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The ecological risks of antibiotics in aquatic environments have raised great concerns worldwide, but the chronic effect of antibiotic contaminants on cyanotoxin production and release remains unclear. This study investigated the long-term combined effects of spiramycin (SP) and ampicillin (AMP) on microcystin (MC) production and release in both unicellular and colonial Microcystis aeruginosa (MA) through semi-continuous exposure test. At exposure concentration of 300 ng L−1, MA growth rates were stimulated till the end of exponential phase accompanied with the up-regulation of photosynthesis-related gene. The exponential growth phases of unicellular and colonial MA were prolonged for 2 and 4 days, respectively. The stimulation rate of growth rate and MC content in unicellular MA were significantly higher than that in colonial MA. The highest concentrations of intracellular MC (IMC) and extracellular MC (EMC) were observed in the binary mixture at equivalent SP/AMP ratio (1:1). The promotion of IMC concentration was in consistent with the stimulated expression of MC-synthesis-related gene and nitrogen-transport-related gene. The malondialdehyde content and activities of superoxide dismutase and catalase in unicellular MA were significantly higher than those in colonial MA. The EMC concentration and the antioxidant responses of both unicellular and colonial MA significantly increased with exposure time. Long-term exposure to mixture of SA and AMP at environmentally relevant concentrations would aggravate the disturbance to aquatic ecosystem balance through the stimulation of MA proliferation as well as the promotion of MC production and release.

Tetracycline (TC) antibiotics are widely used in livestock and poultry breeding. However, limited work has been done on the partition of TCs between suspended sediment (SPS) and overlying water or on the seasonal effects of rainfall events on the behavior of TCs in receiving rivers. Here, we assessed the impacts of rainfall events in different seasons on the concentrations and fate of TCs in a typical watershed. Concentrations of TCs in river water, SPS, and surface sediment were determined before, during, and after rainfall events. Results indicated that the sequence of TC concentration levels in river water was wet season > normal season > dry season. Rainfall events in all seasons increased the concentrations of TCs in river water. The concentration of TCs in SPS reached 104 ng/g. The SPS concentrations were only 22–78 mg/L, while the daily fluxes of TCs in particulate form contributed 39%–62% of the total (dissolved and particulate) daily fluxes in river water. The increases in TCs in river water were mainly attributed to internal release from sediment during rainfall events in the dry season but to external input during rainfall events in the wet season. The degradation products of TCs with higher concentrations and greater toxicity than their parent compounds should be considered in the ecological risk assessment of TCs. This research demonstrated that manure application should not be conducted in the normal season or before rainfall events, especially heavy rainfall.

In this paper, we study the formation of finite-time singularities of smooth solutions to the compressible Euler equations with damping in arbitrary dimensions for isentropic, polytropic fluid flows. The radial component of initial momentum is assumed to be large enough and the smooth solutions are assumed to be decay at far fields, but it is not required that the initial velocity field has a compact support. It is shown that the smooth solutions to the Cauchy problem will break down in a finite time. Our result partially complements the work for the compactly supported initial velocity field (Sideris et al., 2003).

The initial–boundary value problem for three-dimensional quantum hydrodynamic models is considered outside a unit ball. It is proved that the smooth solution will blow up in a finite time provided that a weighed functional associated with the initial momentum is large.

Intensifying human activity coupled with climate change increase the transport of excess riverine nitrogen (N) and phosphorus (P) loading from catchment to lake, leading to eutrophication and harmful algal blooms worldwide. To improve understanding of multi-temporal patterns of riverine N and P export and their hydro-biogeochemical controls over both episodic events and long-term trend, we analyzed and interpreted high-frequency data of total nitrogen (TN), ammonia-nitrogen (NH

Global climate change increased the frequency of extreme rainfall events, leading to higher flood risk. In addition to the personal and property losses, another important consequence of a flood disaster was release and exposure risks from emerging contaminants, which was usually overlooked. The remobilization and fate of the antibiotics induced by floods remain unclear. We captured antibiotic concentrations around the Chaohu Lake after an unprecedented flood with a range of 5.0-317 ng/L. Higher concentrations in polder waters than their receiving rivers were attributed to the antibiotic release from soil particles and the sharp increase of water: soil ratio by flood storage. Source apportionment analysis of antibiotics implied that diffuse pollution by manure application and aquaculture activity was the predominant sources. Commonalities of spatial variations of antibiotics in polders were related to the condition of waterlogging and pollution source. The total antibiotic storage for all submerged polders was estimated at 27.9 kg. The concentrations and risks from pumping floodwater detained by polders into the lake were much higher than that from discharging flood directly into the lake. The retention-reaction-remobilization process would pose unexpectedly high risks for the lake. This study provided a new sight for constructing ecological wetland flood storage areas.

