Combining dredging with modified zeolite thin-layer capping to control nitrogen release from eutrophic lake sediment.

Dredging is widely used to control internal sediment nitrogen (N) pollution during eutrophic lake restoration. However, the effectiveness of dredging cannot be maintained for long periods during seasonal temperature variations. This study used modified zeolite (MZ) as a thin-layer capping material to enhance dredging efficiency during a year-long field sediment core incubation period. Our results showed that dredging alone more effectively reduced pore water N, N flux, and sediment N content than MZ capping but showed more dramatic changes during the warm seasons. The N flux in dredged sediment in summer was 1.8 and 2.5 times that in spring and autumn, respectively, indicating a drastic N regeneration process in the short term. In contrast, the combination method reduced the extra 10% pore water N, 22% N flux, and 8% sediment organic N content compared with dredging alone and maintained high stability during seasonal changes. The results indicated that the addition of MZ to the surface of dredged sediment not only enhanced the control effect of dredging by its adsorption capacity but may also smooth the N regeneration process via successive accumulation (in the channel of the material) and activation of bacteria for months, which was evidenced by the variation in microbial diversity in the MZ treatment. As a result, the combination of dredging with modified zeolite simultaneously enhanced the efficiency and stability of the single dredging method in controlling sediment N content and its release, exhibiting great prospects for long-term application in eutrophic lakes with severe pollution from internal N loading.

Phosphorus release from the sediment of a drinking water reservoir under the influence of seasonal hypoxia.

Seasonal sediment internal phosphorus (P) release may cause water eutrophication and impair water quality in drinking water reservoir. During a year-long field investigation, the effects of the microenvironment on the release of internal phosphorus were meticulously analyzed using high-resolution peepers technique and microelectrode system. The release mechanisms of P fractions from the reservoir sediments were also explored. The results showed that seasonal fluctuations in temperature, dissolved oxygen, redox potential, and pH at the sediment-water interface impacted the release of P fractions from the studied reservoir sediment. Higher diffusive fluxes of soluble reactive PO43- and Fe2+ across the sediment-water interface (SWI) were observed in the warmer season and were approximately 14.5 times and 16.5 times than those in winter, respectively. Driven by seasonal hypoxia, the reservoir sediment functioned as a P sink in winter and became a P source in summer and autumn. The reduction of Fe-bound P and mineralization of organic P were the primary mechanisms driving sediment P release, which explains the increased P flux in the warmer season and lower P flux in winter. The findings indicated that elevated temperatures and anaerobic conditions were conducive to the activation of P in sediments, whereas lower temperatures and aerobic conditions promoted the immobilization of P. This study provided new insights into seasonal P cycling in reservoirs that can contribute to the formulation of targeted reservoir management strategies.

Iron bound phosphorus predominates the contribution of phosphorus to lake system from terrigenous source: The evidence from the small watershed scale.

The reduction of exogenous emissions of phosphorus (P) is a crucial measure for resolving eutrophication in lakes. However, the input of terrigenous materials still potentially contributes to an increase of P load in lake systems. In this study, we examined the phosphate oxygen isotope (δ18OP) of various P fractions in soils and sediments in a small lake watershed, namely, Shijiuhu watershed. The high-resolution in-situ diffusive gradients in thin films (DGT) technology was also used to survey the dynamic processes of P diffusion from sediment particles to the water. The results demonstrated that lighter δ18OP values (16.2-19.5‰) for individual P fractions in lake sediments were detected compared to other land-use patterns, indicating the cumulative biological P recycling on anaerobic condition. Fe bound P (Fe-P) overall had heavier δ18OP values (17.3-24.8‰) than some of Ca bound P (Ca-P) and equilibrium values, suggesting that Fe-P conserved the parental isotope signatures from terrigenous source and could act as the ideal tracer for the lake sediments. The mixing effect of terrigenous detrital input and biological mineralization made the source identification uncertain by using Ca-P, which had a wider range of δ18OP values (13.0-26.6‰). Additionally, significantly positive correlation (r = 0.551-0.913, p<0.05) between soluble reactive P (SRP) and Fe2+ in interstitial water obtained using DGT measurement revealed the conspicuous release and desorption of solid Fe-P toward the water. High diffusion fluxes from the sediments toward the overlying water further demonstrated that the desorption of Fe-P in the soil-originated sediments toward the solution conspicuously facilitated the accumulation of SRP in lake water. The first-time application of δ18OP isotope combined with in-situ DGT techniques certified that it's feasible for the contribution confirmation from terrigenous to lacustrine environments, and presented the direct evidence for management strategy making about P control and eutrophication restoration at the catchment scale of lakes.

