Association of individual resilience with organizational resilience, perceived social support, and job performance among healthcare professionals in township health centers of China during the COVID-19 pandemic.

Background: Primary healthcare professionals were overworked and psychologically overwhelmed during the COVID-19 pandemic. Resilience is an important shield for individuals to cope with psychological stress and improve performance in crises. This study aims to explore the association of individual resilience with organizational resilience, perceived social support and job performance among healthcare professionals in township health centers of China during the COVID-19 pandemic. Methods: Data from 1,266 questionnaires were collected through a cross-sectional survey conducted in December 2021 in Shandong Province, China. Descriptive analysis of individual resilience, organizational resilience, perceived social support, and job performance was conducted. Pearson correlation analysis was used to examine the correlations among these variables, and structural equation modeling was performed to verify the relationships between these variables. Results: The score of individual resilience was 101.67 ± 14.29, ranging from 24 to 120. Organizational resilience (ß = 0.409, p < 0.01) and perceived social support (ß = 0.410, p < 0.01) had significant direct effects on individual resilience. Individual resilience (ß = 0.709, p < 0.01) had a significant direct effect on job performance. Organizational resilience (ß = 0.290, p < 0.01) and perceived social support (ß = 0.291, p < 0.01) had significant indirect effects on job performance. Conclusion: During the COVID-19 pandemic, the individual resilience of healthcare professionals in township health centers was at a moderate level. Organizational resilience and perceived social support positively affected individual resilience, and individual resilience positively affected job performance. Furthermore, individual resilience mediated the effect of organizational resilience and perceived social support on job performance. It is recommended that multiple stakeholders work together to improve the individual resilience of primary healthcare professionals.

Dredging method effects on sediment resuspension and nutrient release across the sediment-water interface in Lake Taihu, China.

Environmental sediment dredging is one of the most common methods for the remediation of contaminated sediments in lakes; however, debate continues as to whether the effectiveness of dredging methods contributes to this phenomenon. To determine sediment resuspension and nutrient release following dredging with a variety of dredging methods, four dredging treatments at wind speeds of 0-5.2 m/s were simulated in this study, namely suction dredging (SD), grab dredging (GD), ideal dredging with no residual sediments (ID), and non-dredging (ND). Field sediments from suction and grab dredging areas (including post-dredged and non-dredged sediments) of Lake Taihu were used to assess the release abilities of soluble reactive phosphorus (SRP) and ammonia nitrogen (NH4+-N) from the sediment-water interface. The effects of residual sediments on nutrient concentrations in water were also evaluated. The results reveal that inhibition of resuspension of particulate matter and nutrients released through sediment dredging decreases with increasing levels of residual sediment. Total suspended particulate matter content in the mean water columns of ID, SD, and GD under wind-induced disturbance (1.7-5.2 m/s) decreased by 67.5%, 56.8%, and 44.3%, respectively; total nitrogen and total phosphorus in ID (SD) treatments were 19.8% (12.9%) and 24.5% (11.2%) lower than that in ND treatment. However, there were ~ 1.6 and 1.5 times higher SRP and NH4+-N in the GD treatment compared with the ND treatment at the end of the resuspension experiment (0 m/s). A significant increase in the SRP and NH4+-N release rates at the sediment-water interface was also observed in field sediments from a grab dredging area, indicating that GD may pose a short-term risk of nutrient release to the water body. Hence, dredging methods with less residual sediments both during and after dredging improves the dredging quality.

Preliminary evidence of nutrients release from sediment in response to oxygen across benthic oxidation layer by a long-term field trial.

In aquatic ecosystems, ecological processes such as organic matter mineralization and nutrient cycling are regulated by benthic O2 in sediments, and application of in situ techniques in field environments has the potential to better define the links between O2 dynamics and the unique biogeochemical phenomena occurring in these regions. The effects of benthic O2 on sediment nutrients release were identified on the basis of field specific observations conducted over one and a half years at Taihu Lake. Sediment dredging (SD) practices have sharply reworked the benthic boundary oxidation layer, and the oxygen penetration depth (OPD) in the SD responded as expected to the new-born surface, increasing immediately (7.5 ± 0.8 - 10.5 ± 0.6 mm) after dredging, then further increasing with an unusually high heterogeneity when a significant submersed macrophytes (SM) coverage of about 40% was implemented. Multiple correlation analysis revealed that OPD was responsible for PO43- and NH4+ release. A lower benthic oxygen flux was immediately observed in dredging-related sediments in the case of dredging compared to SM or the control (CK), which suggested that oxygen demand is low in the uppermost sediments because of the degradable fresh organic carbon removal. SD and SDSM implementation was most successful at continuously reducing the size of PO43- released from sediments over one and a half years, and a significant seasonal-dependent release was also observed. The direction of flux was consistent among SD and SDSM, suggesting the potential to reduce internal PO43- release even further with the invasion of SM communities. Our results indicated that ecological engineering practices could alleviate internal nutrient loads from the contaminated bottom sediment, which was probably in positive response to benthic oxygen changes.

