Arsenic taint of Bangladeshi groundwater arises from a combination of three factors, viz. , the beginning, mobilization and the conveyance of Arsenic.

The pandemic arsenic pollution in the Bengal Basin was likely caused by overlying effects of the discriminatory entrapment of arsenic in organic-rich deltaic deposits when the sea degree rose, hindering entry of air to the aquifier, whilst microbic oxidization of the organic C depleted the dissolved O in the groundwater. Arsenic mobility in the aquifiers is mostly controlled by surface assimilation and desorption reactions and by precipitation and disintegration reactions.

Attachment of arsenous anhydride to an Fe oxide surface is an surface assimilation reaction, whereas the release of arsenic from such a surface is a desorption reaction. Formation of a solid stage from constituents present in aqueous solution is Solid-phase precipitation whereas disintegration of volcanic glass within an aquifer is solid-phase disintegration. Arsenic surface assimilation and desorption reactions are influenced by alterations in pH, happening of redox reactions, presence of viing anions, and solid-phase structural alterations at the atomic degree. Solid-phase precipitation and disintegration reactions are controlled by solution chemical science, including pH, oxidation-reduction province, and chemical composing.

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Pyrite and arsenopyrite are absent or really rare in aquifer deposits from the Bengal Basin. This and the low concentration of sulfate in groundwater go against the postulated pyrite oxidization hypothesis. Arsenic gets preferentially entrapped in the organic-rich, clayey flood-plain and delta deposits, and any delta or flood plain that developed into fen or swamp is prone to incorporate As-contaminated groundwater.

Three mechanisms are by and large used to explicate the release of arsenic into land H2O. These are reductive disintegration of FeOOH and release of occluded arsenic to groundwater, oxidization of arsenical fool’s gold, competitory exchange of occluded arsenic with phosphate from fertiliser. However, barely any of the arsenic pollution is due to the fertilizer-phosphate or pyrite oxidization. On the other manus, it is thought that the distribution of arsenic taint is due to the distribution of inhumed peat sedimentations which drives the decrease of FeOOH, which is non limited by geographics or clip. ( 335 words )

Question 1 ( B )

Table 1: Frequency tabular array for the Cook Inlet Basin groundwater Wellss as sampled by the USGS. The Kanai Peninsula Borough has been completed, as an illustration.

Arsenic Concentration

/µg l-1

Municipality of


Matanuska-Susitna Borough

Kanai Peninsula Borough

& A ; lt ; 5












































Entire figure of Wellss




Number of Wellss demoing As degrees above WHO limits




% of Wellss demoing As degrees above WHO limits




Average As concentration

/µg l-1




* Number of Wells demoing As degrees above WHO Limits:

†Calculation of Average As concentration/µg l-1 for the Municipality of Anchorage:

‡Calculation of the % of Wellss demoing As degrees above WHO Limits: :

Question 1 ( degree Celsius )

Arsenic distribution in environment is complex, due to the chemical signifiers in which it may be present, and because of the uninterrupted cycling of its different signifiers through air, dirt and H2O. Most arsenic in the ambiance comes from high-temperature procedures such as coal workss, firing flora and volcanic activity. The arsenous anhydride is released into the ambiance as arsenic trioxide where it adheres onto the surface of atoms which are dispersed by the air current and finally fall back to the Earth.

Natural, low-temperature biological reactions affecting bug besides let go of arsenic into the ambiance. Microbes moving on arsenous anhydride in dirts and deposits generate arsine gas which reacts with O in the air and is converted back to non-volatile signifiers of arsenous anhydride.

In well-oxygenated H2O and deposits, arsenous anhydride is present as arsenate. Some chemical signifiers of arsenic adhere strongly to clay and organic affair and can impact how they behave, giving a potency for arsenic to be released from H2O and deposits.

