Estuarine environmental flow assessment based on the flow-ecological health index relation model: a case study in Yangtze River Estuary, China.

Environmental flow (e-flow) is the water demand of one given ecosystem, which can become the flow regulation target for protection and restoration of river or estuarine ecosystems. In this study, an e-flow assessment based on the flow-ecological health index (EHI) relation model was conducted to improve ecosystem health of the Yangtze River Estuary (YRE). Monitoring data of hydrology, biology, and water environment in the last decades were used for the model establishment. For the description of the YRE ecosystem, an EHI system was developed by cumulative frequency distribution curves and adaption of national standards. After preprocessing original flow values into proportional flow values, the generalized additive model and Monte Carlo random sampling were used for the establishment of the flow-EHI relation model. From the model calculation, the e-flow assessment results were that, in proportional flow values, the suitable flow range was 1.05-1.35, and the optimum flow range was 1.15-1.25 (flows in Yangtze River Datong Station). For flow regulation in two crucial periods, flows of 42,630-65,545 m3/s or over 14,675 m3/s are needed for the suitable flow of YRE in summer (June-August) or January, respectively. An adaptive management framework of ecological health-based estuarine e-flow assessment for YRE was contrived due to the limitation of current established model when facing the extreme drought in summer, 2022. The methodology and framework in this study are expected to provide valuable management and data support for the sustainable development of estuarine ecosystems and to bring inspiration for further studies at even continental or global levels.

Sensitivity-Tunable Terahertz Liquid/Gas Biosensor Based on Surface Plasmon Resonance with Dirac Semimetal.

In this paper, we study the sensitivity-tunable terahertz (THz) liquid/gas biosensor in a coupling prism-three-dimensional Dirac semimetal (3D DSM) multilayer structure. The high sensitivity of the biosensor originates from the sharp reflected peak caused by surface plasmon resonance (SPR) mode. This structure achieves the tunability of sensitivity due to the fact that the reflectance could be modulated by the Fermi energy of 3D DSM. Besides, it is found that the sensitivity curve depends heavily on the structural parameters of 3D DSM. After parameter optimization, we obtained sensitivity over 100°/RIU for liquid biosensor. We believe this simple structure provides a reference idea for realizing high sensitivity and a tunable biosensor device.

Effects of water temperature on growth performance, digestive enzymes activities, and serum indices of juvenile Coreius guichenoti.

This study was conducted to determine the optimal temperature for Juvenile Coreius guichenoti, which is critically endangered in China. Test fish with an initial body weight range of 17.60-18.78 g were reared in 5 independent recirculating aquaculture systems (RAS) with three tanks (50 fish/tank) for 8 weeks. The water temperature of the RAS was set at 14 °C, 18 °C, 22 °C, 26 °C, and 30 °C, respectively. At conclusion of the feeding trial, the effects of water temperature on C. guichenoti were analyzed based on survival, growth performance, digestive enzymes activities, and antioxidant capacity. The results showed that the fish survived in all temperature groups. The fish in the groups (26 °C and 30 °C) had higher values of body length, body weight, specific growth rate, weight gain rate, and daily gain than those in the group (22 °C). The lowest values of growth performance were observed in the groups (14 °C and 18 °C) among the 5 groups. The lowest values of feed conversion ratio (FCR) were observed in the group (26 °C). Regression analysis identified the minimum FCR at 26.55 °C. The feeding rates (FR) were increased gradually with the increase of temperature. Regression analysis identified the maximum FR at 28.33 °C. The activities of protease and lipase in the gut were higher than those in the liver, while amylase activity was lower in the gut than that in the liver. There were no significant differences in activities of protease and lipase among different parts of the intestinal tract at the temperatures range from 18 to 26 °C. When the temperature was out the optimal range, C. guichenoti would be under chronic stress, resulting in decreased lysozyme activity and cortisol concentration. Inconclusion, the optimal temperature for juvenile C. guichenoti is 26.55-28.33 °C based on the maximal growth performance and feed utilization.

Land use, hydrology, and climate influence water quality of China's largest river.

