Toxicity threshold of lead(Pb) to nitrifying microorganisms in soils determined by substrate-induced nitrification assay and prediction model

Lead （Pb） contamination has often been recorded in Chinese field soils. In recent years, efforts have been made to inves- tigate Pb toxicity thresholds in soils with plant growth and microbial assays. However, the influence of soil properties on Pb toxicity impacts on soil microbial processes is poorly understood. In this study ten soils with different properties were collected in China to investigate the relationships between thresholds of Pb toxicity to soil microbes and soil properties. The effect of soil leaching on Pb toxicity was also investigated to determine the possible influence of added anions on Pb toxicity during dose-response tests. Toxicity was inferred by measuring substrate-induced nitrification in leached and non-leached soils after Pb addition. We found that soil microbe Pb toxicity thresholds （ECx, x=10, 50） differed significantly between the soils; the 10% inhibition ratio values （ECI0） ranged from 86 to 218 mg kg-1 in non-leached soils and from 101 to 313 mg kg in leached soils. The 50% inhibition ratio values （EC50） ranged from 403 to 969 mg kg^-1 in non-leached soils and from 494 to 1 603 mg kg^-1 in leached soils. Soil leaching increased EC50 and EC50 values by an average leaching factor （LF） of 1.46 and 1.33, respectively. Stepwise multiple regression models predicting Pb toxicity to soil microbes were developed based on ECx and soil properties. Based on these models, soil pH and organic carbon are the most important soil properties af- fecting Pb toxicity thresholds （R2〉0.60）. The quantitative relationship between Pb toxicity and soil properties will be helpful for developing soil-specific guidance on Pb toxicity thresholds in Chinese field soils.

普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响及校正方法

磷灰石是火成岩、变质岩和沉积岩中广泛分布的含铀矿物,开展磷灰石U-Pb年代学研究对揭示岩浆演化过程、示踪溯源等方面具有重要意义。激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)是开展磷灰石U-Pb年龄微区分析的重要手段之一。当前,基体匹配磷灰石U-Pb定年矿物标样缺乏和标样中不可避免的普通铅是制约LA-ICP-MS高精度磷灰石U-Pb年龄分析的主要瓶颈。本文对比研究了标样中普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响,采用含普通铅的磷灰石MAD作外标直接开展U-Pb年龄校正,获得的被测样品年龄会产生显著的系统偏差(最大约6%);采用207Pb法或Tera-Wasserburg图解法先校正标样中普通铅,再利用校正后的数据进行元素分馏和仪器漂移校正则可获得准确的磷灰石U-Pb年龄,与推荐值偏差在2%以内。另一方面,为消除标样中普通铅对分析结果的影响,本文还采用水蒸气辅助激光剥蚀方法,实现以NIST612玻璃作为外标准确分析磷灰石U-Pb年龄,解决了磷灰石U-Pb定年微区分析高质量标样缺乏的难题。本研究通过对标样中普通铅进行预校正或采用非基体匹配分析,建立了高精度LA-ICP-MS磷灰石U-Pb定年新方法,将促进磷灰石U-Pb年代学在地球科学研究中的应用。

Toxicity of cadmium and lead on tropical midge larvae,Chironomus kiiensis Tokunaga and Chironomus javanus Kieffer(Diptera:Chironomidae)

Objective:To investigate the acute toxicity of cadmium and lead on larvae of two tropical Chironomid species,Chironomus kiiensis(C.kiiensis) Tokunaga and Chironomus javanus(C. javanus) Kieffer.Methods:Different larval instars(first-fourth) were exposed using a sialic non-replacement testing procedures to various concentrations of cadmium and lead.Results: In general,younger larvae(first and second instars) of both species were more sensitive to both metals than older larvae(third and forth instars).The toxic effects of the metals on C.kiiensis and C. javanus were influenced by the age of the larvae(first to fourth instars),types of metals(cadmium or lead) and duration of larval exposure(24,48,72 and 96 h) to the metals.Conclusions:Cadmium was more toxic to the chironomids than lead and C.javanus was significantly more sensitive to both metals than C.kiiensis(P<0.05).

