Pb and Cd binding to natural freshwater biofilms developed at different pH: the important role of culture pH

The effects of solution pH on adsorption of trace metals to different types of natural aquatic solid materials have been studied extensively, but few studies have been carried out to investigate the effect of pH at which the solid materials were formed on the adsorption. The purpose of present study is to examine this effect of culture pH on metal adsorption to natural freshwater biofilms. The adsorption of Pb and Cd to biofilms which were developed at different culture pH values (ranging from 6.5 to 9.0) was measured at the same adsorption pH value (6.5). The culture pH had considerable effects on both composition and metal adsorption ability of the biofilms. Higher culture pH usually promoted the accumulation of organic material and Fe oxides in the biofilms. The culture pH also affected the quantity and species of algae in the biofilms. The adsorption of Pb and Cd to the biofilms generally increased with the increase of culture pH. This increase was minor at lower pH range and significant at higher pH range and was more remarkable for Cd adsorption than for Pb adsorption. The notable contribution of organic material to the adsorption at higher culture pH values was also observed. The profound impacts of culture pH on adsorption behavior of biofilms mainly resulted from the variation of total contents of the biofilm components and were also affected by the alteration of composition and properties of the components.     

On the effect of pH in aromatic photonitration upon nitrate photolysis

This paper studies the pH effect on the photonitration of catechol, 1-naphthol, naphthalene, and benzene. The pH trend is influenced by the generation of HNO(2) and peroxynitrous acid (HOONO) upon nitrate photolysis. HNO(2) can be involved in a direct and an indirect nitration process. Direct nitration follows the pH distribution of HNO(2) (flexus around 3). Indirect nitration, possibly involving nitrosation+oxidation, would be highest around pH3. HOONO can be involved in electrophilic nitration, where the initial formation rate of the nitroderivatives is proportional to [H(+)], or take part in nitration directly, in which case a less important pH effect in photonitration is observed. The relative importance of the various nitration pathways for each substrate determines the resulting pH effect in photonitration upon nitrate photolysis.     

Effect of pH on the growth and activity of heterotrophic sediment microorganisms

Low pH markedly reduced heterotrophic microbial activity in sediment-lake water systems. A marked reduction in both the rate and the total amount of oxygen consumed occurred as pH decreased. In addition, low pH and also low temperature (0°C) resulted in longer turnover times (Tn) and also smaller V_max values when the kinetics of ¹⁴C-glucose, ¹⁴C-glycine, and ¹⁴C-glutamic acid utilization were examined. When the response of the microorganisms to heavy metals was examined, mercury was generally more toxic than lead over the pH range of 4.5 to 7.5 but both metals were more toxic at pH 4.5 than at higher pH levels. Mercury also inhibited oxygen utilization and ¹⁴C-glucose mineralization more than lead at all pH levels. Bisulfite reduced microbial activity at all pH levels although it was always more toxic to the sediment microorganisms at pH values of 4 and 5 than at pH 7.     

Sector Analysis of pH Values in the Northeastern Region of Puerto Rico

Abstract

Acid rain precipitation has become a major environmental concern. Many long-range projects in the United States and Europe are devoted to the problems associated with acid rain pollution. In Puerto Rico, there has been no formal study on acid rain. The rainfall pH values and the air-mass trajectory of the northeastern part of the island of Puerto Rico on the surface were analyzed from January 1998 to December 2000. The air-mass trajectory was classified in five different sectors, according to where it originates. The mean pH value measured during that period showed a tendency toward acidity. The 80% of the air-mass trajectory that arrived at the station occurred in Sector I, with a pH value of 4.30. The lowest pH value measured was 4.16, and it occurred in Sector V, where the air mass originates in the northwest part of the island.     

