American Society of Agronomy

Shedding a light on contaminants


Source: American Society of Agronomy

Measuring soil pollution quickly, accurately

Name a current environmental challenge. Global climate change? Loss of endangered species? What about soil contamination?

Soil pollution rarely makes headlines, though it is a prevalent global issue. According to the European Environment Agency, 39 member states in Europe had over 2.5 million contaminated soil sites in 2011.

Sharon O’Rourke, researcher at University College Dublin, explains why soil pollution is a public concern. “Soil contamination degrades soil health and can impair soil function. This can have knock-on effects for agriculture, by lowering yield and even rendering some sites unfit for food production.”

Public health is also affected. Many pollutants are linked to cancers, neurological damage, and lower IQs, among other things.

In the last decade, the EU has expressed the need for policy that adequately protects soil resources. Specifically, it is interested in starting a soil monitoring program in Europe. In theory, soil monitoring is a fairly simple process. First, a baseline survey of soils’ chemical components is needed. After time has lapsed, soils can be re-measured. When compared to initial measurements, soils with increased levels of harmful compounds can then be identified and cleaned up.

Unfortunately, there is a major limitation. According to O’Rourke, standard soil tests are costly and time consuming. Though the amount of time required to analyze samples varies, traditional processing can take up to a week or more to complete.

Spectroscopic technologies are a promising alternative to traditional analytical methods. First, they can reduce soil processing time from a week to mere minutes. Operational costs are relatively low, and the accessibility of these instruments is relatively good. And the equipment is available. O’Rourke reports, “Many soil science laboratories are now equipped with the technology platforms.”

A spectrometer is a device that rapidly measures a range of wavelengths. Many varieties exist, each of which is capable of detecting a different type of energy. Heat and light energy are just two examples.

The instruments used in O’Rourke’s work specifically measure radiation released or absorbed by an object. Many soil properties can be estimated, since materials have unique energy signatures. These properties include organic compounds, pH, and a wide range of elements. Some sensors have the capability to determine a soil’s organic compounds. Others are best used to determine the mineral makeup of a soil.

O’Rourke’s study used three sensor types to measure soils from the Irish National Soil Database. The chemical makeup of these soils was previously determined using standard wet chemistry techniques. In all, 42 different properties were analyzed. These included pH, organic carbon, and several elements. O’Rourke and her colleagues discovered that, when used individually, each instrument could accurately predict up to 15 properties.

O’Rourke and her colleagues then applied an averaging technique to their results. When results from sensors were combined, the number of accurately predicted soil properties increased to 25.

This is an important leap, since a number of the properties identified were environmentally significant trace elements. “This method certainly has the potential to be refined, and to be used as a screening tool,” O’Rourke says. “I can see potential for quick screening of soil to detect elevated levels of heavy metals.”

Read more about O’Rourke’s work in Soil Science Society of America Journal. The research was funded by the European Union Seventh Framework Program ([FP7/2007-2013]) under grant agreement no. 303314.

Soil Science Society of America, is a peer-reviewed international journal published six times a year by the Soil Science Society of America. Its contents focus on research relating to physics; chemistry; biology and biochemistry; fertility and plant nutrition; genesis, morphology, and classification; water management and conservation; forest, range, and wildland soils; nutrient management and soil and plant analysis; mineralogy; and wetland soils.

Photo credit Sharon O’Rourke.

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