Influences of multiple environmental factors on water quality patterns is less studied in large rivers. Landscape analysis, multiple statistical methods, and the water quality index (WQI) were used to detect water quality patterns and influencing factors in China's largest river, the Yangtze River. Compared with the dry season, the wet season had significantly higher total phosphorus (TP), chemical oxygen demand (COD), total suspended solids (TSS), and turbidity (TUR). The WQI indicated "Moderate" and "Good" water quality in the wet and dry seasons, respectively. Compared with other sites, the upper reach sites that immediately downstream of the Three Gorges Dam had lower TP, TN, TSS and TUR in both seasons, and had lower and higher water temperature in the wet and dry seasons, respectively. Water quality patterns were mainly driven by heterogeneity in land use (i.e., wetland, cropland, and urban land), hydrology (i.e., water flow, water level), and climate (i.e., rainfall, air temperature). Water quality in the wet season was primarily driven by land use while the joint effect of land use and hydrology primarily drove in the dry season. Decision-makers and regulators of large river basin management may need to develop programs that consider influences from both human and natural drivers for water quality conservation.

Clarifying the Correlation of Ice Adhesion Strength with Water Wettability and Surface Characteristics.

Although icephobic surfaces have been extensively investigated in the past decades, a controversy remains on the relationship between water repellency and ice repellency. Little insight has been truly obtained on the dependence of ice adhesion on the surface/interface characteristics because of the limited range of these characteristics that have been investigated in the past. In this study, we prepared 37 coatings with a wide range of surface characteristics. The measured ice adhesion strength was discussed in correlation with water wettability and surface topological parameters. It was verified that parameters related to water wettability, such as water contact angle, contact angle hysteresis, and an index of work of adhesion with water, (1 + cos θrec), do not have a simple correlation with ice adhesion strength. Thus, they should not be used as a design parameter for low icephobic surfaces. The current study points out that the study of surface texture should be carried out in conjunction with surface chemistry/energy consideration. Without control of the surface chemistry, the correlation between surface texture parameters will lead to inconsistent conclusions because of the uncertainty of the contact mode. Our investigation indicates that low ice adhesion strength (<50 kPa) is attainable with a smooth surface (root-mean-squared roughness < 50 nm) when a low surface energy (<15 mJ/m2) is maintained. This finding opens a new paradigm for the design of icephobic coatings away from the conventional practices of using superhydrophobic and oil-infused surfaces.

Rapidly Spreading Human Immunodeficiency Virus Epidemic Among Older Males and Associated Factors: A Large-scale Prospective Cohort Study in Rural Southwest China.

BACKGROUND: Increasing risk of human immunodeficiency virus (HIV) heterosexual transmission can raise the potential for a more diffuse and generalized epidemic. In response to the paucity of data on HIV incidence among heterosexuals in China, we conducted a large-scale, population-based cohort study located in rural southwest China. METHODS: Baseline enrollment for the study was conducted from 2013 to 2014 and follow-up at 12 months was from 2014 to 2015 among adults 20 years or older in 3 rural counties of Southwest China. Study participants were informed of the study by brochures and leaflets distributed in outreach activities. Interviews and blood collection were conducted in private rooms. Blood samples were tested for HIV infection. RESULTS: The HIV prevalence of the sample was 0.29% (95% confidence interval [CI], 0.27-0.30) (2063 of 722,795) among the total adult population of 1,090,296 potential participants 20 years or older at baseline. Of the 720,732 individuals who tested HIV-negative at baseline, 493,990 (69%) completed the follow-up. Overall HIV incidence was 2.73 (95% CI, 2.38-3.08) per 10,000 person-years (PY) (235 of 860,627 PY). Human immunodeficiency virus incidence was associated with males, older age, less than secondary schooling and not currently being married. Human immunodeficiency virus incidence was 71.28 (95% CI, 35.21-107.35) per 10,000 PY among males aged 50 to 69 years who had less than secondary schooling and were divorced or widowed. Heterosexual sex was the dominant transmission mode for HIV seroconversions (99.0%). CONCLUSIONS: Older heterosexual males were at disproportionate risk of HIV infection. Health authorities in China need to develop and implement innovative interventions suitable for the broader population of older heterosexuals.

