Environmental and Agricultural Microbiology. Группа авторов

Читать онлайн книгу.

Environmental and Agricultural Microbiology - Группа авторов


Скачать книгу

      3.2.1 Non-Essential Heavy Metals

      The toxicity and carcinogenicity potential of some frequently present non-essential heavy metals like mercury, chromium, lead, arsenic, and cadmium are described in this section.

       3.2.1.1 Arsenic

      Arsenic present in periodic table of period 4 and group VA in metalloid state. The inorganic form includes trivalent arsenite (AsIII) and pentavalent arsenate (AsV) and methylated metabolites are organic form of arsenic, e.g., monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and trimethylarsine (TMA) oxide. Atmospheric pollutions occur through arsenic due to volcanic eruption, soil erosion, and anthropogenic activities [24]. In ores, arsenic generally exists in powdery amorphous and crystalline forms. It enters in to the environment through withstand of rocks, mining and smelting methods, pesticide practice in agriculture, and coal ignition. It causes ground water as well as surface water contamination and exists as arsenate (AsV) and arsenite (AsIII) in maximum groundwater. Its high concentrations in drinking water create toxic effect to animal and human [22].

       3.2.1.2 Cadmium

      Cadmium is a highly toxic and nonessential heavy metal for environment. Moderate concentration of cadmium (around 0.1/kg) is commonly found in the soil crust. The maximum amount of cadmium compounds are accumulated in sedimentary rock and phosphates of marine (contain nearly 15 mg/kg) [29] and naturally released to environment by abrasion of rocks and soil, forest fires, and volcanic eruption. The anthropogenic activities are also responsible for cadmium pollution such as metal plating, metallurgical alloying, ceramics, mining, and other industrial operations. It is used as a protecting guard on alloys and steel, in paints


Скачать книгу