Sector analysis of pH values in the northeastern region of Puerto Rico

Acid rain precipitation has become a major environmental concern. Many long-range projects in the United States and Europe are devoted to the problems associated with acid rain pollution. In Puerto Rico, there has been no formal study on acid rain. The rainfall pH values and the air-mass trajectory of the northeastern part of the island of Puerto Rico on the surface were analyzed from January 1998 to December 2000. The air-mass trajectory was classified in five different sectors, according to where it originates. The mean pH value measured during that period showed a tendency toward acidity. The 80% of the air-mass trajectory that arrived at the station occurred in Sector I, with a pH value of 4.30. The lowest pH value measured was 4.16, and it occurred in Sector V, where the air mass originates in the northwest part of the island.     

DO和pH值在短程硝化中的作用

在SBR反应器中对DO和pH值在短程硝化和半亚硝化过程中的作用进行试验研究,结果表明,控制低DO和适宜的pH值在短程硝化过程中起着重要的作用.本试验条件下,当DO为0.5～1.0 mg/L、pH值为7.5～8.0时,在SBR反应器中很容易实现短程硝化;当DO＞0.3 mg/L时,DO越低,出水NO2--N积累率越高;当pH值＞6.8时,不会影响系统NO2--N积累的稳定性.另外,研究结果还表明,通过控制DO和pH值可以实现半亚硝化.本试验条件下,当进水氨氮浓度为120 mg/L时,控制DO为0.3～0.4 mg/L可实现出水半亚硝化;当进水氨氮浓度为200 mg/L时,控制DO为0.5～0.6 mg/L或pH值为6.8也可以实现出水半亚硝化.     

氨法脱硫洗涤液pH的计算模型

应用酸碱质子理论,根据质子平衡方程建立了氨法脱硫洗涤液相关离子浓度与pH的相关性模型,并对其影响因素进行了讨论。研究表明:脱硫洗涤液理论计算pH与实测的pH基本吻合。结合实验验证了影响洗涤液pH的硫元素存在形态与脱硫洗涤液pH之间的相图关系,并提出模型修正方法。模型可作为氨法脱硫洗涤液pH的合理计算方法。     

水体pH和曝气方式对藻类生长的影响

利用水族箱微宇宙研究了藻类在不同pH和曝气条件下的生长和种类变化.使用天然湖水,一组试验每天调节pH,使其分别保持在8.0、8.5、9.0和9.5;另一组试验是设定不同的曝气方式,分别为不曝气、完全曝气、昼间曝气和夜间曝气,定期测定水体叶绿素a和藻类组成.pH试验结果显示,在pH 8.0～9.5范围内,pH 8.5下藻类生长状况最好,pH 9.5下生长最差,人为改变pH使其远离8.5能够抑制藻类生长.曝气试验结果显示,曝气不能抑制水体中藻类的生长,昼间曝气甚至还有明显的促进作用.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Bioaccumulation of aluminium in the freshwater snail Lymnaea stagnalis at neutral pH

This study examined the accumulation of aluminium (Al) by the freshwater snail Lymnaea stagnalis at neutral pH, when most Al would be predicted to be in an insoluble form (Al(OH)(3)). Snails were exposed to a range of Al concentrations (38-285 microg l(-1)) for 30 days, followed by 20 days in clean water. Aluminium was measured using atomic absorption spectroscopy. Significant accumulation of Al occurred in the whole soft tissues, gut, digestive gland and kidney at the latest by day 10. High concentration factors were observed, ranging from 4.5 x 10(3) in the whole soft tissues to 6.3 x 10(4) in the kidney, corresponding to actual concentrations of 800 to 7500 microg g(-1), respectively. Proportionality between environmental (water) and tissue concentrations of Al was observed in the gut but not in the other tissues. Following transfer to clean water, rapid loss of Al from the whole soft tissues and gut was seen over the first 10 days. Loss of Al from the digestive gland was much less as a proportion of the total, with approximately 90% of the Al remaining in the tissue. In contrast, significant loss of Al from the kidney occurred between days 20 and 30, even in the continued presence of Al; little further loss occurred following transfer to clean water. Aluminium is clearly available to the snail at neutral pH, the most likely route of entry being the gut. This could facilitate entry of the metal into the food chain. The possible roles of the digestive gland and kidney in the handling of Al are discussed.     

