| 其他摘要 | Soil is one of the major components of the environment, by which human's survival and development could maintain. But pollution of heavy metals in soil has been more and more serious during recent several decades. Comparing with the other pollutants, heavy metal pollutants are of special characters, such as covered, long-term and irreversible, for which they became permanent pollution in soil, and they would ultimately harm to health of mankind through food chain, so study and control of the heavy metals pollution are of great significance. In this research, Donnan Membrane Technique and a computer program named ECOSAT (Equilibrium Calculation Of Speciation And Transport) were used to study the mobility of heavy metal ions in soil for the first time in China. The results of both methods were compared and validated with each other. In addition, red muds, which were produced by the Aluminous production Plant of Guizhou, were used to control the mobility of heavy metals in soil. Two soils were studied at different soil solution ratio, one is the soil around a bridge (QBT for short), the other lies underside the smelting factory (BXT for short hereinafter) in Duyun, Guizhou province. BXT is polluted badly, but QBT pollution is light. From these studies, we have obtained the several conclusions as following: 1. Some experimental conditions for Donnan Membrane Technique were improved. JAM-I homogeneous ion exchange membrane, which is made at home, replaced BDH membrane that was used by Erwin. By using the JAM-I homogeneous ion exchange membrane, the equilibrium time become shorter, furthermore it is cheap and can be obtained easily. The mixed solution of KNO3 and Ca(NO3)2 was displaced by KNO3 solution used as the background electrolyte. Error brought by the difference of Ca concentration was avoided. The other conditions for Donnan Membrane Technique were as following. The flow velocity of the peristaltic pump is 2.0mI/min.The equilibrium time is 48 hours. 2. Donnan Membrane Technique succeeded not only in citric acid systems, but also in soil-water system. Several metals could be measured simultaneously with this method, without disturbing the balance between the measured system and the round condition, moreover, all the metals did not interfere each other. 3. The concentrations of free heavy metal ions in QBT were in line with the total metals that were distilled through 2mol/L HNO3. The concentrations of free copper and zinc ions were in direct ratio with the total metals, and they decreased with the decreasing of the total metals, i.e. soil solution ratio. The changes of the concentrations of free nickel 'and cadmium ions were contrary to those of the copper and zinc ions. With the decreasing of the soil solution ratio, the trend of change was the same after adding red muds into it. The concentrations of free heavy metal ions increased after appending red mud derived from confederate process, but decreased after appending red mud derived from Bayer process. The larger the ratio adding was, the more the concentration changed, and the concentration changes of nickel and cadmium ions were larger than those of the copper and zinc ions. 4. The concentrations of free heavy inetals ions were in direct ratio with the total metals, which were distilled through 2mol/L HNO3 in BXT, and they decreased with the total metals. After appending red muds into it, the free concentrations of copper and zinc ions changed little, but those of nickel and cadmium ions changed out of the way. For the concentrations of free nickel ion, it changed as before after adding red muds at the ratio of 0.50%, while it increased firstly after appending red muds at the ratio of 2.00%, but decreased largely at the soil solution ratio of 1:100. For cadmium ion, it changed as nickel ion at the ratio of 2.00%. The concentrations of free copper and zinc ions in BXT decreased little after appending red muds at the ratio of 2.00%, and hardly changed at the ratio of 0.50%. While the cpncentrations of free nickel and cadmium decreased obviously after appending red muds at the ratio of 2.00%. The change of the concentration was still biggish after appending red muds derived from Bayer process at the ratio of 0.50%, but smaller than that of 2.00%. While the concentrations of free cadmium ions increased after appending red mud derived from confederate process at the ratio of 0.5 0%. 5. All experiments processes were modeled through ECOSAT. The results of modeling and measuring were consistent, except .for Zn ion. Thereby we conclude that ECOSAT is a good model to study the soil-water system. 6. Contributions of soil sorbents to the heavy metals adsorptions were modeled through ECOSAT at different soil solution ratio. The sorbents in soil included soil organic matter, iron hydroxides, clay and the Donnan gel of soil organic matter. It -. showed that the contribution bound to clay was very little, and could be neglected. Copper was mainly contributed in soil organic matter, and accounting 80%. With the decreasing of the soil solution ratio, the contributions of copper bounded to soil organic matter and the Donnan gel of soil organic matter decreased slowly, but the contribution bounded to iron hydroxides increased. Zinc was mainly contributed in soil organic matter and iron hydroxides, and accounting 40% respectively. With the decreasing of the soil solution ratio, the contribution of zinc bounded to soil organic matter increased little, and the contribution bounded to iron hydroxides was not changed, but the Donnan gel of soil organic matter decreased slowly. Nickel was mainly bounded to the soil organic matter and iron hydroxides, and cadmium was almost bounded to the soil organic matter. The contributions of nickel and cadmium were not affected by the soil solution ratio. 7. No matter what kind of red muds and how much was the ratio appending in soil, all heavy metals contributing in'the soil sorbents changed a little after adding red muds into soil. The proportion of soil organic matter decreased little, while the proportion of iron hydroxide increased correspondingly. In different soil solution ratio, the trend of change was same, but the range was larger |
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