Genomic and Pathologic Characterization of the First FAdV-C Serotype 4 Isolate from Black-Necked Crane.

Fowl adenoviruses (FAdVs) are distributed worldwide in poultry and incriminated as the etiological agents for several health problems in fowls, and are capable of crossing species barriers between domestic and wild fowls. An FAdV strain was, for the first time, isolated from black-necked crane in this study, and was designated as serotype 4 Fowl aviadenovirus C (abbreviated as BNC2021) according to the phylogenetic analysis of its DNA polymerase and hexon gene. The viral genomic sequence analysis demonstrated that the isolate possessed the ORF deletions that are present in FAdV4 strains circulating in poultry fowls in China and the amino acid mutations associated with viral pathogenicity in the hexon and fiber 2 proteins. A viral challenge experiment with mallard ducks demonstrated systemic viral infection and horizontal transmission. BNC2021 induced the typical clinical signs of hepatitis-hydropericardium syndrome (HHS) with swelling and inflammation in multiple organs and showed significant viral replication in all eight organs tested in the virus-inoculated ducks and their contactees at 6 dpi. The findings highlight the importance of surveillance of FAdVs in wild birds.

[Sediment Pollution and Dredging Effect of Waiqinhuai River].

The Waiqinhuai River is an important urban landscape flood channel in Nanjing, which has been seriously polluted by industrial and domestic sewage for many years. To fully understand the characteristics of Waiqinhuai river sediment pollution and provide a decision-making basis for dredging, the sediment interface microenvironment and nutrient content of river sediment collected from method-typical sections in the upper, middle, and lower reaches were determined, and the organic index and pollution index methods were used to evaluate the sediment pollution condition. We also simulated the effect of desilting on the reduction of endogenous release in sediment according to pollutant characteristics of vertical distribution. The results showed that the average dissolved oxygen concentrations at the upper, middle, and lower sediment interfaces were 4.62, 3.25, and 3.41 mg·L-1, respectively; the concentrations were exhausted at 4.4, 3.5, and 5.5 mm, respectively, which were typical characteristics of urban river pollution. The average contents of TN, TP, and OM in the surface sediment of the investigated reach were 1734 mg·kg-1, 1337 mg·kg-1, and 4.82%, respectively. The organic pollution index of TN and OM in the sediment was 0.48 on average, which was at the clean level, whereas the individual pollution index of TP was 3.18 on average, which was at the severe pollution level. The results of simulating the dredging depth of 30 cm showed that the release rates of SRP and iron divalent were reduced by 42%-82% and 88%-96%, respectively, whereas the release rate of ammonia nitrogen was increased. The results of DGT determination and phosphorus speciation analysis showed that the phosphorus activity of surface sediment decreased significantly after desilting, and DGT-P and Mobile-P decreased by 9%-11% and 1%-35%, respectively, compared with those in the control treatment. These results indicated that the sediment of Waiqinhuai River was seriously polluted by endogenous phosphorus, and desilting could reduce the release of endogenous phosphorus to a certain extent, which may be an important method for improving the water quality of the Waiqinhuai River.

Seasonal sediment phosphorus release across sediment-water interface and its potential role in supporting algal blooms in a large shallow eutrophic Lake (Lake Taihu, China).

