[Spatial distribution and evaluation of nitrogen, phosphorus and organic matter in surface sediments from western lakeside belt of Lake Taihu].

The surface sediments in western lakeside belt of Taihu Lake were collected. The spatial distribution of nutrients and pollution evaluation were studied. The results showed that concentration of the nitrogen, phosphorus and organic matter in the surface sediments had an increasing tendency from inshore to the far shore. The concentration of organic matter in the sediments ranged from 2261.78 mg x kg(-1) to 11963.10 mg x kg(-1), with the average of 7 124.00 mg x kg(-1). Total nitrogen concentration in the sediments ranged from 343.20 mg x kg(-1) to 1 390.12 mg x kg(-1), with the average of 819.20 mg x kg(-1). The total phosphorus concentration in the sediments ranged from 197.46 mg x kg(-1) to 570.85 mg x kg(-1), with the average of 379.39 mg x kg(-1). The C/N ratio in the lake sediment was 9.5. Organic matter and nutrient were from alga and aquatic plant in lake. Based on the organic index and organic nitrogen, we can concluded that the surface sediments in western lakeside belt of Taihu Lake still belong to less clean category. The average values of organic index and organic nitrogen were 0.037% and 0.044%, respectively. The organic index and organic nitrogen in offshore were high, which indicated the risk of organic pollution.

[Pollution characteristics and evaluation of nitrogen, phosphorus and organic matter in surface sediments of Lake Changshouhu in Chongqing, China].

In order to reveal spatial distribution characteristics of nutrient in the surface sediments of Lake Changshouhu, contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) of 62 surface sediments samples were determined and compared with other urban (suburban) lakes in China. C/N and the correlation of TN, TP and OM had also been analyzed. The results showed that the average contents of TN and TP were 2 255.89 mg x kg(-1) and 622.03 mg x kg(-1) respectively. Nitrogen and phosphorus pollution were very serious all over the lake, with a significantly different spatial distribution. The average content of OM was 2.80%. So the contents of TN, TP and OM were in the middle level compared with other lakes. 87.10% of C/N was between 5 and 14 (72.58% within which was between 6 and 13) and 3.23% of C/N was between 2.8 and 3.4, which showed that OM came from algae, phytoplankton and zooplankton. Besides, a small part of OM came from aquatic organisms. OM and TN were significantly correlated (Pearson coefficient was 0.849), but with less significant correlation to TP. The spatial distribution characteristics of OM were very similar with that of TN. The content of OM in water samples collected from western and middle waterbody was higher than that in eastern waterbody, which was the same as TN. By evaluating pollution situation with organic index and organic nitrogen, the average organic index was 0.386 which was on the III level still belonged to clean category. However, the average number of organic nitrogen was up to 0.214% which was on the IV level indicated the pollution degree. This showed that the lake Changshouhu was in a serious pollution situation especially in nitrogen pollution.

[Influence of disturbance intensity on nitrogen, phosphorus and permanganate index release of Potamogeton crispus during soaking in water].

Influence of various disturbance intensities on nitrogen, phosphorus and permanganate index (PI) release of Potamogeton crispus were investigated during the plant soaking in water, and the plant materials were collected in an urban lake of Beijing. Results showed that more rapid release of TP and PI from Potamogeton crispus were caused by disturbance, NH4(+) -N and TN in water were significantly increased (ANOVA, p < 0.05) under the condition of high disturbance (120 r/min) for 240 h. However, PI and TP were significantly decreased (ANOVA, p < 0.05) after 240 h disturbance in all treatments. When the release equilibrium of 2.13 g dry mass Potamogeton crispus in one liter of water was reached, the PI, TN, and TP released from unit mass Potamogeton crispus were 35, 5.1 and 4.1 mg x g(-1), respectively. The release ratio of TP from Potamogeton crispus was the highest, while the release ratio of PI was the lowest. The simulated experiment results showed that the highest pollution load to water released from Potamogeton crispus was the TP among the three nutrients. Phosphorus is one of the key factors which causing water eutrophication in lake, thus after submerged plants declining in lake, the field research of phosphorus release and migration from submerged plants into water is the focus of future research work.