Optimum dredging time for inhibition and prevention of algae-induced black blooms in Lake Taihu, China.

Dredging, which is the removal of polluted surface sediments from a water body, is an effective means of preventing the formation of algae-induced black blooms. However, an inappropriate dredging time may contribute to rather than inhibit the formation of black blooms. To determine the optimum dredging time, four treatments were simulated with sediment samples collected from Lake Taihu: dredging in January 2014 (DW), April 2014 (DA), July 2014 (DS), and no dredging (UD). Results showed that typical characteristics associated with black blooms, such as high levels of nutrients (NH4 (+)-N and PO4 (3-)-P), Fe(2+), ∑S(2-) ([HS(-)] + [S(2-)]), and volatile organic sulfur compounds (VOSCs), including dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS), were more effectively suppressed in the water column by DW treatment than by UD treatment and the other two dredging treatments. The highest concentrations of NH4 (+)-N and PO4 (3-)-P in the UD water column were 4.09 and 4.03 times, respectively, those in the DW water column. DMS levels in the UD and DS water columns were significantly higher (p < 0.05) than those in the DW water column, but DMDS and DMTS levels were not significantly different between the treatments. After several months of dredging, surface sediments of the DW and DA treatments were well oxidized, and concentrations of Fe(2+) and ∑S(2-) were lower than those in UD and DS treatments because of material circulation between sediments and the water column. Water content, which is important for the transport of matter to the overlying water, was lower in the dredged sediments than in the undredged sediments. These factors can suppress the release of Fe(2+) and ∑S(2-) into the water column, thereby inhibiting the formation of black blooms. Black coloration occurred in the UD water column on the seventh day, 2 days later, and earlier, respectively, than the DW and DS water columns and almost on the same day as in the DA water column. This phenomenon is mainly attributed to the oxidation of the new sediment surface in the DW and DA water columns, suppressing the release of sulfur into the water column, because of a long incubation period. Thus, dredging in the winter can prevent the formation of black blooms, while dredging in summer may contribute to them.

[Environmental Effect of Substrate Amelioration on Lake: Effects on Phragmites communis Growth and Photosynthetic Fluorescence Characteristics].

Growth of rooted aquatic macrophytes was affected by the nature and composition of lake bottom sediments. Obviously, it has been recognized as an important ecological restoration measure by improving lake substrate and then reestablishing and restoring aquatic macrophytes in order to get rid of the environmental problem of lake. This study simulated five covering thickness to give an insight into the influence of substrate amelioration on Phragmites communis growth and photosynthetic fluorescence characteristics. The results showed that the total biomass, plant height, leaf length and leaf width of Phragmites communis under capping 5 cm were much more significant than those of capping 18 cm (P < 0.01), at the 120 d, the underground: shoot biomass ratio and fine root: underground biomass ratio were also much higher than those of other treatments (P < 0.05), which indicated that capping 18 cm treatment would significantly inhibit the growth of Phragmites communis , but the growth of control group Phragmites communis was slightly constrained by eutrophicated sediment. In addition, as the capping thickness growing, the underground: shoot biomass ratio of the plant would be reduced dramatically, in order to acquire much more nutrients from sediment for plant growing, the underground biomass of Phragmites communis would be preferentially developed, especially, the biomass of fine root. However, Photosystem II (PS II) photochemical efficiency (Fv/Fm), quantum yield (Yield), photochemical quenching (qP), non-photochemical quenching (qN) of Phragmites communis under different treatments had no significant differences (P > 0.05), furthermore, with much greater capping thickness, the photosynthesis structure of PS II would be much easier destroyed, and PS II would be protected by increasing heat dissipating and reducing leaf photosynthetic area and leaf light-captured pigment contents. In terms of the influence of sediment amelioration by soil exchange on the growth and photosynthetic fluorescence characteristics of Phragmites communis, plant growth could be effectively promoted under capping 2 cm and capping 5 cm by increasing the Eh value and nutrient content, whereas plant under capping 18 cm would be much easier adaptive to low-light stress in winter season, of which capping 2 cm treatment was conducive to enhance the initial slope of RLCs (α), maximum electron transport rate (ETRmax) and minimum saturating irradiance (Ek). With regard to the harness of environmental problem of lake, the eutrophication status of lake will be mitigated by using multi-ecological measures to control the internal nutrients content once the external loading was first effectively controlled.

