by Julia Jasonsmith and Trent Ellerington, SGS Australia
Over the years, I've come to notice that many of us who work in the Earth and Environmental sciences have no idea what our colleagues in these same fields do and how they do it.
Within the group of friends with whom I was conducting my PhD research, for example, was someone who studied the origin of a group of meteorites; another modelled the climate in recent geological time; and a third studied how rocks behaved under pressure (we called him the rock squasher).
As a scientist who works with soil and water chemistry, and having a background in ecology, I had - and still have - very little idea about how my friends figured out the amazing things they did and what their jobs now involve on a day to day basis. Yet we all now have PhDs in Earth Sciences.
This lack of understanding between scientists extends to even very specific sub-disciplines and here's where this blog comes in.
My personal expertise are in field work, data analyses, and research - I go into the field to try and comprehend how all its different parts are interacting, and how and where the chemicals might be. I then collect samples to get an understanding of what the chemicals are and how they are behaving. But analysing the actual samples? NO!
I've done it before, it's really hard, and not something suited to my skill set. Using the data produced by chemical analyses is definintely something I do, but that's another story for another blog.
The thing is, how we handle environmental samples in the field and the laboratory has a critical role in the behaviour of chemicals in said samples. If samples are transported in conditions which are too hot, volatile chemicals may flux off. If the person collecting samples produces too much sweat and /or uses too much sunscreen, samples may be contaminated with zinc (among other chemicals).
Luckily for me, I work with a most excellent laboratory - SGS Australia - to get my samples analysed. Chemical analyses of samples is most definitely what they do and very much suited to their skill set.
If you work or study in the environmental or Earth sciences, and like me don't have a great understanding of what happens once our samples get to the lab, this blog is for you. We've teamed up with SGS to put together some videos of what we each do so that we can all have a better understanding of what it takes to get our samples analysed and to produce the best data possible.
Firstly, context means a lot in Earth and environmental sciences. Why a project is being done dictates what kind of samples are collected, where they are collected from within a landscape, and how they are collected.
The project discussed in this blog aimed to assess nutrient build-up in water bodies and soils within a farm. First up, let's look at water sampling.
Because sediments have a big impact on the water above them, collecting water from the edge of a dam can lead to samples with higher nutrient concentrations than in the water body as a whole. The samples thus collected then over-estimate the concentration of nutrients in the water body. Of course if one is looking for contamination and is worried about livestock drinking from the dam, then the edge of the dam is exactly where one should be sampling from.
Also how careful should we be about cross-contamination? This is an important question as the more careful we are, the more it costs and the harder sampling is to do, but the more reliable our data is.
the volumes of water collected in this project were large (i.e. one to two litres) relative to the potential volumes of water remaining in the sampling vessel (the bucket);
attaining and bringing ultra-pure water and/or detergent to the field for decontamination purposes is expensive and difficult; and
the impacts of some nutrient cross-contamination between samples was deemed trivial;
the sampling vessels used for the project described in this blog were not decontaminated between sampling events. They were primed (that is rinsed thoroughly three times in the water being sampled, before samples were collected) though!
Next up was soil sampling.
Often in the field of contaminated lands, soil samples are collected and placed in glass jars. This is because the chemicals of concern in potentially contaminated sites can interact with plastic and produce misleading results.
We aren't worried about chemicals in the soil interacting with plastic in agricultural sampling. That's why plastic bags, in this case supplied by SGS, were used in the video below.
It should be noted that even though the soils seen in the video were clayey silts and were relatively coarse for soils in this south eastern part of Australia; and even though samples were collected after one of the wettest winters on record, I had to work quite hard to get the soil sample out of the ground. People planning field work for others should keep this in mind - it can be very difficult and time consuming to dig soils in these parts!
As before, the trowel used for sampling the soil in this instance was kept relatively clean, however, decontaminating the trowel using chemical means (i.e. ultra-pure water and/or detergent) between samples was considered inappropriate.
One of the final parts of the day is one which I personally find quite challenging - completing the chain-of-custody form. This is the piece of paper which is placed in the package within which samples are shipped. The reason I find it difficult is because it's done at the end of field work, when I am almost always hot, tired, thirsty, and hungry.
It's also easy to make mistakes - to select the wrong analyses on the form and to therefore get the wrong sample analysed for the wrong chemical. It is easy to select a sample for pesticide analyses, for example, but if that sample is from deep in the soil profile, the impacts of pesticide concentrations are unlikely, relative to surface samples where we should be looking first, and we've wasted time and money getting the sample analysed.
Again, there's a difference between how agricultural samples and samples collected to assess for contamination are stored for transport to the laboratory.
Typically agricultural samples need not be placed into eskies and kept below 6 degrees Celsius as are samples collected to assess for contamination.
Because nitrogen and its different species (nitrate, nitrite, ammonia) were important nutrients to understand in the project for which these samples were collected, it was decided that samples should be placed into an esky with ice. This reduced both the flux of nitrogen from the samples and the conversion of nitrogen from one species to another, and helped ensure that the proportions of nitrogen species to each other in the field could be known as accurately as possible.
After environmental sampling is done and we say goodbye to the samples we have collected at the courier depot, they are shipped off to the laboratory. And what happens when they arrive there? We'll let Trent Ellerington, of SGS Australia, explain.
But wait, there's more! Part two of how samples are processed in the laboratory is presented below.
And that's how we get samples analysed. Simple right!
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