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Background Toxic heavy metals emitted by industrial activities in the mid-latitudes are transported through the atmosphere and deposited in Earth’s polar regions Deposited materials can enter the

Background: Toxic heavy metals emitted by industrial activities in the mid-latitudes are transported through the atmosphere and deposited in Earth’s polar regions. Deposited materials can enter the food chain; and the effects of bio-concentration and bio-magnification may subsequently threaten the health of humans and the health of Arctic ecosystems. The file toxic.csv contains continuous, annually-averaged deposition records (for years dating between 1772 and 2003) of highly toxic thallium, cadmium, and lead. This data indicates higher atmospheric deposition in the early 20th century: data from the early 1900s indicates a tenfold increase in deposition from preindustrial levels, but levels have since decreased 20-50%. Tracer measurements indicate that coal burning in North America and Europe was the likely source of these metals in the Arctic after 1860.

Learning Objectives:

This task is meant to reinforce the concepts of using MATLAB to look through arrays efficiently and effectively. In MATLAB, there are ways to use functions and relational operators to analyze entire arrays with few commands, and there are more classical approaches (using repetition structures and conditional blocks) to analyze arrays one element at a time. In this assignment you will be doing each task twice: Once using MATLAB array notation and once using for loops with conditional statements.

Data:
You may load the data into MATLAB with the command load toxic.csv. The data will then be in an array called toxic. The column information represents:

Column 1: Year AD

Column 2: Cadmium (nanograms per gram)

Column 3: Lead (nanograms per gram)

Column 4: Thallium (nanograms per gram)

 

Directions:

Using MATLAB, create a script file as indicated. Your script should be commented for sufficient comprehension of any variables and associated units. Submit paper copies of your published script.

Section 1: Array Notation

Allowed Syntax:

Complete the following (1) WITHOUT the use of for loops or conditional blocks [i.e. if-elseif…else-end]; (2) you may use syntax requiring the dot operator; (3) you may use relational operators on arrays but you may NOT use them on scalars. (4) you may NOT hard code row numbers in your script (e.g. the1700s =1:28; cannot be used) instead use the find function, if needed.

  1. How many years during the period of this data set have a lead concentration greater than 0.2 ng/g?
  2. For what percentage of the years during the 1800s (1800-1899) is the lead concentration greater than 0.01 ng/g?
  3. What is the most recent year during which lead is greater than 100 times the concentration of cadmium? What is the concentration of Pb that year?
  4. For which year during the 1900s (1900-1999) did cadmium contribute its largest fraction to the total heavy metal concentration (i.e., year with largest Cd/(Pb+Cd+Th))? What is that value? (hint: help max)
  5. [Up to 2pt bonus] During which decades (i.e, 1900-1909, 1910-1919, etc.) of the 1900s did lead concentration exceed 0.3 (ng/g)? (Hint: use the ‘reshape’ function)

Section 2: Repetition Structures and Conditional Blocks

Allowed Syntax:

Complete the following (1) WITH the use of for loops and conditional blocks [i.e. if-elseif…else-end]; (2) you may NOT use any syntax requiring the dot operator; (3) you may use relational operators on scalars but you may NOT use them on arrays. (Relational operators include: <, >, <=, >=, ==, ~=) (4) You may reuse the years that were found using the find function in Section 1.

  1. How many years during the period of this data set have a lead concentration greater than 0.2 ng/g?
  2. For what percentage of the years during the 1800s (1800-1899) is the lead concentration greater than 0.01 ng/g?
  3. What is the most recent year during which lead is greater than 100 times the concentration of cadmium? What is the concentration of Pb that year?
  4. For which year during the 1900s (1900-1999) did cadmium contribute its largest fraction to the total heavy metal concentration (i.e., year with largest Cd/(Pb+Cd+Th))? What is that value? (hint: help max)
  5. [Up to 2pt bonus] During which decades (i.e, 1900-1909, 1910-1919, etc.) of the 1900s did lead concentration exceed 0.3 (ng/g)?

May 20 2020 View more View Less

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