Disparities in HIV and syphilis prevalence and risk factors between older male clients with and without steady sex partners in southwestern rural China.

BACKGROUND: Heterosexual intercourse accounted for 93% of reported HIV cases in Guangxi, and Guangxi had 10% of China's total number of reported HIV cases. Older men are particularly vulnerable to STIs, for example, 46% of Guangxi's HIV cases were men over 50 years of age. As this is an under-studied population in China, effective prevention and control policies have yet to be developed. Thus, the aim of this study was to use a large-scale cross-sectional survey to understand the demographic and behavior factors associated with HIV and syphilis infections among older male clients of female sex workers (FSWs) in a high epidemic area of rural Guangxi, China. METHODS: A large-scale cross-sectional survey was conducted in 2012 among older male clients of FSWs in low-cost commercial sex venues. Questionnaire interviews were administered to collect sociodemographic and sexual behavior information. Blood samples were collected for HIV and syphilis infection tests. RESULTS: Of the 3485 participants, 2509 (72.0%) clients had a steady sex partner and 976 (28.0%) clients had no steady sex partner. The overall prevalence of HIV and syphilis infection were 3.0% and 3.2%, respectively. Compared to those with a steady sex partner, clients with no steady partner had higher odds of HIV infection (AOR: 1.90, 95% CI: 1.27-2.86), syphilis infection (AOR: 1.53, 95% CI: 1.02-2.30), and having factors associated with HIV or syphilis infection, including non-commercial casual sex encounters in last month (AOR: 3.29, 95% CI: 2.42-4.46), >10 years of commercial sex history (AOR: 1.31, 95% CI: 1.12-1.53), >2 incidents of commercial sex in last month (AOR: 1.53, 95% CI: 1.19-1.96), and aphrodisiac use in last month (AOR: 1.40, 95% CI: 1.16-1.70). Clients with no steady partner had lower odds of having heterosexual intercourse (AOR: 0.66, 95% CI: 0.56-0.79), awareness and knowledge of HIV/AIDS (AOR: 0.75, 95% CI: 0.64-0.88), and having had HIV tests (AOR: 0.65, 95% CI: 0.44-0.98). CONCLUSION: Older male clients of low-cost commercial sex venues in rural southwestern China are at high risk for HIV and syphilis infection, especially those with no steady sex partner. Improved interventions are urgently needed for this neglected risk population.

Design and synthesis of peptide conjugates of phosphoramide mustard as prodrugs activated by prostate-specific antigen.

A series of Glutaryl-Hyp-Ala-Ser-Chg-Gln-4-aminobenzyl phosphoramide mustard conjugates (1a-e) was designed and synthesized as potential prodrugs for site-specific activation by PSA in prostate cancer cells. All conjugates were found to be substrates of PSA with cleavage occurring between Gln and the para-aminobenzyl (PAB) linker. Structure-activity relationship studies on these conjugates indicated that introduction of electron-withdrawing fluorine(s) on the phenyl ring in the PAB linker uniformly improved the chemical stability of the conjugates while the position of substitution affected differently the self-immolative process of conjugates upon proteolysis. Introduction of a fluorine at ortho position to benzylic phosphoramide as in 1b results in better stability of the conjugate prior to activation while maintaining its antiproliferative activity upon activation by PSA. The conjugate 1b with 2-fluoro substitution was identified as a promising lead for further evaluation and optimization in the development of prostate cancer-targeted prodrugs.

Prevalence of transmitted HIV-1 drug resistance remains low in Guangxi, China, eight years after scale-up of highly-active antiretroviral therapy.

