Dr. Yan GAO Institute of Agricultural Resources and Environment Water Management and Resources Utilization Research Group

Management of Freshwater Ecosystem Using Bio-remediation Technologies. Nitrogen and Phosphorus Cycle in Aquatic Ecosystems Resource Utilization of Aquatic Plants Development of Algae Control Technologies and Utilization of Algae Biomass Crop Nutrient Management and Non-point pollution control Our researches included, but not limited to the following areas

1. Bio-remediation Technologies   Ecology Engineering —Confined Growth of Water Hyacinth to Reduce Eutrophication in Taihu and Dianchi Lakes

 Development of technologies and Support Facilities—harvesting vessel, facilities for reducing volume of aquatic plant biomass, water reduction equipment for water hyacinth processing

Confined Growth of Water Hyacinth at Caohai, Dianchi Lake （ 13 Aug ） The coverage reached ~4.3 km 2  TP Concn. in Caihai was decreased from ~1.5 mg L -1 in 2009 to ~ 0.3 mg L -1 in 2011 (decreased by ~80% when compared with 2009).  TN Concn. in Caihai was decreased from ~15 mg L -1 in 2009 to ~ 4 mg L -1 in 2011 (decreased by ~75% when compared with 2009). According to the year-round data:

2. Nitrogen Cycling Study—the loss of nitrogen via Denitrification in Eutrophic water Table 1 Nitrogen assimilated by E. crassipes and nitrogen removal in Caohai from May to November in 2011  In 2011, assimilation of nitrogen by E. crassipes removed 52% of the total N from influent (936 t), or 64% of the removed N (761 t). The N mass balance suggested that about 36% of total N removal via the processes of nitrification and/or denitrification (Wang et al., 2013).

Table 2 Mass balance of the added N-15 in water with or without cultivation of E. crassipes  using N-15 tracing method combined with mass balance estimation, revealed that an unaccounted proportion (~ 26-34%) of the added 15 NO 3 − could be mainly due to gaseous loss by denitrification that was stimulated by cultivation of E. crassipes when compared with non-planted treatments (Gao et al., 2012). N-W: labeled 15NO3- without cultivation of macrophytes ; N-E: labeled 15NO3- water with cultivation of macrophytes; A-W: labeled 15NH4+ water without cultivation of macrophytes, A-E labeled 15NH4+ water with cultivation of macrophytes;

Direct measurement of N 2 production from denitrification  Challenge— there was still lack of direct evidence concerning N 2 production via denitrification in the field scale  In most circumstances, N 2 is the main gaseous product of denitrification in aquatic ecosystems  it is difficult to estimate gaseous emission of nitrogen (N 2 ) produced via denitrification process due to high concentration of N 2 in the air

Method 1: Improved Floating Chamber Method Fig.1 Sketch diagram of enclosed chamber for in situ collecting N 2 O and N 2 released from water with or without cultivation of Eichhonia crassipes

Effects of E. crassipes cultivation on 15 N atom % excess of N 2 released from water.  According to results of the repeated-measures MANOVA, N-15 at.% excess of N 2 -N released from the planted water (0.003±0.001 to 0.35±0.07) was significantly (p≤0.05) higher than from the unplanted water (0.005±0.003 to 0.15±0.03)

The abundance of denitrifying gene (nirK, nosZ, and nirS) on E. crassipes roots and water within root zone was significantly (p<0.005) higher than that in the water without cultivation of E. crassipes.

Method 2: In situ collection of gas released from water and in-consequence N 2 analysis

Table 1 Recoveries of Standard Gases with known concentrations of N 2, O 2, CH 4 and N 2 O Recovery%= (Concentration of a specific gas in the collected gas samples)/( Standard Gas with certain concentration of a specific gas)×100

Location of the sampling points in the pond Case Study—Estimation of N 2 and N 2 O Emission from Eutrophic Pond Water

Composition of gas released from the eutrophic pond water

Temporal changes of N 2 and N 2 O ebullition fluxes at the different locations of the pond  At warmer seasons of Sep. and Oct., the average N 2 ebullition flux of the pond water ranged from g m 2- h -1 to g m -2 h -1  These fluxes were greatly higher than thosse observed in Dec to Jan (0.004±0.002 g m -2 h -1 )

Case Study—Estimation of N 2 and Greenhouse gases emission from Caohai Lake with growth of different types of aquatic plants

Individual gas flux released from water area with growth of different types of aquatic plants

Device for collecting gas released from different layers of water – what does it mean?

3. Resource utilization of the Aquatic Plants Organic Fertilizer Production

Biogas production and application of digested water hyacinth slurry on farmland

Utilization of water hyacinth silage to feed sheep and goose

4. Alga harvesting technology and algal biomass utilization Harvesting the alga in lake Storage the alga after harvesting Biogas Production using the alga Application of the digested alga slurry on farmland