沉水植物菹草对营养盐的吸收利用途径及其对水质净化效能分析

发布时间：2019-06-07 17:20

【摘要】：沉水植物是淡水生态系统中重要的初级生产者,参与了淡水生态系统中氮、磷营养盐的循环过程,通过恢复沉水植物是修复富营养化水体的一种常用方法,因此研究沉水植物吸收氮、磷营养盐的过程具有重要意义。本文选择典型的沉水植物—菹草为研究对象,通过开展一系列室内模拟实验,考察了菹草茎叶(断枝)对营养盐的吸收效果;探讨了富营养条件下菹草吸收营养盐的途径;比较了贫富营养条件对菹草吸收和利用营养盐途径的影响。主要结果如下:(1)菹草茎叶(断枝)在富营养水体中,其断枝的茎长和鲜重有显著增长(p0.05),菹草茎叶(断枝)盖度为50%和100%的处理组中的平均单株石芽数为2.09和2.67个。在试验条件下,随着菹草茎叶(断枝)盖度的增加,水体中氮磷营养盐的衰减速率越快。第3 d时盖度为50%和100%的处理组中TN和TP均显著下降(p0.01),当水体中NH_4~+-N大于0.35 mg·L-1时,菹草优先吸收NH_4~+-N再吸收NO3--N。此外,水体中的浮游和底栖藻类明显下降,系统中浮游优势藻由绿藻属的鼓藻和小球藻逐渐变成微囊藻和绿藻,而底栖藻类表现出蓝藻门的藻类逐渐增多的趋势,而不再以绿藻藻类为主要藻类的群落结构。(2)在试验条件下,沉积物包被组中水体中的氮磷营养盐消减的最快,在第18 d时水体中的TN和TP较起始时的消减率分别为62.58%、90.07%,其他4组TN的衰减率均小于60%;沉积物中的无机氮主要氮形态为NH_4~+-N,其中沉积物裸露的处理组沉积物中NH_4~+-N和TP的消减率要高于沉积物包被组,沉积物包被组中NH_4~+-N和TP较起始时的消减率分别为39.05%、10.95%,表明沉积物中的营养盐存在部分向水体中释放的过程。因此,菹草在富营养化水体中根系可以吸收沉积物中的氮磷营养盐,同时沉积物中的氮磷营养盐可以向水体中释放供菹草茎叶吸收。(3)在贫富营养条件下,菹草最大茎长、单株平均株重、RGR以及菹草叶片的光合作用速率差异不大。实验开始后,贫富营养条件菹草的氮磷含量逐渐升高,第42 d和60 d时PTN和PTP分别达到极大值,两者差异不显著(p0.05)。在富营养条件下水体中的氮磷营养盐和菹草的PTN和PTP之间呈显著负相关(p0.05),而在贫营养条件下,菹草体的氮磷和水体中的氮磷无直接关系。第30 d时富营养组中水体TN消减达到73.57%,第18 d时富营养盐组TP消减达到87.50%,对照组中TP消减率为51.02%,但对照组中水体TN有小幅度上升。菹草在贫富营养条件下吸收营养盐的途径不同,在富营养条件下,菹草可以利用根系和茎叶共同吸收营养盐,但是在贫营养条件下,菹草只能利用根系吸收水体中的营养盐。所以营养状态的改变可以改变菹草吸收营养盐的方式。
[Abstract]:Submerged plants are important primary producers in freshwater ecosystems and participate in the cycle of nitrogen and phosphorus nutrients in freshwater ecosystems. Restoring submerged plants is a common method to repair eutrophication water bodies. Therefore, it is of great significance to study the process of absorbing nitrogen and phosphorus nutrients by submerged plants. In this paper, crispus, a typical submerged plant, was selected as the research object, and a series of laboratory simulation experiments were carried out to investigate the effect of stem and leaf (branch breaking) on the absorption of nutrients, and the ways of absorbing nutrients by crispus under eutrophication conditions were discussed. The effects of rich and poor nutritional conditions on the absorption and utilization of nutrients by Potamogaster crispus were compared. The main results were as follows: (1) the stem length and fresh weight of crispus were significantly increased in eutrophication water (p0.05). The average number of stone buds per plant in 50% and 100% treatment groups was 2.09 and 2.67, respectively. Under the experimental conditions, the faster the decay rate of nitrogen and phosphorus nutrients in water was with the increase of stem and leaf coverage (branch breaking) of Potamogaster crispus. On the 3rd day, TN and TP decreased significantly in the treatment group with coverage of 50% and 100% (p0.01). When NH_4~-N in water was greater than 0.35 mg 路L-1, crispus preferred to absorb NH_4~-N and reabsorb NO3--N.. In addition, the algae in the water body decreased significantly, and the dominant algae in the system gradually changed from chlorella and Chlorella to microcystis and green algae, while benthos algae showed a trend of increasing algae in the phylum cyanophyta. The community structure of green algae was no longer the main algae. (2) under the experimental conditions, the nitrogen and phosphorus nutrients in the water body of the sediment coating group decreased the fastest. On the 18th day, the attenuation rates of TN and TP in water were 62.58% and 90.07%, respectively, and the attenuation rates of TN in the other four groups were less than 60%. The main nitrogen form of inorganic nitrogen in sediment is NH_4~-N, in which the reduction rate of NH_4~-N and TP in sediment exposed treatment group is higher than that in sediment coating group. The decreasing rates of NH_4~-N and TP in sediment coating group were 39.05% and 10.95%, respectively, indicating that part of the nutrients in sediments were released into water. Therefore, the roots of crispus can absorb nitrogen and phosphorus nutrients in sediments, and the nitrogen and phosphorus nutrients in sediments can be released into the water for absorption. (3) under the condition of rich and poor nutrition, the maximum stem length of crispus can be obtained. There were no differences in photosynthesis rate among average plant weight, RGR and P. crispus leaves. After the experiment, the content of nitrogen and phosphorus increased gradually in rich and poor nutritional conditions, and the PTN and PTP reached the maximum on the 42nd and 60th day, respectively, and there was no significant difference between the two groups (p0.05). There was a significant negative correlation between nitrogen and phosphorus nutrients in water and PTN and PTP in Potamogaster crispus under eutrophication condition (p0.05), but there was no direct relationship between nitrogen and phosphorus in Potamogaster crispus under the condition of poor nutrition. On the 30th day, the TN of eutrophication group decreased by 73.57%, the TP of eutrophication group decreased 87.50% on the 18th day, and the TP reduction rate of control group was 51.02%, but the TN of water body increased slightly in the control group. Crispus can absorb nutrients by roots and stems and leaves under the condition of rich and poor nutrition, but under the condition of poor nutrition, crispus can only use roots to absorb nutrients in water. Therefore, the change of nutritional status can change the way Potamogpus crispus absorbs nutrients.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X52;X173

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