利用指示生物评价稻田系统磷素面源污染潜力

Evaluation of nonpoint-source pollution potential caused by phosphorus in rice-field ecosystem by using indicator organism

基于长期肥料定位试验,选择具有不同磷素面源污染特征处理,分析水绵生物量(干物质量)、氮磷含量与土壤、水体氮磷含量的关系,探讨利用水绵生物指示磷素面源污染力的可能性。结果表明:水绵生物量与土壤总磷、Olsen-P含量极显著相关,而与土壤总氮、有效氮以及田面水总氮、总磷含量无明显相关。根据水绵生物量与土壤Olsen-P的回归方程以及文献报道的太湖地区磷素面源污染阈值(土壤Olsen-P=30 mg/kg),得出水绵生物量45g/m^2为该区域稻田磷素面源污染的生物指示阈值;因太湖地区稻田系统土壤供氮能力稳定,水绵磷含量与水绵N:P极显著相关,所以水绵化学计量值N:P也是稻田系统供磷能力的有效生物指示;根据水绵N:P与稻田土壤Olsen-P含量回归方程,可得出水绵N:P=9.57是判断该区域磷素面源污染的阈值,水绵N:P低于9.57即需对稻田生态系统磷库容量高度重视。

According to long-term fertilizer experiments the fertilizer treatments with different phosphorus nonpoint pollution characteristics were used and the relationships were analyzed between the biomass（dry matter） and nitrogen and phosphorus contents of Spirogyra sp. and the nitrogen and phosphorus contents of both paddy soil and surface water to explore the feasibility of using Spirogyra sp. as an indicator organism showing phosphorus-caused nonpoint-source pollution potential. The re- suits showed that the Spirogyra biomass was significantly correlated to the total phosphorus and Olsen- P contents of the soil but its correlations to the total nitrogen and available nitrogen of soil and to the total nitrogen and total phosphorus contents of surface water were relatively poor. According to a lit- erature-published threshold value（soil Olsen-P = 30 mg/kg） of phosphorus nonpoint pollution in the Taihu Lake area and the regression equation between the Spirogyra biomass and the s0il Olsen-P, 45 g/m2 Spirogyra biomass could be used as a threshold value for organism to indicate phosphorus non- point pollution in the area. Because the nitrogen supply of rice-field ecosystem in the area was stable and both phosphorus content and N/P ratio of Spirogyra sp. were very significantly correlated,the N/P ratio of Spirogyra sp. was also an effective biological indicator of phosphorus supply of rice-field eco-system ~ From the regression equation between the N/P ratio of Spirogyra sp. and the Olsen-P content of paddy soil it was concluded that the N/P ratio = 9.57 could be used as a threshold value of determi- ning phosphorus nonpoint-source pollution in the area, and when the N/P ratio were less than 9.57 great importance should be attached to the phosphorus storage capacity of rice-field ecosystem.