温度和pH值对CANON工艺的影响试验研究

采用2组SBBR反应器研究了进水氨氮浓度为160 mg NH⁺₄-N/L、间歇曝气并且曝停比为2 h∶2 h、DO为2.0～2.5 mg/L (曝气)/ 0.2～0.4 mg/L(停曝)和HRT为48 h时,温度和pH值对CANON工艺的影响,试验结果表明,CANON工艺最适温度和pH值分别为30℃和8。在一定温度范围内（不大于30℃）,CANON系统的氨氮转化速率和脱氮效能随着温度的升高而升高。温度达到35℃时,厌氧氨氧化反应速率较低而不能把亚硝化反应生成的NO^-₂全部转化为氮气,此时较高的DO(2.0～2.5 mg/L)不利于淘汰CANON系统内的硝酸菌,部分氨氮将通过全程硝化反应被氧化为NO^-₃。而在pH值为6～9的范围内,CANON 系统均可实现硝酸菌的“洗脱”,避免全程硝化反应的发生。     

DO和pH值在短程硝化中的作用

在SBR反应器中对DO和pH值在短程硝化和半亚硝化过程中的作用进行试验研究，结果表明，控制低DO和适宜的pH值在短程硝化过程中起着重要的作用。本试验条件下。当DO为0．5～1．0mg／L、pH值为7．5—8．0时。在SBR反应器中很容易实现短程硝化；当DO〉0．3mg／L时，DO越低，出水NO2^-N积累率越高；当pH值〉6．8时，不会影响系统NO2^-N积累的稳定性。另外，研究结果还表明，通过控制DO和pH值可以实现半亚硝化。本试验条件下，当进水氨氮浓度为120mg／L时，控制DO为0．3—0．4mg／L可实现出水半亚硝化；当进水氨氮浓度为200mg／L时，控制DO为0．5—0．6mg／L或pH值为6．8也可以实现出水半亚硝化。     

pH对生物滤池处理含H_2S和NH_3混合恶臭气体的影响

研究了pH对生物滤池处理含H2S和NH3混合恶臭气体的影响,以及不同pH下的物质转化情况和去除机制。结果表明,不同pH下,生物滤池对H2S和NH3的去除率是不同的。在强酸性(pH为2左右)和中性(pH为7左右)条件下,H2S均有较好的去除效果,这分别归于嗜酸性硫细菌和非嗜酸性硫细菌的生物降解作用。低pH下,NH3的去除归于化学中和作用;中性(pH为7左右)条件下,NH3有较高的去除率,主要依靠生物硝化作用。通过考察pH对生物滤池处理效果的影响,确定了生物滤池处理含H2S和NH3混合恶臭气体的pH控制条件和去除机制,为恶臭气体生物处理工艺的选择提供依据。     

Influence of pH on the toxicity of nitrophenols to Microtox and Spirotox tests

The toxicity of mononitrophenols and dinitrophenols (DNP) to luminescent bacteria Vibrio fischeri (Microtox test) and ciliated protozoan Spirostomum ambiguum (Spirotox test) was evaluated. Spirotox was more sensitive to the tested nitrophenols (NPs) than the Microtox test. 2,5-DNP was the most toxic and 2-NP was the least toxic to the both bioindicators. The toxicity depended greatly on the pH of the medium. The highest changes were observed for DNPs, where the toxicity decreased more than 20-times when the pH increased from 6 to 8. No significant decrease of the toxicity was found for NPs, when the pH increased from 6 to 7. Greater increase of the pH to 8 caused from 1.5 to 4-fold decrease of the toxicity.     