Seasonal sediment internal phosphorus (P) release is known to affect annual algal blooms in eutrophic lakes. In this study, a year-long field investigation and laboratory sediment core incubation were conducted to study the relationship between sediment internal P cycling and algal growth in Lake Taihu. The results indicated that the concentrations of water total phosphorus (TP) and chlorophyll-a (Chla) correlated with seasonal temperature and were assumed to be caused by internal P release. From cold winter to warm seasons, sediment internal P (porewater P concentration and P flux) exhibits dynamic changes. Sediment porewater soluble reactive phosphorus (SRP) and its flux in the summer were approximately five times and eight times those during winter, respectively. The release of sediment mobile P in the summer decreases its concentration and can supply SRP for algal blooms. Laboratory core incubation indicated that Chla and phycocyanin concentrations in the overlying water showed similar changes to sediment porewater P and P flux when cores were incubated from low to high temperature. The results of this study indicated that warmer conditions could increase the sediment porewater P concentration and sediment P flux into the bottom waters and consequently enhance sediment P availability to algae. This study provides new insights into the relationship between internal sediment P cycling and algal blooms in Lake Taihu.

Effects of different chemical agents on changes in sediment phosphorus composition and the response of sediment microbial community.

Controlling the release of sediment phosphorus (P) using chemical agents is a promising method for controlling internal P in eutrophic lakes. However, mineral P formation and changes in the organic P composition after sediment amendment with P-inactivation agents remain poorly understood. Furthermore, little is known about the changes in the sediment microbial community composition after remediation. Here, various ratios of poly aluminum chloride (PAC) and lanthanum-modified bentonite (LMB) were added to nutrient-rich sediments and incubated. Sequential P extraction, solution/solid-state 31P nuclear magnetic resonance (NMR), and microbial analyses were periodically performed on the inactivated sediments. The results indicate that PAC and LMB effectively reduced sediment iron-bound P and organic P, respectively, markedly increasing the content of aluminum- and calcium-bound P in the sediment, respectively. Solid-state 31P NMR results confirmed the formation of rhabdophane (LaPO4. nH2O) in the LMB-amended sediment. Solution 31P NMR results showed that PAC preferentially reduced the organic P fractions of pyrophosphate, whereas LMB efficiently reduced the organic P fractions of orthophosphate, monoesters, and diesters in the sediment. Compared with the control sediment, PAC addition can cause short-term negative effects on sediment microbes at high doses, whereas LMB addition can increase bacterial diversity or richness in the sediment. These results provide a deeper understanding of the differences between PAC and LMB in internal sediment P control.

Controlling internal nitrogen and phosphorus loading using Ca-poor soil capping in shallow eutrophic lakes: Long-term effects and mechanisms.

Clean soil is a potential capping material for controlling internal nutrient loading and helping the recovery of macrophytes in eutrophic lakes, but the long-term effects and underlying mechanisms of clean soil capping under in-situ conditions remain poorly understood. In this study, a three-year field capping enclosure experiment combining intact sediment core incubation, in-situ porewater sampling, isotherm adsorption experiments and analysis of sediment nitrogen (N) and phosphorus (P) fractions was conducted to assess the long-term performance of clean soil capping on internal loading in Lake Taihu. Our results indicate that clean soil has excellent P adsorption and retention capacity as an ecologically safe capping material and can effectively mitigate NH4+-N and SRP (soluble reactive P) fluxes at the sediment-water interface (SWI) and porewater SRP concentration for one year after capping. The mean NH4+-N and SRP fluxes of capping sediment were 34.86 mg m-2 h-1 and -1.58 mg m-2 h-1, compared 82.99 mg m-2 h-1 and 6.29 mg m-2 h-1 for control sediment. Clean soil controls internal NH4+-N release through cation (mainly Al3+) exchange mechanisms, while for SRP, clean soil can not only react with SRP due to its high Al and Fe content, but also stimulate the migration of active Ca2+ to the capping layer, thus precipitating as Ca-bound P (Ca-P). Clean soil capping also contributed to the restoration of macrophytes during the growing season. However, the effect of controlling internal nutrient loading only lasted for one year under in-situ conditions, after which the sediment properties returned to pre-capping conditions. Our results highlight that clean Ca-poor soil is a promising capping material and further research is needed to extend the longevity of this geoengineering technology.

[Effects of Sediment Dredging on the Reduction in Sediment Internal Loading of Lake Taihu and the Self-recovery Ability of Benthic Organism].

