蓝藻碎屑堆积对湖泊沉积物矿化特征的影响

Effects of algal-detritus accumulation on the mineralization characteristics of lake sediment

蓝藻水华暴发形成的大量有机碎屑,沉降到沉积物表面,影响沉积物有机质矿化,进而影响碳氮磷循环.本实验选择于桥水库湖心区作为沉积物采样点,通过设置不同密度藻屑添加组(×1倍组和×20倍组)及空白对照组,研究藻屑堆积对沉积物矿化特征的影响及其环境效应,为蓝藻水华影响下的饮用水环境修复和科学管理提供一定的理论依据.结果表明:(1)藻屑添加降低了上覆水pH值,改变了沉积物生物酶活性.藻屑添加密度越大,上覆水pH值越低、波动越大,反映了培养过程异养微生物活性的变化.×1倍组的转化酶活性较高;×20倍组蛋白酶活性和碱性磷酸酶活性较高.(2)藻屑添加对沉积物的矿化途径和沉积物产物的释放速率产生了显著影响.藻屑添加密度越大,有机质矿化速率越大.其中,×1倍组主要增强好氧矿化,释放CO2;×20倍组主要增强厌氧产甲烷矿化,释放CH4.(3)不同密度的藻屑添加组,其氮磷扩散、释放通量存在明显差别.×1倍组以沉积物吸附为主,其上覆水NH4^+和PO4^3-平均释放速率与对照组差异较小;×20倍组的NH4^+在第0~10天以沉积物吸附为主,之后和PO4^3-均以向上覆水中释放为主,其NH4^+和PO4^3-平均释放速率(分别为0.223)和0.075 mg/(L·d))明显大于其他实验组.因此,大量蓝藻堆积明显促进沉积物的碳氮磷矿化,释放大量CO2、CH4和氮磷营养盐至上覆水中,对湖泊水环境造成污染,为蓝藻的生长繁殖作贡献.

A large amount of organic algal-detritus after cyanobacterial bloom settled on the surface of the sediment,which has an effect on the mineralization characteristic of sedimentary organic matter,and then the biogeochemical cycle of carbon,nitrogen,and phosphorus. In this study,the central area of Yuqiao Reservoir was selected as the sediment sampling point. By the addition treatments of different densities of algal-detritus( ×1 and ×20 treatments) and blank controls,the effects of algal-detritus accumulation on the mineralization and their environmental effects were studied to provide some theoretical basis for drinking water environmental restoration and scientific management under the influence of cyanobacteria bloom. The results showed that the addition of algal-detritus lowered the pH value of overlying water and changed the activity of biological enzymes in the sediments. The higher the density of algal-detritus,the lower the pH value of the overlying water and the greater the fluctuation were. The ×1 treatment had higher invertase activity,meanwhile the ×20 treatment had higher protease activity and alkaline phosphatase activity. Secondly,the addition of algal-detritus had a significant effect on sedimentary mineralization pathways and release rates of mineralization products.The higher the density of algal-detritus,the greater the mineralization rate of sedimentary organic matter was. Moreover,the × 1 treatment mainly enhanced aerobic mineralization with the increasing release of CO2;the ×20 treatment mainly enhanced anaerobic methanogens mineralization with the increasing release of CH4. Thirdly,the diffusion and release fluxes of nitrogen and phosphorus were significantly different in algal-detritus addition treatments with different densities. Sediment adsorption was dominated in the×1 treatment,in which the average release rates of NH4^+and PO4^3-in overlying water differed slightly from the blank controls. In the×20 treatment,the flux of NH4^+showed the tendency of sediment adsorption in the initial ten days and transferred to releasing potential in the remained time,while the releasing flux of PO4^3-to overlying water was existed during the whole incubation period. The average release rates of NH4^+and PO4^3-in the ×20 treatment( 0.223 mg/( L·d) and 0.075 mg/( L·d),respectively) were significantly higher than those of the other treatments. In general,the accumulation of high density of algal-detritus promotes the mineralization of organic carbon,nitrogen,and phosphorus,releasing a large amount of CO2,CH4,and nutrients to the overlying water,which decreases water quality and contributes to the growth and reproduction of cyanobacteria.