生物表面活性剂对河道底泥重金属的淋洗效果比较

为了比较生物表面活性剂性质、活性剂浓度和淋洗时间等对河道底泥中重金属淋洗效果的影响。研究中选取了3种不同的生物活性剂即茶皂素、皂角苷和槐糖脂。研究结果表明:活性剂不同,淋洗效果不同;生物活性剂的胶束形成性质会影响淋洗效果;在3种活性剂中,临界胶束浓度低的槐糖脂淋洗效果最好;此外,活性剂浓度为8%时,淋洗效果已达到最佳。淋洗时间对淋洗效果的研究则证明:茶皂素、皂角苷和槐糖脂对重金属淋洗动力学过程可以用Elovich方程进行描述,淋洗过程为非均相扩散过程。研究中还对淋洗前后重金属形态进行了分析,淋洗可以有效去除底泥中弱结合态(离子交换态和碳酸盐结合态)重金属,使得强结合态的重金属所占比例增加,从而降低重金属的生物有效性。     

有机酸淋洗修复复合重金属污染河道底泥研究

针对高粘性Ｃｕ、Ｚｎ复合重金属污染河道底泥,采用酒石酸、草酸、柠檬酸三种有机酸作为淋洗剂对污染土进行淋洗修复,通过振荡淋洗方法,探究淋洗剂浓度、淋洗时间对重金属去除率的影响规律,采用ＢＣＲ三步提取法对淋洗前后土壤重金属形态进行分析。研究结果表明:3种有机酸对Ｚｎ的去除率优于对Ｃｕ的去除率,得到最佳淋洗方案为浓度0．4ｍｏｌ／Ｌ的酒石酸淋洗2．0ｈ,对Ｃｕ、Ｚｎ的去除率分别为29．19％、67．8％。通过ＢＣＲ形态分析发现有机酸可有效降低重金属弱酸提取态、可还原态浸提浓度,并能一定程度上提高残渣态含量,这有利于降低重金属环境风险。     

生物活性剂淋洗对河道底泥重金属毒性和生态风险影响评价

以河道底泥为研究对象,采用Tessier五步连续提取法比较了淋洗前后底泥中重金属的形态分布变化,并采用生物活性评价法,浸出毒性法,地累积指数法和潜在生态风险指数法比较及评价了生物活性剂槐糖脂淋洗前后底泥重金属的生物活性、浸出毒性和生态风险系数的变化。研究同时还采用三维荧光对底泥中溶解性有机质进行了分析。结果表明:淋洗后底泥重金属形态分布发生变化,重金属的迁移能力降低,生物活性和危害性降低,浸出毒性减小,单一和综合潜在生态风险降低,说明淋洗是一种有效的降低底泥重金属环境危害的方法。经淋洗后的底泥中重金属稳定性提高,对生态风险小,可以进一步进行资源化利用。     

珠江长州断面底泥重金属污染潜在生态危害评价

测定了珠江广州河段长州断面底泥中重金属镉、铬、铜、铅的质量比,采用Tessier形态分类法对它们在底泥中的存在形态进行了提取和测定。监测分析表明,该断面底泥中镉、铬、铜、铅质量浓度均高于全国湖泊底泥中的平均值。该断面底泥中镉、铬、铜、铅质量比分别为广东土壤背景值的49.50倍、3.62倍、14.24倍、5.51倍,底泥成为这些重金属的富集地。镉以可交换态为主,占总量的比例为47.47%;铬和铅以残渣态为主,占总量的比例分别为42.35%和47.28%;铜主要以有机态及硫化物结合态为主,占49.06%;残渣态较低,占18.26%。采用潜在生态危害指数法对该断面底泥中的镉、铬、铜、铅进行了潜在生态危害评价,结果表明:镉潜在生态危害强,铬、铜、铅的潜在生态危害轻微。     