Sediment dredging has a great effect on the control of lake internal loading and is one of the important methods for lake internal loading management. In this study, the dredged area of Taihu Lake was used as the main object. An estimation of the reduction in whole lake internal loading of Taihu Lake in decade years was carried out. At the same time, we evaluated the effect of sediment dredging on the control of internal loading in the northern area of Taihu Lake (Zhushan Bay and Meiliang Bay). The results indicated that a total of 42 million cubes of sediment was dredged from Taihu Lake, and the total nitrogen, total phosphorus, and organic matter in the dredged sediment was estimated to be approximately 6.26×104 tons, 1.83×104 tons, and 11.7×105 tons, respectively. This was roughly equal to the 20 years of external loading pollution accumulated in Taihu Lake. From a long-term perspective, sediment dredging could effectively increase the water quality of Meiliang Bay within five years and that where the external loading has been controlled effectively. However, the water quality of Meiliang Bay subsequently rebounded, but dredging still reduced the nitrogen and phosphorus content in surface sediment. On the contrary, dredging could not effectively control the internal loading of Zhushan Bay, which still had a large input of external loading. The amount of sediment internal loading recovered to the original level of the pre-dredging period. In a six-year-long period of continuous monitoring of the benthic organism community of Zhushan Bay, the results indicated that sediment dredging could cause negative effects on sediment dredging initially, but the density and biomass of the benthic organisms in the dredged area had later been recovered to the un-dredged level. There was no difference between the dredged and un-dredged areas with regard to the diversity indices of benthic organisms. The results of this study indicated that sediment dredging can effectively control the lake internal loading. However, the maintenance period of dredging effects was related closely to the input intensity of the external loading. In addition, sediment dredging did not have a large influence on the benthic organism community and could recover to the original level depending on self-recovery.

Response of internal phosphorus loading from dredged and inactivated sediment under repeated resuspension in a eutrophic shallow lake.

In this study, a laboratory sediment resuspension simulation system (RSS) was used to investigate the effect of wind-induced (5.3 and 8.7 m/s) repeated sediment resuspension on internal phosphorus (P) in sediment treated by dredging and La-modified clay (LMC) based inactivation in a shallow lake. The results indicated that the dredged sediment had a better capability to resist repeated wind disturbance than the LMC-inactivated sediment. The concentration of suspended solids (SS) in the inactivated treatment (70.7 mg/L) was 1.7 times that in the dredged treatment (41.7 mg/L) under moderate wind disturbance, and was similar for the two treatments under strong wind disturbance. Nevertheless, dredging performed better than inactivation in reducing 44 % total phosphorus (TP) in overlying water (43 % reduction by inactivation) and 31 % mobile P in sediment (27 % reduction by inactivation) under moderate wind disturbance (p < 0.01) compared with control treatment. Inactivation performed better in reducing 57 % P in porewater (52 % reduction by dredging) and 81 % P flux (13 % reduction by dredging) (p < 0.01) compared with control treatment. Surprisingly, under strong wind disturbance, LMC inactivation could still reduce 18 % P in porewater and 75 % P flux (p < 0.01), whereas dredging increased 25 % P in porewater and 13 % P flux compared with control treatment (p < 0.01). LMC inactivation can increase the sediment P adsorption capacity and decrease the equilibrium P concentration (EPC0) when compared with control treatment. The contrasting control effects of the two methods were probably due to the different P buffer mechanisms for the two treated sediment. The wind disturbance-induced sediment P release was controlled by the inactivation of Fe and co-inactivation of Fe and La at the surface of dredged and LMC-inactivated sediments, respectively. The results of this study indicated inactivation can be a better method to control sediment internal P loading with repeated strong wind disturbances in eutrophic lakes.

Characterization of internal phosphorus loading in the sediment of a large eutrophic lake (Lake Taihu, China).

