含磷材料固化锌、铅污染土的路用性能试验研究

采用新型含磷材料(KMP)及水泥(PC)分别对锌、铅污染土进行固化处理。通过无侧限抗压强度、水稳性、回弹模量和压汞试验,探究固化污染土作为路基填料的力学及耐久特性。结果表明:常规养护条件下,KMP和PC固化污染土强度随龄期和掺量增长而提高,强度越大;锌、铅复合污染条件下,固化污染土强度最低。经过泡水试验,固化试样强度均有所下降且7d强度损失较高;铅、锌复合污染条件下,强度降低幅度最高,水稳系数为0.52~0.58。固化污染土回弹模量低于固化未污染土但高于未固化污染土回弹模量,且KMP试样回弹模量高于水泥试样回弹模量的6.7%~24.2%。相对PC固化污染土,KMP试样微孔隙多、中、大孔隙较少,结构致密。

EICP修复重金属污染土的环境耐久性研究

为探究脲酶诱导碳酸钙沉淀(enzyme induced carbonate precipitation,EICP)技术修复重金属污染土的环境耐久性,分别对EICP修复后的锌、铅污染土进行酸液浸泡、冻融试验和雨淋试验,探讨了EICP修复锌、铅污染土在不同环境条件下的耐久性及其影响规律。结果表明,在不同浓度、不同类型酸液条件下,EICP修复后的锌、铅污染土中可交换态和碳酸盐结合态的重金属离子浸出量随p H值降低,碳酸盐结合态含量降低,可交换态含量逐渐增加,且硫酸环境下的稳定性大于硝酸环境下的稳定性;随着冻融循环次数的增加,EICP修复后的锌、铅污染土中可交换态离子浸出量增加,碳酸盐结合态含量减少;在大雨条件下,Zn^(2+)、Pb^(2+)主要在前20 min内进行释放,并由上往下迁移;经EICP修复重金属污染土在酸液、冻融循环和雨淋条件下具有良好的耐久性。

Effects of Red Mud on the Remediation of Pb, Zn and Cd in Heavy Metal Contaminated Paddy Soil

[Objective] To study the remediation efficiency of red mud on Pb, Zn and Cd in the heavy metal contaminated paddy soil of mine area, to clarify its remediation mechanism and fertilizer efficiency on heavy metal contaminated soil. [Method] The soil incubation experiment was conducted to study the effect of red mud on the pH values and electrical conductivity （EC）, and the remediation efficiency of red mud on lead （Pb）, zinc （Zn） and cadmium （Cd） in heavy metal contaminated soil. [Result] Red mud addition reduced the content of exchangeable Pb, Zn and Cd in the soil significantly. Compared with the control, when incubated for 30, 60 and 90 d with the red mud dosage of 4% （W/W）, the exchangeable Pb content was decreased by 39.25%, 41.38% and 50.19%; exchangeable Zn content was decreased by 49.26%, 57.32% and 47.16%; and exchangeable Cd content was decreased by 19.53%, 24.06% and 25.70%, respectively. The application of red mud had significant impact on the share of Pb, Zn and Cd contents in five forms, and different amounts of red mud application all reduced the proportion of exchangeable Pb, Zn and Cd to the total Pb, Zn and Cd. In addition, the proportion of exchangeable Pb, Zn and Cd to total Pb, Zn and Cd decreased with the increasing amount of red mud addition. [Conclusion] The study provided references for reasonable application of red mud and reduction of heavy metal pollution in paddy soil.

Effect of Amendments on Growth and Element Uptake of Pakchoi in a Cadmium, Zinc and Lead Contaminated Soil

A pot experiment was carried out to study the effects of two amendments, limeand calcium magnesium phosphate, on the growth and Cd, Pb, Zn, Cu, Mu, Fe, N, P and K uptake ofpakchoi (Brassica chinensis) in a Cd, Pb and Zn polluted acid soil in the southern part of China.The growth of pakchoi was apparently improved by lime and calcium magnesium phosphate application,the uptake of Cd, Pb, Cu and Zn by pakchoi was significantly depressed and the symptom caused byheavy metals pollution was eliminated. Meanwhile, the absorption of N, K and Mn was also inhibitedby these amendments. Soil pH was the main factor controlling the uptake of the heavy metals bypakchoi. This suggests that lime and calcium magnesium phosphate could be used as effectiveamendments for eliminating the toxicity of heavy metals to the vegetable and inhibiting theirabsorption by the crop.

