基于复合球团的以生物质焦油为还原剂的铬渣无害化处理

结合目前铬渣解毒现状,提出生物质焦油热解还原铬渣的新技术,利用生物质气化副产物焦油作为解毒剂,进而提高铬渣解毒和资源化水平,降低能耗。将生物质焦油和铬渣混合制成球团通过热解实现Cr(VI)向Cr(III)的形态转化,对影响焦油热解还原铬渣的主要因素:温度、铬渣粒径、球团尺寸、铬渣与焦油当量比等进行探讨。结果表明:还原铬渣的质量随温度升高而提高,温度超过400℃后无明显变化,减小铬渣粒径与球团尺寸可明显提高还原质量。当热解温度为400℃,还原时间10 min,铬渣与焦油当量比2.29,铬渣粒径0.074 mm,球团粒径2.5 mm时,可得到Cr(VI)还原率98.65%的还原铬产品。     

基于粒径分布的不同异位修复工艺除Cr特性

以我国某铬盐厂的铬污染土壤为研究对象,采用改进的BCR顺序提取法研究了粒径对不同修复工艺(异位淋洗、异位稳定化、湿法解毒)去除土壤中各形态Cr的影响。实验结果表明:粒径是影响铬渣污染土壤总铬和Cr(VI)去除的关键影响因素之一,粒径越细,越有利于3种异位修复工艺对土壤中Cr(Ⅵ)的去除或还原,粒径越细越有利于异位淋洗工艺对总铬的消减。粒径对水溶态Cr、酸溶态Cr的去除影响显著,粒径越细,水溶态Cr、酸溶态Cr的去除率越高,水溶态Cr和酸溶态Cr的分离或去除是不同异位修复工艺实现铬渣污染土壤中Cr(Ⅵ)高效去除的有效手段;粒径对可还原态Cr的去除影响不显著,pH是影响可还原态Cr去除的主要影响因素;粒径对可氧化态Cr含量提升显著,尤其是对异位稳定化和湿法解毒工艺,粒径越细,可氧化态Cr增大倍数越高;粒径对残渣态Cr的去除影响不显著。     

铬渣的热解无害化处理

采用热解工艺无害化处理铬渣,探讨了稻秆在铬渣无害化处理中的作用.研究了热解温度、稻秆与铬渣质量比、铬渣粒径及保温时间对铬渣热解无害化处理的影响,并分析了热解前后热解产物中铬元素形态的变化.结果表明,热解工艺能有效地将铬渣中Cr(Ⅵ)还原,稻秆热解过程中产生的气相挥发分对Cr(Ⅵ)的还原起核心作用.较为适宜的热解条件:热解温度为400 ℃,稻秆与铬渣质量比为0.10,铬渣粒径<2 000 μm,保温时间为10 min.在该热解条件处理下,热解产物中的Cr(Ⅵ)质量浓度为121 mg/kg,低于热解前铬渣中的Cr(Ⅵ)(3 400 mg/kg).热解后,可交换态及碳酸盐结合态铬含量降低,大部分铬转化成了稳定的有机结合态和残渣态,极大地降低了铬渣的危害.第一作者:张大磊,男,1982生,博士研究生,研究方向为固体废弃物热处理.     

铬渣秸秆共热解产物铬稳定性研究

生物质铬渣共热解工艺是新型的铬渣处理工艺,该工艺能有效地将铬渣中的Cr(Ⅵ)还原为Cr(Ⅲ).而由于共热解产物总铬含量较高,因此考察了铬渣与秸秆共热解过程中铬稳定性.通过考察共热解产物成分及形态分析、pH影响实验、淋洗实验及长期稳定性实验,对共热解铬渣的铬环境安全性进行评估.结果表明:(1)共热解温度对铬渣形态有较大影响,可交换态及碳酸盐结合态铬含量随共热解温度升高而逐渐降低,800℃时候可交换态铬降至＜0.1％(质量分数,下同),碳酸盐结合态铬为1.2％;共热解后最稳定的残渣态铬含量随共热解温度升高而逐渐升高.(2)当pH＞7时,两种共热解产物总铬溶出量极低,基本都小于6mg/kg;当pH≤7时,总铬的溶出量显著增加,最高超过500 mg/kg.但由于解毒铬渣的酸中和能力极强,因此铬释放风险较低.(3)共热解产物的总铬累积溶出量极低,根据拟合结果计算出其100年填埋时间的总铬溶出量不超过1.3 mg/kg.长期稳定性实验表明,自然堆置过程中共热解产物的Cr(Ⅵ)含量逐渐降低.     