[Simulation research on the release of internal nutrients affected by different dredging methods in lake].

A simulated experiment was carried out to study release features of internal source under different sediment dredging methods and the difference between two lake areas in Lake Taihu was also studied. The contaminated sediments were sampled from two sites in Meiliang Bay which were the Inner Bay (A) and the Outer Bay(B). Release rates of phosphorus after ideal dredging and suction dredging are about 20% and 72% of the control and the phosphorus release rate in Inner Bay(A) is about 80% of Outer Bay(B). Release rates of ammonia after ideal dredging and suction dredging are about 40% and 83% of the scallop dredging, but dredging process may even promote the release of ammonia in a short time, the ammonia release rate in Inner Bay(A) is about 150% higher than that in Outer Bay(B). Under the microcosm experiment condition, the ideal dredging method and the suction dredging method may have a better control of internal source in contrast with the scallop dredging. Altogether, sediment dredging may be a useful approach to decrease the release of internal source in the selected sites when the external nutrients are effectively controlled. Consider all kinds of dredging projects, the suction dredging should be the ideal option for sediment dredging in Lake Taihu.

[Black water bloom induced by different types of organic matters and forming mechanisms of major odorous compounds].

Self-made glass reactors were employed to study the occurrence of black water bloom induced by different types of organic matters, to clarify the precursor of volatile organic sulfur compounds (VOSCs), and then to preliminarily study its degradation mechanisms under laboratory-controlled conditions. Our research indicated that provided organic matrix were as high as 1.0 g x L(-1), all organic matters could blacken the lake water regardless of sulfur appearance or not. However, compared with sulfur-free compounds that took more than 13 d to blacken the water, sulfur containing materials could accelerate the occurrence of black color to 7-13 d and increase the water chromaticity to above 410 which causing offensive odor consisted chiefly of DMDS, DMTS and DMTeS. Based on the function of methionine on the production of VOSCs, methionine was identified to be the precursors of VOSCs. Methionine was readily broke down by sulfate-reducing bacteria (SRB) (also other bacteria) (at 95% with the duration of 35 d) to produce hydrogen sulfide, methanethiol, and dominantly dimethylpolysulfides such as DMDS, DMTS and DMTeS. And the occurrence of black color had been advanced from 13 d to 8 d. Methanogenic bacteria slightly inhibited the degradation of methionine and reduced the evolution of sulfide. Therefore, the addition of methanogenic bacteria inhibitor set the formation of black color ahead by 1 d. Methionine was also degraded by nonbiodegradation, but it was a secondary pathway and cannot completely degrade methionine to blacken the water.

[Influence of dredging on sediment resuspension and phosphorus transfer in lake: a simulation study].

A simulated experiment was conducted to investigate the impacts of sediment dredging on sediment resuspension and phosphorus transfer in the summer and winter seasons under the common wind-wave disturbance, and the contaminated sediment used in this study was from Meiliang Bay, Taihu lake. The result showed that 20 cm dredging could effectively inhibit the sediment resuspension in study area, dredging in winter has a better effect than that in summer, and the higher values of the total suspended solid (TSS) in undredged and dredged water column during the process of wind wave disturbance were 7.0 and 2.2, 24.3 and 6.4 times higher than the initial value in summer and winter simulation respectively. The paired-samples t-test result demonstrated that total phosphorus (TP) and phosphate (PO4(3-)-P) loading positively correlated to TSS content in dredged (P<0.01) and undredged water column (P<0.05), which proved that internal phosphorus fulminating release induced by wind-wave disturbance would significantly increase the TP and PO4(3-)-P loading in the water column. The effect of dredging conducted in summer on the TP and PO4(3)-P loading in the water column was negative, but not for winter dredging (P<0.01). The pore water dissolved reactive phosphorus (DRP) profile at water-sediment interface in summer simulation was also investigated by diffusive gradients in thin films (DGT) technique. Diffusion layer of the DRP profile in undredged sediment was wider than that in dredged sediment. However, the DRP diffusion potential in dredged sediment was greater than that in undredged sediment, showing that dredging can effectively reduce the risk of the DRP potential release in dredged pore water, but also would induce the DRP fulminating release in the short time under hydrodynamic action. Generally, dredging was usually deployed during the summer and the autumn. Considering Taihu Lake is a large, shallow, eutrophic lake and the contaminant distribution is spatially heterogeneous, it is vital to determine the optimal time, depth and scope of dredging.