Effect of Heavy Metal Pollution on Potassium Behavior in Typic Udic Ferrisol

The indirect influence of heavy metal contamination of soil on nutrient availability, an important aspect of soil quality, may need to be taken into consideration when determining overall effects of heavy metals. A laboratory experiment was performed to study the effects of combined pollution of Cu, Ph, Zn and Cd on soil K status as indicated by chemical fractions, adsorption-desorption and quantity/intensity (Q/I) relationship of K in a Typic Udic Ferrisol (generally called red soil), by employing uniform design and single factor design. Compared to the control, content of exchangeable K was decreased, but that of soluble K increased in the samples contaminated with heavy metals. Due to heavy metal pollution, potassium adsorption was reduced by 5% to 22%, whereas the desorption percentage of adsorbed K increased by 2% to 32%. The Q/I curves shifted downward, potassium buffering capacity (PBCK) decreased, and equilibrium activity ratio values (ARoK) increased with increasing heavy metal pollution. These influences followed the sequences of Ph>Cu>Zn and combined pollution>single one. Displacement of K from canon exchange sites and decrease in soil CEC due to heavy metals should be responsible for the changes of soil K behaviours. The findings suggest that heavy metal pollution of soil might aggravate the degradation of soil K fertility by decreasing K adsorption and buffering capacity and increasing desorption.

Characteristics of Some Heavy Metals in Acid Sulfate Topsoils, Eastern Australia

Forty-five acid sulfate topsoil samples (depth < 0.5 m) from 15 soil cores at 11 locations along the New South Wales coast, Australia, were selected to investigate the chemical behavior of Zn, Mn, Cr, Co and Pb in these soils. The amount of HCI-extractable Mn was much smaller than the mean value of the total Mn documented for other soils. This may be attributed to enhanced mobilization of Mn from the soils under the extremely acidic and seasonally flooded conditions encountered in the investigated soils. The pH-dependency of soluble Zn and Mn was strongly affected by the availability of acid reactive Zn and Mn compounds. There were fairly good relationships between soluble Zn and acid reactive Zn compounds, and between soluble Mn and acid reactive Mn compounds. Soluble Zn and soluble Mn concentrations were important controls on exchangeable Zn and Mn concentrations, respectively. In contrast to the suggestion by other authors that adsorption of Co was closely associated with Mn oxides present in soils, the exchangeable Co in the investigated acid sulfate soils was not clearly related to the abundance of Mn minerals. In addition to the fact that there are few Mn minerals present in the soils, this might also be because the availability of canon exchange sites on the crystal surfaces of Mn oxides was reduced under extremely acidic conditions.

Effect of Heavy Metals on Phosphorus Retention by Typic Udic Ferrisols: Equilibrium and Kinetics

A study was conducted to examine the effect of heavy metals (Cu,Pb, Zn and Cd in combination or alone) on the equilibrium andkinetics of phosphorus (P) retention in typic udic ferrisols by usingboth equilibrium and flow techniques. Fourteen soil samples withvarying artificial contamination of Cu, Pb, Zn and Cd were prepared.Heavy metal pollution led to increases in retention capacity andmaximum buffering capacity (MBC) of soil P. The rate of P retentionwas also increased and the time to reach equilibrium was advanced byheavy metals addition.

Treatment of mine drainage generated by lead-zinc concentration plant

The purification efficiency in the treatment of the mine drainage generated by the mineral processing industry in Mengzi,Yunnan Project, China, was investigated, and the influences of the treated drainage on the mineral electrodes' electrochemical behaviors were tested. Experiments with different doses of polyacrylamide(PAM) and polymeric ferric sulfate(PFS) at different pH values were carried out, and the advanced purification by activated carbon(AC) was conducted. Compared with PFS, the better coagulant for removal efficiency is PAM, under the optimal conditions, the removals of Pb2+, Zn2+, Cu2+ and COD reduction from solution were 94.8%, 79.9%, 87.6% and 85%, respectively. In the advanced purification, the particle size of activated carbon and agitation time played important roles in the removal efficiency. Each pollute concentration could meet the emission standard of pollutants for lead and zinc industry(GB25466—2010). The wastewater without treatment affected galena and sphalerite electrochemical behaviors greatly, after treatment by the technology, the effects disappeared, which proved the reliability of the technology for wastewater treatment.