[Relationship between the DO and the environmental factors of the water body in Lake Erhai].

The contents of DO and nitrogen (N), phosphorus (P), chlorophyll a in water from Lake Erhai were analysed by combining the nitrogen and phosphorus forms in sediment. The results indicated that the DO contents of the water from Lake Erhai varied from 6.61 to 7.42 mg/L from 1992 to 2009, which is generally decreased. The minimum mean value was 6.42 mg/L in September. The trend of the DO contents from north to south was decreasing, and also decreased with the increasing of the water depth in Lake Erhai, the DO content was 5.15 mg/L at the water bottom. The relationship between the contents of DO and N, P was negative, and the relativity of different months was greater than that of different years. The relationship between the contents of DO and the contents of labile-P, organic-P, NH4(+) -N in sediment was negative, which was positive with the contents of Fe/Al-P, inorganic P and NO3(-) -N. The relationship between the contents of DO and chlorophyll a in water was negative, which indicated that Lake Erhai is aerobic, and is approaching anaerobic gradually. With the increasing of released content of N and P, the increasing of alga biomass was accelerated and the worsening of water body eutrophication also can be promoted by the decreased DO content in water from Lake Erhai.

[Characteristic analysis of the adsorption/desorption of nitrogen and phosphorus in the sediments of Taihu Lake].

The adsorption isotherms curves of 90 simples were studied in Taihu Lake through the experiment of adsorption/desorption. And the relation between the equilibrium concentrations, NAP, adsorption efficiency and corresponding parameter in interstitial water and sediment has been analyzed, in order to analyze the "source" and "collection" of Taihu. The results showed that the isotherms curves of nitrogen and phosphorus in the sediment had significant correlations in the range of the concentrations of experiment. The average equilibrium concentrations of nitrogen and phosphorus are 1.10 mg/L and 0.11 mg/L respectively. The average of NAP of nitrogen and phosphorus are 23.55 mg/kg and 11.72 mg/kg respectively. The NAP of nitrogen and phosphorus are higher in the area of serious pollution. The average adsorption efficiency of nitrogen and phosphorus are 23.14 L/kg and 102.09 L/kg respectively. Significant correlations were found between the equilibrium concentrations of adsorption/desorption of nitrogen and phosphous and corresponding parameter in interstitial water or sediment. Overall the sediment is the "source" of the nitrogen and phosphorus.

[Classification and pollution characteristic analysis for inflow rivers of Chaohu Lake].

Based on main pollution sources and characteristics of inflow rivers of Chaohu Lake, the inflow rivers are clustered and the pollution levels are classified by statistical methods. In addition, the correlation between algal biomass and the river nutrients input loads is derived according to the inflow river water quality monitoring parameters and the Chl-a concentrations in lake areas. Results show that the inflow rivers are classified into three groups. Urban pollution, soil and water conservation, and non-point source pollution are the major factors which influence water quality respectively. The input loads of permanganate index, NH4(+) -N, TN, TP from urban pollution rivers to the whole lake are 41.29%, 89.49%, 72.27% and 60.14% to all inflow rivers respectively. Organic pollution is the main pollution source of inflow rivers by factor analysis. The pollution rank of nine inflow rivers are as follows: Nanfei River > Shiwuli River > Paihe River > Shuangqiao River > Zhegao River> Yuxi River> Baishishan River > Zhaohe River> Hangbu River. The algal biomass and the NH4(+) -N, TN, TP inputs of inflow rivers are positively correlated.

[Effect of different type sediments on transformation of phosphorus forms and growth of Myriophyllum spicatum].

