改性活性炭对土壤镉的吸附性影响

目的研究3种改性活性炭对菜地、河流底泥、荷花底泥镉吸附性的影响。方法对活性炭进行酸改性、碱改性和氧化改性,采用双硫腙分光光度法测定镉含量。结果对实验土样,最佳活性炭添加量为0.025 g/g。随着初始镉含量的升高,土壤对镉的吸附量不断增大。结论 3种改性活性炭相比普通活性炭对湿地土壤的镉吸附量均有不同程度的提升,荷花底泥中,酸性、氧化改性活性炭相比普通活性炭,吸附效果提高7.7%,8.3%,吸附效果提升显著。     

全自动淋洗样品预处理-气相分子吸收光谱法测定土壤阳离子交换量

称取经风干并过2mm筛孔的网筛的土壤样品2.000g置于反应瓶中,采用全自动淋洗仪,加入1.00mol·L~(-1)乙酸铵溶液80mL对土样进行处理。经过前处理,土样中的阳离子全部被NH_4~+离子所取代。此时,仪器将自动吸入乙醇对土样进行反复淋洗。淋洗结束后,将土样完全转移至蒸馏瓶中进行蒸馏。馏出液接收于预置有20g·L~(-1)硼酸吸收液20mL的100mL比色管中,待管中溶液总体积达到90mL时,取下比色管,加水定容至100.0mL。此吸收液中氨氮的含量用气相分子吸收光谱法进行测定。此吸收液最长可放置24h,在24h以内测定结果不受放置时间的影响。标准曲线系用氨氮标准溶液(0.10～2.00mg·L~(-1)范围内)按气相分子吸收光谱法进行测定并制作。土样的阳离子交换量(CEC)系根据所测得的氨氮含量按公式换算求出。按此方法分析了4种土壤标准物质,所测得的CEC值与认定值相符,其测定值的相对标准偏差(n=6)均小于2.0%。     

以对甲基苯磺酸作为淋洗液用离子色谱法测定酸雨中的有机酸

本文研究了用对甲基苯磺酸作为淋洗液测定液相中HCOO~-和CH_3COO~-的离子色谱条件,该方法对HCOO~-和CH_3COO~-的最低检出限分别为48ppb和93ppb。该方法与用进口的辛磺酸作为淋洗液的方法进行了对比实验,并用于两广实际酸雨样品中甲酸和乙酸的测量。     

柱萃取法测定农作物中的残留农药和土样中的二噁英

经均质的固体样品，根据含水量的不同和被测定组分的差异，分别与硅藻土、硫酸钠、弗罗里硅土等吸附剂混匀成可流动的粉末，装填成柱，然后以不同极性溶剂淋洗。多数情况下，所得溶液不需要进一步净化即可进行色谱分析．用极性溶剂如乙酸乙酯淋洗，选用任一种分散剂均能有效测定作物中的农药残留．在最佳条件下，一些有机磷、有机氯、氨基甲酸酯、拟除虫菊酯农药在某些粮谷、水果和蔬菜中以及多氯二苯并二恶英（ＰＣＤＤｓ）在土样中的添加回收率均大于８０％．实践证明该方法具有省时、省试剂、省净化程序等优点．     

环境化学开放性实验设计:重金属污染土壤的化学淋洗*

介绍了一个开放性环境化学实验。该实验以被重金属污染的土壤为研究对象,分别使用稀盐酸、乙二胺四乙酸、氯化钙为淋洗剂,对其进行化学淋洗修复。通过电感耦合等离子体光谱仪分析比较修复前后土壤中铅、镉的含量,用以帮助学生加深理解配合/螯合作用、酸-碱反应、离子交换反应、胶体的性质、土壤重金属形态、土壤性质与组成等相关环境化学知识。实验所用的土壤样品由学生自选,不同类型土壤的理化性质影响淋洗效果,从而增加了实验结果的不确定性。本实验贴近学科前沿且联系工程实际,可激发学生独立思考和探索精神,提高学生的科研能力与解决复杂问题的能力。     

鼠李糖脂对镧的淋洗效果及影响因素研究

以La为目标污染物,通过鼠李糖脂淋洗土壤试验,考察鼠李糖脂对La的淋洗效果及溶液pH影响,以淋洗前后不同形态稀土元素含量变化为基础,分析淋洗剂对La的稳定性和流动性的影响。结果表明:鼠李糖脂对土壤中稀土元素吸附能力较弱,最佳淋洗pH为6.9,最大淋洗效率为10.24%,相同条件下Cu,Zn的最大淋洗效率分别为67.75%和18.33%。淋洗剂pH值对淋洗效果的影响较大,考察的3个pH值中淋洗剂pH为6.9时淋洗效果最佳。多次淋洗有助于提高La的淋洗效率,最大累积效率为17.76%。当淋洗剂pH=10时,多次淋洗累积效率为7.42%,由于淋洗剂为碱性,使得体系中氧化结合态稀土元素的含量不断升高,该条件下稀土元素稳定性指数MF相对其他条件最大提高了33.67%,有助于稀土元素在土壤中的固化。     

