Environmental Monitoring, Field Study and Practical Skills
Exam focus
Field sampling design, instruments, ecological survey methods, indices and data interpretation.
Core rules
- Sampling: grab (instant) versus composite (mixed over time or space); random, systematic or stratified designs.
- Water: pH meter, DO meter, turbidity meter, conductivity meter, titration for BOD and COD.
- Air: respirable dust sampler for PM₁₀ and PM₂.₅, gas analysers; noise: sound level meter in dB(A) with slow or fast response.
- Ecology: quadrat for density, frequency and abundance; line and belt transects; point-intercept; mark-recapture for animals.
- Density = number of individuals / area sampled; frequency = number of quadrats containing the species / total quadrats × 100.
- Remote sensing and GIS help map land use and detect change; GPS fixes coordinates.
Worked example
Ten 1 m × 1 m quadrats are laid in a grassland. Species X occurs in 6 quadrats with 24 individuals in total. Frequency = 6/10 × 100 = 60%. Density = 24 / (10 × 1 m²) = 2.4 individuals m⁻². Frequency measures distribution across quadrats; density measures number per unit area. A species can be frequent but low in density.
Traps
- Reporting frequency as density.
- Using a grab sample to characterise a fluctuating river.
- Forgetting to calibrate pH, DO and sound meters.
- Placing quadrats only where the vegetation looks interesting, which biases the sample.