Field evidence of decreased extractability of copper and nickel added to soils in 6-year field experiments

The phytotoxicity of added copper (Cu) and nickel (Ni) is influenced by soil properties and field aging. However, the differences in the chemical behavior between Cu and Ni are still unclear. Therefore, this study was conducted to investigate the extractability of added Cu and Ni in 6-year field experiments, as well as the link with their phytotoxicity. The results showed that the extractability of added Cu decreased by 6.63% (5.10%–7.90%), 22.5% (20.6%–23.9%), and 6.87% (0%–17.9%) on average for acidic, neutral, and alkaline soil from 1 to 6 years, although the phytotoxicity of added Cu and Ni did not change significantly from 1 to 6 years in the long term field experiment. Because of dissolution of Cu, when the pH decreased below 7.0, the extractability of Cu in alkaline soil by EDTA at pH 4.0 could not reflect the effects of aging. For Ni, the extractability decreased by 18.1% (10.1%–33.0%), 63.0% (59.2%–68.8%), and 22.0% (12.4%–31.8%) from 1 to 6 years in acidic, neutral, and alkaline soils, respectively, indicating the effects of aging on Ni were greater than on Cu. The sum of ten sequential extractions of Cu and Ni showed that added Cu was more extractable than Ni in neutral and alkaline soil, but similar in acidic soil.

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用自动电位滴定仪测定水的总硬度实验

水的总硬度测定采用EDTA进行络合滴定。实验中用自动电位滴定仪代替人工进行样品分析,由颜色突变判断滴定终点改为电位突变,具有高硬度样品预判断、滴定干扰小、准确度高、节省人力、便于数据记录统计比较等优点。     

利用EDTA溶液淋洗修复重金属污染土壤

通过室内模拟实验,采用振荡淋洗的方法研究了不同浓度、pH值、淋洗时间的EDTA溶液对污染土壤中Ph、Cu、Ni、Zn、Cr的去除,并利用一级反应动力学模型对实验数据进行拟合。结果表明：在实验条件下,EDTA为0．05mol／L、pH值=7、液土比为10：1、淋洗时间为18h的条件下能达到对污染土壤重金属最大去除率,去除率分别为zn85．26％、Cu21．65％、Pb16．76％、Ni7．83％、Cr6．29％。模型拟合结果表明,转移系数最大的是Cr,其次是Cu、Pb、Zn,最后是Ni,说明在土壤淋洗过程中Cr最先达到质量转移的平衡状态,然后是Cu、Pb、Zn,最后是Ni。     

铁屑内电解法处理EDTA溶液中络合铜离子

采用批式试验和现代仪器分析研究了铁屑内电解法处理EDTA溶液中络合铜离子,考察了溶液浓度、溶液pH、温度和铁屑粒径等因素对铜离子去除过程的影响.结果表明,铜离子去除过程符合表观一级动力学方程.在pH 2.0～11.0范围内,pH值越低越利于铜离子去除;在酸性条件下溶液pH随内电解进行升高,在碱性条件下溶液pH随内电解进...     

基于烟气脱硫的碱式硫酸铝吸收剂Al3+含量测量试验

为了准确测量碱式硫酸铝溶液中Al3+质量浓度,以PAN为指示剂,用CuSO4标准溶液反滴定EDTA,分析得到4个干扰因素的优化测量条件.结果表明,碱式硫酸铝溶液中Ca2+对Al3+质量浓度测量无干扰,最佳稀释倍数应以待测液稀释后Al3+质量浓度在0.141 ～0.423 g/L为目标确定,EDTA最佳过量程度为50％ ～ 150％,Al3+与EDTA最佳配位应控制pH=3.42～3.91、煮沸3～5 min.误差分析表明,试验平均方法回收率为98.86％,Al3+质量浓度实测值较理论值相对误差范围为-0.47％ ～-0.33％,标准偏差为0.002 g/L,相对标准偏差(RSD)小于1％,试验结果准确可靠、数据稳定.以XO作指示剂、锌盐溶液为标准溶液返滴定对比试验表明,由于受到Al3对指示剂的封闭作用,滴定终点难以判断,实测值较理论值相对误差范围为-2.62％ ～ 3.42％,测量结果平均准确度降低2.156％.     

人为干预条件下油菜对镉、铬污染土壤的生物效应

采用盆栽模拟试验,研究了在强化剂乙二胺四乙酸钠(EDTA)、柠檬酸(CA)和钝化剂石灰存在的条件下,土壤存在单一Cd、Cr及复合Cd、Cr污染时,甘蓝型油菜“甘杂1号”(Brassica napus L.)对Cd、Cr的吸收富集效应.结果表明:1)1.6 mg/kg的Cd和170 mg/kg的Cr单一及复合污染能够促进油菜的生长;2)当Cd为1.6 mg/kg、Cr为170 mg/kg时,10 mmol/kg的EDTA和CA能够有效促进油菜对Cd、Cr的吸收富集,相比对照,无论是单一还是复合污染,其Cd、Cr累积量都有显著增加,但10 mmol/kg的EDTA和CA均抑制了油菜的生长,植株的叶面出现了不同程度的失绿、发黄、脱水、脱落等症状;3)当向污染土壤中添加1.5 g/kg钝化剂石灰时,油菜各部分Cd、Cr的质量比相比对照显著下降,但对油菜的正常生长没有显著影响;4)各部分Cd、Cr质量比随添加强化剂、钝化剂的不同,有明显的变化.研究表明,“甘杂1号”油菜对低浓度Cd、Cr单一及复合污染表现出一定的耐性和吸收能力.     