OBJECTIVES: Highly-active antiretroviral therapy (HAART) was scaled up in Guangxi, China in 2005. The number of individuals receiving free HAART increased dramatically from June 2010 under the Guangxi Government's anti-HIV programme. We aimed to determine the prevalence of HIV-transmitted drug resistance (TDR) of Guangxi. METHODS: HIV-positive, antiretroviral-naive individuals were recruited from the east (Hezhou), south (Qinzhou), west (Baise), north (Guilin) and centre (Laibin) of Guangxi. The pol gene of the virus from the individuals was analysed. RESULTS: The overall prevalence of HIV TDR was 3.2% (7/216, 95% CI 0.9-5.5). The prevalence rates in Baise, Guilin, Hezhou, Qinzhou and Laibin are 4.9% (2/41, 95% CI -1.7 to 11.5), 2.3% (1/44, 95% CI -2.1 to 5.7), 4.7% (2/43, 95% CI -1.6 to 11.0), 2.6% (1/38, 95% CI -2.5 to 7.7) and 2.0% (1/50, 95% CI -1.9 to 5.9), respectively. No significant difference in the prevalence was found among them. No factors were found to be associated with TDR, including CD4 cell counts, viral loads and genotypes. The subtypes CRF01_AE, CRF07_BC, CRF08_BC and B were found. Subtype CRF08_BC is the predominant subtype in Baise while CRF01_AE is the predominant subtype elsewhere in Guangxi. CONCLUSIONS: The prevalence of TDR in antiretroviral-naive patients in Guangxi remains low 8 years after scale-up of HAART.

A retrospective analysis of heavy metals and multi elements in the Yangtze River Basin: Distribution characteristics, migration tendencies and ecological risk assessment.

The Yangtze River is the third longest river in the world with more than 6300 km, covering 0.4 billion people. However, the aquatic ecosystem of the Yangtze River has been seriously damaged in the past decades due to a rapid development of economic and industrialization along the coast. In this study, we first established a dataset of fifty elements, including nine common heavy metals (HMs) and forty-one other elements, in the Yangtze River Basin through the collection of historical data from 2000 to 2020, and then analyzed their spatiotemporal distribution characteristics. The results indicated that the Three Gorges Reservoir (TGR), a region formed by the construction of the Three Gorges Dam (TGD), may act as a sink for these elements from upstream regions. The concentrations of seven elements in surface water and 13 elements in sediment obviously increased from the upstream region of the TGR to the TGR. In addition, ten elements in the surface water and 5 elements in the sediments clearly decreased, possibly because of the interception effects of the TGD. On a timescale, Cr obviously tended to migrate from the water phase to the sediment; Pb tended to migrate from the sediment to the water phase. In the ecological risk assessment, all common HMs in surface water were supposed to have negligible risks as protecting 90 % of aquatic organisms; Cd (210.2), Hg (58.0) and As (43.1) in sediment posed high and moderate ecological risks using the methodology of the potential ecological risk index. Furthermore, Hunan Province is at considerable risk according to the sum of the potential risk index (314.8) due to Cd pollution (66.8 %). These fundamental data and results will support follow-up control strategies for elements and policies related to aquatic ecosystem protection in the Yangtze River Basin.

The First Report of Tritrichomonas Foetus and Tetratrichomonas Buttreyi in Raccoon Dogs (Nyctereutes Procyonoides) in China.