EDTA和柠檬酸淋洗去除污染粉土柱中Pb的研究

以场地重金属污染的修复治理为背景,通过室内压实制备Pb污染土柱以模拟现场污染土,采用乙二胺四乙酸二钠二水合物(EDTA)和柠檬酸对Pb污染粉土柱进行淋洗,考察淋洗剂类型、淋洗剂浓度、淋洗时间和污染土中Pb的负载量等各个因素对污染土中Pb的释放特性的影响。研究表明:相较于柠檬酸,EDTA对Pb的去除效果明显更优。随淋洗时间延长,不同浓度的EDTA对Pb的淋洗效率趋于一致。污染土中Pb负载量越小,EDTA对Pb的去除率越高,64.5%～83.6%的Pb可以从污染土中解吸出来;柠檬酸浓度越高,对Pb的去除效果越好。由于柠檬酸浓度较低时易吸附于土体表面,并且抑制Pb的解吸,低浓度柠檬酸淋洗总体效果偏差,最高去除率仅为11.4%。因此,现场修复Pb污染土若采用EDTA可采用较低浓度(0.005 mol/L)淋洗,而若选择柠檬酸需要提高其浓度。     

基于EDTA淋洗离心—硫酸盐还原菌固化法去除污泥中重金属镉的研究

为研究如何分离和去除污泥中重金属镉（Cd）,采取二氨基乙烷四乙酸(ethylene diamine tetraacetic acid, EDTA)淋洗离心与硫酸盐还原菌( sulfate-reducing bacteria, SRB)固化相结合的方法进行了污泥试验并统计分析了污泥中重金属Cd的形态分布和含量变化。结果表明：在离心力100g、淋洗时间12 h、淋洗2次和离心温度30 ℃的条件下采用EDTA对污泥原样进行淋洗离心,污泥中Cd含量由6.793 mg/kg降至5.241 mg/kg,去除率达22.8%。然后采用SRB对淋洗离心后的污泥试样进行固化,不稳定态Cd含量由2.589 mg/kg降至1.103 mg/kg,固化后污泥中的Cd含量低于《绿化种植土壤》（CJ/T 340-2016）中重金属要求的Ⅳ级标准2 mg/kg。与传统单一修复方法相比,该联合方法有效地降低了污泥中活性大、污染程度高形态Cd的含量,减轻了其环境危害性。     

污水污泥中重金属形态分析研究

采用stover连续提取方法对沈阳市北部污水处理厂的压缩污泥进行重金属提取,并对污泥中Cu、Zn、Cd、Mn、Ni和Pb等重金属之类的形态分布进行分析。结果表明:Cu主要以金属硫化物的形态存在,约占总含量的90.46%;Zn和Mn的形态分布主要为碳酸盐结合态、有机结合态和金属硫化物,Zn的以上三种形态约占总含量的99.11%,而Mn有机结合态约占总含量的52.89%;Cd和Ni主要以碳酸盐结合态、金属硫化物和可交换态形态存在,其中Cd的碳酸盐结合态约占总量的46.77%,Ni的以上三种形态约占其总量的95.02%;Pb以碳酸盐结合态为主要形态,约占总量的99.90%。     

非原位淋洗处理深圳河污染底泥的试验研究

本文研究了采用非原位高级氧化淋洗方法对深圳河受污染底泥进行的处理。该方法即:根据预先设定的两个底泥淋洗处理目标——"理想处理目标"和"性价比处理目标",分别使用不同的淋洗药剂和步骤对深圳河污染底泥处理。研究结果表明,非原位高级氧化淋洗处理可有效去除污染底泥中大部分有机污染物和重金属,但较难去除以强结合态存在的重金属。淋洗药剂成本直接决定整个处理过程的总费用。若直接照搬相关标准限值作为处理目标,将导致淋洗药剂用量增加,处理费用会显著提高;若根据底泥污染情况提出较为实际的处理目标,则可大大降低处理费用。     