The changes of the different phosphorus (P) forms in sediments, overlying water and the diversity of dry weight and root forms of Myriophyllum spicatum were studied using different type sediments under simulating condition. The characteristic of transformation of P forms and growth of submerged plant Myriophyllum spicatum were illustrated. The results indicated that the P release was promoted by adding the silver sand in sediment, and their P concentrations in the overlying water were increased. The chemical characteristic of the sediments were changed by adding NH4 Cl, which restrained the P release from their sediments and decreased the P concentration in their overlying water. About 49%, 107% of their plant, root dry weight and 19% root length of Myriophyllum spicatum from different treatments were raised by adding silver sand in sediments. The root growths of the Myriophyllum spicatum from different treatments were restrained and their agings were promoted by adding NH4 Cl in sediments. The P release from sediments were accelerated by the growth of Myriophyllum spicatum, and the early decay of Myriophyllum spicatum can increase the P accumulation in sediment. The changing trend of different P forms in the sediments decreased firstly, and then increased with the Myriophyllum spicatum growthing, their contents of Fe/Al-P form in sediments varied greatly (41%-57%). The P release and adsorption in sediments were mainly affected by their root length index of Myriophyllum spicatum from different treatments. The P release in sediment was accelerated through their changing penetrate capacity by root diameter increasing.

[Pilot-scale comparison research of different constructed wetland types to treat eutrophic lake water].

Comparison research of different constructed wetland types to treat lake Wulihu water was carried out. Under the condition of the loading rates 0.8 m3/(m2 x d), the removal efficiencies of the vertical flow wetland (VFW), subsurface flow wetland (SFW) and free surface wetland(FSW) had the following results: To ammonia nitrogen (NH4(+)-N) the average removal rates were 33.2%, 27.4% and 14.1%, respectively; To total nitrogen (TN) the average removal rates were 52.3% , 50.1% and 19.2%, respectively; To total phosphorus (TP) the average removal rates were 58.8%, 57.9% and 26.3%, respectively; To permanganate index the average removal rates were 37.2%, 38.3% and 14.8%, respectively; To chlorophyll a (Chl-a) the average removal rates were 86.9%, 96.1% and 55.3%, respectively. Obviously, VFW and SFW are more effective than FSW at treating eutrophicated water such as Lake Wulihu which with characters of low organically pollution and with high nitrogen and phosphorus pollution, and the VFW is the most effective on the removal of NH4(+)-N, TN and TP. SFW is the most effective on the removal of permanganate index and Chl-a. The effluent stability of VFW is better than SFW, and the SFW is better than FSW.

[Variation of nitrogen and phosphorus concentration in water-sediment system and influence of overlying water on the algae growth].

The effect of biosidal treatment of initial sediment, addition of inhibitor and addition of phosphorus on the transform of nitrogen and phosphorus in the sediment-water simulative system were studied. S. quadricaudain was cultured in overlying waters took from the above experiment sets when the above experiment completed. The result indicated that, biosidal treatment enhanced the concentration of TP while there was no obvious effect on N. The TP, DTP and TN concentrations were closely between inhibitor addition set and the control set in the sediment-water simulative system but the content of NO3(-)-N of the set with inhibitor addition reached 19.2 mg x L(-1), which was much higher than that of the control set. The sediment significantly adsorbed the P added to the system, and the content of TP decreased when the system reached balance. Algae biomass of the biosidal treatment set was higher than that of the control set, and the main cause was sterilizer leaded to higher concentration of TP of the biosidal treatment set. The highest Algae biomass of the group with inhibitor (224.5 x 10(4) unit x L(-1)) was much higher than that of the control set (26 x 10(4) unit x L(-1)), and that was 5-10 times than that of other sets (sterilized set 22.5 x 10(4) unit x L(-1), set with P added 38.5 x 10(4) uni x L(-1)). Inhibitor restrained the microorganism from using some nutrition which was important to alga's growth. At the beginning, the addition of P had no remarkable effect on the alga growth, but along with the experiment, the alga of the P addition set adapted to the environment and algae biomass exceed that of the control set. The increase of biological bioavailable phosphorus of sediment in biosidal treatment set and addition of inhibitor sets were caused by the increase of algae biomass and thus the increase of liable organic phosphorus.

[Seasonal variation of bioavailable phosphorus in sediments in northeast part of Taihu Lake].