Assessing availability, phytotoxicity and bioaccumulation of lead to ryegrass and millet based on 0.1 mol/L Ca(NO_3)_2 extraction

This study was conducted to assess availability, phytotoxicity and bioaccumulation of lead （Pb） to ryegrass （Lolium perenne L.） and millet （Echinochloa crusgalli） based on the 0.1 mol/L Ca（NO3）2 extraction. Effect of soil properties on availability, phytotoxicity and bioaccumulation of Pb to the two plants was also evaluated. Five soils with pH values varying from 3.8 to 7.3, organic carbon （OC） contents from 0.7% to 2.4%, and clay contents from 11.6% to 35.6% were selected. Soils were spiked with Pb to achieve a range of concentrations： 250, 500, 1000, 3000 and 5000 mg/kg. Pb availability in the spiked soils was estimated by extracting soil with 0.1 mol/L Ca（NO3）2. The results indicate that plants yield decreased with decreasing soil pH and increased with increasing soil clay and OC content. Negative relationship between available Pb and the relative dry matter growth （RDMG） of the two plants were significantly related. Available Pb used to assess EC20 （20% effective concentration） and EC50 （50% effective concentration） of millet was 119 and 300 mg/kg, respectively. Available Pb used to assess EC20 and EC50 of ryegrass was 63 and 157 mg/kg, respectively. Bioaccumulation, expressed as bioconcentration factors of Pb, was inversely related to soil pH, soil OC and clay content. Strong relationships were found between available lead and uptake by the two plants （P was 0.92 and 0.95 respectively）. In general, 0.1 mol/L Ca（NO3）2 available Pb may be used to assess the availability, phytotoxicity and bioaccumulation of lead to the two plants tested.

Effect of acetate on lead toxicity to microbial biomass in a red soil

A laboratory incubation experiment was conducted to elucidate the effect of acetate on lead bioavailability and toxicity to microbial biomass in a red soil. Results indicated that the application of acetate along or at the lower lead levels of 100 and 200 μg/g soil stimulated the soil microbial biomass. The addition of acetate at the higher lead levels of 300, 450 and 600 μg/g soil caused significantly greater reductions in the biomass carbon(C mic ) and the biomass nitrogen (N mic ), compared with the control or the same lead levels applied individually. A greater increase in the biomass C:N ratio occurred by acetate addition at the same lead levels. The concentration of 0.01 mol/L CaCl 2 extractable lead was considerably higher in the lead plus acetate treatments than at the same lead levels with no acetate. Based on these results, it was concluded that the application of acetate might have suppressed the lead adsorption in the soil which in turn resulted in its more bioavailability and hence more toxicity to the soil microbial biomass.

Effect of lead acetate toxicity on experimental male albino rat

Objective:To evaluate the effect of different doses of lead acetate(1/20,1/40 and 1/60 of LD_(50))on body weight gain,blood picture,plasma prolein profile and the function of liver,kidney and thyroid gland.Methods:Male albino rats were divided into four groups,the first group represented the health control animals,while the second,third and fourth groups were ingested orally with sub lethal doses of load acetate(1/20,1/40 and 1/60)of the oral LD_(50),respectively.One dose was ingested every two days during the experimental period(14 weeks)including the adaptation time.Blood was collected and used for all analysis.Results:The results showed that,the ingestion of Pb^(2+)induced significant stimulation in glutamic-pyruvic transaminase(ALT)and glutamic-oxalacetic transaminease(AST)activity.Also,total soluble protein and albumin contents of plasma were significantly decreased,while the content of globulin was changed by the Pb^(2+)treatments.The cholinesteiase activity was inhibited,but the activities of alkaline and acid phosphates and lactate dehydrogenase were stimulated,while plasma glucose level was elevated as a result of lead acetate intoxication.In case of blood picture,Pb^(2+)ingestion reduced the contents of hemoglobin and RBCs count of intoxicated rat's blood and the plasma levels of T3,T4 and blood WBCs count were decreased.Conclusions:It can be concluded that lead acetate has harmful effect on experimental male albino rats.Therefore,the present work advises people to prevent exposure to the lead compound to avoid injurious hazard risk.

