代写CENG0036 Prevention and remediation of environmental contamination代做留学生SQL 程序
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Project – Evaluating pollution management for mining operations
This project will discuss a variety of ways in which we prevent, mitigate and remediate environmental contamination associated with mining operations.
To be submitted via Moodle before 09:00 on the 12th of March 2025
Generative AI Category 2: AI tools can be used in an assistive role for the following purposes only: proofreading and structuring your submission. If considerable changes have been made to your content, then this could be considered academic misconduct. Background research may be performed using GenAI but it is expected that any information obtained from GenAI is critically evaluated and validated using literature sources. Where you have used GenAI for proofreading it is still recommended to do final proofreading yourself as often technical terms can be changed altering the meaning completely. If you do use GenAI then you must acknowledge the use of it.
Please note. In order to randomise each of your projects, the questions will be linked to your student number, which is an eight-digit number;
The fifth and sixth digits will correspond to XX, and the seventh and eighth to YY;
E.g.: 18163849; XX = 38 and YY = 49.
Please show your working out to obtain all the marks in each question.
Error marks will be carried forward where possible if you make a mistake in your calculations (indicated by ecf on feedback).
If you refer to any literature beyond the lecture material, please cite and reference the source of that material. Please ensure you re-write material from both lecture notes and from alternative sources to use in your answers.
1) POLLUTION
Identify two sources of pollution that might be encountered in association with open-pit mining. Outline the nature of each problem, evaluate their impacts on the environment and suggest an appropriate mitigation measure for each. [8 Marks; 4 for each example]
2) EVALUATING AND MITIGATING ENVIRONMENTAL IMPACT
a) Consider the case of an abandoned coal mine, releasing acidic effluent into a well vegetated floodplain next to a large river, which is used for bathing by the public. The flowrate of the effluent is the square root of (XX × YY litres per second into the local environment.
i. State your effluent flowrate. [1 Mark]
ii. What forms of contamination and damage may result from the inflow of effluent into the environment described above? [2 Mark]
iii. Describe the strategy you would design and implement to resolve the issues associated with the contamination derived from the effluent entering the local environment. [5 Marks]
iv. Explain how the local environment impacts on your design choices. [2 Marks]
v. Evaluate your choice of strategy against other potential solutions to the issue; why is it the most appropriate solution? [2 Marks]
b) What might govern your target water quality, and why? [2 Marks]
c) The Wheal Jane Mine was formerly a tin producing mine in Cornwall, that closed in 1991. Following closure, a series of events led to an industrial accident in 1992, releasing pollution into the local environment.
i. Outline the cause of the Wheal Jane incident in 1992; what happened and what were the short-term mitigation measures to manage the pollution? [4 Marks]
ii. Discuss the combination of active and passive strategies that have been applied to mitigate the issues in the longer term. Have they been wholly effective, or could more be done to clean up the pollution at the site? Explain your answer. [4 Marks]
3) COMPARING EXPECTED AND ACTUAL DISCHARGE pH
The presence of pyrite in mine workings leads to the production of acidity (excess protons; low pH value). This is a positive feedback loop, producing increasing volumes of acidity until all the available pyrite is consumed.
This increased acidity also dissolves other minerals (particularly sulphide minerals). The total amount of sulphur discharged from both reactions is present in the water as sulphate (SO42-).
Subtracting the amount of sulphate associated with the dissolved metals, we can use the residual value to calculate how much acidity has been produced, and so what the pH value of the water should be, assuming no other interactions occur.
Table 1 an example of the composition of the effluent discharged from a mine waste deposit, composed of biotite gneiss and muscovite schist. Calculate the expected pH value and compare it with the actual value.
Table 1: Hydrochemical analyses of discharge water from the mine waste deposit (mg L-1).
|
pH: 3.8 |
SO4-2: 4000 × (100/XX+10) |
Ca2+: 185 |
Mg2+: 57 |
|
AlT: 75 |
Cu2+: 19 × (100/YY+1) |
FeT: 2 |
MnT: 12 |
|
Na+: 46 |
K+: 17 |
SiT: 19 |
Cl-: 27 |
XT indicates total dissolved concentration
a) Calculate the molecular weight of sulphate (g mol-1). [2 Marks]
b) Calculate the molar concentration (mmol L-1) of Sulphate and Cu in discharge waters. [4 Marks]
c) Calculate sulphate release from pyrite (accounting for the sulphate released from Chalcopyrite [2 S for each Cu in CuFeS2]) in mmol L-1. [3 Marks]
d) State the amount of H+ released from pyrite weathering in mol L-1. [2 Marks]
e) Calculate the predicted pH value. [2 Marks]
f) Compare the predicted pH value with the actual value. What does this suggest about the environment in which the acidity is being generated? Explain your answer. [5 Marks]
4) THE GENERATION AND ATTENUATION OF CONTAMINATION FROM A METALLIFEROUS MINE WASTE DEPOSIT
The generation of acidity in question 3 may be affected by the composition of the mine waste deposit. Calculate the time scale for the depletion of pyrite and calcite from the waste rock dump, using the data in table 2 below.