Distribution Of Cadmium And Nickel Among Various Forms In Natural And Contaminated Soils Amended With Edta

Because of its strong chelating capacity, application of ethylenediaminetetraacetic acid (EDTA) to soils may change the amount and distribution of heavy metals among their various chemical forms. Therefore, a greenhouse experiment was conducted using two cultivars of Brassica species (Brassica juncea and Brassica carinata) as hyper accumulator test crops on natural and artificially Cd and Ni contaminated soils. Both natural and metal amended soils were treated with disodium salt of EDTA at 0 and 1 g kg^–1 soil. After harvest of crops, soil samples were fractionated into water soluble plus exchangeable (WE), carbonate (CARB), organic matter (OM), Mn oxide (MnOX), amorphous Fe oxide (AFeOX), crystalline Fe oxide (CFeOX) and residual (RES) fractions. In metal amended soils, Cd and Ni were found predominantly in the AFeOX fraction in the absence of EDTA application and in the WE fraction in EDTA treated soil. Application of EDTA resulted in the redistribution of Cd among different forms and increased significantly Cd in the WE fraction with a concomitant significant decrease in the OM fraction. In natural soils, more than 40% of the total Cd was present in the RES fraction while in contaminated soil it was only 5%. Nickel in the WE fraction increased significantly while it considerably decreased in the CARB, OM, MnOX, AFeOX and CFeOX fractions with EDTA addition. This indicated that applied EDTA is capable to move Cd and Ni from the less soluble or more stable forms (CARB, OM, MnOX, AFeOX and CFeOX) to the most soluble form (WE). N natural soils, Ni in the RES fraction was found upto 49%, whereas only 10% of the total Ni was observed in contaminated soil, irrespective of EDTA treatment. In general, the amount of Cd recovered after harvest of both the Brassica cultivars did not differ significantly in any fraction except the WE fraction. The amount of Ni recovered in the AFeOX fraction was significantly higher after harvest of B. juncea as compared to B. carinata.Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Effects of EDTA and plant growth-promoting rhizobacteria on plant growth and heavy metal uptake of hyperaccumulator Sedum alfredii Hance

Phytoremediation is a cost-effective and environment-friendly strategy for decontaminating heavy-metal-contaminated soil. However, the practical use of phytoremediation is constrained by the low biomass of plants and low bioavailability of heavy metals in soil. A pot experiment was conducted to investigate the effects of the metal chelator ethylenediaminetetraacetic acid (EDTA) and EDTA in combination with plant growth-promoting rhizobacteria (Burkholderia sp. D54 or Burkholderia sp. D416) on the growth and metal uptake of the hyperaccumulator Sedum alfredii Hance. According to the results, EDTA application decreased shoot and root biomass by 50% and 43%, respectively. The soil respiration and Cd, Pb, Zn uptake were depressed, while the photosynthetic rate, glutathione and phytochelatin (PC) contents were increased by EDTA application. Interestingly, Burkholderia sp. D54 and Burkholderia sp. D416 inoculation significantly relieved the inhibitory effects of EDTA on plant growth and soil respiration. Compared with the control, EDTA + D416 treatment increased the Cd concentration in shoots and decreased the Pb concentration in shoots and roots, but did not change the Zn concentration in S. alfredii plants. Furthermore, EDTA, EDTA + D54 and EDTA + D416 application increased the cysteine and PC contents in S. alfredii (p < 0.05); among all tested PCs, the most abundant species was PC2, and compared with the control, the PC2 content was increased by 371.0%, 1158.6% and 815.6%, respectively. These results will provide some insights into the practical use of EDTA and PGPR in the phytoremediation of heavy-metal-contaminated soil by S. alfredii.     

催化燃烧／库仑滴定法测定植物叶片中硫

以三氧化钨为催化剂，燃烧处理植物叶片，硫转化为SO2，后者被吸收液吸收后采用库仑滴定法测定。方法快速简便，测定植物叶片中硫的含量，相对标准偏差为1．5％，适用于大批量样品的快速测定。     

乐安江沉积物对重金属的吸附模式研究──表面络合模式在天然沉积物研究中的应用

应用表面络合理论及其研究方法对乐安江沉积物的表面特征及对重金属的吸附特性进行了研究．进行了乐安江沉积物样品的表面电位滴定实验及样品对重金属Ｃｕ、Ｃｄ的吸附实验．应用图解法及ＦＩＴＥＱＬ优化程序确定了表面络合模式中的相应参数，并对模式的预测能力进行了检验．研究了３种表面络合模式即恒定容量模式，扩散层模式和三层模式的拟合应用情况．结果表明，３种表面络合模式均能较好地描述天然沉积物的吸附过程，但哪种模式从化学原理上看更正确尚不能证明．从模式计算的难易程度分析，扩散层模式有一定优势．模式应用中应特别强调的是模式参数间的相关性和一致性．