Nuclear Quantum Effects on Nonadiabatic Dynamics of a Green Fluorescent Protein Chromophore Analogue: Ring-Polymer Surface-Hopping Simulation.

Herein, we have used the "on-the-fly" ring-polymer surface-hopping simulation method with the centroid approximation (RPSH-CA), in combination with the multireference OM2/MRCI electronic structure calculations to study the photoinduced dynamics of a green fluorescent protein (GFP) chromophore analogue in the gas phase, i.e., o-HBI, at 50, 100, and 300 K with 1, 5, 10, and 15 beads (3600 1 ps trajectories). The electronic structure calculations identified five new minimum-energy conical intersection (MECI) structures, which, together with the previous one, play crucial roles in the excited-state decay dynamics of o-HBI. It is also found that the excited-state intramolecular proton transfer (ESIPT) occurs in an ultrafast manner and is completed within 20 fs in all the simulation conditions because there is no barrier associated with this ESIPT process in the S1 state. However, the other excited-state dynamical results are strongly related to the number of beads. At 50 and 100 K, the nuclear quantum effects (NQEs) are very important; therefore, the excited-state dynamical results change significantly with the bead number. For example, the S1 decay time deduced from time-dependent state populations becomes longer as the bead number increases. Nevertheless, an essentially convergent trend is observed when the bead number is close to 10. In contrast, at 300 K, the NQEs become weaker and the above dynamical results converge very quickly even with 1 bead. Most importantly, the NQEs seriously affect the excited-state decay mechanism of o-HBI. At 50 and 100 K, most trajectories decay to the S0 state via perpendicular keto MECIs, whereas, at 300 K, only twisted keto MECIs are responsible for the excited-state decay. The present work not only comprehensively explores the temperature-dependent photoinduced dynamics of o-HBI, but also demonstrates the importance and necessity of NQEs in nonadiabatic dynamics simulations, especially at relatively low temperatures.

[Spatial-temporal Distribution and Source Analysis of Polycyclic Aromatic Hydrocarbons in the Sediments of Poyang Lake].

The concentrations, spatial-temporal distribution, and influencing factors of 16 polycyclic aromatic hydrocarbons (PAHs) in the sediments of Poyang Lake were studied, and a quantitative source analysis of PAHs in different areas of the lake was conducted. PAHs were widespread within the sediments. The concentrations of ∑16PAHs in the surface sediments of all sites ranged from 203 to 2 318 µg·kg-1. The concentrations of PAHs in the surface sediments of the lake body were higher than those in the surface sediments of the inlet rivers. The ratio of PAHs in Poyang Lake was 4 rings > 5 rings > 6 rings > 3 rings > 2 rings; the composition of 4-ring PAHs was dominant, and its content accounted for 86.11% of ∑16PAHs. The 2- and 3-ring and some 4-ring PAHs, including Flua and Pyr, were more susceptible to SOM, and the 4 through 6-ring PAHs were more susceptible to ORP and heavy metals and other environmental factors. Spatially, the higher concentration of ∑16PAHs occurred in the area of the lake adjacent to Duchang County and Poyang County, where the terrain was relatively closed, and the water exchange with the surrounding area was less than that in other sections, which was not conducive to the migration, transformation, and degradation of pollutants. In the temporal distribution, the changes in PAHs concentration level and the development of GDP in Jiangxi Province showed high consistency, and the influence of economic development and human activities might have been the main reason for the increasing PAHs concentration level. The main sources of PAHs in surface sediments of Poyang Lake included petroleum pollution and oil and coal and biomass combustion sources, and there were some spatial differences in PAHs sources in different regions. This study can provide a reference for PAHs pollution in surface sediments of Poyang Lake, which is important for the ecological environmental protection and management of Poyang Lake.

[Augmenting locking plate with autologous bone graft for the treatment of nonunion of long bone fracture in the lower extremity with retaining of the original intramedullary nail].

