以洱海主要入湖河流水体悬浮颗粒物为研究对象,运用稳定同位素技术,研究了不同季节、不同河流水体悬浮颗粒物中有机碳、氮的来源,探讨了其与流域环境和人类活动之间的关系.结果表明:①入湖河流水体悬浮颗粒物δ13C的离散程度为夏季＜秋季＜冬季＜春季,变化范围分别为-25.1‰ ～-16.9‰、-30.0‰～-l0.7‰、-20.9‰～-11.0‰和-28.6‰～-14.4‰;δ15N的离散程度为冬季＞夏季＞春季＞秋季,变化范围分别为-0.5‰～8.8‰、5.4‰ ～ 10.6‰、3.4‰～7.9‰和6.2‰ ～8.7‰.②入湖河流水体悬浮颗粒物有机质的来源,春季以陆源C3植物和自生有机质为主,并且C3植物来源的有机质贡献呈逐渐增大趋势；夏季主要来源于陆源C3植物；秋季仍以陆源C3植物和水生植物的混合来源为主,但水生植物来源有机质比例有所上升；冬季则以陆源C3、C4植物和水生植物来源有机质混合来源为主.③入湖河流水体悬浮颗粒物中的氮,春季主要来源于土壤流失和水生植物残体,并且土壤流失氮比例逐渐升高；夏季主要来源于土壤流失；秋季来源于土壤流失、化学肥料和水生植物死亡的共同作用；冬季来源于化学肥料、土壤流失和水生植物,并且化学肥料带来的氮比例有所上升.%The sources of organic carbon and nitrogen, and the seasonal changes of their suspended paniculate matter from inflow river of Erhai Lake were studied by stable isotope techniques. The relationships of the two contents with natural and anthropogenic activities were also discussed. The results showed that ratios of the carbon and nitrogen isotopes of suspended particulate matters were - 28. 6‰ to - 14. 4‰ and 3. 4‰ to 7. 9‰ in spring, - 25.1‰ to - 16. 9‰ and 5. 4‰ to 10. 6‰ in summer, - 30. 0‰ to - 10. 1‰ and 6. 2‰ to 8. l‰ in fall, and -20. 9‰ to - 11. 0‰ and -0. 5‰ to 8. 8‰ in winter, respectively. The seasonal changes of their isotopic compositions were observed in the study area. The C3 plants and aquatic plants were mainly the mixed source of the organic matter in spring, and the contribution of C3 plants source gradually increased; in summer it mainly came from land-based sources of C3 plants; in fall it was still C3 plants and aquatic plants mixed source, but the contribution of aquatic source increased; when winter, C4 plants mixed into C3 and aquatic plants source. The nitrogen source in the spring derived from soil erosion and aquatic plant residue, but the contribution of soil erosion was higher; it mainly came from soil erosion in summer; mixed soil erosion, fertilizer and the death of algae in fall; soil erosion, fertilizer and plant residues were the source and the contribution of nitrogen from fertilizer increased in winter.
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