微波法处理含铬废渣的可行性分析

微波辐照解毒铬渣是一项新技术,为考察该技术应用的可行性,本文对铬渣解毒前后性状的变化进行了讨论。结果表明,该技术能较完全地使高价铬转化为低价铬,解毒渣中铬主要以三价形态存在,铬渣毒性得到消除;解毒渣浸出液中Cr6+浓度远低于国家危险废物鉴别标准,解毒渣已不属于危险固体废弃物,其在环境条件下可安全存放。说明该技术具有应用前景。     

Cr(Ⅵ)污染土壤的热解还原无害化处理

提出了用热解还原法对含铬土壤进行无害化处理的新技术,研究了热解温度、热解时间及土壤有机质对铬无害化处理的影响,分析了热解前后土壤中铬的元素形态的变化.同时还探讨了热解还原过程中Cr(Ⅵ)的无害化机制.结果表明,土壤中的有机质在热解还原过程中产生的挥发分对Cr(Ⅵ)的无害化起核心作用;在200～600℃范围内,Cr(Ⅵ)的还原量随着热解温度升高而增大,500.0℃最适合于经济有效地实现Cr(Ⅵ)的热解还原处理;Cr(Ⅵ)的热解还原过程较快.铬的形态分析结果表明,热解后可交换态和碳酸盐结合态铬量大大降低,大部分铬转化成了活性低的残渣态,极大地降低了铬的危害.     

利用一氧化碳工业废气解毒铬渣的方法及条件优化

结合铬渣解毒及一氧化碳工业废气利用现状,提出采用一氧化碳工业废气解毒铬渣的方法。实验对反应温度、反应时间、铬渣质量、铬渣粒径等影响因素进行研究和筛选,用响应面法(RSM)分析了各因素对反应的影响及各因素之间交互性,建立反应的多元回归方程,并通过热力学分析进一步研究方法优越性的机理。结果表明:温度是该工艺铬渣解毒效率的关键影响因素,反应温度越高,解毒效果越好,优选反应温度范围350~400℃;浸出毒性目标值设定为1.0 mg·L~(-1),反应温度为400℃,铬渣质量为40 g,浸出毒性可降低至0.6 mg·L~(-1),还原率达99.85%;多元回归方程拟合性验证结果良好,RSM分析方法在条件优化中有较好的实用价值。     

钢渣预处理含铬废水及其废渣与铬渣的固化

用钢渣对含铬废水进行预处理,探讨了钢渣粒度、用量、废水pH值和添加硫酸亚铁还原剂的影响.结果表明,经硫酸亚铁还原处理后再用钢渣处理比单纯用钢渣处理的效果明显提高,采用钢渣/总铬质量比为40的100目钢渣处理经硫酸亚铁还原后的含铬废水,总铬和Cr6 去除率分别达79%和84%,采用钢渣柱进行的两级淋滤实验进一步表明该方法可作为工业上含铬废水处理的预处理段.处理后的废钢渣同工业铬渣一起进行水泥固化,标准养护20 d后固化体表面Cr6 浸出率、破碎至5 mm粒径以下和酸雨淋溶下的浸出液Cr6 浓度均符合安全标准,可作为普通建材或进行填埋处置.     

还原稳定化法修复六价铬污染土壤的中试研究

为探索还原稳定化法修复六价铬污染土壤的工程可行性,以某化工厂铬渣堆存场内六价铬污染土壤为研究对象,开展还原稳定化法修复六价铬污染土壤的中试研究。结果表明,DARAMEND-M、硫酸亚铁(Fe SO4)和多硫化钙(CPS)3种药剂对土壤中Cr(Ⅵ)的还原率超过了99%,糖蜜对Cr(Ⅵ)的还原率达93.9%。经糖蜜和DARAMEND-M处理的下层土壤,水溶态铬+交换态铬由原来的21.77%分别下降至6.26%和2.95%;经Fe SO4和CPS处理的渣土混合物,水溶态铬+交换态铬由22.12%分别下降至4.58%和2.94%,铬的稳定性明显增强。采用糖蜜、DARAMEND-M和Fe SO4处理后可以降低土壤p H值,而CPS处理则提高土壤p H值;糖蜜和DARAMEND-M有助于提高土壤微生物量碳含量。总体而言,糖蜜和DARAMEND-M适合修复低Cr(Ⅵ)污染土壤,在还原稳定化效果和长效性方面,DARAMEND-M药剂优于糖蜜;Fe SO4和CPS在修复高Cr(Ⅵ)污染土壤方面具显著效果。     

