Chemistry Essay代写:土壤

2017-02-15 13:00

土壤是极其重要的自然资源从农业以及环境的视角。良好的土壤健康不仅有助于提高农产品的质量和产量,但也很重要的回收大量的有机生物。然而,污染土壤的各种污染物,如重金属、杀虫剂或石油碳氢化合物,会导致严重的环境和生物效应。这种污染会直接危害动物和人类,渗入饮用水来源,破坏植物和植被,以及影响特有微生物和昆虫生活在土壤中。表层土壤中发现的微生物,通常扮演关键角色的酶回收氮、磷、硫、以及有机质的分解,因此影响全球回收养分、碳和其他元素。除了营养循环、土壤微生物也会影响土壤的物理性质分泌细胞外多糖,稳定土壤总量,进而影响水潴留,入渗率、结壳,土壤侵蚀度。因此,微生物的健康被认为是土壤健康的良好指标。土壤中重金属污染物发现欺诈造成有害影响的四个方面:1)这些重金属可以经过氧化还原循环,在这个过程中导致精子生产从而导致氧化应激生物,2)他们可以直接绑定到巯基蛋白组,导致蛋白质失活和变性,3)他们可以绑定到细胞内谷胱甘肽(GSH)或抗氧化酶(例如SOD、过氧化氢酶、谷胱甘肽还原酶/ peroxideaes)和减少细胞的抗氧化能力;4)这些重金属也可以争夺metal-cofactor绑定metallo-enzymes并导致其失活。最近的工作在重金属污染对土壤的影响表明,微生物、酶的活动(由微生物产生的),也可以作为土壤健康的指标。这些研究的土壤酶用于脱氢酶,beta-glucosidase,纤维素,酚氧化酶,脲酶、酰胺酶、磷酸酶和arylsulphatase。大多数的研究已经由监测污染物对土壤的酶活性。虽然一个有效的方法,这些研究废水中所含污染物对微生物有一个系统的影响,以便减少或增加土壤酶活性可能是由于其他原因,而不是由于直接影响污染物的各种酶。另外测试污染物可以被微生物代谢或环境因素分解,所以它们对微生物酶的影响可能是次要产品。一些研究已发表在重金属污染物的影响一直在检查纯化酶体外,但是他们很少,不是很彻底。在本文中,我们系统地研究的影响等的酶(Mg + 2,+ 2,+ 2,Cd + 2,Hg + 2,铜+ 2)在碱性磷酸酶(ALP)活性,并表明,重金属如汞柱+ 2,铜+ 2抑制酶比Cd + 2更强烈,和+ 2。然而,正二价碱土金属如Ca + 2,和Mg + 2激活酶,Mg + 2作为酶的激活剂比Ca + 2。此外,单价碱金属离子如Na +对高山活动没有影响。我们还研究了高山活动结合重金属的影响.

Chemistry Essay代写:土壤

Soil is a natural resource that is utmost importance from an agricultural as well as environmental perspective. Good soil health not only helps improve the quality and yield of agriculture products, but is also important for recycling of significant amounts of organic biomass. However, pollution of soil by various pollutants, such as heavy metals, pesticides or petroleum hydrocarbons, can lead to serious environmental as well as biological effects. This pollution can directly harm animals and human being, leach into drinking water source, damage plants and vegetation, as well as affect the endemic microorganisms and insects living in the soil. Microorganisms that are normally found in the top soil play key roles in enzymatic recycling of nitrogen, phosphorous, and sulfur, as well as the decomposition of organic matter; thus they impact global recycling of nutrients, carbon and other elements. In addition to nutrient recycling, soil microbes can also affect physical properties of soil as they secrete extra-cellular polysaccharides which stabilize soil aggregates, which in turn affect water retention, infiltration rate, crusting, erodibility of soil. Thus, microbial health is considered a good indicator of soil health. Heavy metal pollutants found in the soil con cause their deleterious effects by one of four ways: 1) These heavy metals can undergo redox cycling and in the process lead to oxyradical production which then causes oxidative stress in organisms, 2) they can bind directly to sulfhydryl groups of proteins and lead to protein inactivation and denaturation, 3) they can bind to intracellular glutathione (GSH) or antioxidant enzymes (e.g. SOD, Catalase, GSH reductase/ peroxideaes) and reduce the antioxidant ability of cells; and 4) these heavy metals can also compete for metal-cofactor binding of metallo-enzymes and lead to their inactivation. Recent work on the effect heavy metal pollution on soil have shown that like microorganisms, activity of the enzyme (produced by microorganisms), can also be used as indicators of soil health. The soil enzymes that have been used for these studies are dehydrogenase, beta-glucosidase, cellulose, phenol oxidase, urease, amidase, phosphatase and arylsulphatase. Most of these studies have been carried out by monitoring enzyme activities of pollutant treated soil. Though a valid approach, the pollutants in these studies could have a systematic effect on the microorganism and so that the decreased or increased soil enzyme activity could be due to other reasons, and not due to the direct effect of the pollutant on various enzymes. Additionally the tested pollutants could be metabolized by the microorganisms or broken down by the environmental factors, and so their effect on microbial enzymes could be secondary product. A few studies have been published in which the effect of heavy metal pollutants have been examined on purified enzymes in vitro, however they are very few and not very thorough. In this thesis, we have systematically examined the effect of the various of heavy enzymes such as (Mg+2, Ca+2, Co+2, Cd+2, Hg+2, Cu+2) on alkaline phosphatase (ALP) activity, and show that the heavy metals such as Hg+2, Cu+2 inhibited the enzyme more strongly than Cd+2, and Co+2 . However, the positive bivalent alkaline-earth metals such as Ca+2, and Mg+2 activated the enzyme