[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.

[Calculation of environmental dredging depth of heavy sediments in Zhushan Bay of Taihu Lake metal polluted].

Horizontal distribution of heavy metals in surface sediments of Zhushan Bay was investigated, and core sediment samples were collected in the representative area. Core sediments were divided into oxide layer (A), polluted layer (B), upper polluted transition layer(C1), lower polluted transition layer(C2) and normal mud layer(D) from top to bottom. The change of total contents of Cr, Ni, Cu, Zn, As, Cd, Hg, Pb and contents of biological available Cr, Ni, Cu, Zn, As, Cd, Pb with depths were analyzed. Ecological risk assessment of heavy metals in sediments was done by potential ecological risk index method. At last, environmental dredging depth was calculated. The results shows that the contents of Cr, Ni, Cu, Zn, As, Cd, Hg, Pb are 30.56-216.58, 24.07-59.95, 16.71-140.30, 84.31-193.43, 3.39-22.30, 0.37-1.59, 0.00-0.80 and 9.67-99.35 mg x kg(-1), respectively. The average concentrations of Cr, Ni, Cu, Zn, As, Cd, Hg, Pb are 79.74, 37.74, 44.83, 122.39, 10.39, 0.77, 0.14 and 40.08 mg x kg(-1), respectively. Heavy metals in the surface sediments of Zhushan Bay mainly distribute in the west bank and the estuaries of Taige canal, Yincun Port, and Huanshan River,and Cd pollution is relatively serious. There is an accumulative effect of heavy metals in Zhushan Bay, and the contents of biological available metals decrease with depths. Ecological risk grades of Cd in layer A and B are high, and the comprehensive potential ecological risk grades of each layer are in middle or low. The environmental dredging layers are A and B, and the average dredging depth is 0.39 m.

[Effects of sediment on the growth of Microcystis and Anabaena in Yanghe reservoir].

Batch culture experiments were used to study the effect of leachate from sediment of Yanghe reservoir on the growth of Microcystis and Anabaena isolated from Yanghe reservoir. The results showed that the growth of Microcystis was significantly inhibited when the addition of anaerobic leachate from sediment in M11 culture medium was high (> or = 20% V/V). The maximum biomass of Microcystis was lower than that grown in pure M11 culture medium. But there was an obvious promotion on the growth of Anabaena when anaerobic leachate from sediment was added. The growth rate of Anabaena increased 36.6%, 47.2% and 36.0%, respectively, compared to M11 culture medium when adding 2%, 20% and 50% (V/V) anaerobic leachate. Compared to adding anaerobic leachate, aerobic leachate had no influence on the growth of Microcystis, while the growth rate of Anabaena was promoted by aerobic leachate. The growth rate of Anabaena increased 37.2% compared with M11 when adding 20% (V/V) of aerobic leachate. But after addition of Fe-citrate to the mixed culture medium (50% M11 culture medium +50% anaerobic leachate), the maximum biomass of Microcystis significantly increased. The results suggest that high organic matter concentration decreases iron availability for Microcystis.

[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.

[Seasonal variation characteristics of algae biomass in Chaohu Lake].

The biomass and distribution of algae community in Chaohu Lake were investigated in 2008. At the same time, the seasonal variations of algae translocation between the sediment and overlying water were also quantitative studied by self-made "algae up/down trap". Chaohu Lake was dominated by Cyanobacteria all the year, and dominant Cyanobacteria species changed in different seasons. In spring, Anabaena was the dominant species, and Microcystis was the subdominant species; In the whole summer and autumn, the dominant species is Microcystis. Algae biomass increased significantly from May and the maximum appeared in August, was 146.37 mg x m(-3) with Chl-a. The value of algae biomass were 9.75-16.24 mg x kg(-1) in the surface sediments, and the minimum appeared in Summer, then the algae biomass increased gradually with the maximum value in winter. Translocation process between the sediment and the overlying water occurred throughout the study period. The recruitment rates increased at first with the maximum rates in early August, was 0.036 8 mg x (m2 x d) (-1), and then had a downward tendency. However the sedimentation rates increased slowly firstly with the maximum rate in early September, then it decreased sharply, was 0.032 1 mg x (m2 x d)(-1). Multiple stepwise regression showed that temperature was the most significant factor for the algae biomass in Chaohu Lake, Total nitrogen (TN) and Total phosphorus(TP) are sub-important factors.

[Seasonal occurrence characteristics of different forms of nitrogen in the sediments of Chaohu Lake].

