水中有机质矿化作用的生物地球化学室内模拟研究

LABORATORY BIO-GEOCHEMICAL STUDY ON MINERALIZATION OF ORGANIC MATTER IN WATER

有机质矿化直接影响到生物过程，对水生生态系统物理化学性质的调节起重要作用。而有机质矿化高时间分辨率下生物地球化学作用过程尚不十分明确。针对上述问题，我们利用水族箱培养的方式监测了有机质在24h内的分解和矿化行为，研究了硝化细菌在此过程中的作用。研究所用水样采自贵阳花溪河，分别用大豆、玉米和混合饵料作为有机质在三个水族箱中进行对比实验。对硝化细菌起作用前后铵氮、亚硝酸盐氮、硝酸盐氮和溶解有机质8℃进行每隔2h的监测研究。结果显示，投放大豆饵料的水箱中三氮之和平均为16．41mg／L，玉米水箱中为0．37mg／L，混合饵料水箱中为6．05mg／L。与以往认识不同，我们发现硝化细菌释放2h后，三个水箱内铵氮含量平均升高37．16％，亚硝态氮含量平均升高5．98％，而硝态氮则出现降低现象，最大可降低64．85％。同时，微生物分解和矿化作用造成三个水族箱8℃值平均升高13％～16％，明确地指示了细菌的活动作用。8℃值的变化揭示，在硝化细菌释放后有机质分解加速，生物成因碳比例明显增加。

Mineralization of organic matter in a water ecosystem could affect its biological process by regulating its physical and chemical characters, hence playing an important role. And the high contents of ammonium, nitrite and nitrate produced in the mineralization decomposition would lead to the eutrophication and deterioration of waters. However, the high temporal resolution bio -geochemical process remains unknown. Therefore, we tested the decomposition and mineralization of organic matter within 24 hours in an aquarium to investigate the role of nitrobacteria in the process. Water used in the experiment was sampled from the Huaxi River in Guiyang, and comparison experiment was made by putting three portions of organic matter into three aquaria, soybean, corn and blended stuff, respectively. We tested the following items every two hours before and after those nitrobacteria worked, respectively, i. e. , ammonium, nitrite, nitrate and the δ^13C values of dissolved organic matter. It is found that the total contents of ammonium, nitrite and nitrate in the aquaria with soybean feed are 16.41 mg/L, while those for corn and blended stuff are 0.37 and 6.05 mg/L respectively. Moreover, unlike previous conception, it is found that two hours after the releasing of nitrobacteria, the contents of ammonium and nitrite in three aquaria showed an average increase by 37.16 % and 5. 98% respectively; while those for nitrate decrease as high as 64.85%. Meanwhile, the δ^13C increases by 13%- 16% because of microbial decomposition and mineralization, which indicates the function of bacteria. Variations in δ^13C indicate that the decomposition of organic matter is accelerated and the proportion of biogenetical carbon increases significantly.