BACKGROUND: In recent years, the trichomonosis in raccoon dogs in China had occurred frequently. Pentatrichomonas hominis had been described in raccoon dogs in China in some previous studies. PURPOSE TO REVEAL: whether raccoon dogs can be infected by other trichomonad species besides P. hominis, and clarify the prevalence and species distribution of trichomonad in raccoon dogs. METHODS: Herein, the 389 fecal samples were collected from farm-raised raccoon dogs in Hebei Province, all the samples were detected using the microscopic examination and several fecal samples containing trichomonad-like organisms were processed, cultured, stained, and photographed. Meanwhile, all the samples were screened by the species-specific nested PCR based on the small subunit rRNA (SSU rRNA) gene of P. hominis,Tritrichomonas foetus and Tetratrichomonas buttreyi, respectively, and all positive secondary PCR amplications obtained in this study were sequenced, aligned and analysed. RESULTS: 62 fecal samples (15.9%,62/389) were trichomonad-positive under light microscopy, and the trichomonad-like cells were clearly observed in the culture contents. The PCR results showed that 100 samples were trichomonad-positive, including 45 P. hominis-positive samples (11.6%,45/389), 32 T. foetus-positive samples (8.2%,32/389), and 33 T. buttreyi-positive samples (8.5%,33/389), respectively. Double mixed infections were observed in 10 samples. The prevalence of T. foetus and P. hominis were both significantly higher in raccoon dogs with diarrhea (13.9%, and 25.0%) than that in raccoon dogs without diarrhea (7.6%, and 9.3%) (p < 0.05).All samples confirmed as trichomonad-positive under microscopy were also found to be trichomonad-positive by PCR analysis. The sequencing and phylogenetic analysis demonstrated the sequences obtained in this study belonged to P. hominis, T. foetus and T. buttreyi SSU rRNA, respectively. Among them, the T. buttreyi SSU rRNA sequences obtained in this study harbored the new sequence polymorphisms. Based on preliminary morphological and molecular analyses, raccoon dogs are considered as the new host of T. foetus and T. buttreyi. CONCLUSION: This is the first report about the identifcation and prevalence of T. foetus and T. buttreyi in raccoon dogs in China, and the results increase our knowledge about the host range and prevalence of trichomonad species.

Dam construction alters planktonic microbial predator‒prey communities in the urban reaches of the Yangtze River.

While dam construction supports social and economic development, changes in hydraulic conditions can also affect natural aquatic ecosystems, especially microbial ecosystems. The compositional and functional traits of multi-trophic microbiota can be altered by dam construction, which may result in changes in aquatic predator-prey interactions. To understand this process, we performed a large-scale sampling campaign in the urban reaches of the dam-impacted Yangtze River (1 995 km) and obtained 211 metagenomic datasets and water quality data. We first compared the compositional traits of planktonic microbial communities upstream, downstream, and in a dam reservoir. Results showed that Bacteroidetes (R-strategy) bacteria were more likely to survive upstream, whilst the reservoir and downstream regions were more conducive to the survival of K-strategy bacteria such as Actinobacteria. Eukaryotic predators tended to be enriched upstream, whilst phototrophs tended to be enriched in the reservoir and downstream regions. Based on bipartite networks, we inferred that the potential microbial predator-prey interactions gradually and significantly decreased from upstream to the downstream and dam regions, affecting 56% of keystone microbial species. Remarkably, functional analysis showed that the abundance of the photosynthetic gene psbO was higher in the reservoir and downstream regions, whilst the abundance of the KEGG carbohydrate metabolic pathway was higher upstream. These results indicate that dam construction in the Yangtze River induced planktonic microbial ecosystem transformation from detritus-based food webs to autotroph-based food webs.

Dam construction reshapes sedimentary pollutant distribution along the Yangtze river by regulating sediment composition.

Dam construction has far-reaching impacts on pollutant accumulation and the pollutant-induced quality of aquatic environments. Nonetheless, its large-scale effects on pollutant distribution in sediments, which greatly contribute to the environmental impacts of coexisting pollutants, remain poorly understood. We collected sediments from the Yangtze River during the dry and normal seasons (with 'normal' defined in terms of precipitation level), and examined how dam construction alters the spatial trajectories of both inorganic and organic pollutants in the sediments. Sediment composition exhibited linear variation from the upper to the lower reaches, with clay and silt particles dominating the sediment in the Three Gorges Reservoir and sand particles dominating in the middle-lower reaches. Accordingly, upstream of the Three Gorges Dam (TGD), sedimentary carbon, nitrogen, phosphorus, heavy metal, polycyclic aromatic hydrocarbons (PAHs), and oxygenated PAHs (OPAHs) contents increased toward the TGD owing to its regulation of the spatial variation in sediment particle size. The TGD caused upstream sedimentary accumulation of pollutants to be higher nearer to the TGD than in the upper reaches by 17%-129% for carbon, nitrogen, and phosphorus, 7%-51% for heavy metals, 30% for PAHs, and 140% for OPAHs. Pollutant content was sharply lower below the TGD, by 0.58-11.15 times for carbon, nitrogen, and phosphorus, 0.1-2.6 times for heavy metals, 1.7 times for PAHs, and 5.6 times for OPAHs. Upstream of the TGD, levels of NH4+-N, the main form of N in the interstitial water of the Yangtze River, increased lineary toward the TGD, whereas those of NO3--N and NO2--N decreased. Sedimentary organic matter source contributions were consistent along the Yangtze River, being on an average 46% for C3 plants and 28% for soil organic substances, further confirming the dam's regulatory effect on pollutants. These findings provide a foundation for future assessments of the environmental impact of dam-induced river fragmentation and hydrological alterations, and for developing advanced watershed pollutant management strategies.