Seasonal characteristics of the free nitrogen (FN), the exchangeable nitrogen (EN), the acid hydrolysable nitrogen (HN) and the residual nitrogen (RN) in the surface sediment of Chaohu Lake were analyzed by sequential extraction method. The correlations among the nitrogen fractions with the total nitrogen (TN) and the mineralizable nitrogen (MN) were discussed considering the seasonal variations of the TN and MN. The results show that the concentrations of FN, EN and TN are lower in summer and higher in autumn and winter, NH4(+)-N is the main fraction of FN and EN. TN concentrations are much higher in West Chaohu Lake with the maximum concentration of 2280.47 mg/kg in the west lake center than in the East Chaohu Lake. The seasonal order of mineralizable nitrogen (MN) content is winter> spring > autumn > summer. The bio-available nitrogen fraction varies with different seasons, which is the amino acid nitrogen (AAN) in spring, EN in summer and autumn, FN in winter. The study about seasonal occurrence characteristics of nitrogen fractions in sediment provided foundational data for lake ecological security evaluation and nitrogen release evaluation.

[Heavy metals pollution and its stability assessment of sediments in flowing rivers around lake Taihu].

16 main inflow and outflow rivers around Lake Taihu were chosen as the research object, and the concentrations and distribution of four heavy metals (Pb, Cd, Cu and Zn) in the surface sediments of these river estuaries were detected. The pollution extent and stability were analyzed by using three-step sequential extraction method (BCR method). Aim of this study is to control heavy metal pollution of Lake Taihu and provide the basic information. Based on the results, the monitored river estuaries all had been contaminated by different degrees, and four heavy metals' concentrations all exceeded the threshold effect level (TEL) at most sampling sites. A distinct spatial heterogeneity was found in extracted fractions of these heavy metals distribution: northern rivers > southern rivers, inflow rivers > outflow rivers. The Stability Assessment Code (SAC) for different metals varied in the descending order of Cd, Zn, Pb and Cu. Compared with Pb and Cu, Cd and Zn had a higher second release potential and ecological risk.

[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.

[Physiological responses of Myriophyllum spicatum to ammonium nitrogen].

With the sediment applied with 0, 0.24%, and 0.48% NH4Cl (treatments CK, SN1, and SN2) as the substrate, a greenhouse experiment was conducted to study the physiological responses of Myriophyllum spicatum to ammonium nitrogen. The NH4+ -N concentration in the sediment, pore-water, and overlying-water ranged in 12.35-870.32 mg x kg(-1), 1.09-1036.05 mg x L(-1) and 0.10-24.30 mg x L(-1), respectively. Comparing with those in CK, the plant height, root length, and fresh biomass of M. spicatum in treatments SN1 and SN2 decreased by 15.66% and 55.52%, 45.72% and 67.65%, and 19.69% and 81.16%, respectively. The SOD activity in M. spicatum leaves and roots was SN1 < SN2 < CK, but the peroxidase (POD) and catalase (CAT) activities in the leaves were SN2 < SN1 < CK, while those in the roots were significant higher in SN, and SN2 than in CK. The malondialdehyde (MDA) contents of leaves and roots in SN1 and SN2 were increased by 46.30% and 82.75%, and 19.66% and 55.19%, respectively. It was suggested that NH4+ -N had toxic effects on M. spicatum, and the higher the NH4+ -N concentration in sediment, the more obvious the physiological responses of M. spicatum exhibited.

Seasonal dynamics of phytoplankton in relation to key aquatic habitat factors in a polluted urban small water body in Tianjin, China.

To evaluate the seasonal dynamics of phytoplankton and its relationships with aquatic habitat factors in polluted urban landscape lakes, annual investigations have been carried out in the West zone of Xinkai Lake. The results showed that the lake belongs to the eutrophic-supertrophic type in terms of key habitat factors measurement. The seasonal succession of phytoplankton community was determined. The dominant cyanobacterial species Oscillatoria tenuis Ag. bloomed in autumn, although the other species with higher degrees of dominance never bloomed in the year investigated. Significant correlations between some habitat factors and phytoplankton biomass were observed.

[Diurnal variations in purifying-tanks when use Pontederia cordata treating the Malodorous River water].

Aquatic plants (Ponsederie cordaza) were waked in two purifying-tanks to investigate the effects of illumination intensity and aeration on diurnal variations of Chla, SP, POD of Ponsederia cordaza and pH, DO, COD, NH4+ -N, TP of water from purifying-tanks when treating the malodorous river water at seven different times, another blank purifying-tank was set as a control. Comparative studies and correlation analysis of these different indicators were carried out to improve the plants working efficiency and provide scientific basis for optimal operation of plant purifying-tanks. Results showed that all indicators affected by changes of light, TP shows best correlation coefficient Cr = 0.93, p < 0.01) of physicochemical indicators and SP behaves best correlation coefficient Cr = 0.91 , p < 0.01) of plant physiology indicators in non-aeration purifying-tank;aeration is necessary as diurnal average of DO shows an increase of 0.13 mg/L by treatment of plant meanwhile 1.8 mg/L by plant with aeration,purifying-tanks with aeration got 7.1%, 6.3% higher removing rates of COD, NH4+ -N and 38% less TP removing rate than non-aeration plant purifying-tanks (p < 0.01); with aeration treatment, significant reduction of Chla, SP content (p < 0.05) and increase of POD activity (p < 0.05) observed in plants; the changes of illumination intensity and aeration can significantly affect physiological characteristics of plants and should be considered carefully and need further study when treating malodorous river water by plant purifying-tanks.