OBJECTIVE: To explore clinical effect of attaching locking plate with bone grafting based on retaining the original intramedullary nail in treating non-union after intramedullary nail fixation of long shaft fractures of lower limbs. METHODS: A retrospective study was conducted on 20 patients treated with non-union fractures after intramedullary nailing of long shaft fractures of lower limbs from June 2015 to June 2020. All patients were treated with the original intramedullary nailing and bone grafting from the iliac bone, and were underwent open reduction plate internal fixation and bone grafting for old fractures. Among them, 14 were males and 6 were females, aged from 35 to 56 years old with an average of (42.2±9.6) years old. Nine patients were femoral shaft fracture and 11 patients were tibial shaft fracture. According to characteristics of fracture end nonunion, 6 patients were stable/atrophic, 9 patients were unstable/large, and 5 patients were unstable/atrophic. The nonunion time ranged from 8 to 12 months with an average of(9.8±2.0) months after the initial surgery. Visual analogue scale (VAS), knee range of motion, bone healing time, complications and fracture-end healing were recorded before and at the latest follow-up. RESULTS: All patients were followed up for 18 to 48 months with an average of (36.3±10.5) months. The incision of all patients were healed at stageⅠwithout complications such as infection or internal fixation ruptur. Healing time of femur and tibia was (8.5±2.6) months and (9.5±2.2) months. Knee joint motion increased from preoperative (101.05±8.98) ° to postoperative (139.35±8.78) ° at the latest follow-up (t=-12.845, P<0.001). VAS decreased from preoperative (5.15±1.72) to postoperative (0.75±0.96) at the latest follow-up (t=11.186, P<0.001). CONCLUSION: On the basis of retaining the original intramedullary nail, the addition of locking plate internal fixation and autogenous iliac bone grafting have advantages of simple operation, less trauma, fewer complications and high fracture healing rate. It is one of the effective surgical schemes for the treatment of nonunion after intramedullary nail fixation of long bone fracture of lower extremity.

Nonadiabatic Derivative Couplings Calculated Using Information of Potential Energy Surfaces without Wavefunctions: Ab Initio and Machine Learning Implementations.

In this work, we implemented an approximate algorithm for calculating nonadiabatic coupling matrix elements (NACMEs) of a polyatomic system with ab initio methods and machine learning (ML) models. Utilizing this algorithm, one can calculate NACMEs using only the information of potential energy surfaces (PESs), i.e., energies, and gradients as well as Hessian matrix elements. We used a realistic system, namely CH2NH, to compare NACMEs calculated by this approximate PES-based algorithm and the accurate wavefunction-based algorithm. Our results show that this approximate PES-based algorithm can give very accurate results comparable to the wavefunction-based algorithm except at energetically degenerate points, i.e., conical intersections. We also tested a machine learning (ML)-trained model with this approximate PES-based algorithm, which also supplied similarly accurate NACMEs but more efficiently. The advantage of this PES-based algorithm is its significant potential to combine with electronic structure methods that do not implement wavefunction-based algorithms, low-scaling energy-based fragment methods, etc., and in particular efficient ML models, to compute NACMEs. The present work could encourage further research on nonadiabatic processes of large systems simulated by ab initio nonadiabatic dynamics simulation methods in which NACMEs are always required.

[Kinetic Release Characteristics of Organic Phosphorus of Sediment-water and Water Quality Risks].

To reveal the characteristics of organic phosphorus release from lake sediments and its potential impact on water quality, six lake sediments from Yunnan Plateau and the middle and lower reaches of the Yangtze River in China were selected. We studied the differences in the kinetics of dissolved organic phosphorus (DOP) and dissolved inorganic phosphorus (SRP) release from sediments. The effects of organic phosphorus morphology and dissolved organic matter (DOM) characteristics on sediment phosphorus release were investigated, and the water quality risks of sediment DOP release were discussed. The results showed that:① the release kinetics of sediment DOP and SRP were similar; both followed the second-order kinetic model, starting with a rapid release phase, followed by a slow release, and the release curve gradually leveled off and reached the maximum release. ② The release of organic phosphorus was related to organophosphorus morphology and organic matter. Active organic phosphorus (LOP) and medium active organic phosphorus (MLOP) were the DOP forms mainly released into the overlying water during the rapid release phase. The proportion of LOP and MLOP to total organic phosphorus (DTP) decreased in the late release stage, whereas the proportion of non-active organic phosphorus (NLOP) increased; further, the degree of humification and aromaticity of organic matter gradually increased with phosphorus release, and its activity decreased, resulting in a slower release rate at the later stage. ③ Compared with that of SRP, the risk of DOP release was higher, accounting for 47%-77% of the total amount of DTP. It was also found that the higher the nutrient level of the lake, the greater the release of DOP and the higher the water quality risk. Therefore, not only the release of inorganic phosphorus but also that of organic phosphorus should be of concern in the process of phosphorus release from lake sediments to prevent the underestimation of phosphorus release and water quality risk.