Lake Taihu suffers from severe algal blooms every year, which is attributed primarily to the release of sediment phosphorus (P), namely the internal P loading. However, the overall internal P loading and the P hotspots in sediment have not been fully studied. This paper presents several methods, including sequential P extraction, the use of diffusive gradient in thin film (DGT), and intact core incubation to give a detailed investigation of sediment internal P loading as well as its roles in algal dominated zones (ADZs) and grass dominated zones (GDZs) in Lake Taihu. Sediment microbial composition was also analyzed to investigate its relationship with P fractions. The results indicate that the total P and the mobile P fraction in the ADZ sediments are generally higher than those of the GDZ sediments. The percentage of sediment mobile P to TP is similar to the mobile P in their distributions. In contrast, calcium bound P accounts for most of the TP in GDZ, while mobile P contributes the most to TP in ADZ. Overall, sediment can release 256 tons of TP and 217 tons of soluble reactive phosphorus (SRP) over a period of six months in the warmer seasons. Similarly, a high concentration of DGT-measured P was observed in ADZs that are recognized as P hotspots in Lake Taihu. Sediments in ADZ and GDZ was dominated by the bacteria Firmicutes and Proteobacteria, respectively and which were closely related with mobile P and calcium bound P in sediment, respectively. GZD seems to be able to retain more P in sediments, thereby reducing its contribution to of internal P loading. These results indicate that the difference in sediment composition between ADZ and GDZ affects their roles in sediment internal P loading, therefore, different management strategies should be used to combat sediment internal P loads in the two zones.

Prediction of microvascular obstruction by coronary artery angiography score after acute ST-segment elevation myocardial infarction: a single-center retrospective observational study.

BACKGROUND: Some coronary artery angiography (CAG) scores are associated with the no-reflow phenomenon after percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI). However, quality evidence regarding the association between the CAG scores and microvascular injury is still needed. Our study aimed to validate the ability of the CAG scores in predicting microvascular obstruction (MVO) detected by cardiac magnetic resonance (CMR) imaging. METHODS: From October 2020 to October 2021, 141 consecutive patients with acute STEMI who underwent primary PCI and CMR were retrospectively reviewed. CMR imaging was performed between 3 and 7 days after PCI. The patients were divided into MVO and non-MVO group based on the CMR results. Three CAG scores (SYNTAX score, SYNTAX II score and Gensini score) were used to assess the severity of coronary artery atherosclerotic burden. RESULTS: A total of 122 patients were included (mean age 60.6 ± 12.8 years). MVO occurred in 51 patients (41.8%). Patients with MVO had higher SYNTAX scores, SYNTAX II scores and Gensini scores than those without MVO (all p < 0.001). The Gensini score (r = 0.567, p < 0.001) showed the strongest correlation with infarction size than SYNTAX score (r = 0.521, p < 0.001) and SYNTAX II score (r = 0.509, p < 0.001). The areas under the receiver operator characteristic curves of SYNTAX score, SYNTAX II score and Gensini score for predicting MVO patients were 0.726, 0.774 and 0.807. In multivariable regression analysis, peak troponin I (odd ratio [OR] = 1.236, p = 0.001) and SYNTAX II score (OR = 11.636, p = 0.010) were identified as independent predictors of MVO. CONCLUSIONS: In patients with acute STEMI undergoing primary PCI treatment, the peak troponin I and SYNTAX II score may be an independent predictor of MVO.

[Influence of Different Types of Dewatering Agents on the Solidification Effect and Physical and Chemical Properties of Sediment].

In order to study the comprehensive effects of different types of dehydrating agents on the dewatering and solidification of dredged sediments, this study took the dredged sediments of Taihu Lake as the research object and selected microorganisms, polymeric iron aluminum salts, organic polymers, organic-inorganic composites, and aluminum salt microorganisms. These five types of composite dehydrating agents were used to conduct a three-month solidification test on the dredged sediment by means of geotechnical pipe bag solidification. The results of the study showed that the dehydration efficiency of organic polymers and organic-inorganic composite chemicals was better. After one month, the water content of sediment dropped to 61.78% and 63.26%, respectively, which then dropped to 40.56% and 32.16% after three months. Compared with that of the unsolidified sludge, the total nitrogen of the bottom sludge after solidification by the organic-inorganic composite agent was reduced by 74.82%, reaching 591 mg·kg-1, primarily due to the reduction in ammonia nitrogen. The solid sludge contained mainly aluminum-bound phosphorus, calcium-bound phosphorus, and iron-bound phosphorus. Among them, four groups (organic-inorganic composite) had the largest reduction in active phosphorus, with the lowest being 64.3 mg·kg-1. In addition, organic polymer agents had the best curing effect on heavy metals, the comprehensive ecological risk index of heavy metals was reduced by 51.3%, and the leaching toxicity concentration was far below the standard threshold. This study showed that organic polymers and organic-inorganic composite medicaments have a better effect on the dehydration and solidification of bottom sludge and thus have good application prospects.