以meso四-(对磺基苯)卟啉为柱后衍生剂同时测定微量镉、汞、锌的离子色谱法

提出了以TPPS_4为柱后色谱衍生试剂的同时测定微量汞、镉和锌的离子色谱分析法,研究了影响衍生反应速度的因素。在含氯化钠的pH 10.3～12的硼酸钠缓冲介质中,以PAR催化TPPS_4与待测金属离子反应,以硅质键合相阳离子交换剂为固定相、酒石酸—氯化钠为流动相,于10min左右定量分离金属离子并将镉的淋洗顺序调至锌前。用于废水、硅酸盐和大米分析,结果满意。     

电感耦合等离子体原子发射光谱法测定铀铌混合氧化物中镉、锡和锌

铀铌混合氧化物样品0.200 0g用硝酸8mL,氢氟酸2mL进行微波消解后,经苯乙烯-二乙烯苯-磷酸三丁酯萃取柱分离铀与镉、锡、锌,采用电感耦合等离子体原子发射光谱法测定淋洗液中镉、锡和锌的含量。选择镉、锡、锌的分析谱线依次为226.502,189.989,213.856nm。3种元素的质量浓度均在一定范围内与其对应的发射强度呈线性关系,方法的检出限(3s)为0.003~0.02mg·L~(-1)。加标回收率为94.0%~101%,测定值的相对标准偏差(n=6)为3.7%~7.4%。     

镉基体分离及纯镉中杂质成分的ICP-MS法测定

研究了用阴离子交换树脂分离纯镉中铜、锌、铅、铁的条件，所得优化分离条件为：717型阴离子交换树脂柱，样品溶液为2mol/L HCl溶液；三段淋洗液依次为2mol/L HCl溶液、0．2mol/L HBr 0．25mol/L HNO3的混合酸溶液及3mol/L HNO3溶液。经ICP-MS测定证明，95％以上的镉得到分离，95％以上的铜、锌、铅、铁可以分离测定，有效地降低了ICP-MS测定纯镉中铜、锌、铅、铁时镉基体的干扰。     

离子色谱线性梯度淋洗分离阴离子的计算机模拟

建立了使用氢氧化钠淋洗液时用计算机模拟离子色谱梯度淋洗分离阴离子的新方法,研究了在线性梯度淋洗过程中不同时间阴离子在色谱柱中的位置及所在位置的淋洗液浓度,得出阴离子在不同时间的容量因子、迁移速度,通过积分得到保留时间。再根据离子色谱峰峰形变化的规律,得到色谱峰峰形的参数。模拟色谱图保留值与实验值的相对误差小于5%,模拟色谱图的色谱峰峰形与实验所得到的色谱图的色谱峰峰形也非常接近。     

Effects of acid rain on soil humic compounds

The modifications induced by acid rain on the solubility, molecular configuration and molecular weight distribution of humic (HA) and fulvic (FA) acids were studied. A natural soil was subjected to simulated acid rain until a soil pH of 4 was obtained; HA and FA acids were then extracted and characterised. The results obtained were compared both with those of natural soil and with those of a soil subjected to acid rain. Elute analysis indicates the continuous release of soluble organic compounds as a consequence of acid rain simulation, although no relationship was found with the process of soil acidification. The yields of HA and FA show that HA values are the same while FA amount is higher in the natural soil; in acid soils their water solubility increases. The molecular weight distribution shows that HA consist of a mixture of compounds of different molecular weights; they are molecules for the most part larger than 100 kDa and their distribution is not changed by soil acidification. FA can be considered to form a much more homogeneous system; in natural soil, the molecules are larger than 50 kDa, while in acidified soil they are for the most part smaller than 3 kDa.     

模拟酸雨对土壤中铁、锰、锌的浸出特征

酸雨是指pH值小于5·6的大气降水,它不仅危害土壤,还通过土壤间接地危害整个生态系统,因此生态系统酸沉降的承受能力很大程度上取决于土壤对酸雨的敏感性〔1,2〕。我国能源以煤炭为主,大气中硫、氮含量较高,酸雨中SO42:-NO3-的比值范围大致在4:1到15:1之间〔3〕。同时,我国酸雨主要分布在长江以南地区,这正好与酸性土壤分布区相重叠,很大程度上加剧了对土壤的破坏程度。本文用ICP-AES法研究了在模拟酸雨作用下,土壤中生物必要元素Fe、Mn、Zn的释放水平和释放特征。1实验部分1.1仪器及工作条件电感耦合等离子体-原子发射光谱分析仪(IC…     