[Effect of inactivation agents on the phosphorus release from sediment of Lake Dianchi at different temperature].

The influence of temperature on P release from sediment of Lake Dianchi was discussed. Two kinds of inactivation agent schemes (Al2SO4.18H2O and PAC-Polymeric Aluminum Chloride) were used. The results show that the P release amount from sediment increased as the environmental temperature increased. As temperature raised 10 degrees C, the TP release amount increased 1.22%-38.69%, the DTP release amount increased 4.79%-76.82%. From 25 degrees C to 35 degrees C, the sediment had the largest P release increment. When temperature rose, the oxygen demand in the overlying water increased. Then the transformation speed of Fe3+ to Fe2+ increased, and then the release of Fe-P in sediment accelerated. On the other hand, microbe activity made the release possible through the transformation from organic-phosphorus to inorganic-phosphorus. The inactivation agents used here have significant effect on restraining the phosphorus release from sediment and the capture of particles containing phosphorus in overlying water. PAC had better P inactivation effect than Al2SO4 at 25 degrees C. Inhibition rate of P release from sediment by PAC was about 0.49%, 1.32%, 1.03% higher than Al2SO4 at 5, 15 and 25 degrees C, respectively. As the temperature rose to 35 degrees C, the capacity that PAC restricted P was weakened, so the effect of P release inhibition was weakened. Inactivation rate of Al2SO4 was higher about 2.25% than PAC to P from sediment at 35 degrees C. Temperature of sediments in PAC sets is 2-3 degrees C lower than that of Al2SO4 sets.

[Buoyancy regulation and vertical distribution of Planktothrix mougeotii in the simulator experiments].

The dominance of gas-vacuolated cyanobacteria is often attributed to their buoyancy and buoyancy in response to environmental conditions. Lake simulator experiments (4 m high and 1 m diameter) and pyrex bottle experiments (10 L) were applied to investigate the buoyancy regulation and vertical distribution of Planktothrix mougeotii in eutrophic lakes at 28 degrees C. During light phase, the filaments stratify in the 2-3 m after 8 h light exposure and the biomass at the layer attach maximum after 12 h light exposure. During dark phase, the filaments are tent to migrate to the surface. 20% of filaments migrate to the surface after 12 h and 50% of filaments migrate to the surface after 48 h. The buoyancy regulation under light condition is that filaments stratify in 10 micromol x (m2 x s)(-1) layers, and the filaments above the layer sink down, while those suspended below the layer float up. The amplitude of diel changes in buoyancy is related to photon irradiance, and the change of buoyancy in light [100 micromol x (m2 x s)(-1)]/ dark is higher than its in light [25 micromol x (m2 x s)(-1)]/ dark. Carbohydrate ballasting may be the only mechanism for buoyancy changes in Planktothrix mougeotii filaments during the period.

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands.

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. verticillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.

[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.

[Effects of different concentration ammonium-n on Hydrilla verticillata antioxidant enzymes under Cd stress].

In this paper, submersed plant Hydrilla verticillata was cultivated in a 1/10 Hoagland culture medium added with different concentration NH4 + -N (0, 0. 5, 2. 0, 4. 0 mg x L(-1)) and 10 mg x L(-1) cadmium to study the effects of NH4 + -N on H. verticillata growth and its antioxidant enzyme system under Cd stress, and approach the degradation mechanism of submersed macrophyte in eutrophic and polluted water bodies. The results showed that under 10 mg x L(-1) Cd stress, the chlorophyll content of H. verticillata decreased obviously, and SOD and POD activities increased first but declined then. NH4 + -N accelerated the stress effect of Cd. Under 0. 5 h joint stress of Cd and NH4 + -N, SOD activity increased significantly, while such an increase needed 3 hours under single Cd stress. Relative to chlorophyll and protein, antioxidant enzyme system was an early sensitive index, and SOD was more sensitive than POD. After two days exposure to Cd plus NH4 -N, H. verticillata was mainly stressed by Cd, and NH4+ -N stress could be neglected.