曝气对于河道底泥与上覆水体的影响

以受污染河道底泥和上覆水为研究对象,通过室内模拟实验,对比分析不同曝气深度对于底泥与上覆水体的影响。结果表明,曝气措施可以显著提升底泥的氧化还原电位与上覆水体的DO浓度,抑制厌氧微生物活动,阻止致黑致臭物质产生。曝气深度对上覆水体的污染物去除有重要影响。在相同的曝气量的前提下,距离底泥更近的曝气方式,其底泥及上覆水体的改善效果更佳。曝气深度最深的H0试验组在试验结束时,其上覆水体的COD、氨氮与总磷等去除率分别达到了27.2%、70.4%和33.8%。     

镧改性沸石覆盖控制河道底泥污染物释放实验研究

通过模拟实验,考察了天然沸石和镧改性沸石对于黑臭河道底泥污染物释放的处理效果。结果表明,由于底泥释放,空白对照组中上覆水体的污染物浓度出现不同程度的上升。天然沸石组和镧改性沸石组均可降低上覆水体中化学需氧量及氨氮、总磷等的浓度。30d后,镧改性沸石组中水体的化学需氧量、氨氮、总磷分别下降了13.2%、23.4%、55.2%,其中对于总磷的去除效率明显优于天然沸石组。     

河道底泥处理的研究

河道底泥作为水体的重要组成部分,累积了大量的污染物,尤其是当外源污染得到有效控制后,沉积在底泥中的氮、磷、重金属等污染物会再次从底泥释放到上覆水体中来,对水体造成严重的污染。因此,良好的底泥生态环境对于水环境污染控制具有重要意义。主要从底泥异位处理和原位处理两大方面,列举了一些底泥修复方式,并对未来的河道底泥处理提出了一些建议和展望。     

疏浚水流扰动作用下的河道底泥污染物释放效应

河流湖泊疏浚时,由机械扰动水流造成的底泥再悬浮污染物释放作用十分明显。通过循环长直水槽试验,研究了水动力学条件对底泥污染物内源释放效应的影响。分别在上覆水体静止和流动情况下,分析了水体CODcr,的变化规律。结果表明水体的自净作用在动水条件下显著增强。动态水流通过减小底泥一水界面浓度边界层厚度和破坏底泥一水界面底泥表面结构,增大底泥污染物释放速率和通量。底泥CODcr释放量随着流速的增加而增大,随着水深的增加而减小。但是在水深较浅时,波浪会破坏底泥表层结构,引起底泥污染物的再悬浮释放。单位时间单位面积底泥污染物释放量随着时间的增加而迂回减小,底泥内部污染物向泥一水界面的扩散维持了底泥内源释放效应。     

河道污染底泥处理技术

河道底泥既是接纳河道水体污染物的"沉积库",也是向上覆水释放污染物的"源"。污染底泥是河道主要污染源之一,对河道水环境影响很大。随着河道外源污染的有效控制和河道水体治理的推进,污染底泥引起的内源污染问题日益突出,亟需对河道底泥进行修复和底泥污染物的释放予以控制。本文综述了河道底泥修复技术现状,并对污染河道底泥修复技术提出了展望。     

The effect of capping with natural and modified zeolites on the release of phosphorus and organic contaminants from river sediment

A microcosm system that included river sediment, water and different zeolite capping materials (natural zeolite, surfactant-modified zeolite (SMZ), or aluminum modified zeolite (AMZ)) was designed to study the effect of capping on the release of phosphorus and three organic pollutants (phenol, pyridine, and pyrene) from the sediment to the overlying water over the course of three month. For the same amount of the three capping materials, the efficiency of phosphorus inactivation was in the order of SMZ>AMZ>natural zeolite. The inactivation of phosphorus was mainly caused by the covering effect, co-precipitation and adsorption by the capping materials. The different zeolites gave different results for the release of phenol, pyridine, and pyrene from the sediment. When natural zeolite was used as the capping material, there was no effect on the release of pyrene and pyridine, whereas capping the sediment with SMZ or AMZ inhibited the release of pyrene and pyridine but to different extents. However, for controlling the release of phenol from the sediment, aluminum modified zeolite was the most efficient material, whereas no effects were observed when natural zeolite or SMZ were used. The different capabilities of the zeolite materials for controlling the release of different organic pollutants are related to the differences in the electrical properties of these pollutants.     