模拟酸雨对冶炼厂土壤中Cd释放行为影响的研究

模拟株洲地区降水酸度及离子组成,用pH3．5、pH4．5、pH5．6的模拟酸雨对株洲冶炼厂土壤样品（S1）进行了Cd动态淋溶试验。结果表明,酸雨加速了土壤中Cd的释放,表现为模拟酸雨pH值越低Cd释放量越大;且在pH3．5、pH4．5的平均释放水平是对照组（pH5．6）的3．97和2．94倍;其释放量与土壤中Cd的原始含量、赋存形态关系密切;淋出液中Cd与Zn呈显著的正相关关系,相关系数均大于0．94;与Pb呈负相关关系,冶炼厂Cd的来源应与工厂Zn的生产关系密切,在pH3．5、pH4．5的模拟酸雨作用下分别是国家饮用水源水质标准值的1037倍、768倍。随着淋溶的进行,酸雨可加速工厂土壤中Cd的释放,对人类存在着直接或潜在的危害性。     

Model study of acid rain effect on adsorption of trace elements on soils using a multitracer

Using a radioactive multitracer and model acid rain (HCl or H₂SO₄ solution), batch experiments were performed to examine the pH effect on the adsorption-desorption equilibrium of 16 elements on soils as a model study of an acid rain effect. Kaolin, black soil (original and with organic matter almost removed) and Kureha soil (original and with organic matter almost removed) were used as adsorbents. Characteristic dependence on the pH value of the suspension was observed for the adsorption of the elements on kaolin and the soils. The results of this model study indicate that acid rain decreases the retention of cations, while it increases or does not change the adsorption of anions on soils. Organic matter in soils has a positive effect on the extent of adsorption of most elements investigated.     

A new approach to study cadmium complexes with oxalic acid in soil solution

This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH(2)) were observed. In order to verify the possible formation of complexes with OAH(2), aqueous solutions of OAH(2) with traces of Cd(II) were investigated as model systems. Signals corresponding to several distinct molecular complexes between cadmium and oxalic acid were detected in the model solutions using negative-ion ESI-MS, which follow the general formula [Cd(n)(X,Y)((2n+1))](-), where n is the number of cadmium atoms, X=Cl(-), and Y=OAH(-). Some of these complexes were also identified in the ESI mass spectra taken from the soil solutions.     

铈对酸雨胁迫下大麦种子萌发的影响

研究了铈对酸雨胁迫大麦种子萌发的影响,随着雨ｐＨ值的增加,大麦发芽势,发芽率、幼苗地下与地上部干重及叶绿素含量递减,根系质膜透性递增;酸雨对铈浸种的大麦种子的胁迫作用减轻,表明有缓解酸雨胁迫种子萌发的作用。     

电感耦合等离子体质谱法测定土壤中镉和总汞

建立电感耦合等离子质谱法测定土壤中镉和总汞的方法。土壤样品在电热板上用盐酸和硝酸于100℃低温消解,重量法定容,取上清液上机测定。镉和总汞含量分别在0.502~10.20 ng/g,0.212~5.010 ng/g范围内线性良好,相关系数(r2)大于0.999,土壤中镉和总汞的检出限分别为0.021,0.002μg/g,测定结果的相对标准偏差分别为1.99%,5.57%(n=6),加标回收率分别为97.5%~101.1%,87.5%~92.9%。该方法样品处理简单快捷,检出限低,准确度和精密度高,适合土壤中镉和总汞含量的测定。     

Interaction and fractionation of added cadmium in some typical soils of the Danubian Lowland

This study was conducted to investigate the effect of time on cadmium (¹⁰⁹Cd) availability in four typical soils of the Danubian Lowland through the modified Tessier’s sequential extraction procedure as well as its short-term sorption in the bulk soils and their two grain-size fractions. Results of the fractionation study showed that there were significant changes in the proportional distribution of cadmium in all studied soils during 180 days of incubation with spiked cadmium. Generally, the proportions of cadmium associated with the most weakly bound fractions (water soluble and exchangeable) tended to decrease with corresponding increases in the residual fraction during the incubation. The extent of cadmium sorption in all studied soils was high, exceeding 95% of the spiked amount after 60 min of incubation, likely due to slightly alkaline character of the soils. The finding that soil particles less than 10 μm sorbed up to 51% of the spiked cadmium in soils is of great importance since they could play a role in colloid-facilitated transport of cadmium through preferential pathways, as previously observed in the region. Addition of 1 M ammonium nitrate into the soil solution generally decreased cadmium sorption in all four soils. The lowest extractabilities of Cd were obtained using 1 M ammonium nitrate as a single extractant, whereas 0.025 M ammonium ethylenediaminetetraacetate solution extracted the highest proportions of cadmium from the studied soils.     

Effect of stabilizers in the thermal treatment of PVC—XI.: Effect of the reaction products on the stability of PVC mixtures stabilized by barium and cadmium stearates

The effects of cadmium and barium chlorides and stearic acid on the thermal stability of PVC mixtures stabilized by barium and cadmium stearates respectively and by their equimolar combination have been studied under static conditions of thermal treatment at 180° in air. The stabilizing effect of cadmium stearate drops in the presence of stearic acid owing to the formation of higher co-ordination cadmium compounds, only formed in the simultaneous presence of cadmium chloride, stearic acid and hydrogen chloride. The synergism is thought to be associated with the possibility of formation of a complex compound of barium stearate with cadmium chloride or stearic acid.