2.1. Prof. Ravi Krishna

So, we will continue with our discussion on sampling. So, last class we talked about sampling and the objectives of sampling, different objectives that we can think of. So, one of the things we had discussed is in terms of location is the sampling objectives. You need sampling objectives and this objectives based on objectives, we can do a sample location, where do you want to sample, what do you want to sample, okay, right, ok.

Sampling is crucial in environmental studies, and it begins with defining clear objectives. The objectives will dictate where and what to sample. For example, if a researcher wants to understand pollution levels in a lake, they need to identify specific locations around the lake to collect samples and what contaminants they are looking for. This ensures that the data collected is relevant and useful for analysis.

Imagine a chef wanting to create a new soup. To get the perfect taste, the chef must decide which ingredients to sample and from where to source them. If they choose the wrong ingredients or bad quality, the soup won't turn out well, just as poor sampling methods might lead to inaccurate environmental assessments.

So what is the definition of sample? So we discussed that definition of a sample is a quantity, it is amount. So what is our goal of sampling? So, our goal of sampling is eventually we would like to get some measure of concentration. This is our goal, concentration. Concentration means concentration is mass by volume or mass. It is a mass fraction or a mass concentration. So, it is either you are talking about rho A1, you are talking about rho A 2 two or you are talking about WA3.

A sample is defined as a specific quantity of material selected for analysis. The primary goal of taking samples in environmental science is to measure concentrations of various substances, often expressed as mass per unit volume. For example, in water testing, if we need to know how much of a pollutant is in a liter of water, we calculate the mass of the pollutant and divide it by the volume of water sampled. Understanding these concentrations helps in assessing environmental health and compliance with safety standards.

Consider a lemonade stand. If you want to ensure your lemonade tastes just right, you might sample a cup first. By tasting it, you determine how much sugar (mass) to add relative to how much lemonade (volume) you have. Similarly, environmental scientists sample to figure out what's present and in what amounts.

So, if we want to get this, this is the information we want, we need this and this. So, this brings us, this denominator here is what we would call as the sampling volume, the sample volume, we will come back to this in a minute after this discussion.

Sampling volume refers to the amount of material collected for analysis—whether it's air, water, or soil. The size of the sample affects the accuracy and reliability of the results. A smaller sample may not represent the entire environment accurately; hence, choosing the right sample volume is essential. Scientists must consider the concentration of the substance they are studying and the limits of their analytical instruments to determine the appropriate sampling volume.

Think of a sponge soaking up water. If you have a tiny sponge and a large puddle, the sponge may not capture enough water to give a true representation of the puddle’s water quality. Using an adequately sized sponge (sample) ensures that you can get a good idea of the entire puddle’s condition.

Let me take an example of one of the analysis methods. So I have to give you an example of one of the analysis methods before we go on with this. So, what we mean by sample volume, ok. What is the analytical instrument you are all familiar with? You can just name some and I will pick, what is the most commonly known analytical instrument? Example of an analytical instrument. GC. GC...

In the context of sampling, analytical instruments like Gas Chromatographs (GC) and High-Performance Liquid Chromatographs (HPLC) are crucial in measuring the concentrations of various substances in samples. These instruments help determine the presence and amount of pollutants, enabling researchers to assess environmental quality. Understanding which instruments to use is critical in developing effective sampling strategies.

Imagine a musician tuning their instrument before a concert. The musician needs to know which notes to play to create harmony. Likewise, environmental scientists must be equipped with the right instruments to accurately ‘tune in’ to the environment's chemical ‘notes’ they are studying.

So, we will do total suspended solids in water. So what we are measuring really is Rho 32. We are measuring solids in water, we are not measuring chemical concentration, we are measuring solids concentration in water. So it is like this. You take a water sample. The water sample looks muddy, okay. It looks muddy, then you know that something is there in the water sample, yeah.

Total Suspended Solids (TSS) are particles suspended in water, which can be an indicator of water quality. To measure TSS, scientists collect a water sample, filter it to separate the solids from the liquid, and then weigh the dried solids left on the filter paper. This measurement informs how cloudy or polluted a water body might be, enabling better management and protection of water resources.

Think of boiling spaghetti. When you pour the water into a colander to separate the pasta, the water you see below is clear, while the pasta remains. If the water had lots of debris, it would be cloudy, similar to muddy water with suspended solids. Similarly, scientists filter water to understand what’s floating around inside it.

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