Moringa oleifera leaf ethanol extract ameliorates lead-induced hepato-nephrotoxicity in rabbits

Objective: To evaluate the effect of Moringa oleifera leaf ethanol extract as an adjunct treatment on lead acetate induced hepatonephrotoxicity in rabbits. Methods: Thirty-six male New Zealand White rabbits were assigned into two main groups. The first group(14 rabbits) served as normal control. The second group(22 rabbits) was administered orally with lead acetate at a dose of 40 mg/kg/day, 5 days/week for 8 weeks. At the 4 th and the 8 th week of treatment, 6 animals(3 animals at each period) of the second group were sacrificed while the remaining animals(16 rabbits) were assigned randomly into 2 subgroups(8 rabbits each): treated and non-treated. The first subgroup was orally given 1 m L phosphate-buffered saline for further 4 weeks while the second subgroup was administered orally with Moringa oleifera leaf ethanol extract at a dose of 400 mg/kg/day for the same period. Blood samples were collected to determine hematological and serum biochemical indices. Tissue specimens were collected from the liver and kidney for evaluation of the oxidant/antioxidant markers and for histopathological examinations.Results: Lead acetate exposure decreased the mean body weight gain, hematocrit, hemoglobin, mean corpuscular volume, and lymphocytes count. Moreover, it markedly increased counts of monocytes and platelets, serum enzyme activity, levels of creatinine, total cholesterol, triglycerides, and low-density lipoprotein cholesterol. Malondialdehyde level was markedly increased while the reduced glutathione content was significantly decreased in liver tissue of lead intoxicated-rabbits. Histopathological alterations were also noticed in the liver and kidney of lead intoxicated rabbits. Moringa oleifera leaf ethanol extract significantly improved hematological and serum biochemical parameters and histopathological structure of the liver and kidney. Conclusions: Moringa oleifera leaf ethanol extract ameliorates hemato-biochemical and histopathological alterations caused by lead acetate and improves hepatic and renal functions.

STUDY ON THE RELATIONSHIP BETWEEN SPECIATION OF HEAVY METALS AND THEIR ECOTOXICITY——I. TOXICITY OF Cu, Cd , Pb AND Zn IN SEAWATER TO THREE MARINE ALGAE IN THE PRESENCE OF DIFFERENT COMPLEXATION AGENTS

Heavy metal is a main pollutant in the marine ecosystem . so study on the effect of heavy metal on phytoplankton is important . Algae (Chaetoceros sp . , Dunaliella sp . ., Dicrateria zhanjiangenis Hu . var . sp .) were laboratory cultured to observe the effect of heavy metals on their growth . The effect of different metal ion concentration , the detoxication effect of complexation agents and the growth of algae in different media and different nutrition levels were studied to evaluate the effect of metal speciation . It is proved that trace amount of heavy metals can stimulate the growth of algae cells but that high concentration is lethal . The sequence of toxicity is Cd2+】Zn2+】Pb2+ . In ordinary nutrition conditions , the detoxication sequence of complexation agents to Chaetoceros sp . is EDTA 】 sodium salicylate 】 sodium oxalate 】 sodium citrate 】 sulfanilic acid 】 O-phenanthroline . This is in good conformity with the stability constant sequence of these agents with copper and good evidence that

Reply to 'Statistical testing and distribution for lead chloride toxicity'

We are very grateful for the letter written by Dr Lange,and indeed apologize for the mistakes noted in the word-ing of our text regarding statistical analysis.This wasdue to changes carried out while revising the manuscriptat the request of reviewers,whom we thank for,point-ing out several issues that were actually similar to thosenoted by Dr.Lange.Unfortunately,we were unable todescribe and discuss our findings properly in the context