[Purification effects of large-area planting water hyacinth on water environment of Zhushan Bay, Lake Taihu].

Using water hyacinth and other fast-growing and high biomass of floating plants to purify polluted water has become an efficient and effective ecological restoration method at present. Effects of nutrients adsorption and water purification of planting water hyacinth on water quality in Zhushan Bay were studied. The results indicated that no anoxia was observed in water hyacinth planting areas because of wave disturbance and strong water exchange. Concentrations of TN and TP in water hyacinth planting areas were higher than that in the outside of stocking area (the content ranged 3.03-7.45 mg/L and 0.15-0.38 mg/L, respectively), and the content changes ranged 3.37-8.02 mg/L and 0.15-0.36 mg/L,respectively. The higher concentration of TN and TP in water indicated the water body was heavily polluted. Water hyacinth roots have a strong ability to adsorb suspended solids and algae cells, the concentration of Chl-a in stocking areas was higher than that in stocking fringe and outside, the maximum Chlorophyll in the stocking region in August was 177.01 mg/m3, and at the same time the concentrations in planting fringe and outside were 101.53 mg/m3 and 76.96 mg/m, respectively. Higher Chl-a content on water hyacinth roots indicated that water hyacinth had strong blocking effects on algae cells, and demonstrated it had a great purification effects on eutrophicated water, and it also provides a basis for the larger polluted water bodies purification in using water hyacinth.

[Impacts of Asian clams (Corbicula fluminea) on lake sediment properties and phosphorus movement].

To examine the impact of Corbicula fluminea on sediment properties and phosphorus dynamics across sediment-water interface in lake, the microcosm experiment was carried out with sediment and lake water from the estuary of Dapu River, a eutrophic area in Taihu Lake. Rhizon samplers were used to acquire pore water, and soluble reactive phosphorus (SRP) flux across sediment-water interface and sediment properties were determined. The activity of C. fluminea destroyed the initial sediment structure, mixed sediment in different depths, increased oxygen penetration depth, sediment water content, and total microbial activity in sediment. The downward movement of overlying water was enhanced by the activity of C. fluminea, which decreased Fe2+ in pore water by oxidation. The production of ferric iron oxyhydroxide adsorbed SRP from pore water and decreased SRP concentration in pore water, and this increased iron bound phosphorus in corresponding sediment. The emergence of C. fluminea accelerated SRP release from sediment to overlying water, and enhanced SRP flux increased with the rise of introduced C. fluminea density. Metabolization of C. fluminea might play an important role in accelerating SRP release.

[Mechanism of phosphorus adsorption and immobility by sediments in innercity heavily polluted canal].

The mechanisms of phosphorus (P) adsorption and immobility were investigated in laboratory experiments. The sediments and waters used were taken from an inner-city heavily polluted canal. Addition of KH2PO4 into the operated experimental units, with and without (i.e., static) intermittent sediment resuspension, were made similar to the external P input and carried out periodically. The results show that the amount of the accumulative P adsorption onto the sediments was up to 363.4 mg x kg(-1) under the conditions of sediment disturbance over a 39-day period, and it was evidently higher than that (213.2 mg x kg(-1)) under static conditions. Sequential fractionation indicated that most of the incorporated P was accounted for in the Fe/Al-P. There were over 61% in the case of intermittent sediment disturbance and up to 83% in the case of static conditions. Based on the bioavailability of Fe/Al-P, 40.6% of the incorporated P was accounted for in non-occluded Fe/Al-P of the sediments under intermittent sediment disturbance conditions. This value increased to 59.5% under static conditions. In addition, more than 23% of the incorporated P was accounted for in HCl-P of the sediments under intermittent sediment disturbance conditions, on the other hand, the concentration of HCl-P kept relatively constant under static conditions. After 39 d of P adsorption by the both sediments, the values of the maximum sorption capacity (S(max)) decreased,while zero equilibrium P concentration (EPC0) and P saturation P(%) increased. However, the extent of EPC0 and P% under intermittent sediment disturbance conditions was obviously lower than that under static conditions. It was hopefully suggested that intermittent sediment disturbance can not only accelerate the P adsorption but also enhance the P retention by sediments.