Effects of vegetation cover on phosphorus loss from a hillslope cropland of purple soil under simulated rainfall: a case study in China

Nutrients and sediment lost through runoff to surface and ground water represents a risk to human and environmental health. In order to understand the mechanisms of nutrient and sediment loss under different levels of vegetation cover, we conducted a simulated rainfall experiment on hillslope cropland in the Sichuan Basin of China. The experiment was performed on a 4.5 m long × 1.5 m wide × 0.6 m deep plot to analyze the mechanisms of overland flow, subsurface flow, sediment yield, and P loss for bare soil, and soil with 25, 50, 75, and 90% vegetation coverage. The results showed that total sediment loss and total bioavailable P (BAP) loss by overland flow decreased with increasing coverage; the rate of P release from fertilizer decreased with increasing time during a rain event and increasing coverage; and the growth in vegetation shoots and roots improved soil physical properties around roots, thus increasing P absorbance and the infiltration rate. Hence, we suggest increasing vegetation coverage to conserve soil and reduce BAP loss by sediments, and paying more attention to groundwater affected by pollutant transport through subsurface flows.     

电动导排孔隙水对泥-水界面氮释放通量的控制效果研究

孔隙水是底泥氮素污染的主要载体和释放源头,对富含氮素的孔隙水予以分离和脱除是控制内源氮释放的潜在方案。以富营养化湖泊底泥为研究对象,采用自制底泥孔隙水电动导排装置,在上覆水深度为20 cm的条件下进行底泥孔隙水电动导排,共设置对照、重力排水(0 V/cm电压梯度)和间歇通电(0.5 V/cm电压梯度,4 h On/4 h Off)3组实验,分析了泥-水界面氮浓度及释放通量的变化特征,监测了孔隙水及底泥中氮形态、pH等理化参数,评估了电动导排孔隙水对泥-水界面氮释放通量的控制效果及影响因素。结果表明：电动导排孔隙水可有效降低泥-水界面的氮释放通量,实验进行632 h后,通电实验组泥-水界面累计DTN释放通量为282.28 mg N/m²,与对照组相比氮释放通量削减95.61%。电动导排孔隙水使阳极孔隙水呈酸性,阴极孔隙水呈碱性,pH的改变促进了底泥中可转化态氮(TTN)的活化,与重力排水相比,电动导排孔隙水后底泥离子交换态氮(IEF-N)去除率由11.11%~12.97%提升至12.59%~22.31%。电动导排孔隙水后底泥总氮脱除量为47015.72 mg/m³,累计能耗为162.38 kWh/m³。     

国内城市黑臭水体内源污染治理技术研究进展

城市黑臭水体不仅影响景观,还会威胁人类健康。其中,内源污染是水体污染的重要来源。文章对内源污染的形成及危害、异位和原位治理技术定义及优缺点等内容进行了总结。主要结论如下:底泥清淤能快速转移污染底泥,但易破坏水底的生态系统,且会给环境带来二次污染;底泥覆盖能减少底泥污染物向水体释放,但不能移除污染物,仍存在污染物释放到水体的风险;投放化学药剂能有效去除污染物,但可能带来水体毒性以及引起污染物的异常释放,一般适用于应急处理;微生物修复底泥效果好,但目前还处于实验室和中试试验阶段;底泥曝气能加快底泥复氧速度,有效改善黑臭水体污染情况,但其耗能高,受设备因素限制而少应用于实践。在城市黑臭水体内源治理实际工程中,应依据不同治理技术的优缺点制定具体实施方案,以修复城市水体生态环境。     

Silicate Release from Sand-Manipulated Sediment Cores: Biogenic or Adsorbed Si?

The influence of an addition of either sand and/or spring-bloom algae on the efflux of nutrients from intact sediment cores from the Baltic Sea was studied in a flow-through experiment. The addition of sand significantly increased the efflux of silicon (Si) from sediment, but the algal addition did not. The effects on phosphorus (P) were not as clear, and fluxes of nitrogen (NH₄ and NO_2?+?3) remained relatively unaffected by the additions. The small effect of the algal addition was caused by the short time-period covered by the experiment and possibly by adsorption of released Si by the sediment. A follow-up bottle experiment showed that despite the apparently lower content of easily available Si and biogenic silica, BSi, in the sand, the sand-induced Si efflux was caused by release of Si from the sand itself, rather than by indirectly increasing the dissolution of BSi present in the sediment.     

