Measuring Moisture Content of Soil:
Gravimetric Method
❑ Weigh the Sample (Wet Weight): Weigh the sample immediately after collection
(wet weight).
❑ Dry the Sample: Place the sample in an oven at 105°C for 24 hours to completely
dry it.
❑ Weigh the Sample (Dry Weight): After the sample has dried, weigh it again (dry
weight).
❑ Calculate Moisture Content: The moisture content is calculated as the difference in
weight between the wet and dry soil, divided by the dry weight.
Or Simply Use Soil Moisture sensor
Tests for Soil Organic Matter (SOM)
Soil organic matter reflects the carbon-based components in the soil, including
decomposed plant and animal material.
1. Loss on Ignition (LOI)
➢ Estimates SOM by burning off organic material.
➢ Procedure:
❑ Dry the soil sample at around 105°C to remove moisture.
❑ Heat at 400–550°C in a muffle furnace for 2–4 hours.
❑ Calculate the weight loss as a percentage of the original dry soil weight.
2. Colorimetric Method for OM test
➢ Rapid estimation of organic matter using colour changes.
➢ Procedure:
❑ Compare soil colour with standardized Munsell soil colour charts or use a
chemical reagent test.
3. Walkley-Black Method (Wet Oxidation)
➢ Measures SOM by oxidizing organic carbon with potassium dichromate.
➢ Since organic matter is primarily composed of carbon, this method indirectly
estimates organic matter (OM) by measuring the organic carbon present.
➢ Procedure:
❑ Mix soil with K2Cr2O7 and sulfuric acid.
❑ The heat generated oxidizes the organic carbon in the soil.
❑ Back-titrate with ferrous ammonium sulfate.
❑ SOM is estimated from the carbon content.
2Cr2O72− + 3C +16H+ →4Cr3++3CO2 + 8H2O
Drawback: This method does not measure all organic carbon (70–90% recovery).
✓ . Electrical Conductivity (EC) Test for Soil Salinity
➢ Measures the ability of the soil solution to conduct electricity, which correlates with the
salt concentration.
➢ Procedure
❑ Mix a soil sample with distilled water in a 1:2 or 1:5 soil-to-water ratio.
❑ Shake/Stir for about 30 minutes and let the solids settle.
❑ Measure the EC of the supernatant using an EC meter.
➢ Interpretation:
Results are in deci-siemens per meter (dS/m).
• Non-saline: <2 dS/m
• Slightly saline: 2–4 dS/m
• Moderately saline: 4–8 dS/m
• Highly saline: >8 dS/m
Case Study: Plastic Pollution
Microplastics (MPLs) (plastic particles from < 5 mm to 1 μm in diameter) or Nanoplastics
(NPLs) (plastic particles <1 µm in diameter)
Primary MPLs enter the environment within small ranges through various channels, e.g.,
through residues of personal care products or abrasion during washing (e.g., laundering of
synthetic textiles clothing).
Secondary MPLs are those produced in the environment by fractionation, erosion, and the
action of ultraviolet radiation from sunlight on larger plastics
❑MPLs have been reported in almost all water bodies.
❑Preliminary studies have indicated that the internalization of MPLs can
lead to adverse effects on biota and human health
These effects on living Moreover, the
organisms are related Secondly, the plastic can
hydrophobicity of MPLs
to physical particle produce long-term toxicity
and their surface
damages that can since the additives are not
characteristics make
cause inflammatory covalently bound to the
them potential vectors
lesions, originating polymers and, once
for other pollutants and
from the potential of internalised, could be
pathogens, further
their surface, to released
worsening their
interact with the environmental and
tissues. health impacts
Sampling:
A total of 39 samples were collected at the kitchen faucet of private households, and 3
samples were collected in public fountains
❑ In each sampling site, 5 L of drinking water was collected in amber glass bottles that
were pre-rinsed with methanol, HPLC-water, acetone, and the tap water of each site.
❑ Before the sample collection, the tap was left running for 2 min to avoid
contamination associated with the first aliquot.
❑ During sampling, the taps were opened to full water pressure.
❑ Moreover, 3 blank water samples were collected using the same approach but using
HPLC water to fill the bottles in the kitchens of 3 volunteers.
Sample pre-treatment and extraction preparation
❑ Samples were filtered through fine membranes to isolate micro(nano)plastic particles.
❑ Filters with pore sizes sufficient to capture both microplastics and smaller particles
were used
Analytical Method:
❑ The method involved water fractionated filtration
❑ Toluene ultrasonic-assisted extraction
❑ HPLC
❑ HRMS
❑ Multivariate Anlysis (PCA, Box plots)
Results:
Polymer Identification: The study identified several polymers in the tap water samples,
including PE, PP, polyisoprene (PI), polybutadiene (PBD), polystyrene (PS), PA, and
polydimethylsiloxanes (PDMS). PE, PP, and PA were the most frequently detected
polymers.
Concentration Levels: PI and PBD were found at the highest concentrations, with PI
reaching up to 9 µg/L in one sample. The median and mean values of the total polymer
concentrations measured in the samples were 514 and 1,583 ng/L, respectively.
Microplastics Under SEM
Microplastics form Scrubs under Microscope
