广西环江铅锌矿尾砂坝坍塌对农田土壤的污染及其特征

广西环江县因铅锌金属矿区尾砂坝坍塌导致大面积农田污染甚至绝收.为此,对矿区下游污染区和非污染区的农田土壤、尾砂和河流沉积物进行了系统调查和研究.调查结果表明,农田遭受As、Pb、Zn和cd污染,土壤酸化严重,pH值最低至2.5,全硫含量高达2.29%.X-衍射鉴定结果表明,受污染土壤中存在大量硫铁矿,这是导致土壤酸化的主要物质.由于强酸性淋溶作用的影响,污染农田中La、Ce和Nd等稀土元素发生明显的向下淋溶现象,导致表层土壤La、Ce和Nd元素含量明显低于未污染农田.从土壤剖面分布来看,污染点的土壤中As、Pb和Zn仍主要集中分布在表层0～30 cm范围,发生土壤酸化现象的土层深度仍局限于0～70 cm范围.     

One-step formation of oligopeptide-like molecules from Glu and Asp in hydrothermal environments

Biopolymer accumulation in the absence of enzymes is an essential step for the chemical evolution of primitive life-like systems, and successful simulation experiments of prebiotic biopolymer formation have suggested that oligopeptides could have formed near submarine hydrothermal vent environments on primitive earth. However, the yield and length of oligopeptides -- typically limited to 6-mers -- seems to be inadequate. One reason is the rapid formation of diketopiperazines (DKPs) from dipeptides. In this study, using a hydrothermal microflow reactor, we show that the one-step synthesis of oligopeptide-like molecules of length up to 20-mers proceeds from Glu and Asp. Yields of up to 0.17-0.57% were obtained in an acidic solution within 183 s at 250-310 degrees C, as evaluated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis and different types of high-performance liquid chromatography (HPLC) analyses. The present study indicates that Glu and Asp may have played important roles in the chemical evolution of oligopeptide-like molecules in hydrothermal vent environments on primitive earth.     

稀土元素对梅园主要土壤动物群落结构组成的影响

为阐明不同稀土处理对梅园土壤动物群落组成的影响,采用手拣法、干漏斗法和湿漏斗法对梅园各稀土处理区土壤动物群落组成进行系统调查,共得土壤动物标本8076个,隶属于4门15纲31目.其中昆虫纲物种最为丰富,有12目,占全部种群数的58.41%;;鞘翅目、膜翅目、蜱螨目、双翅目和弹尾纲等5种优势类群占土壤动物个体总数的81.44%.5种稀土处理区中,杂食性土壤动物功能团所占的比例均高于植食性功能团所占的比例,且杂食性土壤动物所占的比例依次为对照区(CK)(La处理区(下同)(Ce区(Pr区(Nd区(Sm区.不同浓度稀土处理区中土壤动物类群和个体数量均随着稀土浓度增加而减少,杂食性功能团所占的比例也高于植食性功能团所占的比例,且杂食性功能团所占的比例依次为对照区(CK)(25区(mg·kg-1处理区,下同)(50区(100区(500区(1000区(2000区(3000区.以Pr处理后的土壤动物物种数多,个体数量大,优势集中性指数高,优势物种优势性极明显,其它4种稀土在类群数、个体数、优势集中性指数和优势类群优势性和Pr规律基本相同,依次为Nd、Sm、Ce和La,但均比CK小.因此,5种稀土及其不同浓度处理区土壤动物群...     

Ce3+对厌氧颗粒污泥产VFA的影响

采用批式实验,以葡萄糖和乙酸钠为基质,研究投加不同浓度稀土Ce³⁺对稳定驯化和长期贮存的厌氧颗粒污泥消化产VFA的影响.结果表明,Ce³⁺浓度<1 mg/L时可降低消化过程中的VFA浓度,促进丁酸向乙酸的转化以及乙酸转化为甲烷;Ce³⁺浓度为1～10 mg/L时则抑制细菌活性,不利于乙酸和丁酸的降解.稀土Ce的投加对以葡萄糖为基质的厌氧颗粒污泥消化产VFA中各组分的质量分数影响较小,厌氧消化前期和中期VFA产物主要为丁酸和乙酸,两者含量之和约为96%,丙酸含量<3%.以乙酸钠为唯一基质厌氧消化时,0.05 mg/L Ce³⁺的投加对乙酸钠降解具有一定促进作用,可提高反应速率和去除率.污泥经过长期贮存活性降低,但含稀土Ce的厌氧颗粒污泥活性高于不含稀土的污泥,利用含稀土Ce的污泥有利于反应器再启动.     