Controlled release of biofunctional substances by radiation-induced polymerization: 1. Release of potassium chloride by polymerization of various vinyl monomers

The release behaviour of a drug from flat circular capsules obtained by radiation-induced polymerization at low temperatures and with different hydrophilic properties has been studied. The effect of various factors on release property was investigated. The release process could be divided into three parts, an initial quick release stage, stationary state release stage and a retarded release stage. Release behaviour in the stationary state was examined using Noyes-Whitney and Higuchi equations. It was shown that the hydrophilic property of polymer matrix expressed by water content was the most important effect on diffusion and release rate. Rigidity of the polymer may also affect diffusivity. The first quick release step could be attributed to rapid dissolution of drug in the matrix surface due to polymer swelling.     

Effect of the anionic‐group/cationic‐group ratio on the swelling behavior and controlled release of agrochemicals of the amphoteric,superabsorbent polymer poly(acrylic acid‐co‐diallyldimethylammonium chloride)

A series of amphoteric, superabsorbent polymers [poly(acrylic acid‐co‐diallyldimethylammonium chloride)] with different molar ratios of anionic groups to cationic groups were prepared by solution polymerization to investigate their swelling behaviors and the controlled release of agrochemicals. Various factors, including the solution pH, the concentrations of different salt solutions, and the temperature, were studied. The dynamic parameters of hydrogels at different temperatures suggested that diffusion was Fickian at lower temperatures, whereas non‐Fickian diffusion prevailed at higher temperatures. A copolymer hydrogel with a low anionic‐group/cationic‐group ratio showed a higher swelling capacity in water and higher salt tolerance. Also, the anionic‐group/cationic‐group ratio was not the dominant factor in determining the water retention. A poly(acrylic acid‐co‐diallyldimethylammonium chloride) hydrogel could control the release of agrochemicals effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 986–991, 2006     

电渗-帽封联用技术对底泥内源污染释放的阻控效果

近年来关于河湖底泥内源污染的原位控制技术受到了广泛的关注和应用。本文针对水体底泥内源污染的释放问题,研究了“电渗-帽封”联合技术的控制效果。电渗处理试验结果表明,电压越高,电渗处理后底泥向上覆水中释放的氨氮量越低,但总磷释放量升高。后续的帽封试验结果表明,使用天然粗河砂效果最好,且帽封厚度越高,材料粒径越小,对污染物释放的控制效果越好。采用20V电渗电压预处理实际底泥,并采用3～5mm粒径的天然粗河砂作为帽封材料,在3cm帽封厚度条件下,对污染物释放的阻控效率可达到66.9%。本研究的结果表明,“电渗-帽封”技术具有良好的底泥污染阻控效果,可以作为一种有效的原位处理方法来阻止底泥内源污染的释放,但其潜在的生态环境效应还需要进一步关注。     

氨水溶液降膜蒸发实验

发生器和吸收器的传热性能是影响制冷机组和双工质发电机组做功效率的关键因素,为了提高中低温地热（余热）在热泵机组和地热双工质发电系统中的利用效率,本文选用50%和60%的氨水溶液作为循环工质,对约6 m长的竖管降膜蒸发器的传热特性进行实验研究,分别讨论喷淋密度和热水温度对垂直降膜蒸发器的传热系数、氨蒸气量和蒸发压力的影响。结果表明,降膜蒸发器的传热系数和氨蒸气量随喷淋密度的增加先增大后减小,传热系数和蒸发压力随着热源温度的增大而增加;50%和60%的氨水溶液喷淋密度最佳值分别在0.2200～0.2500 kg/(m·s)和0.2600～0.2900 kg/(m·s);传热系数和热源温度呈线性关系。氨水溶液的实验传热系数明显高于现有文献中水的实验传热系数,通过两种不同浓度的溶液对比发现,60%的氨水溶液传热性能明显优于50%的氨水溶液。