[Spatio-Temporal Variation of Release Flux of Sediment Nitrogen and Phosphorus in High-Risk Period of Algal Bloom in Lake Erhai].

Spatial and temporal characteristics of release fluxes of sediment nitrogen (N) and phosphorus (P) were investigated in the high-risk period of algal blooms in Lake Erhai. Moreover, the influence factors were examined. Results show that the release flux of N and P increased in recent years, exhibiting a clear increase in the period from 2009 to 2013, and a slight increase in the period since 2013. The release flux of dissolved total nitrogen (DTN) ranged between 11.71-14.15 mg·(m2·d)-1, within which the release flux of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) were 6.39-8.42 mg·(m2·d)-1 and 5.31-5.73 mg·(m2·d)-1, accounting for 58% and 42% of the DTN, respectively. The release flux of dissolved total phosphorus (DTP) ranged between 0.11-0.14 mg·(m2·d)-1, within which the release flux of dissolved organic phosphorus (DOP) and dissolved inorganic phosphorus (DIP) were 0.04-0.05 mg·(m2·d)-1 and 0.07-0.09 mg·(m2·d)-1, accounting for 34% and 66% of the DTP, respectively. The distribution of release flux of N showed a decreasing order:south > north > middle, while P was north > middle > south. The release flux of N increased by 17%, 13% and 23%, and the release flux of P increased by 19%, 28%, and 29% in north, middle, and south part of Lake Erhai from 2009 to 2018. Comparing the years 2009, 2013 and 2018, although the contents of N and P were stable, the release flux of N and P in the sediment was enhanced due to increasing pH and decreasing DO. Therefore, the increasing release of nitrogen and phosphorus from sediments, caused by changes in the water environment factors, should be paid attention to for the protection of Lake Erhai.

[Correlation Analysis of Water Quality Between Lake Inflow and Outflow: A Case Study of Poyang Lake].

The relationships between inflow and outflow water quality data for Poyang Lake from 1996 to 2016 are discussed and the main influencing factors are identified. TN and TP were the main factors causing a decline in water quality in Poyang Lake during the study period. The water quality of both the inflow and outflow rivers was generally good between 1996 and 2003; however, water quality declined over the study period, which is attributed to an increase in nutrients loads in the watershed. From 2004 to 2011, the water quality of the "Five Rivers" decreased significantly, which caused the water quality of Poyang Lake to decline. Due to the high purification capacity of Poyang Lake, the water quality of the outflow during this period was relatively good. A decline in water quality after this point was affected by pollution loads and hydrological conditions. Specifically, from 2012 to 2016, water quality in Poyang Lake and of the inflow water declined further. This was combined with a decrease in the water-purification capacity of the lake due to changes in the hydrological conditions, resulting in lower water quality at the outflow. Overall, the water quality of the inflow river has been closely related to the water quality in Poyang Lake. The concentrations of TN were significantly higher in the southern and eastern areas of Poyang Lake compared to the western areas. Higher nutrient loading from the Ganjiang River and the Xinjiang River has been an important driver. The concentrations of TP in the southern area of the lake have been significantly higher than in the eastern and western areas. This is attributed to comparatively high TP loads in the Ganjiang River and the Fuhe River. Compared to the changes in hydrological conditions, variations in nutrient loading have had a greater effect on water quality in the lake.

[Effects and Differences of the Release of Dissolved Organic and Inorganic Phosphorus in Different Sediments Covered by Different Materials of Erhai Lake].

