Chromium is mobile under a. Oxidizing conditions, where Cr(VI) is the predominan

Question

Chromium is mobile under

a. Oxidizing conditions, where Cr(VI) is the predominant oxidation state

b. Reducing conditions, where Cr(III) is the predominant oxidation state

c. Alkaline conditions, where Cr hydroxides are present

d. None of the above

Reactive permeable barriers remediate uranium by

a. U(VI) reduction leads to U reductive precipitation

b. Intercepting a polluted plume and precipitating mobile uranyl into solid U(IV) particles

c. Reducing uranium(VI) to U(IV) where a reduced metal such as Fe0 acts as the reductant

d. All of the above

The mineral source of As in much of South, East, and Southeast Asia is

a. The low lying deltas

b. The Ganges-Brahmaputra-Meghna River system

c. The Himalayas

d. Goundwater pumping

Arsenic is released from reduced mineral arsenopyrite (FeAsS) through

a. Reductive dissolution upon contact with strong reductants like carbon

b. Oxidative precipitation upon contact with strong oxidants like O2

c. Reductive precipitation upon contact with strong reductants like carbon

d. Oxidative dissolution upon contact with strong oxidants like O2

e. None of the above

The oxidized form of arsenic, As(V)

a. Associates weakly with Fe(OH)3 in soils

b. Binds tightly with Fe oxides in soils

c. Is very mobile in the presents of Fe oxides

d. Can be oxidized by oxygen during the dry season

Under mucky permanent wetlands and oxbow lakes

a. Arsenic is immobilized by iron oxides

b. Arsenic is released when iron oxides undergo reductive dissolution

c. Arsenic concentrations are lower due to plant uptake

d. Microbial cycling of arsenic is inhibited

You take a handful of soil from your backyard in LA and measure the arsenic concentration in the soil. You find out the concentration of As in your backyard is higher than the As concentration in the soils of Cambodia. Why then is As a problem in southeast Asian groundwater and not here in CA?

a. Because of the As bound in the minerals in southeast asia are weakly bound compared to in CA

b. Because of climate: the monsoons and vegetation contributing reducing conditions there, which we don’t have here in southern CA

c. Because the WHO suggested limit is different for different countries

Explanation / Answer

Ans.

1.(a). oxidation state.

Explanation - Hexavalent chromium refers to chemical compounds that contain the element chromium in the +6 oxidation state.chromium (VI) can occur under oxidizing conditions,where Cr(VI) is the predominant oxidation state.In this state they contaminants ground water.

2.(a.) U(VI) reduction leads to U reductive precipitation

Explanation - Reductive precipitation is an effective method of attenuating the mobility of uranium (U) in subsurface environments.

3.(b) The Ganges-Brahmaputra-Meghna River system.

Explanation - The mineral source of As in much of South, East, and Southeast Asia,The Ganges-Brahmaputra-Meghna River system here main geogenic sourse is holocene sediments comprising sand silt clay in parts of bengal delta province west bangal and gangatic plain of bihar.

4.(d) Arsenic is released from reduced mineral arsenopyrite (FeAsS) through - Oxidative dissolution upon contact with strong oxidants like O2. In shallow aquifer due to oxidation the lowering of water table than release of arsenic.

5.The oxidized form of arsenic, As(V) - (c) Is very mobile in the presents of Fe oxides Dissolution of iron oxide under redusing condition is main process.

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