Tracing the sources of phosphorus in lake at watershed scale using phosphate oxygen isotope (δ18OP).

Phosphorus (P) is normally considered as the limited nutrient for shallow freshwater lakes and can potentially trigger eutrophication on account of high concentrations. Due to the various transportation and transformation processes, P source apportionment and management in lake ecosystems have become more and more difficult. Combining with sequential extraction of P fractions and mineralogical analysis, the isotopic compositions of oxygen in phosphate (δ18OP) of resin-extractable P from the different samples including soil, estuary sediments, pond sediments, and lake sediments in the Shijiuhu Lake catchment, China, were investigated. The results showed that δ18OP values ranged from +15.23 to +21.92‰ in agricultural soil, +16.53 to +24.10‰ in estuary sediments, +18.90 to +20.90‰ in pond sediments, and +17.42 to +19.70‰ in lake sediments. Isotopic signatures indicated that chemical fertilizers with heavier δ18OP values (+20.70 to +26.50‰) were the predominant contributors of P in the soil. The river transportation together with Fe/Al-P desorption on anaerobic condition simultaneously stimulated the enrichment of P in the lake sediments, even though the biotic activity regulated the isotope values moving toward the equilibrium. Eroded soil was the important source of P in lake and pond sediments via drainage and runoff, and conserved the source isotope signal in the samples. Stronger biotic activity in the aquatic environments dragged δ18OP values toward the equilibrium. However, conspicuous off-equilibrium isotope signature suggested the terrestrial sources in the aquatic ecosystems. The calculation of two end-member linear mixing models suggested that soils also predominantly controlled the P occurrence in the lake sediments with contribution higher than 80%, indicating that decreasing inputs from the agricultural activities is important in P reduction on catchment scale. Generally, δ18OP from different sources can provide indirect and important evidences for the identification and management of P sources in the lake catchment.

Efficient removal of phosphorus from constructed wetlands using solidified lanthanum/aluminum amended attapulgite/biochar composite as a novel phosphorus filter.

Developing a suitable substrate with high phosphorus (P) sorption capacity, low solubility, and high hydraulic loading for constructed wetlands (CWs) is crucial for their functions. In this study, we used attapulgite and biochar as base materials to prepare a lanthanum/aluminum (La/Al) amended attapulgite/biochar composite as a novel P filter using a one-step drying process and subsequent high-temperature thermal treatments. Results indicated that the solidified poly aluminum chloride (PAC) amended attapulgite/biochar (SAl@AB) has a higher solubility than the solidified La-modified attapulgite/biochar (SLa@AB) and the solidified PAC and La co-modified attapulgite/biochar (SAlLa@AB). Therefore, SAl@AB is not suitable to be used as a substrate for constructed wetlands (CWs). Batch studies indicated that SLa@AB and SAlLa@AB have maximum P sorption capacities of 12.8 mg/g and 21.3 mg/g, respectively. The P sorption rates are higher than those found in most substrates used in constructed wetlands. Additionally, pH and coexisting ions exert minor effects on the P removal performance of SAlLa@AB. Column experiments indicated that longer hydraulic retention time (HRT) favors the removal of influent P. A 120-day column experiment indicated that an average of 95% of the P influent (10 mg P/L) could be removed by the SAlLa@AB with an HRT of 8 h. The P forms analyzed by sequential extraction indicated that P removed by SAlLa@AB occurs through the formation of calcium-bound and Al-bound P fractions, which can account for 68.7% and 18.8% of the total phosphorus, respectively. The formation of lanthanum/aluminum phosphate precipitation was the main P removal mechanism of SAlLa@AB. This was further confirmed by an XPS analysis, showing a formation of La-O-P and Al-O-P inner-sphere complexes after P sorption by SAlLa@AB. The results of this study indicate that SAlLa@AB was a promising substrate for future CWs.