In this work, the effects of four covering materials on the release of total dissolved phosphorus (DTP), dissolved organic phosphorus (DOP), and soluble reactive P (SRP) in different sediments of Erhai Lake were simulated. The results showed that the max release of DTP was reduced in covering material, which attributed to the changes of pH, Eh and characteristics of dissolved organic matter (DOM) by the effect of covering material. The application of iron oxide material significant reduced the release of DTP in the northern and southern part of the lake, with decrease rate of 44.3% and 35.7%, respectively. by contrast, the application of aluminum oxide material significant reduced the release of DTP in the middle part sediment, with decrease rate of 29.6%. Furthermore, the release of SRP and DOP in different sediments has significant difference after added different material. In northern part of sediment, the release of SRP and DOP reduced by 35.6% and 36.2% after added iron oxide material. This is because iron oxide can reduce the pH and Eh but increase the availability of DOM in northern, and then benefits for inhibiting the release of SRP and DOP. In the middle, the release of sediment SRP and DOP reduced by 28.9% and 31.6% after added aluminum oxide material. This is because the aluminum oxide can facilitate the availability of DOM in middle, and then inhibits the release of SRP and DOP. In southern part of the lake, the release of sediment SRP and DOP reduced by 47.4% and 16.5% after added iron oxide material. This is largely attributed to the effect of iron oxide on the pH and Eh. Therefore, to control the release of P in the sediment from Lake Erhai, iron oxide material should be selected in the northern and southern parts, whereas aluminum oxide should be selected in the middle part of the lake.

[Characteristics of Water Extractable Organic Nitrogen from Erhai Lake Sediment and Its Differences with Other Sources].

The 47 samples from Erhai Lake surface sediments were collected in different seasons. The distribution and structure characteristics of sediment water extractable organic nitrogen(WEON) were investigated by using the combined techniques of UV-Vis absorption and three-dimensional excitation-emission matrix spectra(3DEEMs). The differences in DON of various sources(overlying water, pore water, inflow Rivers and wet deposition) were explored to analyze its effects on sediment. The results showed that:1the temporal distribution followed the pattern of summer > spring > autumn > winter, with the spatial WEON distribution of northern > southern > central. 2 The humic degree of Erhai sediment WEON was relatively high and mostly composed of fulvic acid, which mainly contained UV-like humic-like fluorescence peak A and high-excited tryptophan fluorescence peak B. This indicated that it was mainly affected by terrestrial input and microbial activity. 3 There were two fluorescent components(C1, C2) in the sediments and other sources of Erhai Lake. The component C1 was the endogenous visible ultraviolet peak formed by biodegradation, while the component C2 was the tryptophan peak. The bioavailability of wet deposition samples was comparatively high, greatly impacting Erhai Lake in heavy rainfall. The DON bioavailability in the inflow river was the lowest, which was prone to be accumulated in sediments. 4The DON component C1 and C2 in overlying water had significant negative correlation with Erhai sediment WEON contents(r=-0.79, P<0.01;r=-0.944, P<0.01). This suggested that the overlying water DON components could indirectly reflect the sediment WEON content of Erhai Lake, namely the higher the fluorescence components C1 and C2 in overlying water DON were, the lower the sediment WEON content was.

[Temporal and Spatial Variation Characteristics of Nitrogen and Phosphorus in Sediment Pore Water and Overlying Water of Dianchi Caohai Lake].

The vertical variation in the contents of nitrogen and phosphorus with different forms in pore water and overlying water was continuously measured for twelve months in Dianchi Caohai Lake. The research revealed the difference of N or P concentration between pore water and overlying water and the contribution of nitrogen and phosphorus forms. It is significant to understand the formation of N and P and the ratio of N/P in pore water in the fields of lake eutrophication and the control of internal nutrient-loading. The results demonstrated that:①Sediment pore water ρ(NH4+-N) was significantly higher than that in overlying water. But for NO3--N, it obeyed the opposite rule. From Feb. to Nov., ρ(SRP) was higher than that in overlying water, while the opposite rule was found in Dec. and Jan.. ②In sediment pore water, ρ(NH4+-N) or ρ(SRP) presented the maximum contribution ratio of DTN (78%) or DTP (61%), respectively. While, in overlying water, the maximum contribution ratio was DON(44%) or DOP(81%), respectively. Compared to those in spring and winter, the contribution of ρ(NH4+-N) and ρ(SRP) increased distinctly and the contribution of ρ(NO3--N), ρ(DON) and ρ(DOP) dropped obviously in summer and autumn. ③The temporal variations for the ratios of DTN/DTP, (NH4+-N+NO3--N)/SRP and DON/DOP in pore water were all in the following sequence:spring> winter> summer> autumn. In overlying water, the N/P ratio in spring was relatively higher than that in the other three seasons.

