Cremers D A, Ebinger M H, Breshears D D, Unkefer P J, Kammerdiener S A, Ferris M J, Catlett K M, Brown J R
Advanced Chemical Diagnostics and Instrumentation Group, Los Alamos National Lab., NM 87545, USA.
J Environ Qual. 2001 Nov-Dec;30(6):2202-6. doi: 10.2134/jeq2001.2202.
Improving estimates of carbon inventories in soils is currently hindered by lack of a rapid analysis method for total soil carbon. A rapid, accurate, and precise method that could be used in the field would be a significant benefit to researchers investigating carbon cycling in soils and dynamics of soil carbon in global change processes. We tested a new analysis method for predicting total soil carbon using laser-induced breakdown spectroscopy (LIBS). We determined appropriate spectral signatures and calibrated the method using measurements from dry combustion of a Mollisol from a cultivated plot. From this calibration curve we predicted carbon concentrations in additional samples from the same soil and from an Alfisol collected in a semiarid woodland and compared these predictions with additional dry combustion measurements. Our initial tests suggest that the LIBS method rapidly and efficiently measures soil carbon with excellent detection limits (approximately 300 mg/kg), precision (4-5%), and accuracy (3-14%). Initial testing shows that LIBS measurements and dry combustion analyses are highly correlated (adjusted r2 = 0.96) for soils of distinct morphology, and that a sample can be analyzed by LIBS in less than one minute. The LIBS method is readily adaptable to a field-portable instrument, and this attribute--in combination with rapid and accurate sample analysis--suggests that this new method offers promise for improving measurement of total soil carbon. Additional testing of LIBS is required to understand the effects of soil properties such as texture, moisture content, and mineralogical composition (i.e., silicon content) on LIBS measurements.
目前，由于缺乏一种快速分析土壤总碳的方法，土壤碳储量估算的准确性难以提高。一种可在野外使用的快速、准确且精确的方法，对于研究土壤碳循环以及全球变化过程中土壤碳动态的研究人员来说将大有裨益。我们测试了一种利用激光诱导击穿光谱法（LIBS）预测土壤总碳的新分析方法。我们确定了合适的光谱特征，并使用来自一块耕地的软土干燃烧测量值对该方法进行了校准。根据这条校准曲线，我们预测了来自同一土壤以及在半干旱林地采集的一种淋溶土的其他样本中的碳浓度，并将这些预测值与其他干燃烧测量值进行了比较。我们的初步测试表明，LIBS方法能够快速、高效地测量土壤碳，具有出色的检测限（约300毫克/千克）、精密度（4 - 5%）和准确度（3 - 14%）。初步测试表明，对于形态各异的土壤，LIBS测量值与干燃烧分析结果高度相关（调整后的r2 = 0.96），并且一个样本可以在不到一分钟的时间内通过LIBS进行分析。LIBS方法很容易适配到野外便携式仪器上，这一特性与快速准确的样本分析相结合，表明这种新方法有望改进土壤总碳的测量。需要对LIBS进行更多测试，以了解土壤质地、含水量和矿物成分（即硅含量）等土壤性质对LIBS测量的影响。