Toxicity and bioaccumulation of heavy metals in Phanerochaete chrysosporium

The responses of the growth and metabolism activity of Phanerochaete chrysosporium （P. chrysosporium） to cadmium （Cd）, lead （Pb） and their combined pollution stress, were investigated in plate and liquid culture conditions. The diameter of colony, biomass ofP. chrysosporium, ligninolytic enzyme activities and bioaccumulation quantity of heavy metals were detected. The results indicated that Cd was more toxic than Pb to P. chrysosporium and the toxicity of Cd and Pb to P. chrysosporium was further strengthened under Cd＋Pb combined pollution in different culture conditions. Heavy metals Cd and Pb had indirect influence on the production of ligninolytic enzymes by directly affecting the fungal growth and metabolic activity, and by another way in liquid culture. In addition, the results provided an evidence of the accumulation of Cd and Pb on the mycelia ofP. chrysosporium.

生活垃圾焚烧系统中Pb和Cd的迁移转化特性

为明晰垃圾焚烧系统中Pb和Cd的迁移转化特性,以处理规模500 t/d的城市生活垃圾焚烧系统为研究对象,对系统中不同位置产生的灰渣中Pb和Cd富集特性、浸出毒性和赋存形态进行分析。结果表明:底渣和二三烟道中主要晶相矿物为SiO_(2)和CaCO_(3),水平烟道灰、尾部烟道灰中主要晶相矿物为SiO_(2)、KCl、NaCl、CaCO_(3)和CaSO_(4),布袋除尘器灰中CaOHCl为Ca(OH)_(2)吸收HCl形成的产物;Cd和Pb分别在尾部烟道灰和布袋除尘器灰中富集程度最高,水平烟道灰中Cd、尾部烟道灰和布袋除尘器灰中Pb和Cd的浸出浓度高于《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3—2007)限值;底渣和二三烟道灰中Pb以多种赋存形态存在,水平烟道灰和尾部烟道灰中Pb主要以残渣态形态存在,随着烟气温度的降低,尾部烟道灰和布袋除尘器灰中的酸可溶态Pb含量有所上升;底渣和二三烟道灰中Cd主要以可还原态和残渣态形态存在,水平烟道灰和尾部烟道灰中Cd主要以酸可溶态形态存在,布袋除尘器灰中酸可溶态Cd明显减少,主要为可还原态。

Lead Isotopic Composition and Lead Source of the Huogeqi Cu-Pb-Zn Deposit,Inner Mongolia,China