The concentrations of total phosphorus (TP), bioavailable phosphorus (BAP) and their seasonal changes in the surface sediments (0-10 cm) from three different regions of northeast of Taihu Lake were investigated. The results show that the concentrations of TP and BAP in the sediment are coincided with the corresponding trophic level of the overlying water. The concentrations of TP and BAP in the sediments varied widely not only between sampling sites but also between seasons. There is a significant correlation between BAP and TP in surface sediments, and their regression analysis equation varies with seasons. It is suggested to evaluate potential phosphorus-release risk of the sediment based on the TP concentration of the corresponding seasons.

[Influences of submerged vegetation Hydrilla verticillata on the forms of inorganic and organic phosphorus and potentially exchangeable phosphate in sediments].

The influences of submerged vegetation Hydrilla verticillata on forms of inorganic and organic phosphorous forms and potentially exchangeable phosphate in sediments were investigated under indoors simulating condition. The results show that: (1) Hydrilla verticillata can decrease the amount of OM, CEC and TP evidently ( p < 0.05) and activate the phosphate in sediments. (2) In the forms of inorganic phosphorus, the NaOH-P was significantly influenced (p<0.01) and the labile organic P in the forms of organic P was influenced to a certainty (p < 0.1), while no significant differences were made to the other forms of phosphorous. (3) Hydrilla verticillata can affect the amount of potentially exchangeable phosphate of the sediments, which increased 11.5% for the vegetation-group and decreased 61.0% for the control group during the period of the experiments. The change orientation was oppositional and the degree of change was quite different. This testified that Hydrilla verticillata could increase the amount of potentially exchangeable phosphate of sediments.

[Ecological protection and sustainable utilization of Erhai Lake, Yunnan].

Economic development and increase of population pressure have caused a series of ecological environmental problems of Erhai Lake. These problems include: (1) Quickening of eutrophication process, (2) Decrease of water level and water resources, (3) Habitat deterioration of lakeside zone, and (4) Overfishing and slow depletion of aboriginal fish. Pollutant loading of Erhai Lake is as follows: COD(Cr) 3 008 t x a(-1), TP 137.31 t x a(-1), TN 1 426.35 t x a(-1). According to the mestrophic target of water quality, loading of nitrogen and phosphorus is far above environmental capacity of Erhai Lake. Erhai Lake is now in a pivotal and hypersensitive period of trophic states change, and the position is very critical. Therefore, some countermeasures to solve the problems are presented as follows: (1) Defining the dominant functions of Erhai Lake, (2) Paying attention to the adjustment of the industrial structure and distribution in the course of urbanization, (3) Setting up lakeside zone reserve, (4) Strengthening the control of tourism pollution, (5) Properly adjusting the water level of Erhai Lake, and (6) Some ecological engineering measures for water resources protection in the basin should be taken through collecting and treating of urban sewages, ecological rehabilitating of the main inflowing rivers, constructing of ecological agricultures and improving of rural environment, ecological restoring of aquatic ecosystem, and soil and water conservation.

[Phosphate adsorption characteristics onto the sediments from shallow lakes in the middle and lower reaches of the Yangtze River].

Adsorption isotherms and kinetics of phosphate onto the 11 sediments taken from shallow lakes in the middle and lower reaches of the Yangtze River were determined in laboratory, and the effect of physical and chemical properties of the sediments on its phosphate adsorption characteristics was also analyzed. The results indicate that: (1) The process of phosphate adsorption onto sediments mainly occurred within 0-10 h, the maximum adsorption rates occurred within 0-0.5 h, and then attends to a dynamic equilibrium; (2) Between the NAP and its organic matter, CEC, total phosphorus, inorganic phosphorus, organic phosphorus, Fe/Al-phosphorus and total nitrogen have remarkable positive correlation; between the maximum adsorption of phosphate and its CEC, inorganic phosphorus, organic matter and total phosphorus have remarkable negative correlation; between the total maximum adsorption of phosphate and its organic matter, CEC, total phosphorus, inorganic phosphorus, organic phosphorus, Fe/Al-phosphorus and total nitrogen have remarkable positive correlation; (3) As regards water quality of the shallow lakes in the middle and lower reaches of the Yangtze River at present, its sediment exists desorption. Between the adsorption-desorption equilibrium concentrations of phosphate onto the sediments and its organic matter, CEC, total nitrogen, the total phosphorus and the content of every form phosphorous have a remarkable positive correlation. Even the sediment from heavily polluted lake also has the tendency to release phosphate into the overlying water in this study.

