高频燃烧红外吸收光谱法测定郑州市郊土壤有机碳的含量

Determination of Organic Carbon in Suburb Soil of Zhengzhou by High Frequency Combustion Infrared Absorption Spectrometry

土壤有机碳含量直接反应土壤肥力,了解郑州土壤有机碳含量对于本市土地合理化利用及治理有重要意义。为克服目前测定土壤中有机碳含量的标准方法中所用试剂要求严格且繁多,实验过程需要大量液体溶液流转,不利于环保,实验过程繁琐,易造成人为误差且不适用于大批量样品检测等缺点。以郑州市市郊三种不同的土壤样品为研究对象,利用高频红外碳硫分析仪,采用单点线性校正法,以铁屑和钨锡混合为助熔剂,先测定土壤样品总碳量,再测定同一样品经高温灼烧后的余碳量,两者差减得到样品有机碳含量。通过对称样量、灼烧温度和助熔剂的用量进行优化,确定称样量为0.18~0.25 g、灼烧温度为430℃、灼烧时间为40 min、混合助熔剂为0.5 g铁屑和1.0 g钨锡。在选定的实验条件下,标准曲线线性良好,决定系数R^(2)为0.9996,方法检出限为0.006%,定量限为0.02%。以国家标准物质GBW07427绘制标准曲线,所采土壤样品根据国家标准方法GB/T 36197—2018进行筛选研磨,分别测定其有机碳含量,结果与依照行业标准方法NY/T 85—1988重铬酸钾容量法测得有机碳含量基本一致。三种样品测定结果的相对标准偏差(RSD,n=11)分别为0.078%、0.10%和0.14%;加标回收率分别为102%、105%和98.4%。相比较传统方法,所建立的方法具有前处理简单、有害试剂使用少、直接固体进样、有利于环保、仪器操作流程简便、测定结果准确等优点,适用于大批量土壤质量检测样品的检测工作。

The content of soil organic carbon directly reflects soil fertility.Understanding the content of soil organic carbon in Zhengzhou is of great significance for the rational use and management of land in this city.At present,the standard methods for determining the content of organic carbon in soil have strict requirements and a variety of reagents.The experimental process requires a large amount of liquid solution circulation,which is not conducive to environmental protection.The experiment process is complicated,which is easy to cause human error and not suitable for large-scale sample detection.In this work,a high-frequency infrared carbon and sulfur analyzer was employed to measure the accurate organic carbon content in the soil.Single point linear correction method was used to calibrate the instrument.Iron filings and tungsten tin were mixed as a fluxing agent.Firstly,the total carbon content of the soil sample was determined.Subsequently,the residual carbon content of the same sample after high-temperature burning was measured,and the total carbon content of the soil sample and the residual carbon content after burning were subtracted to obtain the organic carbon content of the sample.Finally,the symmetrical sample volume,burning temperature,and flux dosage were optimized.As a result,it was determined that the sample weight was 0.18—0.25 g,the burning temperature was 430 ℃,and the burning time was 40 min;the flux was 0.5 g iron filings and 1.0 g tungsten tin mixed flux.Under the selected experimental conditions,the standard curve had good linearity,correlation coefficient(R^(2)) was 0.999 6,the detection limit was 0.006%,and the limit of quantification was 0.02%.The national standard material GBW07427 was used to draw the standard curve under the above parameters.The experiment collected the soil under three different utilization/covering methods in the suburbs of Zhengzhou.The samples were prepared according to the national standard(GB/T 36197—2018),and the results of the organic carbon content were determined according to the above-mentioned experimental methods.This result was basically consistent with the industry standard method(NY/T 85—1988).The relative standard deviations(RSD,n=11) of the three samples were 0.078%,0.10% and 0.14%,respectively;and the recoveries of standard addition were 103%,105% and 98.38%,respectively.Compared with traditional methods,the research method in this article has the advantages of simple pre-treatment,reduced use of harmful reagents,direct solid injection,environmental protection benefits,simple instrument operation process,and accurate determination results.It is suitable for the detection of large quantities of soil quality detection samples.