The Huogeqi orefield located on the northern side of Mt. Langshan, Inner Mongolia occurs in the Middle Proterozoic Langshan Group metamorphic rocks, and the orebodies arc stratiform. In the past twenty years, many Chinese geologists have conducted researches on the Huogeqi Cu-Pb-Zn deposit, but there has been still a controversy on its origin. Some advocate that the deposit is of sedimentary-metamorphic rcworking origin, some hold that it is of sea-floor SEDEX origin, and others have a preference for magmatic superimposition origin. The crux of the controversy is that there is no common understanding about the source of ore-forming materials. In this paper, the Pb isotopic compositions of regional Achaean-Early Proterozoic basement rocks, various types of sedimentary- metamorphic rocks and volcanic rocks in the mining district, Late Proterozoic and Hercynian magmatic rocks arc introduced and compared with the orc-lead composition, so as to constrain the source of the ore lead. The result indicates that （1） sulfides in the ores have homogeneous Pb isotopic compositions, showing a narrow variation range. Their ^206pb/^204pb ratios arc within a range of 17.027- 17.317; ^207Pb/^204pb ratios, 15.451-15.786 and ^208Pb/^204pb ratios, 36.747-37.669; （2） the Pb isotopic compositions of the regional Achaean-Early Proterozoic basement rocks arc characteristic of the old Pb isotopic composition at the early-stage evolution of the Earth, which varies over a wider range, reflecting significant differences in Pb isotopic compositions of the ores. All this indicates that the source of ore lead has no bearing on the basement rocks; （3） the sedimentary-metamorphic rocks in the mining district arc characterized by highly variable and more radiogenic Pb isotopic compositions and their Pb isotopic ratios arc obviously higher than those of ores, demonstrating that ore lead did not result from metamorphic rcworking of these rocks; （4） Pb isotopic compositions of Late Proterozoic diorite-gabbro and Hercynian granite are higher than those of ores. Meanwhile, the Pb isotopic compositions of sulfides in the small-sized strata-penetrating mineralized veinlets formed at later stages arc completely consistent with that of sulfides in stratiform-banded ores, suggesting that these veiniets arc the product of autochthonous rcworking of the stratiform-banded ores during the period of metamorphism and the late magmatic superimposition-mineralization can be excluded; （5） amphibolite, whose protolith is basic volcanic rocks, has the same Pb isotopic compositions as ores, implying that ore lead was derived probably from basic volcanism. So, the source of ore-forming materials for the Huogeqi deposit is like that of the volcanic massive sulfide （VMS） deposits. However, the orebodies do not occur directly within the volcanic rocks, and instead they overlie the volcanic rocks, showing some differences from those typical VMS-type deposits.

皖南解带山铅锌矿成矿岩体锆石U-Pb年代学研究及地质意义

解带山铅锌矿位于皖南铅锌成矿区,本文对解带山花岗闪长斑岩含矿岩体开展了岩相学和锆石U-Pb年代学研究,获得锆石U-Pb年龄为136.4±1.4 Ma,形成于早白垩世,属燕山晚期岩浆活动产物,花岗闪长斑岩相对较低的结晶温度和相对中等的氧逸度有利于铅锌沉淀成矿。

Effects of lead(Pb)-induced oxidative stress on morphological and physio-biochemical properties of rice

In rice,high concentration of lead(Pb)can cause phyto-toxicity affecting several physiological functions.Cultivation of rice varieties that are resistant to Pb-induced oxidative stress is an important management strategy in Pb-contaminated soils.In the current study,we evaluated four different rice cultivars for their response to Pb-induced stress.Three japonica type cultivars X-Jigna,Ediget,and Furat,and one Indica type cultivar Amber 33 were grown in soil containing different Pb concentrations(0 mM,0.6 mM,and 1.2 mM).The soil was treated with 0 mM or 0.6 mM or 1.2 mM Pb solution one month prior to rice seedling transplantation.Thereafter,four-week-old rice seedlings were transplanted into the treated soil and their responses were observed until maturity.The data revealed that a highest concentration of Pb(1.2 mM)induced significant reduction in agronomic traits such as plant height,number of tillers per plant,number of panicles per plant,and number of spikelets per panicle in all the rice cultivars.However,least reduction in the agronomic traits was observed in X-Jigna,whereas the highest reduction in the agronomic traits was observed in Ediget.Antioxidant activity of catalase(CAT),peroxidase(POD),polyphenol oxidase(PPO),and superoxide dismutase(SOD),was evaluated along with the accumulation of superoxide ions(O2.-),protein,proline,chlorophyll,sucrose,glucose,and fructose contents in all the rice cultivars.A significant increase in antioxidant activity and in the accumulation of proline and sucrose contents with the least reduction in the chlorophyll and protein contents was observed in X-Jigna suggesting that X-Jigna is the most tolerant among all the rice cultivars tested against Pb-stress.On the other hand,non-significant and slightly significant increase in the antioxidant activity,less accumulation of proline and sucrose contents,and higher reduction in the chlorophyll and protein contents was observed in Ediget,which further suggest that Ediget is the most susceptible rice cultivar to Pb-stress.In addition,the other rice cultivars Furat and Amber 33,were found to be moderately tolerant to Pb-induced oxidative stress.In summary,our results suggest that tolerance to Pb-induced oxidative stress would be a result of a synergetic action of both enzymatic and non-enzymatic antioxidant systems,leading to a balanced redox status in rice.