土壤中La与P迁移的关联性初步研究

通过室内土柱淋溶试验和人工降雨模拟试验分别观察了元素P和La从土壤表层纵向和横向流失的特征,初步探讨了单一稀土元素La与土施畜禽肥料P随暴雨径流流失的关联性.淋溶试验结果表明,外源La和P在土壤中的纵向迁移都非常困难,La和P的迁移深度分别不超过土壤表层6 cm和8 cm;增加外源La可以降低土壤中水浸提P、NaHCO3浸提P和NaOH浸提P的量,提高HCl浸提P的量,增加残渣态P在TP中的比重;而人工降雨模拟试验结果表明,绝大部分La和总P都是通过径流沉积物相流失(占流失总量的95%以上),对于添加不同剂量的La系列,无论是从土壤表层的流失速率还是流失的总量,总P和La都存在良好的相关性.     

Toxicological effects involved in risk assessment of rare earth lanthanum on roots of Vicia faba L. seedlings

Combined chemical analyses and biological measurements were utilized to investigate potential toxicological effects and possible mechanisms involved in risk assessment of rare earth elements (REEs) on Vicia faba L. seedlings, which were hydroponically cultivated and exposed to various concentrations of lanthanum (La) for 15 days. The results showed that La contents in both the solution and roots increased with the increase of extraneous La, contributing to hormetic dose responses of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and endoprotease (EP) isozymes activities, and HSP 70 production enhanced at low doses but suppressed at higher doses of La. These physiological responses constituted antioxidant and detoxification systems against La-induced oxidative stress. The elevated La levels also contributed to oxidatively modified proteins, which were most responsible for subsequent cell death and growth retardation of the roots. By combination of hormetic and traditional threshold dose levels, the threshold dose range was deduced to be 108-195 μg La/g dry weight in the roots, corresponding to 0.90-3.12 mg/L of soluble La in the culture solution. It suggests that persistent applications of REEs may lead to potential ecological risk in the environment.     

稀土对植物抗逆作用的自由基机制

通过研究及收集的资料，提出在植物生长期中，稀土元素能增加植物的抗逆性，当植物受到酸雨、重金属及盐胁迫时，稀土表现出抗氧化性质，而且稀土对植物的抗逆作用是由于其具有清除含氧自由基的作用。     

自然保护区人类活动天地一体化监管与评价技术体系

基于遥感监测与实地核查相结合的技术,构建了集目标、内容、指标、流程为一体的自然保护区人类活动天地一体化监管与评价的技术体系,在此基础上提出了自然保护区人类活动影响评价方法和模型.最后,为了验证方法体系的可靠性,以河南董寨国家级自然保护区为例进行了示范研究,结果表明：该自然保护区有工矿用地、旅游用地、采石场、农业用地、居民点、其他人工设施和道路7种人类活动类型,人类活动总面积占保护区总面积的16.60%,以农业用地为主,占自然保护区人类活动总面积的89.41%.人类活动主要分布在实验区,实验区人类活动总面积5554.9hm²、总数量231处,分别占人类活动总面积和总数量的68.65%和58.93%.该自然保护区人类活动影响指数为0.000697,人类活动影响较明显,不利于物种和生态系统的保护.     

Recovery of molybdenum from fly ash by gibbsite

The effectiveness of gibbsite (GB), an amorphous aluminum oxide, for the recovery of Mo(VI) from eluates of fly ash of two coal-fired thermal power stations and of roof tile waste was investigated. Upon the qualitative analysis of an eluate of fly ash, 16 elements were detected. Greater amounts of these elements were eluted under acidic conditions (pH 2) than from the neutral or basic eluate of fly ash. GB was used for the adsorption of Mo(VI). Equilibrium adsorption was reached within 1?min. Optimal solution acidity for the adsorption of Mo(VI) onto GB400 (calcined at 400°C) was pH 2. The main adsorption mechanism was ion exchange with a number of hydroxyl groups of GB400. For repeated ad- and desorption of Mo(VI), GB400 could be used at least four times and the recovery percentage of Mo(VI) with sodium hydroxide solution as eluent surpassed 90%. Our results showed that GB400 was very effective for the recovery of Mo(VI) from fly ash.     

Effects of La,Ce on nitrogen removal in sequencing batch reactor

Batch experiments were conducted to study the short-term biological effects of rare earth ions (La³⁺, Ce³⁺) and their mixture on the nitrogen removal in a sequencing batch reactor (SBR). The data showed that higher NH⁺₄―N removal rate, total inorganic nitrogen removal efficiency, and denitrification efficiency were achieved at lower concentrations of rare earth elements (REEs) (<1mg/L). In the first hour of the aeration stage of SBR, the presence of REEs increased the total inorganic nitrogen removal efficiency and NH⁺₄―N removal efficiency by 15.7% and 10%―15%, respectively. When the concentrations of REEs were higher than 1mg/L, the total inorganic nitrogen removal efficiency decreased, and nitrate was found to accumulate in the effluent. When the concentrations of REEs was up to 50.0mg/L, the total inorganic nitrogen removal efficiency was less than 30% of the control efficiency with a high level of nitrate. Lower concentrations of REEs were found to accelerate the nitrogen conversion and removal in SBR.