原位土壤溶液采样及可溶性有机碳(DOC)的紫外吸收光谱直接测定探讨

In-Situ Sampling of Soil Solution and Determination of Dissolved Organic Carbon (DOC) with UV Absorption Method (UVA_(254))

首次采用管壁过滤孔径为微米级(0.1～O.3 μm)的水处理用多孔聚丙烯(腈)空心纤维细管,与注射器或真空管相连,自制成土壤溶液采样器,将空心纤维管埋置或插入土壤中抽取层面土壤溶液,所得溶液无须过滤即可进行各种理化分析和测定,且可连续采样,提出了一种价廉实用的原位土壤溶液取样方法.并根据可溶性有机碳(DOC)在紫外光区的吸收特征,将土壤溶液在254 nm波长处的吸光度(UVA254)与DOC浓度(TOC仪法)进行比较,发现两者有较好的相关性(DOC=38.84×UVA254,n=37,R2=O.82),即直接测定土壤溶液的UVA254,再乘以系数38.84可以估算DOC浓度.与复杂的氧化-比色和昂贵的TOC仪测定法对比,UVA254能快速便捷地估计土壤溶液中DOC的浓度.UVA254也适用于水体DOC的估计.

A tubule of porous polypropylene fibre, which is usually used for water treatment, was applied to in-situ sampling of soil solution for the first time. With filtering pores (0.1 ~ 0.3 μm in aperture) on the walls, the fibre tubule was joined with an injector or a vacuum tube, thus forming a soil solution sampler. After the tubule was laid or inserted into the soil, the device was ready to continuously in-situ extract soil solution. The solution could be used directly for chemical analysis without the need for filtering, demonstrating that this is a simple practical in-situ soil solution sampling method. Based on the light absorption characteristics of dissolved organic carbon (DOC) in the UV spectrum, the UV absorbance of the soil solution at 254 nm was studied. A significant linear correlation was found between UV absorbance at 254 nm (UVA254) and DOC concentration determined with the TOC method (DOC = 38.84 × UVA254,n = 37, R2 = 0.82), allowing quantification of soil solution DOC directly by determining UVA254 and then multiplying it by the coefficient, 38.84. Compared with the complex oxidation-colorimetry and costly TOC methods, this method is quicker and more convenient. Besides, it is also applicable to estimation of DOC concentration in water.