Transport of trace metals and their bioaccumulation in zooplankton from Changjiang (Yangtze River) to the East China Sea.

The present study conducted a comprehensive field investigation on the transport and bioaccumulation of six trace metals (Cr, Cd, Pb, Mn, Ni, Cu) along a transect from Changjiang (Yangtze River) to the East China Sea continental shelf, which exhibited large variations in physiochemical properties (salinity, turbidity, pH, chlorophyll a, total nitrogen, dissolved oxygen, dissolved and particulate organic matter). From riverine sites to marine sites, dissolved Cr and Cd significantly increased, dissolved Pb and Mn showed less variations, while dissolved Cu and Ni showed complex spatial distribution patterns. Particulate trace metals (for Cr, Mn, Ni and Cu) were significantly negatively correlated with salinity. As a result, partition coefficients of trace metals (except Pb) were all significantly negatively correlated with salinity, indicating high salinity facilitated desorption/dissolution of metals from particulate phase. Additionally, the Changjiang derived particulate Pb, Mn, Ni and Cu sharply decreased (particularly for Mn) at the downstream of turbidity maximum zone, suggesting the efficient trapping of metals within this region. We further investigated the site-specific bioaccumulation of trace metals in size-fractionated zooplankton. Metal contents in macro-zooplankton were lower than micro- and meso-zooplankton owing to size-dependent zooplankton communities, while site-specific metal bioaccumulation mainly driven by site-specific zooplankton communities and salinity. The bioaccumulation factors of metals (Cr, Cd, Ni and Cu) were significantly negatively correlated with salinity, indicating high salinity hampered metal uptake which might attribute to competition of cations and formation of less bioavailable inorganic complexes with anions. Overall, high salinity generated two-sided effects (elevated dissolved metal concentrations Vs. reduced metal bioaccumulation) on metal contents in zooplankton (especially for Cr, Cd, Ni, and Cu), resulting in metal- and site-specific metal contents. We noticed relatively higher metal contents in zooplankton at hypoxia sites which could further transfer to predators in the East China Sea, and the underlying mechanisms still require future investigation.

Nonlinear causal analysis reveals an effective water level regulation approach for phytoplankton blooms controlling in reservoirs.

Reservoirs are a rapidly increasing water body providing water supply, irrigation, and many other benefits for human societies globally. However, due to changes in hydrological conditions, building reservoirs tends to bring adverse effects such as eutrophication and phytoplankton blooms, reducing the ecosystem service values. This study focuses on using the empirical dynamic modeling (EDM), an emerging approach for nonlinear analysis, to investigate the nonlinear causal relationship of water level fluctuation (WLF) on phytoplankton biomass and then develop a quantitative model guiding effective phytoplankton blooms controlling based on water level regulations in reservoirs. Specifically, with 9-year continued daily observed data in the Three Gorges Reservoir, we examined the causal effects of different WLF parameters on the dynamics of phytoplankton blooms for the first time. We found that the water level change in the past 24 h (ΔWL) has the strongest causal effect on the daily dynamics of phytoplankton biomass among all WLF parameters (ΔWL, |ΔWL|, and the water level), with a time lag of 2 days. Moreover, EDM revealed a nonlinear relationship between ΔWL and daily dynamics of phytoplankton biomass and achieved a successful prediction for the chlorophyll a concentration 2-day ahead. Further scenario analyses found that both the rise and fall of water level will significantly reduce the chlorophyll a concentration when phytoplankton blooms occur. Nevertheless, on the whole, the rising water level has a more substantial effect on phytoplankton blooms than falling the water level. This result reveals that regulating ΔWL is a simple and effective approach in controlling phytoplankton blooms in reservoirs. Our study reported the nonlinear causal effect of ΔWL on the dynamics of chlorophyll a and provided a quantitative approach guiding effective phytoplankton blooms controlling based on the water level regulation, which might have a broad application in algal blooms controlling in reservoirs and similar waterbodies.

