IntroductionWith the increase of the world's population, food shortage and lack of livable space are the two main problems. Testing the soil can provide information assistance to solve these two problems. We can determine the ability of soil to sustain grain growth by measuring the nutrient levels in the soil, and determine whether the land is suitable for habitation by measuring its pollutant levels. Soil pollution caused by hydrocarbon compounds is a serious problem for land reclamation and environmental engineering activities. Escaping gas analysis, more specificallyTGA-IR, can be used to analyze the degree of hydrocarbon compound pollution in soil, and the measurement limit of mid infrared for extracted substances can reachppmGrade.In terms of nutrient composition determination, near-infrared and mid infrared diffuse reflectance spectroscopy have attracted much attention because they have more advantages than conventional soil analysis methods. Not only does it save costs and time, but it can also complete the setup of large-scale data collection in soil measurement. The ability to obtain information about the physical, chemical, and biological properties of soil from a single spectrum adds to the attractiveness of this technology.

2 Pollution caused by hydrocarbon compounds:TGA-IR Infrared SpectroscopyThere are many cases of contamination by hydrocarbon products. Fuel leakage in fuel storage tanks or transmission pipelines is a common example, as well as rainwater runoff in vehicle washing areas, these are just two examples. Therefore, monitoring soil pollution is crucial in environmental monitoring or land reclamation. thermogravimetric-Infrared（TG-IR）Combined use can qualitatively and quantitatively analyze pollutants without the need for sample preparation. The soil sample obtained contains a concentration of approximately10％m/mDiesel fuel. turn17mgPlace the soil sample inPerkinElmer TGA 4000In the crucible, use10cmLong air chamberTL8000Transmission lineTGAandPerkinElmerConnect the infrared spectrometer (as shown in the figure)2）.

image3aThe weight loss curve of the soil sample shows three distinct overlapping weight loss intervals. In700℃, approximately65%At this stage, the main loss can be considered as organic matter. image3bThis is the result of infrared testing, which shows that when the temperature is significantly higher than the ambient temperature, water vapor increases, indicating that the soil is not completely dry and corresponding to the quality loss of the stage.Gram-SchmidtThe yith peak in the thermal spectrum is approximately at230℃, which corresponds to the weight loss in the second stage. Spectral analysis revealed that this is water vapor, aliphatic compounds, and1745cm-1A mixture of esters. This indicates that the pollutant is a diesel fuel containing a portion of biodiesel (fatty acid methyl esters). The thermal analysis data once again indicates that there are10%The quality loss is consistent with the known diesel concentration.

3 Hydrocarbon compound pollution: mid infraredIf the pollution concentration is very low, sample preparation must be carried out. After solvent extraction, it can be detected by mid infrared spectroscopyppm（10-6）Quantity of pollutants. There are three different infrared spectroscopy methods that can measure hydrocarbon compounds in the environment (these methods are also commonly used to measure oil levels in water).

1）Using fully halogenated solvents (due toC-HExtract non-polar substances in the stretching mode without absorption, and then measure the spectrum of the sample using a relatively long transmission path. This method utilizes a longer transmission path length and a sturdyC-HThe key has high sensitivity, but the required solvent is relatively expensive.

2）Use volatile hydrocarbon solvents (such as pentane or hexane) for extraction. Place a known volume of extraction solution in attenuated total reflection（ATR）On the crystal, perform spectral measurements. This method has low sensitivity, but the solvent used is easy to obtain.

3）Use cyclohexane as the extractant and measure by infrared transmittance method. This method requires a shorter optical path and weaker quantitative bonds, resulting in lower sensitivity compared to previous methods. The advantage is that the solvent used is easily available and the transmission and sampling are convenient. These extraction methods are effective for dry and easily separable soils, but they are not easy if the soil is moist and clumped together. In this case, if the soil is initially crushed, evenly spread on a tray, and then left to dry overnight, better results may be obtained.

4Nutritional evaluation of soil: medium/near-infraredUsing infrared spectroscopy technology to analyze soil nutrition is more effective than using traditional methodsICP-MSorXRFTechnical analysis has many advantages. Firstly, the cost of the system is much lower than traditional methods, both in terms of initial purchase price and subsequent maintenance. Secondly, the detection is fast and can be tested on-site to obtain answers on the spot. Disadvantage: The measurement is not direct, so the chemical statistical model must be associated with the collected broad and large amount of spectral data in order for the results to be meaningful. Both mid infrared and near-infrared diffuse reflectance spectroscopy techniques have been used in soil analysis. Mid infrared spectroscopy can provide richer information about soil properties, as the fundamental vibrations of detected minerals and organic matter are related to soil properties such as the ability to maintain plant growth. Near infrared detection shows relatively simple pan frequency peaks of substances in soil, which have the characteristics of easy overlap and wide absorption peaks.

Mid infrared spectroscopy has been used in sub Saharan Africa to analyze the ability of soil to sustain plant growth. image5It is used on-sitePerkinElmer Spectrum TwoAn example of spectrometer analysis.

5 ConclusionSoil testing is crucial for the sustained population expansion in the world. Although some laboratory based techniques can be used for these measurements, the fact has shown that mid infrared can be used for rapid and low-cost analysis of soil pollution levels and nutrient levels.