Abstract
Endogenous organic nitrogen loadings in lake sediments have increased with human activity in recent decades. A 6-month field study from two disparate shallow eutrophic lakes could partly reveal these issues by analysing seasonal variations of biodegradation and phytoremediation in the sediment. This paper describes the relationship between oxidation reduction potential, temperature, microbial activity and phytoremediation in nitrogen cycling by calculation degradative index of dissolved organic nitrogen and amino acid decomposition. The index was being positive in winter and negative in summer while closely positive correlated with biodegradation. Our analysis revealed that rather than anoxic condition, biomass is the primary factor to dissolved organic nitrogen distribution and decomposition. Some major amino acids statistics also confirm the above view. The comparisons of organic nitrogen and amino acid in abundance and seasons in situ provides that demonstrated plants cue important for nitrogen removal by their roots adsorption and immobilization. In conclusion, enhanced microbial activity and phytoremediation with the seasons will reduce the endogenous nitrogen loadings by the coupled mineralization and diagenetic process.
Highlights
In recent years, the global problems of lakeeutrophication, especially nitrogen distribution or migration, have been greatly concerned due to their wide spreading
Sediments are the main destinations as storing pool of nutrients by diagenetic transformation while some endogenous organic nitrogen release into the sediment leading to a eutrophic restoration under some conditions
The total hydrolysable amino acid (THAA) and hexamine typical shallow urban eutrophic lake that had no large stationary sources of pollution, whilst the lake is subject to discharges by sewage in previous years
Summary
The global problems of lakeeutrophication, especially nitrogen distribution or migration, have been greatly concerned due to their wide spreading. This issue is critical in understanding the mechanism of nitrogen cycling and freshwater ecosystem responses to anthropogenic mediated change. In addition to mostly studied exogenous inputting, some cases had focused mainly in form, content, distribution and seasonal variation of dissolved organic nitrogen (DON) degradation and migration; and others in situ, including the profile of amino acids and its cycle by realizing the comparisons in mineralization, degradation and diagenesis in sediments[1,2]. Phytoremediation is a research point in sediments restoration. All these mutual relations have many uncertainties to further cognition yet
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