Sedimentation supports life-cycle CH4 production and accumulation in a river valley reservoir: A hierarchical Bayesian modeling approach.

Reservoirs have been recognized as a source of methane (CH4). With the gradual increase in the number of the world's reservoirs, predicting the long-term variation of reservoir CH4 emissions is important to understand the global change in carbon cycling due to reservoir creation and operation. Here, we first categorized the origins and transport of organic carbon (OC) by reservoir creation and operation into the following four aspects: a) the decomposition of flooded organic matter, b) the sedimentation of OC from upstream sediment inputs, c) the transition of the aquatic ecosystem from lotic to lentic type, stimulating the production of autochthonous OC; and d) reservoir as the collector of anthropogenic OC inputs from surrounding communities. It was assumed that OC from the four aspects jointly determined the production and accumulation of reservoir CH4 concentration, supporting life-cycle reservoir CH4 emissions. A hierarchical Bayesian model of reservoir CH4 concentration was established and calibrated by observed monthly datasets in 2018 in the Xiangjiaba Reservoir (XJB), a river valley dammed reservoir in the upper Yangtze River, China. The model explained the relative contributions of the four aspects to reservoir CH4 production and accumulation. Approximately 78% of the CH4 concentration was contributed by the decomposition of flooded organic matter during the first 10 years after impoundment. However, the contribution of flooding faded away after 10 years of impoundment. With the increase in reservoir age, sedimentation of OC dominantly determined the reservoir CH4 production and accumulation. Scenario analysis of the XJB's life cycle demostrated that the CH4 concentration in the XJB would reach its peak approximately 70 - 80 years after impoundment. In the cascade system, the upstream reservoir will help to reduce sediment OC input, and to mitigate downstream reservoir CH4 production and accumulation. Our effort provided a new modeling approach for long-term management strategies to reduce reservoir CH4 emissions under global change.

Identifying key drivers of harmful algal blooms in a tributary of the Three Gorges Reservoir between different seasons: Causality based on data-driven methods.

Intense harmful algal blooms (HABs) can occur in the backwaters of tributaries supplying large-scale reservoirs. Due to the characteristics of process-based models and difficulties in modelling complex nonlinear processes, traditional models have difficulties disentangling the driving factors of HABs. In this study, we used data-driven methods (i.e., correlation analysis and machine-learning models) to identify the most important drivers of HABs in the Xiangxi River, a tributary of the Three Gorges Reservoir, China (2017-2018), for the dry season (from October to mid-April) and wet season (from April to September). We utilized the maximal information coefficient (MIC) combined with a time lag strategy and prior knowledge to quantitatively identify the driving variables of HABs. An extra trees regression (ETR) model was developed to assess the relative importance of causal variables driving algal blooms for the different periods. The results showed that water temperature was the most important driver for the duration of the study, followed by total nitrogen. Nitrogen had a stronger effect on algal blooms than phosphorus during both the wet and dry seasons. HABs were mainly affected by ammonia nitrogen in the wet season and by other forms of nitrogen in the dry season. In contrast, rather than the water temperature and nutrients, the operation of the Three Gorges Dam (difference between inflow and outflow discharge rate) was the most significant factor for algal blooms during the dry season, but its influence sharply declined during the wet season. This study showed that the key drivers of HABs can differ between seasons and suggests that HAB management should take seasonality into account.

Spatial and temporal patterns of heavy metals and potential human impacts in Central Yangtze lakes, China.