Table 2: Selected minerals comprising the waste rock in the dump by Volume %
Pyrite (FeS2): 0.57; Anorthite (CaAl2Si2O8): 6;
Silica (SiO2): 24; Calcite (CaCO3): (5/YY) + 0.05;
Albite (NaAlSi3O8): 13; Biotite (Complex): 8;
K-Feldspar (KAlSi3O8): 14; Muscovite (Complex): 10.
The composition of the discharge water is given in the table for question 3. The shape of the dump can be assumed to be a cuboid.
Waste dump height: 20 m;
Waste dump surface area: 2.6 million m2;
Voidage (empty space) within the waste dump: 30 %;
Average density of the rock comprising the waste dump: 2 800 kg m3;
Pyrite density: 5 000 kg m3;
Calcite density: 2 500 kg m3;
The flowrate of the effluent from the deposit is (100/XX) m3 s-1.
a) Calculate the total volume of rock (bearing in mind the voidage!). [2 Marks]
b) Calculate the total weight of rock. [2 Marks]
c) Calculate the weight of pyrite and calcite. [4 Marks]
d) Calculate the molecular weight of pyrite and calcite in g mol-1. [4 Marks]
e) Calculate the total number of moles of pyrite and calcite. [2 Marks]
f) Calculate the molar concentration of sulphate and calcium per litre. [3 Marks]
g) Calculate the molar ion fluxes of sulphate and calcium (note the flux relates to the amount moving through the system per unit time; the ‘flow’ of ions in this case). [2 Marks]
h) Calculate the annual fluxes of sulphate and calcium. [4 Marks]
i) What are the weathering rates of pyrite and calcite? (mol y-1). [2 Marks]
j) What are the mineral lifetimes of pyrite and calcite in the deposit? [2 Marks]
k) What assumptions have we made about the consumption of both minerals, and what might this indicate about the validity of our results? Explain your answer. [4 Marks]
5) DEWATERING OF A SITE
A small open pit is being excavated in a remote location, in order to extract gold from a placer (river sediment) deposit.
The gold is contained within a 25 + (10YY) m thick package of sediment, which is to be mined from a box-cut 60 m long and 60 m wide. The top of the deposit is 5 m below the surface. The water table is at the ground surface.
The plan is to dewater the open pit site to 2 m beneath the base of the package of sediment, in effect depressing the water table. To dewater the site, four wells, each an equal distance from the centre of the pit are planned. The wells also need to be an additional 20 metres away from the edge of the pit to ensure their structural integrity.
The site is to be dewatered over a period of 2 weeks (14 days). Test measurements indicate that the sediment has a transmissivity, of XX + 10m2 d-1, and a storativity of 0.2.
We can use the following formula to calculate the pump rate required to dewater the site to a particular depth, by a particular time after pumping begins:
Bear in mind that the drawdown in this calculation is a function of the number of wells proposed. For one well, it would be the depth to be dewatered to; for multiple wells (as in this example), it is the depth divided by the number of proposed wells. You still drill all the wells to the same depth; the wells are working together to dewater the site.
The following questions will allow you to calculate the pump rate required to dewater the site over 14 days.
a) What depth is the site to be dewatered to? [2 Marks]
b) Calculate the distance to the centre of the pit from each wellhead, r. (Think Pythagoras!). r is the distance of each well acting on the site from its centre, at the depth it is to be dewatered to, ensuring full coverage. [3 Marks]
c) What is the drawdown for each well? [1 Mark]
d) Calculate the pump rate for each well. [4 Marks]
e) What is the total pump rate for the site? [2 Marks]
f) The pump rate at which water must be continually drawn from the wells, in order to maintain a depressed water table, will not be the same as the pump rate required to initially dewater the site.
The following formula can be used to determine the pump rate required in order to maintain the depressed water table.
Where:
Calculate the pump rate required of each well to maintain the depressed water table. Is this less or more than the initial pump rate? [3 Marks]
g) The development of the mine was conditional on remediating the landscape post closure. Choose an appropriate remediation strategy for the site once the deposit has been extracted. What is it about your chosen strategy that makes it best suited for this example? Explain your answer. [6 Marks]
Total of 100 Marks