[Dynamic studies on the effect of nutrients on the growth of Microcystis aeruginosa].

The effects of nitrogen and phosphorus on the growth of Microcystis aeruginosa were investigated by using the Monod equation. The semi-saturation constants of Microcystis aeruginosa to TP (KsP) and TN (KsN) were calculated. The results show that KsN is higher than KsP. This indicates that the effect of TP on the growth of Microcystis aeruginos is further more significant than that of TN. Further analysis finds that extant quantity (X) and special growth rate (micro) of Microcystis aeruginosa increase with TP or TN, and there exists a point of inflection. When the concentrations of TP and TN ranged from 0.005mg/L to 0.2mg/L and from 0.01mg/L to 2mg/L respectively with TP or TN as the single limiting substrate, the growth rate of Microcystis aeruginosa increased rapidly. Because Microcystis aeruginosa exhibits different affinity with TP and TN (according to the semi-saturation constants), the effect of N/P ratio on the growth of Microcystis aeruginosa does not demonstrate at a constant value. No constant ratio can be used to determine the limiting nutrient elements on the growth of Microcystis aeruginosa in any aquatic environment. The effect of N/P ratio on the growth of Microcystis aeruginosa depends on both the N and P concentrations and the N/P ratio.

Origins and mobility of phosphorus forms in the sediments of Lakes Taihu and Chaohu, China.

Phosphorus release from the sediment is generally an important factor for lake eutrophication. We have investigated phosphorus forms in surface sediments from Lake Taihu and Lake Chaohu by a chemical extraction method. The results showed that the concentrations of Fe/Al-bound phosphorus (Fe/Al-P) and organic phosphorus (Org-P) had significant correlations with those of amorphous Fe/Al oxides and organic matter in the sediments. Furthermore, Ca-bound phosphorus (Ca-P) concentrations were well related to total organic carbon (TOC) concentrations. The results also indicated that higher pH weakened the association of phosphates with the Fe/Al hydroxides and then resulted in Fe/Al-P release. The increase of pH was companied with autogenetic progresses of calcium carbonate and then elevated Ca-P concentrations in the sediments. In conclusion, external P loadings determine spatial distribution of P fractions, especially Fe/Al-P and Org-P, and partially contribute to additional Ca-P fractions in these highly human-disturbed lakes. The pH-induced phosphorus mobility in the sediments is very important for these lakes.

Influence of phosphorus on Microcystis growth and the changes of other environmental factors.

The growth processes of Microcystis aeruginosa (FACHB-41) in simulated Taihu Lake water with different phosphorus concentrations were investigated using laboratory microcosms. The algal biomass increased with the increase of phosphorus concentration when it was lower than 0.445 mg/L, while the dissolved oxygen (DO) and pH increased, dissolved inorganic nitrogen(DIN) and light intensity underwater (I) decreased. Responding to the changes of the "environmental factors", the cellular carbohydrate and its ratio to cellular protein decreased generally as phosphorus increased. However, when phosphorus concentration was higher than 1.645 mg/L, the biomass, the "environmental factors", the cellular carbohydrate and its ratio to cellular protein did not change likewise. Since the environmental factors and the physiological and biochemical responses are important factors, the change of environmental factors and cell physiology and biochemistry induced by phosphorus may become the key factors that steer the growth and dominance of Microcystis under certain conditions. To sum up, phosphorus not only stimulate the growth of Microcystis directly by supplying nutrient element, but also has complex interactions with other "environmental factors" and play important roles in the growth processes of Microcystis.