Resolving the influence of nitrogen abundances on sediment organic matter in macrophyte-dominated lakes, using fluorescence spectroscopy

A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition(N, NH4Cl100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4+may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.

Control concept and countermeasures for shallow lakes’eutrophication in China

Research on lake eutrophication in China began in the early 1970s,and many lakes in China are now known to be in meso-eutrophic status.Lake eutrophication has been showing a rapidly increasing trend since 2000.Investigations show that the main reasons for lake eutrophication include a fragile lake background environment,excessive nutrient loading into lakes,excessive human activities,ecological degeneration,weak environmental protection awareness,and lax lake management.Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance,major changes in water chemistry(pH,oxygen,and carbon),lake ecosystem imbalance,and algal prevalence in lakes.Some concepts for controlling eutrophication should be persistently proposed,including lake catchment control,combination of pollutant source control with ecological restoration,protection of three important aspects(terrestrial ecology,lake coast zone,and submerged plant),and combination of lake management with regulation.Measures to control lake eutrophication should include pollution source control(i.e.,optimize industrial structural adjustments in the lake catchment,reduce nitrogen and phosphorus emission amounts,and control endogenous pollution)and lake ecological restoration(i.e.establish a zone-lake buffer region and lakeside zone,protect regional vegetation,utilize hydrophytes in renovation technology);countermeasures for lake management should include implementing water quality management,identifying environmental and lake water goals,legislating and formulating laws and regulations to protect lakes,strengthening publicity and the education of people,increasing public awareness through participation in systems and mechanic innovations,establishing lake region management institutions,and ensuring implementation of governance and management measures.

Spatial distribution of phosphorus forms in sediments with different distances to the estuary of the Dianchi Lake,China

Effects of human activity on the distribution of phosphorus(P)forms were investigated for the sediments and porewaters in Daqinghe Estuary of Dianchi Lake,China.The concentrations of total P(TP),inorganic-P(IP),and organic-P(Org-P),and the ratio of iron-bound P(Fe-P)/calcium-bound P(Ca-P)in the sediments decreased with the increasing distance from the sampling site to the estuary.This is probably due to the flocculant materials,e.g.,ferric and aluminous salts,usually being added in the wastewater treatment processes.The concentration of ammonia in the sediment porewaters significantly decreased with the increasing distance from the sampling site to the estuary.Both concentrations of total nitrogen and nitrogen in the sediment porewaters decreased to some content with the increasing distance from the sampling site to the estuary.However,the concentrations of nitrate,dissolved total P(DTP),and TP did not have strong relationship with the distances from the sampling sites to the estuary.Pollution load and water quantity also had an important influence on the concentrations of P in sediments and its interstitial water in estuary sedimentary area.