Question

Explain why speciation analysis is particularly important for Cr, As, and Se? What are the major valance (oxidation number) for each of these three elements? Describe their impact with regard to plant, and animal/human.

Answer 1

Speciation analysis means distinction and assessment of different oxidation states or chemical forms of a particularized element. It is important for Cr, As and Se because they considered as the carcinogen and they are also responsible for monitoring environmental pollution.

Cr exist in 2 forms: one is Cr (lll) and another is Cr (Vl)

Ar exist in 2 forms: one is As (lll) and another is As (lV)

Se exist in 2 forms: one is Se (lV0 and another is Se (Vl)

Cr (lll) considered as essential micronutrients in the human which is required for lipid metabolism moreover reduces the risk of myocardial infarction and promote the growth of the plants whereas Cr (Vl) severally damage plants and animals. It induced oxidative stress which degrades photosynthetic pigments which are required for plant growth. In humans, it causes many health problems like skin rashes, genetic material alteration, kidney damage, inflammation of the larynx and allergic reactions which may lead to the death of the individual.

Generally, there are two types of Arsenic: inorganic arsenic and organic arsenic. Inorganic arsenic is more toxic than organic arsenic and arsenite is more toxic than arsenate. Effect of arsenic on plants: it will decrease the production of fruits and seed germination, cause chlorosis and wilting and have a great impact on photosynthesis. In humans, arsenic causes anaemia, cancer, burning eyes sensation and hyperpigmentation keratosis. The circulatory collapse in an animal is quite common due to arsenic.

Most common species of Selenium is Se(lV) and Se (Vl) out of which Se(Vl) is more harmful. At an optimum range, selenium is essential nutrients for both plants and humans whereas, at high concentration, selenium incorporates at the place of sulphur in amino acids causing an alteration in the three-dimensional structure of protein leading to impairment of enzymatic function. It is responsible for bioaccumulation in food webs. An excessive amount of selenium in plants leads to oxidative stress which reduces crop yield and Consumption of plants containing selenium leads to hair loss, blindness, diarrhoea and also increase heart rate and respiratory rate.