Phosphorus internal loading and sediment diagenesis in a large eutrophic lake (Lake Chaohu, China).

Sediment phosphorus (P) release and retention are important in controlling whole-system P dynamics and budget in eutrophic lakes. Here we combine short- (seasonal) and long-term (years to decades) studies to quantify the internal P loading and P release potential in the sediments of Lake Chaohu and explore their controlling mechanisms. In the west region of the lake, short-term P diffusive fluxes ranged from 0.2 mg/m2·d-1 to 6.69 mg/m2·d-1 (averaged 2.76 mg/m2·d-1) and long-term net P release ranged from 2.25 mg/m2·d-1 to 8.94 mg/m2·d-1 (averaged 5.34 mg/m2·d-1); in the east region, short-term P diffusive fluxes varied from 0.73 mg/m2·d-1 to 1.76 mg/m2·d-1 (averaged 1.05 mg/m2·d-1) and long-term P release ranged from 0.13 mg/m2·d-1 to 4.15 mg/m2·d-1 (averaged 1.3 mg/m2·d-1). Both short- and long-term P releases were in the same order of magnitudes as the external P inputs (3.56 mg/m2·d-1). Comparison of the long-term and short-term sediment P release indicates that while the high summer P release in the east might only represent a snapshot value, the sediments in the west contribute to large P release for years or even decades, impeding water quality recovery under lake management. Mobilization of surface sediment legacy P accounted for 81% of short-term P release. The long-term release was dominated by remobilization of iron bond P (BD-P) (average 52.1%) at all sites, while Aluminium-bound P (NaOH-rP) exhibited partly reactive and potentially mobile, releasing P to the water column in most sites in the west. Our study demonstrates the importance of sediments as P sources in lake Chaohu. The combination of short- and long-term P release studies can help understand the roles of sediments in regulating the water quality and eutrophication.

Ignored effects of phosphite (P+III) on the growth responses of three typical algae species.

Nowadays, the ubiquitous distribution and increasing abundance of P+III in waterbodies have caused serious concerns regarding its bioavailability and potential toxicity. However, our knowledge on these issues is relatively limited. We addressed previously unknown effects of P+III on three dominate algae species i.e. Microcystic aeruginosa (M. aeruginosa), Chlorella pyrenoidesa (C. pyrenoidesa) and Cyclotella. sp in eutrophic waterbodies in China. Remarkable declines in biomass, specific growth rate and Chl-a of algae cells treated with 0.01-0.7 mg/L P+III as sole or an alternative P source were observed, indicating P+III had an inhibitory effect on the algal growth. Besides, the intracellular enzyme activities e.g superoxide dismutase (SOD) and malondialdehyde (MDA) were significantly increased with P+III stress. M. aeruginosa and Cyclotella. sp cells seemed to be more sensitive to P+III toxicity than C. pyrenoidesa since cell membrane suffered more serious stress and destruction. These findings combined, it confirmed P+III could not be utilized as bioavailable P, but had certain toxicity to the tested algae. It indicated that the increased P+III abundance in eutrophic waterbodies would accelerate the algal cell death, which could have a positive effect against algal blooms. Our results provide new insights into assessing the ecological risks of P+III in aquatic environments.

Clade 2.3.4.4b H5N8 Subtype Avian Influenza Viruses Were Identified from the Common Crane Wintering in Yunnan Province, China.

The seasonal migration of wild aquatic birds plays a critical role in the maintenance, transmission, and incursion of the avian influenza virus (AIV). AIV surveillance was performed during 2020-2021 in two national nature reserves with abundant wild bird resources in Yunnan, China. Four H5N8 AIVs isolates from the common crane were identified by next-generation sequencing. Phylogenetic analysis demonstrated that all eight gene segments of these H5N8 AIVs belonged to clade 2.3.4.4b high-pathogenic AIV (HPAIV) and shared high nucleotide sequence similarity with the strains isolated in Hubei, China, and Siberia, Russia, in 2020-2021. The H5N8 HPAIVs from common cranes were characterized by both human and avian dual-receptor specificity in the hemagglutinin (HA) protein. Moreover, possessing the substitutions contributes to overcoming transmission barriers of mammalian hosts in polymerase basic 2 (PB2), polymerase basic protein 1 (PB1), and polymerase acid (PA), and exhibiting the long stalk in the neck region of the neuraminidase (NA) protein contributes to adaptation in wild birds. Monitoring AIVs in migratory birds, at stopover sites and in their primary habitats, i.e., breeding or wintering grounds, could provide insight into potential zoonosis caused by AIVs.

