测试滞后对岩溶水样性质的影响研究

周长松; 邹胜章; 谢浩; 朱丹尼; 陈宏峰; 俞建国

doi:10.15898/j.cnki.11-2131/td.201711040175

摘要: 样品测试是研究岩溶区水工环问题的重要手段。岩溶区交通不便利、样品运输困难以及测试单位处理样品不及时，导致样品测试存在不同程度的滞后，现有研究还不能有效解释"测试滞后"对岩溶水样性质有何影响。为此，本文以云南宣威市一典型岩溶泉水为研究对象，通过离子色谱仪、原子发射光谱仪等测试手段，对同一时间点采集的泉水样品按照时间序列对K⁺、Na⁺、Ca²⁺、Mg²⁺、Cl^-、SO₄^2-、HCO₃^-、pH、NO₃^-、CO_2（fs）共10项指标进行对比实验，探讨"测试滞后"对岩溶水样性质的影响。结果表明：岩溶水样放置过程中，各指标A类标准不确定度为0.02~1.83，HCO₃^-、Ca²⁺不确定度值显著高于其他指标；Shapiro-Wilk正态性检验结果显示pH、K⁺、Mg²⁺、Cl^-、NO₃^-服从正态分布；随着时间变化，各指标相对偏差变化范围0%~57.38%，其中pH、Ca²⁺、SO₄^2-、NO₃^-的相对偏差在允许误差范围之内；10项指标均值含量与变异系数总体呈显著负相关性（Spearman相关系数为-0.709，P < 0.05），变异系数为Na⁺＞K⁺＞CO_2（fs）＞Mg²⁺＞Cl^-＞SO₄^2-＞Ca²⁺＞HCO₃^-＞pH＞NO₃^-，揭示测试滞后对不同指标的影响程度不同，其中对质量分数低的指标影响尤为突出。在整个实验期间内，水样水质变化可分为5个阶段：以各项指标未出现明显变化的初期稳定阶段（0~3d），以Na⁺、K⁺、Mg²⁺三项指标出现显著变化的初步变化阶段（3~5d），以多项指标发生较为显著变化的混合变化阶段（5~17d），以微生物作用为主的细菌潜在影响阶段（17~35d），以水质趋于稳定的相对平衡阶段（35~75d），其中"细菌作用"和"碳酸平衡作用"是岩溶水样放置过程中存在的两个重要作用机制。研究结果可为提高岩溶水样测试质量提供科学指导。

Abstract:

BACKGROUNDSample testing is important for studying hydrogeology, engineering geology and environmental geology in Karst areas. The inconvenience of transportation, the difficulty of sample shipping and the delayed sample analyses by testing laboratory in Karst areas lead to the lag of sample testing in varying degrees. However, existing research cannot effectively explain the impact of test lag on the properties of Karst water samples.

OBJECTIVESTo make progress on this scientific problem, a typical Karst spring in Xuanwei City, Yunnan Province was selected as research object.

METHODSTen indicators of K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2-, HCO₃^-, pH, NO₃^- and CO_2(fs) of spring water samples were determined by Ion Chromatography and Atomic Emission Spectrometry. These samples were collected at the same time and the same place according to the time series of 1d, 3d, 5d, 7d, 9d, 11d, 13d, 15d, 17d, 35d, 50d, 75d. The effect of test lag on the properties of Karst water samples was discussed.

RESULTSThe results show that test lag had certain influence on analytical results. During 75 days Karst water sample placement, the uncertainty values of type A standard of the indicators were 0.02-1.83, and uncertainty values of HCO₃^- and Ca²⁺ were significantly higher than other indicators. Shapiro-Wilk normality test results showed that the pH, K⁺, Mg²⁺, Cl^-, and NO₃^- follow normal distribution. As time elapsed, the relative deviation ranged from 0% to 57.38%. The relative deviation of pH, Ca²⁺, SO₄^2- and NO₃^- was within the allowable error range. Overall, the mean content and coefficient of variation of ten indicators showed significant negative correlation (Spearman correlation coefficient is -0.709, P < 0.05), and the variation coefficient decreased as follows:Na⁺, K⁺, CO_2(fs), Mg²⁺, Cl^-, SO₄^2-, Ca²⁺, HCO₃^-, pH, NO₃^-. These results revealed that the influence of test lag on different indicators was different, especially on the indicators with low mass fraction. The analysis of indicators changing over time showed that the change process of water quality of the water sample could be divided into five stages:stationary stage (0-3 day), preliminary change stage (3-5 day), mixed change stage (5-17 day), potential impact stage of bacteria (17-35 day) and relative equilibrium stage (35-75 day). Among them, bacterial action and carbonic acid balance were the two most important mechanisms during Karst water sample placement.

CONCLUSIONSThe research results can provide technical support for improving the testing precision of water samples in Karst regions.

测试滞后对岩溶水样性质的影响研究

The Effect of Testing Lag on Chemical Indexes of Karst Water