土壤、底泥中镉的形态分析及其对水体的影响

本文对大藤峡库区土壤、底泥中镉的形态进行了分析测定，结果表明。当年受溃坝影响流入江中的尾矿石多数沉降于锌品厂近距离内的底泥中，且随距离的推移逐渐降低，锌品厂断面镉以碳酸盐结合态、交换态和氧化标结合态占较大的比例，以下断面以交换态、氧化锰结合态和紧结有机态占较大的比例，而未受溃坝影响的土壤中镉含量比较正常，为4ppm．各种环境因素如pH、氧化还原电位、共存离子等对镉的形态分布和向水相释放均有不同的影响．底泥对水中镉的吸附及其后pH变化可能发生的解吸作用是控制河流水中镉浓度的关键。     

长春南湖沉积物重金属污染特征研究

本文对南湖沉积物中重金属形态的分布特征进行了研究。结果表明,南湖沉积物中Cu、Pb、Zn和Ni的有效态含量都很大,对水体环境存在潜在的污染,而且沉积物中各金属赋存形态也不相同,Pb主要存在于铁锰氧化物态,有机物态和残渣态中,Cu主要赋存于有机物结合态中,Zn、Ni以铁锰氧化物态为主。通过地累积指数分析,南湖沉积物中局部地区受到Zn、Ni的轻微污染。     

固化/稳定化重金属污染底泥渗透特性试验研究

采用固化剂对含Cd、Pb、Zn、Mn重金属底泥进行固化/稳定化处理,在酸性条件下,研究了固化底泥的渗透系数变化规律和重金属渗出规律。试验结果表明:渗透初期,渗透系数及Cd、Zn的渗出量逐渐增大,Mn先小幅减小后增大,入渗15 d后均逐渐减小,Cd和Zn的渗出对Mn有抑制作用,Pb的渗出量为0。添加螯合剂EDTA后,渗透系数及Mn的渗出量逐渐降低,入渗30 d后趋于稳定,Pb、Cd、Zn的渗出量先增大,15 d后逐渐减小,重金属的渗出量均有大幅提高,但远小于国家浸出限值,固化效果显著。     

Non-steady state behaviour of heavy metals in contaminated freshwater sediments

The behaviour of heavy metals has been investigated in contaminated sediments of the river Meuse, The Netherlands. Due to temporal changes in temperature and degradability of organic matter, the depths of the redox boundaries fluctuate. This contributes to a non-steady state. As a result of oxidation processes, a distinct peak in heavy metal concentrations in pore water is measured at the sediment-water interface. Because the studied anoxic sediments contain low levels of sulphide, other solid phases are expected to be of importance in the binding of heavy metals. Furthermore, heterogeneity of the sediment and complexation with dissolved organic compounds may result in supersaturation of the anoxic pore waters with respect to discrete heavy metal sulphides, thus influencing heavy metal mobility. Calculations using concentration gradients of heavy metals indicate that diffusive fluxes between the sediment and the surface water contribute to concentrations in the surface water, although significant effects may be confined to specific locations.     

STUDY ON SORPTION OF HEAVY METAL POLLUTANTS BY SEDIMENT PARTICLES

Sorption of heavy metal on sediment particles is studied theoretically am experimentally. Sorption processes of heavy metal pollutants on sediment particles can b well described by Langmuir model. Parameters in the model b,,k and k1 depend on proper ties of sediment and water, and have nothing to do with sediment concentration. By com bining the sorption dynamic equation and the mass conservation equation, the variation c N(sorption content of heavy metal pollutant by specific weight of sediment) and c (con centration of heavy metal pollutant in water phase) with time can be deduced. Further more, formulas for calculating the equilibrium sorption content N and the equilibriur concentration of heavy metal pollutant in water phase c are established too. Experimenta data well coincide with theoretical formulas. These can be treated as the basis for furthe quantitative study of sediment sorption-desorption characteristics.     

