文献阅读问题答案教学文案.doc

文献阅读问题答案

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文献阅读问题
Introduction
1. How do heavy metals entry the soils?
Answer: Entry of soil-borne metal(loid)s into the food chain depends on the amount and source of metal(loid)s input, the properties of the soil, the rate and magnitude of uptakeby plants, and the extent of absorption by animals.
2. Can you give a definition to heavy metal and give us the examples?
Answer: The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic, highly toxic or poisonous at low concentrations. Examples of heavy metals include mercury(Hg), cadmium(Cd),arsenic(As), chromium(Cr), thallium(Ti), and lead(Pb) .
Historically, heavy metal(loid)s toxicity to human health received attention primarily as a result of series of widespread poisoning.
3. Why human kind pays attention to heavy metal(loid)s toxicity?
Answer: Historically, heavy metal(loid)s toxicity to human health received attention primarily as a result of series of widespread poisoning.
4. Can you describe characteristics of heavy metal(loid)s in soil?
Answer: Unlike organic contaminants, metal(loid)s do not undergo microbial or chemical degradation, and the total concentration of these metal(loid)s persist for a long time after their introduction in soils .
5. Can you tell us the difference between phytoextraction and phytostabilization?
Answer: Phytoextraction process is used to remove metal(loid)s in soil; phytostabilization is used to immobilize metal(loid)s in soil.
Sources of heavy metal(loid)s