Last, weathered stone and dirt incorporating arsenous anhydride may be transported by air current or H2O. Since many arsenic compounds tend to adhere strongly to dirty, H2O leaching down does non normally move arsenic through more than a short distance in dirt. ( 200 words )

Question 1 ( vitamin D )

Local variableness in arsenic concentrations depends on good design, dept, and presence of peat in deposits. Drilled Wellss are sealed and H2O enters through the underside of the tubing, so contaminated H2O from higher degrees is excluded.

Wells drilled to beds where peat is absent are improbable contaminated since anaerobiotic bacteriums that encourage disintegration of Fe ( OH ) 3 and release of arsenic do non hold sufficient dead tissue to last. Wells drilled into organic-rich beds are contaminated due to the dissolved Fe ( OH ) 3 nowadays here. Wells drilled into aerated zones have low degrees of arsenic since Fe ( OH ) 3 is stable. ( 99 Wordss )

Question 1 ( vitamin E ) ( I )

Question 1 ( vitamin E ) ( two )

Question 1 ( degree Fahrenheit )

Question 2 ( a )

The diagram above was extracted from the nexus: hypertext transfer protocol: // nevertheless Is have added some labels to the diagram.

Muscle contraction is controlled by motor nerve cells that release the neurotransmitter acetylcholine at the neuromuscular junction. This is the topographic point in the organic structure where axons of motor nervousnesss meet the musculus and transmit messages from the encephalon which cause the musculus to contract or relax. Acetylcholine is synthesised by the motor nerve cells and stored in synaptic cysts at the axon terminus. An action potency at the axon terminal causes voltage-gated Ca ion channels to open and increase the calcium permeableness of the presynaptic terminus cell membrane. Calcium ions enter the presynaptic terminus and do the synaptic cysts to let go of the acetylcholine into the synaptic cleft.

The acetylcholine diffuses across the synaptic cleft and binds to the nicotinic receptors on the postsynaptic membrane of the musculus fiber causation and addition in the permeableness of the ligand-gated Na ion channels. The motion of Sodium ions into the musculus cell consequences in depolarization if the postsynaptic membrane. Once a threshold has been reached, a postsynaptic action potency is generated and propagated over the musculus cell membrane ensuing in contraction. The acetylcholine is quickly broken down into acetic acid and choline in the synaptic cleft by the enzyme acetyl cholinesterase. The choline is so reabsorbed into the presynaptic terminus where it combines with acetic acid to organize more acetylcholine which enters the synaptic cysts.

The active ingredients in some natural and man-made drugs are alkaloids. Alkaloids such as curare and nicotine show structural similarity to neurotransmitters in that they excessively possess positively charged N atoms linked to methyl groups. This structural characteristic allows the alkaloids to adhere at the acetylcholine receptor on the surface of musculus cells and therefore forestalling the acetylcholine from interacting with its receptors. The can ensue in either an counter or an agonistic consequence. Tubocurarine does non bring on musculus contraction like acetylcholine, and is therefore known as an acetylcholine adversary. On the other manus, nicotine mimics the action of acetylcholine doing an action potency to be generated in the musculus cell membrane ensuing in contraction. Therefore, nicotine can be classified as an acetylcholine agonist. ( T4 pgs 36-37 ) . ( 345 words )

Question 2 ( B )

Many medicative drugs like silphion and nicotine come straight from the works land. Others, like acetylsalicylic acids are merely derived functions of botanical natural merchandises. Aspirin comes from the hurting slayer salicylic acid which was originally extracted from the bark of willow trees, whilst anodynes such as morphia are derived from the opium poppy. There may be many more remedies for diseases provided by workss, waiting to be discovered. But how do research workers travel approximately in placing workss that may incorporate medicative merchandises? In a universe where fiscal resources are limited, it would be impossible to test every works species.

Modern research on workss can be perchance done in assorted ways. It is possible to research medicative belongingss of workss by analyzing the molecules of workss that are closely related to workss already known to bring forth utile compounds. Ecological studies can besides be done by choosing workss from peculiar home grounds or that show peculiar features that indicate that they are capable of bring forthing substances that could be exercising and consequence on animate beings. For illustration workss that seem to be immune from predation from insects could bespeak that the works is bring forthing substances that are toxic to insects. Such substances could demo bioactivity in worlds intending that they could be capable of accomplishing some curative effects.

