保存过程对土壤生化指标的影响及保存土样的应用

土壤样品的生化指标反映了样品采集时期的生态与环境信息,具有极为重要的科学研究价值。样品的生化指标在保存过程中是否发生变化,是保存样品应用中应关注的重点问题。本文总结了各类土壤生化指标在不同保存条件、保存时间下的变化,表明长期保存的土壤样品适用于全量元素含量测定、土壤微生物群落结构分析、DNA/RNA序列分析、土壤污染物分析和土壤酶活性的比较研究,而土壤速效成分以及呼吸、硝化等代谢过程相关指标则不宜采用保存土样。土样长期保存应采用风干、磨口玻璃瓶密封、常温保存的方式。保存土样应用过程中应注意避免取样、分析时的环境污染,采用合适的分析测试技术,并考虑不同类型土壤保存效应的差异。随着分析技术的发展,保存土样中更多的历史环境信息将得以发掘,发挥出更大的科研价值。

Effects of Storage on Soil Biochemical Properties and Application of Stored Soil

Biochemical properties of a soil sample may reflect the ecology and environment of the sampling area at the time when it was collected. So soil samples are of ultra-important scientific research value. For various research purposes, soil samples, before use, need certain pretreatment and storage for a certain period of time, which may last for several days or even over a hundred years. Quite a number of large-scale soil sample banks have been established the world over, storing various types of soil samples, which are of significant application value. It is essential for usage of the long-stored soil samples to ensure whether their biochemical properties change during their storage process. In this research, changes in soil biochemical properties relative to storage conditions were summarized, including soil elements, soil nutrients, soil metabolic activities, pH, soil microbes, soil enzymes and soil pollutants. The research found that the contents of soil carbon, nitrogen, phosphorus and metal elements remained almost unchanged in the soil samples during their storage; that information about soil microbial community structure and DNA/RNA sequences could still be extracted from the soil samples; that persistent organic pollutants, hardly degraded, could exist in the samples for long; and that although soil enzyme activities decreased with the storage going on, the differences between the enzymes in activity were preserved. Therefore, long-stored soil samples are still valid for analysis of element contents, microbial communities, DNA/RNA sequence, soil organic pollutants and soil enzyme activities for comparison study. However, contents of readily available nutrients and soil metabolism-related indices varied irregularly during the storage, which indicates that only fresh soil samples can be used for analysis of these indices like nitrate nitrogen, ammonium nitrogen, exchangeable cation and soil respiration rate. Soil samples for long-term storage should be air-dried and then kept in sealed glass bottles at room temperature. There are several issues that matter in the use of long-stored soil samples: 1) Avoiding environmental contamination when soil samples are collected and analyzed; 2) Adopting suitable biochemical analysis methods to guarantee stability and reliability of the measurements; and 3) Considering the differences existing in effect of storage on soil samples relative to soil type. With analytical technology developing on and on, more and more historical environmental information will be excavated from the long-stored soil samples, which will yield higher scientific values.