AGRICULTURAL GREEN DEVELOPMENT IN THE ERHAI LAKE BASIN-THE WAY FORWARD

Pollution of high-altitude lake basins by agriculture and rural activities,and the control of this pollution,have received increasing attention from academic research and government policy in China.Series of restrictions and regulations have been implemented to protect the surface,water quality.These restrictions and regulations have greatly impacted and transformed the agricultural systems and rural livelihoods surrounding these lake basins.Using Erhai Lake basin in Yunnan Province as a case study,three main challenges were identified for concurrently decreasing pollution in the lake and increasing farmer income.It is contended that scientifically-sound environmental protection policies and agricultural green development practices are key to reversing the current situation.This will help to protect the lake from pollution while smallholder farmers will be able to produce healthy food in an environmentally sustainable manner,and with a fair remuneration for all the services farmers providetothe society.

SPATIOTEMPORAL VARIATION OF WATER QUALITY AND ALGAL BIOMASS IN ERHAI LAKE AND ITS ENVIRONMENTAL MANAGEMENT IMPLICATIONS

Elucidating the spatiotemporal pattern of water quality and algal biomass is crucial for accurately tracing pollution sources and reducing the risk of algal blooms in lake systems.This study analyzed the spatiotemporal variability of water quality and algal biomass in Erhai Lake from 1994 to 2021 using water quality index(WQi),Mann-Kendall test and Sen's slope combined methods.The potential causes of water quality deterioration and algal biomass dynamics were also elucidated.The results showed that the historical changes in the water environment of Erhai Lake mainly had three stages:satisfactory(1994-2001),deteriorating(2002-2010)and improving(2011-2021).The changes in water quality and algal biomass were primarily affected by total nitrogen,total phosphorus and chemical oxygen demand in different stages.The water environment of Erhai Lake is currently improving significantly,starting in the southern area that is furthest from the sources of agricultural pollution,especially in summer and autumn.This is attributed to the implementation of control measures resulting in lower pollutant loads at particular times and places.Therefore,it is necessary to continue to promote standardized livestock farming,to strengthen rural wastewater collection and to investigate measures such as the interruption of the endogenous cycle.

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.