[Compositional Characteristics of Sediment Dissolved Organic Nitrogen in Typical Lakes and Its Relationship on Water Trophic Status].

UV-Vis absorbance, fluorescence, and Gas Chromatography Mass Spectrometry (GC-MS) were applied to the comparative study on sediment dissolved organic nitrogen (DON) in five typical lakes (Erhai lake, Dianchilake, Poyang lake, Wuhan Dong lake, and Taihu lake) in different lake regions with different nutrition status, revealing the relationship between structural and compositional characteristics of sediment DON and trophic level of lakes. The obtained results showed that: ①Structure of lake sediment DON in Yungui Plateau region is more stable, compared with those in Eastern Plain region, indicating its lower bioavailability. ②In Yungui Plateau region, the source and compositional characteristics of sediment DON weremore complex in Dianchi lake (a seriously polluted lake), and its sediment DON bioavailabilitywas relatively higher. While, with respect to the less polluted Erhai lake, the source of sediment DON is more simple with a higher stability in DON structure and composition, which is beneficial for maintaining its good water quality. ③In Eastern Plain region, nutrition status of Taihu lake was similer to Donghu lake. The structure and composition of sediment DON was complex. But the lower aromaticityand fewer Aromatic ring substituents abundance made their relatively weak nutrient retention ability, posing risk to water quality. With regard to Poyang Lake, the structure and composition of sediment DON was relatively simple, but nutrient retention ability was relatively strong, which played a positive role in maintaining good water quality. ④P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) values(the content ratio of humic-like substanceto protein-like substances)were in sequence of Dianchi Lake (33.14)>Erhai Lake(21.49)>Taihu Lake(9.06)>Donghu Lake(7.04)>Poyang Lake(4.83), while E(4)/E(6) values (the ratio of UV-Vis absorbance at 465 and 665 nm) were in sequence of Dianchi Lake (27.00)>Donghu Lake(6.65)>Poyang Lake(5.47)>Taihu(3.50)>Erhai Lake(2.31). In addition, P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) and E(4)/E(6) valueswere positively correlated with thecontents of the different nitrogen (N) forms in the sediments. The above information suggested that P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) and E(4)/E(6) values exhibited good discrimination degree among different trophic status lakes, and they were considered to indirectly indicate the nutrition levels of lakes to a certain extent.

[Concentration of Phosphorus in Sediments Interstitial Water as Affected by Distribution of Aquatic Plants in Dianchi Lake].

In order to reveal the effect of aquatic plants distribution on the mass concentration of phosphorus in sediment interstitial water, the mass concentrations of Dissolved Total Phosphorus (DTP), Soluble Reactive Phosphorus (SRP) and Dissolved Organic Phosphorus (DOP) in the sediment interstitial water and overlying water from areas with or without plants in the same site of Dianchi were studied. The vertical variation characteristics of phosphorus forms in sediment interstitial water were analyzed to explore the effect of aquatic plants on the phosphorus forms in sediment interstitial water. The results showed: ①Aquatic plants had an significant effect on the phosphorus mass concentration of the sediment interstitial water in different Dianchi lakes. However, they varied with different distribution sites and depth. ②Aquatic plants significantly decreased the percentage of DOP contribution in the sediment interstitial water. The average contribution of DOP with aquatic plants was 32.87%, while that without plants reached 57.68%; ③Aquatic plants significantly inhibited the release of inorganic phosphorus in sediments and promoted the transformation of DOP. The SRP diffusion flux at sediment-water interface with aquatic plants was increased by 39.99% as compared with that without plants; ④The growth of aquatic plants significantly reduced the concentration of phosphorus in sediment interstitial water, especially DOP, and the reduction rate of the sediment interstitial water DOP was from 38.02% to 85.49%. Therefore, the analysis of the contribution and reduction rate of aquatic plants on the sediment interstitial water DOP was of great importance in understanding the relationship between aquatic plants and DOP, as well as the mineralization of organic phosphorus in sediments.

[Gas Transfer Velocity of CH4 at Extremely Low Wind Speeds].