[Influence of intermittent sediment disturbance-sedimentation process on the bioavailable phosphorus in standing water].

The course of intermittent sediment disturbance-sedimentation, that sediment disturbance was for 10 min and succeeding sedimentation was for 1430 min each day over a 17-day period, was simulated to investigate the variation of bioavailable phosphorus (BAP) in overlying water. The results showed that the concentrations of BAP increased obviously at Oh after each disturbance, and the maximum concentration of BAP was reached up to 2.82 mg x L(-1) after 1 d (the first disturbance). However, the BAP gradually decreased with the sedimentation time increase (1 h, 6 h, 24 h). Moreover, at 0, 1, 6, 24 h after disturbance, the BAP gradually declined with the number of sediment disturbance increase, but the BAP at Oh after each disturbance was higher than that at 1 h, 6 h, 24 h. This may be attributed to the immediate release of bioavailable particulate phosphorus ( BAPP), as a result of sediment disturbance. The average BAPP/BAP was up to 95.0% at Oh after disturbance over a 17-day period, but this value gradually decreased with the sedimentation time increase (1 h, 6 h, 24 h). At 0 h, 1 h, 6 h, 24 h after each disturbance, the equilibrium concentrations of total dissolved phosphorus (TDP) were reached after 5 d (0.053, 0.062, 0.051, 0.045 mg x L(-1)), and the percentage of TDP in BAP also decreased gradually. Therefore, it is considered that sediment intermittent disturbance can accelerate the transformation from TDP to PP and hinder the development process of eutrophication in standing water. Sequential fractionation also indicates that the percentage of refractory phosphorus in Tot-P increased from 72.8% (raw sediments) to 77.3% (sediments after disturbance), attributable to the increase of concentrations of occluded Fe/Al-P. It is hopefully suggested an acceleration of transformation of phosphorus from mobile fractions to refractory fractions.

[Characteristics of sediments and pore water in Lake Nansi wetland].

In order to investigate the influence of sediment physical and chemical characteristics on the vertical distribution of NH4+, PO4(3-) and NO3(-) and their diffusive fluxes at sediment-water surface, pore water equilibrators (Peeper) were employed to obtain multiple pore water profiles from reed and bulrush sediments in Lake Nansihu wetland. The results showed that sediment properties in the planted reed and bulrush fields, i.e. water content, porosity, KCl-extractable NH4+ and NO3(-) were generally greater than those in seldom vegetation, and the porosity in 2-5 cm depth subsurface sediments increased by 57.5%, 34.6%, respectively. Nutrient profiles of NH4+ and PO4(3-) at sediment-water interface exhibited a nearly exponential increase with increasing depth including a concentration maximum at a 8 cm depth, where there was a spike in the NH4+ and PO4(3-) concentration. The diffusive flux (Jx) across the sediment-water interface could be calculated from Fick's first law. The flux calculations showed reed could effectively decreased NH4+ diffusive flux, and the NH4+ diffusive flux, the maximum flux 3.57-4.48 mg/(m2 x d) in reed field, was nearly three times greater than the minimum flux 0.90-1.24 mg/(m2 x d) in seldom vegetation. However, there was a narrow PO4(3-) flux range from 0.02 to 0.04 mg/(m2 x d) in three fields while NO3(-) concentration gradient showed an opposite pattern and diffusive flux occurred in one direction from the overlying bottom water to the sediment pore water. The correlative results suggested that extractable nutrient contents in sediments correlated with pore water content, therefore, controlling extractable nutrient contents appeared to a viable measure to avoid nutrient recontamination to overlying water in wetlands.

[Effects of sediment dredging on benthos community structure and water quality in Zhushan Bay].