Surfactant enhanced remediation of cadmium contaminated soils

An investigation involving the addition of surfactant to remediate cadmium-contaminated soils was perfoemed to determine the optimal surfactant enhanced remediation system. Anionic (sodium dodecyl sulfate, SOS), nonionic (Triton X-100, TX100) and cationic (cetyltrimethylammonium bromide, CTAB) surfactants were used to elucidate the extraction efficiency of surfactant. EDTA and diphenylthiocarbazone (DPC) were also added to enhance the extraction efficiencies of surfactants. Moreover, the pH effect was examined to determine the optimal surfactant systems. The addition of anionic and nonionic surfactants can enhance the desorption rates of cadmium, lead and zinc, whereas the addition of cationic surfactant decreased the desorption efficiency of heavy metals. The desorption efficiency was found to increase linearly with the increasing surfactant concentration below critical micelle concentration (CMC) and remained relatively constant above the CMC. Moreover, the addition of EDTA can significantly enhance the desorption efficiency of heavy metals. Cationic surfactant was shown to be a more effective surfactant than nonionic and anionic surfactants in extracting heavy metals under acidic environment. The desorption efficiency of heavy metal in the surfactant/EDTA mixture system was in the order of Cd > Pb> Zn. However, the addition of DPC lowered the heavy metal removals by 2 to 4 times. Also, increasing pH value can decrease the extraction capabilities of nonionic and anionic surfactants. The results of this study demonstrate that surfactant in combination with complexing agents can be effectively used as chemical amendments to flush cadmium-contaminated soil by proper selection of type and concentration of surfactant and complexing agent at different pH values.     

EXPERIMENTS ON SELF-PURIFICATION OF HEAVY METALPOLLUTANTS IN NATURAL RIVERS

1.INTRODUCTIONThemovementofwater,sedimentandpollutantsandtheinteractionamongtheminnaturalriversareverycomplicated.Movementofwater,sedimentandPOllutantsarerandom.ButfromastatisticalviewPOint,theirmovementfollowssomerules.Twokindsoftypicalcases,thatis,atributarywithheavymetalpollutantsjoiningamainstream,andanunPOllutedtributarywithmuchsedimententeringamainstreamcontaminatedbyheavymetals,arestudiedinthispaper.Besides,flowscenesinnaturalriversaredifferentindifferentseasons.InthenabPeriod,g…     

不同粒径泥沙解吸重金属污染物静态试验研究

从吸附反应动力学方程和质量守恒方程出发，导得静态解吸试验中泥沙剩余吸附量和水相重金属浓度随时间变化的计算公式，并导得泥沙剩余平衡吸附量和水相平衡浓度随泥沙吸附－解吸的特性、泥沙初始重金属吸附量和泥沙浓度变化的计算公式。在此基础上，结合试验进一步研究了不同粒径泥沙解吸重金属污染物的能力。     

农田土壤重金属Cd的环保淋洗剂筛选研究

土壤淋洗是一种有效修复重金属污染土壤的方法,而淋洗剂的选择是淋洗过程的关键因素,直接影响淋洗效率。研究了4种淋洗剂(乙酸、柠檬酸、CaCl₂、FeCl₃)对Cd轻度污染的农田土壤淋洗性能及影响因素。结果表明:淋洗效果依次为FeCl₃＞柠檬酸＞乙酸＞CaCl₂;FeCl₃的淋洗机理是Fe³⁺与土壤中的Cd²⁺离子交换,其水解出的H⁺可促进碳酸盐结合态Cd溶出,Cl^-还可与Cd²⁺形成稳定的螯合物;经优化后的最佳的淋洗条件是固液比为1∶5,浸提时间为4 h,此时乙酸、柠檬酸、CaCl₂和FeCl₃的最大土壤Cd去除率分别为30.24%,24.62%,24.82%,81.90%;pH值对淋洗效果的影响较大,除CaCl₂外,3种淋洗剂的淋洗效果都随pH值的升高而降低(pH值在2.5～5.0范围内),FeCl₃的淋洗效果降低最为显著。研究成果可为Cd污染农田土壤修复提供技术支撑。