苔藓组织游离氨基酸浓度和硫同位素组成对大气硫沉降的响应研究

Most of studies about biological monitoring of atmospheric sulfur deposition are mainly to use the total sulfur concentration of moss tissues to indicate the levels of atmospheric sulfur pollution and the total sulfur δ34S to identify atmospheric sulfur source. But this method cannot effectively indicate the short-term changes of atmospheric sulfur. Therefore, free amino acid in moss tissues will be investigated in this program. We hope to find a sensitive, rapid, scientific and effective biological indicator to respond atmospheric sulfur deposition. Based on the study of the water soluble sulfate in moss tissues, using the basic principles and research methods of isotope geochemistry and phytochemistry, combined with the seasonal variation characteristics of atmospheric SO2 concentration and sulfate concentration of dust, precipitation and PM2.5, which evaluates, whether 20 kinds of free amino acid concentration of moss tissues can be sensitive and effective response of seasonal change of atmospheric sulfur. Through the analysis of time and space change characteristics of atmospheric sulfur δ34S, which investigates, whether the δ34S of free cysteine of moss can be sensitive and effective response of short-term change of atmospheric sulfur sources. And then, by analysis the relationship between the δ34S of total sulfur, the δ34S of sulfate and the δ34S of free cysteine in moss tissues, it will reveal the sulfur isotope fractionation mechanism in the process of sulfate reducing in plants. The results will provide new methods for the biological monitoring of atmospheric sulfur deposition. And help to elevate the theoretical significance of the sulfur isotope fractionation in the process of sulfur metabolism in higher plants. So, this program has important practical significance and innovative.

已有的利用苔藓组织总硫浓度和总硫同位素组成来指示大气硫沉降的方法并不能有效指示大气硫的短期变化。故本研究选择苔藓组织游离氨基酸作为研究对象，希望能找到一种迅速灵敏且科学有效的生物指示剂来响应大气硫沉降。在对苔藓组织溶解性硫酸盐研究的基础上，用同位素地球化学和植物化学的基本原理和研究手段，结合大气SO2浓度和降尘、雨水、PM2.5中硫酸盐浓度的季节变化特征，评估苔藓组织中20种游离氨基酸浓度能否灵敏有效的响应大气硫的季节变化；结合大气硫硫同位素组成的时间和空间变化特征，探讨苔藓组织游离半胱氨酸的硫同位素组成能否灵敏有效示踪大气硫源的短期变化。并进一步对比分析苔藓组织总硫、硫酸盐和游离半胱氨酸硫同位素组成之间的关系，希望能揭示植物硫酸盐还原过程中硫同位素的分馏机理。本研究成果将为大气硫沉降的生物监测研究提供新的思路，有助于深化植物硫代谢过程中同位素分馏理论，具有重要的现实意义和创新意义。

利用苔藓组织总硫浓度和总硫同位素组成能够有效示踪大气硫沉降，但是并不能指示植物组织中硫酸盐的来源。本项目拟以西南地区云南和贵阳为研究区，系统采集植物组织、土壤等样品，对植物组织硫同位素示踪大气硫来源理论体系进行了讨论，阐明了植物组织硫酸盐的硫、氧同位素组成的季节变化特征，揭示了植物组织硫酸盐还原过程中硫、氧同位素的分馏机制，首次定量计算出植物组织中硫酸盐的各来源比例。在城市地区，相当大一部分植物硫酸盐来源于大气SO2氧化，当大气SO2浓度高于30 μg m−3，SO2对植物硫酸盐的贡献率超过50%。同时，本项目还分析了贵阳市苔藓样品的氮同位素组成，对比2006年贵阳市的苔藓同位素组成，探讨了贵阳市氮污染来源十年来的转变情况。2006年市区苔藓的氮主要来自燃煤，动物粪便，而2017年的市区苔藓的总氮主要来自汽车尾气排放的贡献，NOx贡献比例显著增加，这不仅表明城市交通产生的氮污染正在逐渐取代传统的燃煤成为贵阳市区氮污染的主要来源，也表明城市区域大气氮污染的主要成分正在从NHy-N转变为NOx-N。除此之外，还探讨了苔藓组织游离氨基酸浓度与同位素组成对大气污染的指示意义，为下一步研究提供新思路。