Lakes in the central Yangtze River basin have experienced increasing levels of human disturbance during the past several decades, yet large-scale environmental patterns in these lakes and their driving factors remain unclear. Herein we examined spatial and temporal patterns of copper (Cu), zinc (Zn), lead (Pb), arsenic (As), and seven other heavy metals from 16 lakes experiencing a gradient of human disturbance. These lakes were divided among six groups: suburban reservoirs (SR), suburban high-aquaculture lakes (SH), suburban low-aquaculture lakes (SL), suburban no-aquaculture lakes (SN), urban aquaculture lakes (UA) and urban no-aquaculture lakes (UN). Spatially, water-column concentrations of Cd, Ni, Co, Mn, Fe, and Al, and sediment concentrations of Ni were significantly lower in SR compared to other lake groups. Except for Al, heavy metal concentrations did not differ between SN and SL lakes in the water-column or sediments. SH lakes exhibited significantly greater concentrations of Cu, Co, Cr, Mn, and Al in the water-column and Zn in sediments compared to SN lakes. UA lakes contained significantly lower concentrations of Zn, Cd, and Al in sediment compared to UN lakes, though no significant differences were detected within water-column samples. Temporally, with all lake groups combined, summer water-column concentrations of Cd, Pb, Co, Mn, and Al were lower compared to spring and autumn. Additionally, summer sediment concentrations of Zn, As, Co, Fe also were lower compared to autumn. Further results indicated that low-density fish stockings without external feed inputs appeared to have little impact on heavy metals in both suburban and urban lakes. However, high-density fish stockings with external feed inputs were associated with increased heavy-metal concentrations across all lakes. Overall, urbanization has great potential to increase sediment heavy-metal ecological risks. These findings are crucial for developing heavy-metal pollution control and management strategies for freshwater lakes.

Synthesis and structure-activity relationships of nitrobenzyl phosphoramide mustards as nitroreductase-activated prodrugs.

A series of nitrobenzyl phosphoramide mustards and their analogs was designed and synthesized to explore their structure-activity relationships as substrates of nitroreductases from Escherichia coli and trypanosomes and as potential antiproliferative and antiparasitic agents. The position of the nitro group on the phenyl ring was important with the 4-nitrobenzyl phosphoramide mustard (1) offering the best combination of enzyme activity and antiproliferative effect against both mammalian and trypanosomatid cells. A preference was observed for halogen substitutions ortho to benzyl phosphoramide mustard but distinct differences were found in their SAR of substituted 4-nitrobenzyl phosphoramide mustards in E. coli nitroreductase-expressing cells and in trypanosomatids expressing endogenous nitroreductases.

[Surveillance and research on acute meningitis, encephalitis syndrome in Guangxi, China].

OBJECTIVE: To estimate disease burden and epidemiological characteristics of acute meningitis/encephalitis, and provide the basis for the disease control strategy development. METHODS: A syndrome surveillance system was established in Guigang city with a population of 5 020 000. For the suspected cases, serum and CSF were collected, and bacterial culture, latex agglutination test, real-time PCR and ELISA tests were carried out. All involved cases were identified to 6 categories according to WHO case definition. RESULTS: 1424 suspected cases were evaluated in a surveillance of 30 months, yielding the incidence, mortality and mortality of 11.35/100 000 (1424/12 546 500 person years), 0.43/100 000 (54/12 546 500 person years), 3.79% (54/1424) respectively. A total of 103 and 51 cases were confirmed for JE, bacterial meningitis, with a incidence of 0.82/100 000 (103/12 546 500 person years), 0.41/100 000 (51/12 546 500 person years). 96.10% (99/103) of JE cases and 37.30% (19/51) bacterial meningitis cases occurred in < 10 years old children and < 5 years old children. A clinical misdiagnosis rate of 19.42% (20/103) and 15.69% (8/51) were observed for JE and bacterial meningitis. CONCLUSION: Acute encephalitis, meningitis syndrome can cause a higher burden of disease, of which the main components of viral encephalitis. Most of syndrome is occurred in summer and autumn, mainly reported in children of younger than 10 years old. A quite misdiagnosis would be made among meningitis and encephalitis syndrome cases.