Furthermore, a possible attack could be that of ethno vegetation, which assumes that the autochthonal usage of workss can offer strong hints to the biological activities of the works in peculiar. Autochthonal people possess a huge organic structure of cognition that is of great value. Their creativeness is reflected in the rich cognition systems they have developed to conserve and carefully use Earth ‘s resources. This cognition has been passed on from coevals to coevals non by being written down, but through unwritten transmittal. In my sentiment, this could perchance be the most productive of works appraising methods. ( 309 words )

Question 2 ( degree Celsius )

Peoples have been utilizing herbal redresss for ages. From the earliest recorded history, human existences have used points from the environment to bring around unwellness and dainty symptoms. The most effectual of these redresss are still in usage today, but they are no replacing for traditional medical specialty, and of course happening herbs or works must non be considered a primary attention option.

Herbal medical specialty has become progressively popular in recent old ages with many patients utilizing them on a regular basis, frequently without first confer withing with their physician. While many herbal redresss are safe, it is of import to understand that there are hazards involved when utilizing them and a big figure of people could be jeopardizing their wellness by taking herbal medical specialty without holding antecedently checked with a wellness professional. Furthermore, because many herbal medical specialties have important pharmacological activity, and hence possible inauspicious interactions, health care professionals and physicians must be familiar with the curative mode of the substance.

The belief that all herbs are safe due to the natural happening is widespread. However, these are far from being free of side effects. Some merchandises are known to be safe, such as natural tegument attention merchandise ingredients like aloe which is helpful for dry tegument and is otherwise comparatively harmless. Despite this, even when a natural redress is safe, it may non ever be effectual. Using an uneffective redress for handling serious medical conditions can do the implicit in status worse, and failure to handle the status is a major cause of complications from usage of natural redresss.

Some workss may incorporate compounds which are toxic or toxicant like for illustration hemlock. On the other manus, infusions from toxicant workss could be utile if used adequately. Although hazard of decease is really little, some herbal redresss interacting with other medicines result in terrible effects. An illustration of this is the celebrated St John ‘s wort that for many hundred old ages was used for mending lesions. It was found to do many prescription drugs used to handle conditions of bosom disease, ictuss and depression less effectual. It is therefore of import to look out for harmful drug interactions and seek to minimise them. Peoples besides run extra hazards because they tend to name an complaint themselves and take what they think is appropriate ensuing in the danger of wrong diagnosing and therefore taking the incorrect redress. ( T4 pg 57-59 )

An extra hazard in herbal redresss is that although the herb in it self may be safe, it may be contaminated with, or replaced by a much more unsafe substance. This can go on by errors being made by consumers or providers of the herbs as in the instance reported by the Yorkshire Gazette of Saturday, 15 October 1825 page 2 where a adult female called upon a pharmacist to buy preparatory medical specialty for the little syphilis, but she erroneously pick up a little package or arsenous anhydride that had been wrapped up for person else ( T3 pg 7 ) . This nevertheless, can besides happen intentionally – in the nineteenth century, arsenous anhydride was good known as a deathly toxicant, tasteless, and slaying by arsenic toxic condition could be disguised as natural decease from cholera. ( T3 pgs 7-8 ) .

The hazards involved in natural works preparations are chiefly due to their unknown facets, and it could be due to the chief active ingredient every bit good as to the secondary ingredients. Hazards from prescribed drugs are normally know, described and can be discussed with the druggist publishing the drug. On the other manus, although there may be information associated with the natural works preparations, the user is required to measure and construe the hazards. It is therefore recommended that any herbal redress should ever be purchased from topographic points where professional wellness advice can be given and discussed prior to disposal. Further more, by going an educated consumer, and with the aid of the medical physician, one would be able to do an informed determination about utilizing herbal redresss, and so make up one’s mind which option is the best. ( 646 Wordss )

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