Thin boundary theory equation (TBL) is widely used to determine gas fluxes across water-air interfaces, and the gas transfer velocity (k600) is the key environmental factor in the equation. A monthly field campaign was carried out during one year to measure CH4 flux and to probe its exchange rate across the air-water interface in a drinking reservoir and 5 adjacent ponds. The ranges of wind speed and surface water temperature were 0-0.75 m·s-1 and 6.3-30.9℃respectively, and their average values were 0.19 m·s-1 and 19.3℃ respectively. The gas transfer velocity of CH4 varied from 0.20 to 1.99 cm·h-1 with an average of 0.50 cm·h-1. Correlation functions between the gas transfer velocity and the wind speed at 10 m height (U10) and surface water temperature (Tw) were given here to quantify k600. There were significant correlations between the fitted values and actual values both for original and bin-averaged data.

[Vertical Variation of Phosphorus Forms in Lake Dianchi and Contribution to Release].

Columnar sediment samples were collected from the Waihai of Lake Dianchi in northern, central and southern sediment, combined with the data of phosphorus in the overlying water and sediment organic matter, the effects of organic matter and particle size on sediment release were studied, and the influence of different forms of phosphorus release from sediments and their contributions were discussed. The results showed:Sediment pore water ρ(DTP) and ρ(SRP) was negatively correlated with contents of OM, clay (<4.00 µm) and silt (4.00-63.00 µm), but it showed a significant positive correlation with sand (>63.00 µm) content. Theincrease in organic matter content of the sediments significantly reduced the gap water phosphorus mass concentration, and increasing clay and silt contents reduced the gap water phosphorus mass concentration, inhibiting the release of phosphorus in sediments. Potentially mobile phosphorus of the Lake Dianchi sediment was significantly positively correlated with the clay and silt contents, and was significantly negatively correlated with the sand content. It was indicated that clay and silt may enhance the phosphorus movement ability of the sediment, and the sand may enhance the retention of phosphorus in the sediment. In a short time scale, phosphorus of sediment was released mainly in northern Waihai, staying mainly in central and southern; in a longer time scale, phosphorus of sediment was released mainly in northern and central Waihai, staying mainly in southern. Control of phosphorus release from sediments in Lake Dianchi should take into account the effects of different forms of phosphorus, organic matter and particle size, and take corresponding measures to control the release of phosphorus in sediments of northern Dianchi mainly.

[Characteristics of nitrogen pollution and the potential mineralization in surface sediments of Dianchi Lake].

The nitrogen content, its different forms and their spatial distribution were studied by using the 53 sediment samples from different sites in Dianchi Lake. Thereafter, the potential nitrogen mineralization ability of the sediments and their pollution characteristics were also explored to understand the influencing factors of nitrogen pollution and its release risk from the sediment surface to the overlying water of Dianchi. The results showed: (1) the average total nitrogen content of surface sediment in Dianchi Lake was 3 515. 60 mg x kg(-1), which was at a high level from the inlets in Caohai Northeast thinning digging area, Panlong River and the Haikou into Dianchi Lake, but relatively low in Baoxiang River Estuary dredging area. The total organic nitrogen (TON) content, accounting for 85.86% of TN, was at a high level; on the other hand, the dissolved inorganic nitrogen ( DIN) content was lower, which accounted for 14.10% of TN. The spatial distribution of TON and TN kept the same trend, but not the DIN. Compared with other Lakes of China, the nitrogen content of sediment in Dianci was at a high level, and the extent of pollution was just below the serious polluted City Lakes. (2) The average potential mineralizable nitrogen (PMN) content of Lake Dianchi was 1 154.76 mg x kg(-1), accounting for 32.90% of TN, which raised the potential risk of its release into the overlying water. Higher PMN was found in the Caohai Lake area and the inlet of Panlong River in the North, the inlet of Luolong Rive in the Middle Lake, the inlet of Baiyukou Lake and Liangwang River in the South. Nowadays, the pH value of Dianchi Lake was favorable for its sediment nitrogen mineralization, and its nitrogen mineralization was affected by the release of NH4(+) -N from organic matter. In the heavy polluted area, the concentration of the overlying water nitrogen was seriously affected by nitrogen mineralization of sediment from Dianchi, while the light polluted area was less affected.

[Distribution of transferable nitrogen in Poyang Lake sediments and its response to the variation of River-Lake relationship].

