The Soil in my Salad
zones, with the ‘Red Zone’ being an area deemed beyond hope of restoration and which is still off limits to the public even today and remains dotted with trenches and unexploded ordinance. The immediate post-war clean-up programme involved the disposal of ammunition stockpiles, including burning in open pits shells made from lead, copper and brass, fuses made out of copper and zinc together with ammunition containing arsenic. Perchlorates and chlorate, along with small levels of nitroaromatic explosives are also still present in leachates in the topsoil and scientists still recommend that the surrounding land should not be used for agricultural purposes. Returning to my daughters I asked if they still remember the mountains we used to go when they were younger. That forest where they were looking for elves and goblins? Yes, the one that had that big fire three summers ago. The upper layer of the soil lost its stability because burnt tree roots were not strong enough to anchor the vegetation and autumn rains removed all the fine sediments. Now you see rocks where once you might have found elves under mushrooms and it will be a very long time before any trees reappear. Sometimes we don’t need to be worried about runoff of sediments: sometimes this transit is good for other purposes. River sediments feed downstream to agricultural areas. Do you remember last year’s trip to Egypt? We visited the Aswan Dam, what a big wall! Do you remember the lock next to the end of our Nile cruise? Until the construction of these structures, the Nile River flowed freely, containing tons of sediments that were deposited on the river margins. These were very rich and fertile sediments that allowed the development of agriculture to feed the people as far back as the Pharaoh’s time. We see that sediments are the chronicles of the long term history of our land by geology and soil hosts an important part of our recent history. Sometimes we can learn our own history by finding something hidden: from a picture under our bed, to a whole town under a market, as happened recently in Barcelona. Preservation of these archeological sites has been possible because of certain soil behavior. Even if we want to leave these findings under the soil, we have to monitor different parameters, like soil moisture, to ensure its preservation. On a site in Glastonbury, England a group of researchers are establishing what impact the soil conditions are having on the long term sustainability of a prehistoric site. Using soil moisture measurements the team are establishing the true moisture content of the soil by taking accurate readings at different points around the site, the results of which will help them plan the next phase of the preservation of the site.
Sediments are alive! They change their aspect with time, can be darker when wet, paler when dry and yet they are the same. Even their intimate structure changes from one place to another. If you give samples of clays to a good crystallographer, he will be able to tell you where they are from. Is this useful? Ask a criminologists. They know where you have been by just taking a look at your shoes! Think too of sediment research in little known and remote locations like the Sunderbans, West Bengal. India. The collection and study of sediment core samplers to establish the history, chronology and reason behind the existence and development of these islands and mangrove delta falls is important for future conservation. This region is low lying and covered with Sundari trees from which the name of the region may have been derived. The habited islands have been somewhat protected by embankments made by the people whereas the uninhabited islands are open to the elements and populated by the famous man-eating Bengali tigers. Study of the soil and sediments will help predict the impact of rising sea levels on this remote area.
When studying soils, we have to be very careful about how we do it. If we want samples, we need to know exactly what is required and produce as less perturbations as possible in the surroundings. We need to know whether we want an undisturbed sample or perhaps a disturbed sample suffices. Will we be looking at a soil profile or analysing the soil for trace metals. Do we expect to be sampling for volatiles or contaminants so will we need to contain the sample and use a specialist tool? We need to ensure we have the right soil sampling tool for the job in-hand and to remember the important principles: sample per layer, never mix your soil horizons and be sure to avoid the contamination of deeper layers. We never know what a soil can hide but we can be sure that when we investigate a site we can create terrible damage, particularly when using mechanical drilling techniques that could have long term consequences. Even when we want to monitor soil parameters we have to be very careful during installation. It is important, before starting to drill the soil, to know exactly what our requirements are, from site to the laboratory.
So, I continued the discussion with my daughters trying to persuade them that we cannot point to one single step for human evolution? Progress is made by many small steps, step by step but for sure we would not be where we are, eating what we are eating, without the sum of small advances in sediment research and knowledge. Today we can easily monitor the soil moisture to find out the right point of irrigation for our crops, measure and record soil penetration resistance to determine whether we can build a house or an emergence landing field, check whether that nice site is correct to live in, learn about our history, by properly taking care of the archaeological heritage. We have tools to sample soil, with minimal disturbance, in a repetitive way, to be certain that the conclusions that will be reached after analysis will be the right ones and the best decisions will be taken based on our samples. Even your instant messaging app will be useful to get real time information about the status of your crops, of your soil remediation process, or about the Noah’s Ark that has finally been found.
Ramon Quiles, Van Walt Ltd
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