鲁棒fuzzy-PID在污水pH值控制中的应用

某化工企业排放出来的高浓度有机污水酸碱度因工艺的不稳定性而波动较大,在集散控制系统上采用了常规PID控制后,生物中和罐污水的酸碱度超调量偏大,稳态误差也高于预定值,达不到当地的排放要求,加进了模糊建模和鲁棒控制技术后,实施结果表明,酸碱度控制系统的动静态性能指标显著提高,鲁棒fuzzy-PID模糊控制技术对滞后对象具有较高的可控性.     

鲁棒fuzzy-PID在污水pH值控制中的应用

某化工企业排放出来的高浓度有机污水酸碱度因工艺的不稳定性而波动较大，在集散控制系统上采用了常规PID控制后，生物中和罐污水的酸碱度超调量偏大，稳态误差也高于预定值，达不到当地的排放要求，加进了模糊建模和鲁棒控制技术后，实施结果表明，酸碱度控制系统的动静态性能指标显著提高，鲁棒fuzzy-PID模糊控制技术对滞后对象具有较高的可控性。     

Effect of pH and the role of organic matter in the adsorption of isoproturon on soils

Equilibrium measurements were carried out with the herbicide isoproturon on natural adsorbents (brown forest-, chernozem-, sandy soils and quartz) in different buffered media (pH 5, 7, 8 phosphate buffer). Adsorption isotherms were fitted by a multi-step adsorption equation providing numerical information used in the environmental propagation models and risk assessment works. In the adsorption of the slightly polar isoproturon the dissolved organic matter of the soil and the pH play an important role. At molecular level, results are interpreted by taking into consideration the hydrophobic interaction and the formation of hydrogen bonds between the surface and the solute. The observed adsorption behavior indicates that the organic matter content of the soils and its soluble fulvic acid, alkaline soluble humic acid and insoluble humin fractions were considerable different. The chernozem soil containing the highest amount of insoluble organic fraction proved to be a very efficient adsorbent. The brown forest and the sandy soils exhibit rather similar adsorbent properties but at pH 7 the latter containing more fulvic acid adsorbs less isoproturon due to the enhanced solubility of the soil organic matter. In alkaline conditions the negatively charged solute and the surface repel each other and the hydrophobic interactions are also weaker than in neutral media.     

电气石自发电极性对溶液pH和亚硝化胞菌生长影响研究

电气石具有自发电极性,利用傅里叶变换红外光谱分析不同煅烧温度处理下电气石的变化,研究并探讨电气石自发电极性对溶液pH的影响;并借助微生物检测手段,研究电气石自发电极性对微生物生长的影响.结果表明,电气石能调节溶液pH至弱碱性,煅烧温度为800℃时,由于电气石晶胞体积的缩小,电极性增强,pH显著上升(9.8);煅烧温度为1 000℃时,BO3原子团振动峰消失,羟基振动峰和Si-O-Si对称伸缩振动峰强度明显减弱,自发电极性消失,不再具有调节pH的作用.电气石可明显促进亚硝化细菌生长繁殖,缩短细菌适应期,提前进入稳定期,大幅增加细菌数量,5d后投加电气石组中亚硝化单胞菌数量为9.66×108个/mL,远多于对照组中亚硝化单胞菌的数量(8.04×10 7个/mL).     

pH对煤泥水絮凝沉降的影响

选择聚合氯化铝(PAC)/阴离子型聚丙烯酰胺(PHP)、氯化钙(CaCl2)/非离子型聚丙烯酰胺(NPAM)组合与NPAM、PHP、两性离子型聚丙烯酰胺(ZPAM)作为絮凝剂,在对道清选煤厂水采筛下原生煤泥和浮选尾矿的煤泥水进行组合药剂絮凝实验的基础上,考察了pH对煤泥水絮凝沉降的影响。实验结果表明,在不同的pH下,煤泥水的絮凝效果不同:在酸性条件下,宜单独使用有机高分子絮凝剂;在中性至碱性条件下,无机凝聚剂和有机絮凝剂联合使用效果较好。