鎘污染土中生物固氮活性與固氮菌之多樣性

Nitrogenase Activities and Diversity of N2-Fixing Bacteria in Cadmium Contaminated Soils

譚鎮中(C. C. Tan) ； 李振洲(C. C. Lee)

《土壤與環境》 2卷3期 (1999/09) Pp. 281-291

https://doi.org/10.30058/SE.199909.0009

摘要

本研究主要目的為探討鎘鹽添加對土壤生物固氮活性與固氮菌多樣性之影響，並配合田間重金屬污染之觀察，以進一步評估生物固氮作用做為土壤重金屬污染之生物指標的可行性。實驗室的孵育試驗結果顯示，中興大學試驗田土壤之生物固氮活性比土壤呼吸速率對鎘鹽的添加較為敏感，添加鎘1.0 μg g^(-1)時，固氮活性明顯受到抑制，只為不添加鎘的20%。相對的，當鎘添加到1000 μg g^(-1)時，土壤呼吸速率仍未明顯下降。由四群固氮菌（Azotobacteraceae，Spirillaceae，Enterobacteriacea和cyanobacteria）之測數，再藉以估算其多樣性指標，發現除了添加5 μg g^(-1)之處理使多樣性升高外，其它之處理顯示鎘的添加量愈高多樣性指標愈低。桃園鎘污染土中重金屬含量高之土樣，其固氮菌之多樣性較低，但重金屬含量較低的土樣，其固氮菌之多樣性不一定高，可能是受其它物質的影響。彰化重金屬污染土的觀察發現，金屬污染土中能忍受較高重金屬含量之固氮菌比例增多，顯示經過重金屬污染後，細菌族群經由適應的結果會往對重金屬忍受力較高的方向發展。如果對土壤微生物之多樣性以及其對重金屬忍受程度之測定方法能加以改進，使其更方便，則生物固氮活性與微生物多樣性以及其對重金屬之忍受程度可做為評估重金屬對土壤品質影響之生物指標時之一種選擇。

關鍵字

重金屬污染 ； 生物多樣性 ； 生物固氮

並列摘要

The purpose of this study was to investigate the effects of amended cadmium salt on soil nitrogenase activities and N2-fixing bacterial community. The same parameters were investigated in heavy metal contaminated agricultural soils to test the feasibility of using nitrogen fixation as a biological indicator of heavy metal pollution in soils. The results of the incubation experiment indicated that soil nitrogenase activity was more sensitive than soil respiration rate to cadmium contamination. The nitrogenase activity was inhibited by 80% by adding 1 μg g^(-1) of cadmium, whereas soil respiration rate was not inhibited until 1000 μg g^(-1) of cadmium was added. The diversity index of four major groups of N2-fixing bacteria (i.e. Azorobacteraceae, Enrerobacteriaceae, Spirillaceae and cyanobacteria) decreased with the increase of cadmium concentration in the soils, except the addition of 5 μg g^(-1) of cadmium. The diversity indices of N2-fixing bacteria were relatively lower in the cadmium contaminated soils at Taoyuan in which heavy metal content was higher. However, the diversity indices were not necessarily higher in low heavy metal content soils. The results revealed that some other factors might decrease the diversity index in the soils with low heavy metal contents. The N2-fixing bacteria in a heavy metal contaminated soil at Changhua were found more tolerant to heavy metal in agar media. The results obtained in this study indicated that the soil nitrogenase activity, the diversity index and the heavy metal tolerance of N2-fixing bacteria could be used as a biological indicator of heavy metal pollution in soils.

並列關鍵字

Heavy metal pollution ； Biodiversity ； Dinitrogen fixation