Phosphorus removal from sediments by Potamogeton crispus: New high-resolution in-situ evidence for rhizosphere assimilation and oxidization-induced retention.

Macrophytes are usually chosen for phytoremediation tools to remove P in eutrophic aquatic ecosystems, but the lack of test methods hinders the understanding of removal mechanism and application. In this study, we used the novel technologies combined of Diffusive gradients in thin films (DGT), Planar optode (PO), and Non-invasive micro-test technology (NMT) to explore P dynamics in water-sediment continuum and rhizosphere of Potamogeton crispus over time. Results of the high-resolution in situ measurement showed that labile P(LPDGT) fluxes at the surficial sediment significantly decreased from approximate 120, 140, and 200 pg/ (cm2•sec) via 30 days incubation period to 17, 40, and 56 pg/(cm2•sec) via that of 15 days. Obvious synchronous increase of LPDGT was not detected in overlying water, suggesting the intense assimilation of dissolve reactive P via root over time. PO measurement indicated that O2 concentration around the rhizosphere remarkably increased and radially diffused into deeper sediment until 100% saturation along with the root stretch downwards. NMT detection of roots showed the obvious O2 inflow into root tissue with the uppermost flux of 30 pmol/(cm2•sec) from surroundings via aerenchyma on different treatment conditions. Different from previous reports, gradually saturating O2 concentrations around the rhizosphere was principally driven by O2 penetration through interspace attributing to root stretch downward rather than root O2 leakage. Increased O2 concentrations in deep sediment over time finally induced the oxidization of labile Fe(II) into Fe(III) bound P and local P immobilization.

Water-level fluctuations regulate the availability and diffusion kinetics process of phosphorus at lake water-sediment interface.

Sequential extraction and in-situ diffusive gradients in thin films (DGT) techniques were used to determine phosphorus (P) fractions and high-resolution 2D fluxes of labile PDGT, Fe2+DGT, and S2-DGT in sediment systems. The diffusion fluxes were subsequently calculated for different scenarios. Dynamic diffusion parameters between solid sediment and solution were also fitted using the DIFS (DGT-induced fluxes in sediments) model. The results suggested that Fe-bound P (Fe-P) was the dominant pool which contributed to the resupply potential of P in the water-sediment continuum. Significant upward decreases of labile PDGT, Fe2+DGT, and S2-DGT fluxes were detected in pristine and incubated microcosms. This dominance indicated the more obvious immobilization of labile P via oxidation of both Fe2+ and S2- in oxidic conditions. Additionally, these labile analytes in the microcosms obviously decreased after a 30-day incubation period, indicating that water-level fluctuations can significantly regulate adsorption-desorption processes of the P bound to Fe-containing minerals within a short time. Higher concentrations of labile PDGT, Fe2+DGT, and S2-DGT were measured at the shallow lake region where more drastic water-level variation occurred. This demonstrates that frequent adsorption-desorption of phosphate from the sediment particles to the aqueous solution can result in looser binding on the solid sediment surface and easier desorption in aerobic conditions via the regulation of water levels. Higher R values fitted with DIFS model suggested that more significant desorption and replenishment effect of labile P to the aqueous solution would occur in lake regions with more dramatic water-level variations. Finally, a significant positive correlation between S2-DGT and Fe2+DGT in the sediment indicated that the S2- oxidization under the conditions of low water-level can trigger the reduction of Fe(III) and subsequent release of active P. In general, speaking, frequent water-level fluctuations in the lake over time facilitated the formation and retention of the Fe(II) phase in the sediment, and desorption of Fe coupled P into the aqueous solution when the water level was high.