Lead isotope geochemical characteristics of Pb-Zn-Cu deposits on the southwestern margin of Tarim,and their significance

The polymetallic(Pb,Zn,Cu,etc) ore belt on the southwestern margin of Tarim is one of the major regions with the greatest prospecting potential in Xinjiang.Reported in this paper are the lead isotope data for 66 sulfide samples(including 50 galena samples,15 chalcopyrite samples and 1 pyrite sample) collected from such representative deposits as Tamu,Tiekelike,Kalangu,Abalieke,etc.in this ore belt.The Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb in the galena samples range from 17.931 to 18.176,15.609 to 15.818 and 38.197 to 38.944,with the average values of 18.017,15.684 and 38.462,respectively.Those in the chalcopyrite samples range from 17.926 to 18.144,15.598 to 15.628 and 38.171 to 38.583,with the average values of 18.020,15.606 and 38.262,respectively.The pyrite sample has the Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb to be 17.980,15.604 and 38.145,respectively.In combination with the previous Pb isotope data for sulfides,it is found that there is only a slight variation in the Pb isotopic composition of galena,chalcopyrite,sphalerite and pyrite in the ore belt.However,there is some difference in Pb isotopic characteristics between galena and chalcopyrite,especially the Pb isotopic composition of galena shows an obvious linear correlation with some other relevant parameters(e.g.β and γ).The comprehensive analysis suggested that lead in galena(maybe including sphalerite and pyrite) was derived principally from wall rocks and underlying basement,and that in chalcopyrite only originated from the basement.The single-stage model ages of these sulfides couldn't indicate the time limit of metallogenesis(Pb,Zn,Cu,etc.),and the positive linear correlations for the Pb isotopic composition of galena are of no single-stage and two-stage Pb-Pb isochron significance.Furthermore,there are significant differences in Pb isotopic composition characteristics between the genetic type of deposits in this polymetallic ore belt and the Mississippi Valley type(MVT).In addition,the authors also pointed out that there is a phenomenon of differentiation(not paragenesis) for lead and copper elements during the process of metallogenesis in this ore belt.

Residual Regularity in Tissues of Layer after Combined Exposure to Lead(Pb)and Cadmium(Cd)

[ Objective] The study was to investigate residual regularity in tissues of layer after combined exposure to lead （Pb） and/or cadmium （ Cd ）. [ Method] I.aad acetate （100 mg/L） and/or cadmium chloride （50 mg/L） were administered in drinking water to 120 individuals of 40 -week -old hyline layers for 8 weeks. [ Result] Compared with the Cd group, the Cd content in various tissues, except kidney and femur, in Cd ＋ Pb group all increased, but the difference was not significant （P 〉 0.05 ）. The Cd contents in kidney and femur in Cd group were significantly higher than that in Cd ＋ Pb group. Compared with the group Pb, the Pb contents in breast muscle and kidney in Cd ＋ Pb group decreased significantly （ P 〈 0.05 ） ; the Pb contents in femur decreased extremely （ P 〈 0.01 ） ; while the Pb contents in leg muscle, heart and spleen increased significantly （ P 〈 0.05 ） ; the Pb contents in liver and glandular stomach were almost the same. Compared with the control group, the Cd content in various tissues in Pb group increased significantly （ P 〈 0.05 ） ; no significant changes were observed for Pb content in Cd group. [ Conclusion] Deposit of Pb and Cd in poultry body had complex interaction.

