Research methods: Abiotic factors Flashcards
what abiotic factors can be measured using electronic meters?
temperature
pH
dissolved oxygen
light level
wind or water velocity
What must be done to make sure electronic meters are accurate?
must be calibrated by adjusting its reading to be the same as a meter that is known to be accurate
what should be done if a meter cannot be calibrated?
percentage error should be noted so results can be adjusted
what can be used to measure light intensity?
a calibrated light meter
how can a light meter be standardised?
the same person holds it at the same height
or use a meter stick
what 2 methods for measuring humidity are there?
whirling hygrometer
electronic humidity meter
what is a whirling hygrometer?
traditional method for measuring humidity
how does a whirling hygrometer work?
uses two thermometers, one being dry and the other is kept wet
when spun the wet bulb is cooled by the evaporation of the water the dry bulb is not cooled
how do you work out humidity from a whirling hygrometer?
the temperature difference between the wet and dry bulb can be compared to a table of values to estimate humidity
how do you get an accurate result from a whirling hygrometer?
must be spun until there is no further cooling
what is the method for an electronic humidity meter?
make sure it is calibrated and read the number displayed on the screen
how is wind velocity usually measured?
using an electric anemometer
how can the use of an anemometer be standardised?
distance form ground
no obstacles to air flow
axis of rotation must be horizontal or vertical depending on design
impeller type anemometers must face into the wind
what is a Secchi dick used to measure?
water turbidity
what is the method for a secchi dick?
lower the disk into the water until the black and white sectors cannot be distinguished
record the depth of the disk(length of string below water)
what is the method for a secchi dick?
lower the disk into the water until the black and white sectors cannot be distinguished
record the depth of the disk(length of string below water)
what are the limitations of secchi disks?
depth judgement is subjective
sunlight levels may affect visibility
water may not be deep enough for the segments to become indistinguishable
what is the method for a turbidity bottle?
add a standard depth of water to a turbidity bottle
hatched circles at the bottom of the bottle are observed to see which are obscured
note coarsest circle which cannot be distinguished
what are the limitations of turbidity bottles?
judging which circles cant be distinguished is subjective
light levels may affect visibility
what is the most common way to measure the concentration of ions in solution?
colourimetry where the extent of a colour change involving the ions tp be measured is used to estimate ion concentration
what is the method for using test strips?
have bands that change colours when they react with the ion to be measured
strips are dipped into the solutions being analysed and compared with a reference colour chart
what is the method for a electronic ion reader?
add a reagent to test solution
intensity of colour produced measured by light meter that is adjusted to measure specific light wavelength
what is ion selective electrodes?
electronic probe is put into test solution
electrode potential that is produced by the solution between two electrodes is used as a measure of ion concentration
what are the limitations of concentrations of ions in solution? (pH research methods)
presence of other ions can lead to inaccurate results