Amounts and distributions of total transferable nitrogen and different transferable nitrogen forms were studied in the sediments of Poyang Lake with different regimen, in order to reveal the influence of the water level change caused by the River-Lake relationship change on the potential release risks of nitrogen. The results showed that: (1) the contents of the total nitrogen (TN) were between 389 and 3865 mg x kg(-1), and the spatial distribution showed an overall downward trend in the "Five River", the "Hu Xin" and the northern regions; the contents of the transferable total nitrogen (TTN) were between 319.36 and 904.56 mg x kg(-1) and contributed 52% to the TN, and its spatial distribution trend was the same as that of TN. (2) The content of transferable nitrogen followed the order of SOEF-N approximately = SAEF-N > WAEF-N > IEF-N. (3) The dry period advanced and the low water level continued to decline as a result of the change in River-Lake relationship of the Poyang Lake, leading to the prolonged outcropped time of sediments and the increased area, causing the different contents of transferable nitrogen in the sediments at different elevations. The transferable nitrogen content of the sediments in the whole lake during the wet period was lower than that during the dry period. The content of transferable nitrogen followed the order of 12-13 m elevation sediment > 11-12 m elevation deposition material > 10-11 m elevation sediments. The higher the elevation, the longer the sediments were exposed, and the higher the transferable nitrogen content. (4) With the increase of elevation, all forms of N contents increased. The increase of IEF-N and SOEF-N contents as well as their percentages in total transferable nitrogen was relatively small, while the increase of WAEF-N and SAEF-N contents as well as their percentages in total transferable nitrogen was relatively large. If the river-lake relationship changes further, the elevation in the dry period will further decrease, which will lead to the enlarged area and prolonged exposure of sediments, resulting in increase of TN, transferable nitrogen, IEF-N and SOEF-N contents in the sediments. At the coming wet period of next year, the nitrogen release risk from sediments of Poyang Lake might increase.

[Optical signatures of chromophoric dissolved organic matter in water body of Tien Lake].

The water samples of the Tien Lake were collected for the three-dimensional fluorescence spectrum detected. And parallel factor analysis (PARAFAC) and principal component analysis (PCA) were used for the spectra analyzing to know the main factor and relative contribution of the chromophoric dissolved organic matter (CDOM). PARAFAC decomposed CDOM into four components, the humic-like: C1 (240, 415), C3 (265, 525), C4 (255, 505) and the protein-like: C2(230/280, 330). The fluorescence intensity of CDOM components was high in north and estuary of the lake, but low in the other region. All the four components show significant positive correlations (p < 0.01), this result means they may have the same sources. Principal component analysis shows that these four components of the Tien Lake are all from terrestrial organic matter, meanwhile its DTN, DTP, DON may also come with the terrestrial substance. These components of Tien Lake can well be connected with dissolved nutrient salts by nonlinear multiple regression, which means we can use the three-dimensional fluorescence spectrum results of CDOM to indicate the eutrophication degree of Tien Lake.

[Influence of the river-lake relation change on the distribution of heavy metal and ecological risk assessment in the surface sediment of Poyang Lake].

Effects of river (Yangtze River)-lake (Poyang Lake) relation on the distribution and potential ecological risk of Cu, Pb, Zn, Cr and Cd were investigated in surface sediment of Poyang Lake under different waterregimens. The results indicated: (1) the sediments of Poyang Lake were polluted by various concentrations of heavy metals mainly originated from particulates of Yangtze River, and Cu and Pb were the main pollution factors. The pollution level of determined heavy metals followed the order of Cu > Pb > Zn > Cr >Cd. The concentration ranges of Cu, Pb, Zn, Cr and Cd in the sediment of Poyang Lake were 13.1-108.1 mg.kg-1 , 37-119.1 mg.kg-1, 29.9-129.9 mgkg-1, 13.3-98.6 mgkg-1 and 0. 19-2.77 mg.kg-1 during the wet period, and 3.05-69.7 mg.kg-1, 27.5-105 mgkg-1, 18.8-95.4 mg.kg-1, 7.34-70 mg.kg- and 0.033-0.406 mg.kg-1 during the dry period respectively. The region with the highest heavy metal concentrations was located in water input area of the " Five River" and water output area of " Hukou" ; (2)The regions with high risk of heavy metals in sediment were mainly located in the area of the trail of "Five Rivers" during the wet period; while during the dry period, the area with high risk of heavy metals in sediment enlarged, which was not only limited in the area of the trail of "Five Rivers", but also enlarged northwards. The potential ecological risk of "Hukou" was relatively high, however, the potential ecological risk of the sediment in the whole lake during the dry period was lower than that during the wet period. (3) With the change of river-lake relation, water level rose, the maintaining time was shortened during the wet period, the dry season appeared ahead of schedule, the transformation course of Poyang Lake from "Lake morphology" to " River morphology" increased, and the typical river properties were enhanced, which resulted in the decreased potential ecological risk of heavy metals in sediment of the whole lake, however, the area of high risk-region was enlarged northwards.