1. Where does heavy metal in the soil come from?
Answer: Heavy metal(loid)s reach the soil environment through both pedogenic and anthropogenic processes.
Dynamics of heavy metal(loid)s in soils
1. Do metal(loid)s subject to volatilization losses?
Answer: Although most metal(loid)s are not subject to volatilization losses, some metal(loid)s such as As, Hg, and Se tend to form gaseous compounds ].
2. Please tell the difference between specific adsorption and non-specific adsorption.
Answer: In general terms, non-specific adsorption is a process in which the charge on the ions balances the charge on the soil particles through electrostatic attraction, whereas specific adsorption involves chemical bond formation between the ions in the solution and those in the soil surface.
3. Please tell us the relationship between bioavailability of heavy metal and soil
physicochemical property?
Answer: Bioavailability of heavy metal are effected by a number of factors including temperature, steric factors and concentration. All these interactions are controlled by solution pH and ionic strength, the nature of the metal(loid) species, dominant cation, and inorganic and organic ligands present in the soil solution
4. When does the precipitation appear to be the predominant process?
Answer: Precipitation appears to be the predominant process in high pH soils and in the presence of anions such as SO42−, CO32−, OH−, and HPO42−, and when the concentration of the heavy metal(loid) ion ishigh .
5. What is co-precipitation? Can you give an example.
Answer: Co-precipitation of metal(loid)s especially in the presence of iron oxyhydroxides has also been reported and often such interactions lead to significant changes in the surface chemical properties of the substrate. Lu et al. confirmed that co-precipitation of Pb(II) with ferric oxyhydroxides occurred at ∼pH 4 and is more efficient than adsorption in removing Pb(II) from aqueous solutions at similar sorbate/sorbent ratios and pH. .
6. Does the toxicity of As in soil decrease or increase when it presents in compound
of alkylarsine?
Answer: It will be decrease.
Approaches and indicators of bioavailability
1. What is the bioavailability of heavy metal?
Answer: The generic definition of bioavailability is the potential for living organisms to take up chemicals from food (i.e., oral) or from the abiotic environment (i.e., external) to the extent that the chemicals may become involved in the metabolism of the organism.
2. How to indicate the bioavailability of heavy metal?
Answer: Bioavailability of metal(loid)s in soils can be examined using chemical extraction and bioassay tests that determine a fraction of the metal(loid)s is bioaccessible. Chemical extraction tests include single extraction and sequential fractionation. Bioassay involves plants, animals, and microorganisms .
3. What is PBET(physiologically based extraction test)?
Answer: These innovative tests predict the bioavailability of metal(loid)s in soil and sediments when ingested by animals and humans.
Soil amendments for remediation
1. What is the mobilization of soil contaminants?
Answer: The basic principle involved in the mobilization technique is to release the metal(loid)s in to soil solution, which is subsequently removed using higher plants. I
2. Can you explain the mechanism of chelating agents?
For example: application of thiosulphate to soil reduced the amount of Hg volatilized
by B. juncea plants.
Answer: Chelating agents which have high affinity for metal(loid) ions can be used to enhance the solubilization of metal(loid)s in soils through the formation of soluble metal(loid) chelates.
3. Does saline water improve the leaching of heavy metal(loid)s?
Answer: No, Wahla and Kirkham concluded that irrigation of sludge farms with brackish water is not recommended, because saline water increased the mobility of the metal(loid)s and they polluted the drainage water.
4. Does microorganism select heavy metal(loid)s in soil solution for accumulation?
Answer: No, microorganism select heavy metal(loid)s in soil solution for transformation.
5. How can we mobilize the soil heavy metal(loid)s according this paper?
Answer: Mobilization of contaminants can be achieved through solubilization, desorption, chelation, and complexation reactions which result in the redistribution of contaminants from solid phase to solution phase, thereby increasing their bioavailability .
6. Why does lime immobilize the heavy metal(loid)s?
Answer: Liming enhances sorption of heavy metal(loid)s by reducing the H+ concentration and increasing negatively charged sites.
7. It is well known natural zeolite can immobilize heavy metal(loid)s in soil. Can you
tell us what kinds of fraction of heavy metal have changed?
Answer: Zeolites are also useful as metal(loid) scavengers in biosolids containing metal(loid)s. The natural zeolite immobilized Cd, Cu, Cr, Fe, Mn, Ni, Pb, and Zn in biosolids, which transformed metal(loid)s in the exchangeable and carbonate fractions to residual fractions .
8. Biochar has recently been applied as a green material to adsorb metal(loid)s in soil
and water. Do you think so?
Answer: No, biochar has recently been applied as a novel carbonaceous material to adsorb metal(loid)s in soil and water.
Answer:
9.translate the following sentences
l Addition of organic amendments, such as sewage sludge and green waste
composts to soils enhances the physicochemical and biological conditions of soils,
thereby improving plant growth..However, the organic amendments can directly
or indirectly alter the distribution and availability of metal(loid)s in soil.
Translation:添加有机改良剂，类似于污泥和绿色废弃物堆肥能提高土壤的物理化学性和生物性能，并且能促进植物生长。另外，有机改良剂能直接或间接地改变土壤重金属的分配和可利用性。
l They added organic (cow manure) and inorganic (Osmocote, NH4NO3, and KCl)
fertilizers to enhance plant growth and Pb accumulation. The greenhouse study
showed that cow manure decreased available Pb concentrations, but, nevertheless,
this treatment resulted in the highest Pb concentrations in roots and shoots.
Translation:加入有机肥（牛粪）和无机肥（(Osmocote, NH4NO3, and KCl)）加快植物生长和铅累积。温室研究表明牛粪能有效降低铅浓度，然而，尽管如此，这种处理方法造成植物根系和幼苗铅浓度最高。
l Immobilization of contaminants can be achieved mainly through adsorption,
precipitation, and complexation reactions which result in the redistribution of
contaminants from solution phase to solid phase, thereby reducing their
bioavailability and transport in the environment.
Translation:污染物的固定主要可通过吸收作用，沉淀作用和络合反应实现。它们导致了污染物从液相到固相的再分配，并减少了污染物在环境中的生物可利用性和迁移性。
l The decrease in Cd(II) sorption in to soils in the presence of P was attributed to
the formation of soluble Cd-P comlexes.
Translation:土壤中二价镉吸附作用和磷的减少归因于形成了Cd-P络合物。
alkaline-stabilized biosolids that are low in total and/or bioavailable metal(loid)
content can be used as an effective sink for reducing the bioavailability of
metal(loid)s in contaminated soils and sediments. Immobilization of metal(loid)s
by such amendments is achieved through adsorption, complexation, and redox
reactions.
Translation:碱性稳定化污泥总量和生物可利用的金属含量可作为减少污染土壤和沉积物中的重金属生物有效性的一种有效降低法。金属被这样的改良剂固定通过吸收作用，络合作用和氧化还原作用实现。

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