磷灰石ID-TIMS高精度U-Pb定年方法

磷灰石晶体结构呈六方晶系,具有相对高的封闭温度(350~550℃),能够容纳多种元素置换进入晶格内部,是火成岩、沉积岩、变质岩和矿床研究的重要定年矿物。然而,由于磷灰石通常具有较低铀含量和高普通铅含量,精准测定其年龄仍是当前U-Pb测年技术的一大挑战。本文基于^(208)Pb-^(235)U混合稀释剂,通过优化样品清洗、溶解以及柱色谱分离纯化U和Pb等化学前处理流程,建立了磷灰石同位素稀释-热电离质谱(ID-TIMS)高精度U-Pb定年方法,并准确测定了磷灰石标样MAD2和MAP-3的年龄,其^(206)Pb/^(238)U年龄加权平均值分别为474.6±1.7Ma和800.7±1.2Ma,单点定年精度优于0.4%,为磷灰石微区原位标样研发以及样品年龄精准测定提供技术支撑。采用MAP-3作为微区原位校正标样,对磷灰石Durango和Otter Lake进行LA-ICP-MS U-Pb测年分析,通过Tera-Wasserburg谐和图图解法扣除普通铅,获得下交点年龄分别为32.1±0.6Ma(MSWD=1.3,n=36)和910±13Ma(MSWD=1.6,n=36),与前人研究结果在误差范围内一致,进一步证实普通铅含量极低的MAP-3,是一个理想的磷灰石微区原位测年标样。与高普通铅的磷灰石标样相比,使用MAP-3作为外标能直接在数据处理软件中进行数据校正,有效地简化了数据处理过程,提高磷灰石微区原位U-Pb测年结果的可靠性。

Research of Toxic Mechanism on Anaerobic Digestion by Lead

The paper analyzes the influence of lead toxicity by anaerobic granule sludge inhibition and recovering experiments. The result shows that there are different inhibition types at differ-ent lead contents. Higher lead content leads to more inhibition granular sludge, and at the same time, the time of gas recovery is different. Lower lead content per microorganism results in sooner sludge recovery. Microorganisms have a good ability to resist lead toxicity.

Pb-Ca合金板栅电池早期容量衰减的原因

Pb-Ca合金在阀控式铅酸(VRLA)电池中应用广泛。针对Pb-Ca合金浇铸板栅电池的早期容量衰减问题进行研究。用同批次Pb-Ca合金极板,制作不同加酸化成工艺的电池,进行循环测试。充电电流小的电池发生了早期容量衰减,而大电流充电的电池循环性能正常。对发生早期容量衰减的电池进行分析,发现板栅腐蚀界面生成的硫酸铅晶体阻挡层是导致电池发生早期容量衰减的主要原因。提高电池的充电效率,如添加电解液添加剂、化成前对电池反充、增大充电电流等,可以使硫酸铅得以转化,能较好地避免电池发生早期容量衰减。

水相单层氨基改性二氧化硅的制备及Pb^(2+)吸附效果

采用硅烷偶联剂γ-氨丙基三乙氧硅烷(APTES)和(β-氨乙基)-γ-氨丙基三甲氧基硅烷(AEAPTMS),通过水相工艺分别制备出单层氨基改性二氧化硅(SiO_(2)-APTES和SiO_(2)-AEAPTMS,用作吸附剂),采用透射电子显微镜、红外光谱分析仪、热重-差热分析仪、元素分析仪等仪器对其进行了表征,考察了Pb^(2+)吸附效果的影响因素,确定了最佳吸附条件。结果表明:当偶联剂添加量(质量分数)小于15%时,可实现二氧化硅的单层氨基改性;在初始Pb^(2+)质量浓度为200 mg/L,pH值为6,吸附时间为60 min的优化条件下,SiO_(2)-APTES和SiO_(2)-AEAPTMS对Pb^(2+)的最大吸附量分别达到18.48,34.75 mg/g;吸附过程均符合拟二级动力学模型和Langmuir吸附模型,均为单分子层的化学吸附过程;吸附剂重复使用5次后,Pb^(2+)吸附量仍超过最大吸附量的90%,具有良好的循环使用性能。