[Characteristics and bioavailability of organic phosphorus from different sources of sediments in Dianchi Lake].

The content and vertical distribution characteristics of organic phosphorus were studied by collecting core sediments of Dianchi Lake, characterizing the bioavailability of different organic phosphorus species of these sediments by enzymatic hydrolysis. The results indicated that, (1) The inorganic phosphorus represented primary portions of extractable phosphorus of sediments in Dianchi Lake, except for the H2O extractable organic phosphorus (H2O-P(o)). The rank of order of organic phosphorus fractionation in sediments was NaOH extractable organic phosphorus (NaOH-P(o)) > NaHCO3 extractable organic phosphorus (NaHCO3-P(o)) > H2O-P(o) > HCl extractable organic phosphorus (HCl-P(o)). The vertical distribution of NaOH-P(o), NaHCO3-P(o) and H2O-P(o) with relatively high mobility showed the trend of topper layer > middle layer > bottom layer. (2) Labile monoester P predominated in enzymatically hydrolysable phosphorus (EHP) of sediments in Dianchi Lake. The EHP content of NaOH-P0, NaHCO3-Po and H20-P0 in sediments of Dianchi Lake were 0.11-5.93, 0-45.32 and 0-107.11 mg x kg(-1), respectively. The EHP content of different organic phosphorus species followed the order: NaOH-P(o) > NaHCO3-P(o) > H2O-P(o), with the trend of vertical distribution of topper layer > middle layer > bottom layer. The bioavailability of organic phosphorus of different depth showed the order of topper layer > middle layer > bottom layer. (3) EHP was a considerable source of the bioavailable phosphorus of sediments in Dianchi Lake. The protection of water quality in Dianchi Lake should consider the effects of EHP in sediments. When the external phosphorus load was restricted gradually, the biogeochemical cycle of EHP in sediments might play an important role in maintaining the eutrophication of Dianchi Lake.

[Bioavailability of dissolved organic nitrogen components in the lake sediment to alage].

Samples in the sediments of Wuliangsuhai and Erhai Lake were selected, and the technologies of XAD-8 resins separation and three dimensional fluorescence excitation-emission matrix (3DEEM) spectra were applied, in order to study the bioavailability of dissolved organic nitrogen components to alage under the room cultivation. The obtained results showed that: (1) Average loss of DON and DOC from sediments was below 5% after dividing DON into different groups, which means the technology of XAD- 8 resins separation could be used in the study of DON components in the lake sediment. (2) Through 3DEEM analysis, hydrophilic and hydrophobic DON was dominated by protein-like and humic-like materials in the lake sediment, respectively. (3) Under the hydrophilic component condition, growth curves of algae tended to show an "S" shape with a straight upward trend in the sediments of Wuliangsuhai and Erhai lake,with the maximum algal density reaching 535.5 x 10(4) and 709.5 x 10(4) per milliliter, respectively. Meanwhile, the DON concentrations were significantly reduced after cultivation to 2.46 and 2.98 mg x L(-1), respectively, which suggests that hydrophilic DON in the lake sediment was the bioavailable organic nitrogen for alage. (4) Under the hydrophbic component conditions, growth curves of algae tended to show a "unimodal" shape in the sediments of Wuliangsuhai and Erhai lake,with the maximum algal density reaching 113.5 x 10(4) and 275.5 x 10(4) per milliliter,respectively. The DON concentrations were significantly reduced during the early cultivation period, and then kept stable in the late period, which suggests that the hydrophobic DON component bioavailable to alage was low in short-term, and the hydrophobic DON component had hardly any positive effect on the growth of algae.