不同还原药剂修复Cr(Ⅵ)污染土壤的稳定性评估

针对目前铬污染场地修复后的长期稳定性问题,选用轻、重污染土壤和表层渣土混合物为研究对象,在分析其理化特性的基础上,对经CaS_4、FeSO_4·7H_2O和葡萄糖还原后土壤的长期稳定性进行评估,通过设置干燥和淹水2个条件,探究了水分对Cr(Ⅵ)污染土壤长期稳定性的影响。结果表明:针对3种不同类型铬污染土壤,投加CaS_4对土壤中Cr(Ⅵ)的还原效果较FeSO_4·7H_2O和葡萄糖好;在360 d的采样周期内,干燥条件下的3种土壤经CaS_4处理后Cr(Ⅵ)浓度均保持稳定,经FeSO_4·7H_2O和葡萄糖药剂还原后,渣土混合物中Cr(Ⅵ)波动幅度较大,其余2种土壤呈稳定状态;淹水密闭条件下的3种土壤中Cr(Ⅵ)浓度均有下降趋势,特别是渣土混合物在投加FeSO_4·7H_2O和葡萄糖药剂处理后,下降趋势更为明显;在长期稳定性方面,在360 d的实验周期内,与淹水密闭条件相比,经还原修复后的Cr(Ⅵ)污染土壤在干燥条件下的稳定性更强;Cr(Ⅵ)污染土壤经还原后,有效的过量还原剂能在一定程度上抑制土壤中Cr(Ⅵ)浓度变化,且在淹水密闭条件下,土壤中Cr(Ⅵ)浓度呈下降趋势。     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Organochlorine compounds in a three-step terrestrial food chain

The concentrations of 15 organochlorine chemicals (PCBs and pesticides) were studied in a Central European oak wood food chain system: Great tit (Parus major), caterpillars (Tortrix viridana, Operophtera brumata, Erannis defoliaria), and oak-leaves (Quercus robur). Juvenile tits receive organochlorines from the mother via egg transfer and, eventually to a greater extent, from the caterpillar food source during nestling period. The concentrations of PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl, the most abundant in this study) was found in leaf material at ca. 1 ng/g, in caterpillars 10 ng/g, and in bird eggs 170 ng/g on an average and on a dry mass basis.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.     

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.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Radionuclides in pinon pine (Pinus edulis) nuts from los alamos national laboratory lands and the dose from consumption

Abstract

One of the dominant tree species growing within and around the eastern portion of Los Alamos National Laboratory (LANL), Los Alamos, NM, lands is the pinon pine (Pinus edulis). Pinon pine is used for firewood, fence posts, and building materials and is a source of nuts for food—the seeds are consumed by a wide variety of animals and are also gathered by people in the area and eaten raw or roasted. This study investigated the (1) concentration of ³H, ¹³⁷Cs, ⁹⁰Sr, ^totU, ²³⁸Pu, ^{239, 240}Pu, and²⁴¹ Am in soils (0‐ to 12‐in. [31 cm] depth underneath the tree), pinon pine shoots (PPS), and pinon pine nuts (PPN) collected from LANL lands and regional background (BG) locations, (2) committed effective dose equivalent (CEDE) from the ingestion of nuts, and (3) soil to PPS to PPN concentration ratios (CRs). Most radionuclides, with the exception of ³H in soils, were not significantly higher (p < 0.10) in soils, PPS, and PPN collected from LANL as compared to BG locations, and concentrations of most radionuclides in PPN from LANL have decreased over time. The maximum net CEDE (the CEDE plus two sigma minus BG) at the most conservative ingestion rate (10 lb [4.5 kg]) was 0.0018 mrem (0.018 μSv); this is far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem (1000 μSv). Soil‐to‐nut CRs for most radionuclides were within the range of default values in the literature for common fruits and vegetables.     

Degradation and sorption of imidacloprid in dissimilar surface and subsurface soils

Degradation and sorption/desorption are important processes affecting the leaching of pesticides through soil. This research characterized the degradation and sorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) in Drummer (silty clay loam) and Exeter (sandy loam) surface soils and their corresponding subsurface soils using sequential extraction methods over 400 days. By the end of the incubation, approximately 55% of imidacloprid applied at a rate of 1.0 mg kg^?1 degraded in the Exeter sandy loam surface and subsurface soils, compared to 40% of applied imidacloprid within 300 days in Drummer surface and subsurface soils. At the 0.1 mg kg^?1 application rate, dissipation was slower for all four soils. Water-extractable imidacloprid in Exeter surface soil decreased from 98% of applied at day 1 to > 70% of the imidacloprid remaining after 400 d, as compared to 55% in the Drummer surface soil at day 1 and 12% at day 400. These data suggest that imidacloprid was bioavailable to degrading soil microorganisms and sorption/desorption was not the limiting factor for biodegradation. In subsurface soils > 40% of ¹⁴C-benzoic acid was mineralized over 21 days, demonstrating an active microbial community. In contrast, cumulative ¹⁴CO₂ was less than 1.5% of applied ¹⁴C-imidacloprid in all soils over 400 d. Qualitative differences in the microbial communities appear to limit the degradation of imidacloprid in the subsurface soils.