We surveyed the changes of macro-benthos community composition and nutrients concentration in water in Zhushan Bay after it had been dredged 6 months, which aimed to remove the polluted surface sediments. The results showed that the main benthos in the dredged and un-dredged sediments were Limodrilus hoffmeisteri, Pelopia and Bellamya aeruginosa; compared to the un-dredged sediments, the bio-diversity of dredged areas became lower. However, its biomass became higher than that in un-dredged areas. Concentration range changes of TN and TP in overlying water was 1.64-4.45 mg/L and 0.133-0.258 mg/L, respectively. The post-dredged sediments were still in a higher state of nutrients for the higher concentration nutrients in overlying water, macro-benthos were the species that lived in a serious polluted water environment. Using Shannon-Weaver, Simpson, and Goodnight benthic index to evaluate the results show that the dredged area is in the moderately polluted level, but un-dredged area is in the middle-heavily polluted level. According to the benthos fauna surveys and water quality monitoring results, the effective of sediment dredging could play its role only the strict control on the external pollution resources have been made and reduces the effects of polluted water on the sediments.

[Environment effects of algae-caused black spots: impacts on Fe-Mn-S cycles in water-sediment interface].

The driving effects of algal cells settlement in the water-sediment interface on Fe, Mn, S biogeochemistry in laboratory through static cultivation device. Results showed that dissolved oxygen would be exhausted by algae cells in 50 min after the cyanobacteria cells settled to the sediment surface. Soon the water-sediment interface formed the severe anoxia and Fe-Mn oxides and sulfides were deoxidized quickly in the strong reducing environment. The Fe2+, Mn2+ content in interface increased to the summit at the 4th day and their concentrations were 4.40 mg/L and 2.35 mg/L, respectively. When it comes to the end of the experiment, the Fe2+ content had a little reduction and Mn2+ reduced quickly, their concentrations were 3.37 mg/L and 0.97 mg/L at the end of experiment. However, S2- concentration in interface reached the highest at the 2nd day and its content was 0.63 mg/L, and its concentration was only 0.12 mg/L at the end since it has been reduced. The ORP was--150 mV in the sediment surface and indicated that the sediment environment was a strong reducing environment. Phenomenon of algal cells induced black spots in water bodies was the main driving factors on Fe/Mn oxides and sulfides biogeochemistry cycle, and also the extreme anoxia environment would have great harm on the water body's ecology.

[Environment effects of algae-caused black spots: driving effects on the N, P changes in the water-sediment interface].

The impact and driving effect of deposited algal cells in the water-sediment interface on the N, P changes were studied through continuous extracted pore water with home-made static experiment. Results showed that dissolved oxygen in water-sediment interface was depleted in 50 min after algal cells settled. Soon the dead algal cells formed the anoxia and strong reducing environment and the dead cells had a severe anaerobic mineralization in the water-sediment interface, also the water bodies had a intense black and stink phenomenon. PO4(-3) -P, NH4(+) -N concentration in water-sediment interface increased from the 2nd day after added the algal cells to the sediment interface, and its concentration was 4.00 mg/L and 39.45 mg/L, respectively. Its concentration was the 10 fold and 241 fold higher than that the control experiments at the same time (PO4(-3) -P, NH4(+) -N concentration in control experiments was 0.42 mg/L and 0.16 mg/L, respectively). Anaerobic mineralization of dead cells in sediment surface drove the nutrients diffusing upward the overlying water, added the nutrients concentration in water bodies, and it also supplied the nutrient materials for the algal blooms happened again.

[Effects of large-area planting water hyacinth on macro-benthos community structure and biomass].

The effects on macro-benthos and benthos environment of planting 200 hm2 water hyacinth (E. crassipens) in Zhushan Bay, Lake Taihu, were studied during 8-10 months consecutive surveys. Results indicated that average densities of mollusca (the main species were Bellamya aeruginosa) in far-planting, near-planting and planting area were 276.67, 371.11 and 440.00 ind/m2, respectively, and biomass were 373.15, 486.57 and 672.54 g/m2, respectively, showed that average density and biomass of planting area's were higher than those of others. However, the average density and biomass of Oligochaeta (the main species was Limodrilus hoffmeisteri) and Chironomidae in planting area were lower than that of outside planting area. The density and biomass of three dominant species of benthic animal increased quickly during 8-9 months, decreased quickly in October inside and outside water hyacinth planting area. The reason of this phenomenon could be possible that lots of cyanobacteria cells died and consumed dissolve oxygen in proceed decomposing. Algae cells released lots of phosphorus and nitrogen simultaneously, so macro-benthos died in this environment. The indexes of Shannon-Weaver and Simpson indicated that water environment was in moderate polluted state. On the basis of the survey results, the large-area and high-density planting water hyacinth haven't demonstrated a great impact on macrobenthos and benthos environment in short planting time (about 6 months planting time).

[Effects of black spots of dead-cyanobacterial mats on Fe-S-P cycling in sediments of Zhushan Bay, Lake Taihu].

The purpose of the paper was to study the biogeochemical response of Fe-S-P in sediments in an extremely conditions (DO = 0.14 mg x L(-1), Eh = -89.3 mV), which was caused by the dead-cyanobacterial mats. The results showed that organic matter concentration in surficial sediment was higher, and also the Org-P concentration in surface sediments increased 72 mg x kg(-1) than those of natural sediments for the dead-cyanobacterial cells sedimentation on the sediment. The phosphorus bound Fe was dissolved in lower Eh and anoxia in water and it increased the content of activated Fe and PO4(3-) -P in sediments, also the concentration of Fe-P in sediment was lower than that of natural sediments. The concentration of PO4(3-) -P in interstitial water in sediments was higher than that of natural sediments, it would release to the overlying water and could be helpful to the next algae blooms outbreak. Also the activated Fe2+ concentration increased in the sediment in reducing environment (the Dithio-Fe increased 30 micromol than that the natural sediments); moreover, the increased Fe2+ caused the crystalline iron oxides to transform to the amorphous iron oxides. The anaerobic conditions of the water caused the AVS concentration increased and formed massive sulfides, including the production of H2S, which would escape to the atmosphere, but it would be harmful to water column ecological health; the sulfides also increased in surficial sediment for the more production of AVS (the sulfides in dead-cyanobacterial mats district was 50 micromol x g(-1) higher than natural water column).

[Algal-flocculation removal by modified sediment of Taihu Lake in wind action].

Removal effects of cyanobcateria algal cells in chitosan-mediated in-situ-sediment in the sediment resuspension was studied in the laboratory. The research simulated the sediment suspension through quantitative simulated the middle-grade wave of lake Taihu, which usually experienced, by using the Y-type sediment resuspended generator. The results showed that the blue-green algal's removal effect is 93.55% and 99.19% as the dosage adding of chitosan and sediment were (0.100 + 0.200) g x L(-1) and (0.150 + 0.200) g x L(-1), respectively. The removal rate of turbidity of the water body reached 78.60% after still 30 min, in which the chitosan adding dosage was 0.150 g x L(-1); the removal rate of turbidity achieved 93.88% after 8 h of water body still. Furthermore, adding the chitosan could decrease the PO4(3-) -P concentration of water body in a short term. Preliminary results showed that the chitosan which adding dosage was 0.15 g x L(-1) could effectively remove the cyanobacteria cells in middle-grade wave situation; and also indicates using the chitosan-mediated sediment to flocculate the algal bloom of the Taihu Lake has a better application prospect. Contrast study shows that the quantitative simulation method of hydrodynamic intensity and the height of water has the obvious advantage to determine the dosage of chitosan in algal-flocculation removal.

[Distribution characteristic and correlation relationship of reactive sulfur and heavy metals in sediments of Meiliang Bay and Wuli Lake of Taihu Lake].

The distribution characteristic of acid volatile sulfide (AVS), simultaneously extracted metals (SEM), and total metals were studied in the surface and core sediments of Meiliang Bay and Wuli Lake in Taihu Lake. It was found that there were similar distribution characteristics for AVS and SEM in surface sediments, and the concentration of AVS and SEM decreased from the steady deposition area of estuary to the centre of the bay (lake). The ratio of AVS/SEM was < 1 in the surface sediments, indicating that heavy metals in surface sediment might have potential bioavailability. The concentration of AVS increased with sediment depth, followed by decrease with large variation, while the concentration of SEM remained constant. Though comparing the concentration of SEM with total metals, it was shown that the extracted Cu and Ni decreased with sediment depth, indicating that increasing association of Cu and Ni with sulphides in deeper sediment layer, while the lower extracted ratios for Pb and Zn compared with sulfidic sediment illustrated that the AVS should not have a strong controlling on sediment Pb and Zn. From the molar ratio of AVS and reactive iron, it is known that the heavy metals were rather dynamic and active in sediments of studied sites.