Uncertainties in watershed modeling need to be addressed to increase predictive accuracy and enhance model interpretation. Nevertheless, event-based characteristics incorporating management concerns were rarely considered in the sediment modeling within an uncertainty assessment framework, which might lead to biased decision makings in watershed management. In this study, the event-based likelihood measure was developed to improve the understanding and prediction of the sediment dynamics in a data-scarce catchment in the Three Gorge Reservoir Region (TGRR), China. The uncertainty assessment is based on the Generalized Likelihood Uncertainty Estimation (GLUE) approach applied to the Hydrological Simulation Program - Fortran (HSPF) model. The impact of the Nash-Sutcliffe efficiency (NSE) as the traditionally used likelihood measure was also investigated as a comparison. The results showed that the event-based likelihood measure had advantages in judging critical parameters. Sensitive parameters in the soil erosion and channel transport and their impacts on different phrases of sedimentograph were recognized. The event-based likelihood measure was much more discriminating by efficiently eliminating unsatisfactory parameter sets. Better validity in efficiently reducing the parameter uncertainty and a higher identifiability was achieved by the newly developed likelihood measure. The event-based likelihood measure resulted in more progressive reductions in predictive uncertainty in terms of uncertainty bounds and evaluation criteria. The proposed uncertainty assessment framework yields improved predictions and an increased understanding of sediment response behaviors in a data-limited environment.

Endocrine-disrupting compounds (EDCs) enter lakes mainly through river inflow. However, the occurrence, transport and fate of EDCs in the overlying water, suspended particulate matter (SPM) and sediment of inflowing rivers remain unclear. This study investigated the load of seven EDCs in a complex river-lake system of the Taihu Lake Basin during different seasons, with the aims of revealing the transport routes of EDCs and identifying the contributions from different sources. The results indicated that the levels of the seven EDCs in the wet season with high temperature and dilution effects were generally lower than those in the other seasons. EDC enrichment in the sediment was largely affected by the transport and fate of SPM. Moreover, the estrogenic activity and risks of EDCs were the highest in SPM. The mass loadings of particulate EDCs carried by SPM were 2.6 times that of overlying water. SPM plays a vital role in the transport and fate of EDCs in complex river-lake systems and thereby deserves more attention. Nonpoint sources, particularly animal husbandry activities and untreated domestic sewage, were the main sources of EDCs, amounting to 61.5% of the total load.

Water regulation of the Xiaolangdi Reservoir of the Yellow River was chosen as a case to investigate variations in concentrations and bioavailability of heavy metals caused by water conservancy projects in rivers. Water and suspended sediment (SPS) samples were collected at downstream sampling sites along the river during this period. Concentrations and speciation of Zn, Cr, Cu, Ni, and Pb in water and SPS samples were analyzed, and their bioaccumulation was studied with Daphnia magna. This study indicated that the exchangeable and carbonate-bound fractions of heavy metals in SPS decreased along the studied stretch, and the dissolved heavy metal concentrations increased along the river with 1.6–15 folds. This is because sediment resuspension increased along the river during water regulation, giving rise to the increase of heavy metal release from SPS. The dissolved Zn, Cu, Ni, and Pb concentrations were significantly positively correlated with SPS concentrations, and their increase along the river was greater than Cr. The body burdens of heavy metals in D. magna exposed into samples collected from the reservoir outlet were 1.3–3.0 times lower than those from downstream stations, suggesting that the heavy metal bioavailability increased during water regulation. This should be considered in the reservoir operation.

A simplified stationary energy-transport model in semiconductors is studied while the conductivity depends on both electron density and temperature. The existence and uniqueness of classical solutions to the model is proved for small variations of electron density and temperature.

A novel multi-source data fusion method based on Bayesian inference (BIF) was proposed in this study to blend the advantages of in-situ observations and remote sensing estimations for obtaining accurate chlorophyll-a (Chla) concentration in Lake Taihu (China). Two error models (additive and multiplicative) were adopted to construct the likelihood function in BIF; the BIF method was also compared with three commonly used data fusion algorithms, including linear and nonlinear regression data fusion (LRF and NLRF) and cumulative distribution function matching data fusion (CDFF). The results showed the multiplicative error model had small normalized residual errors and was a more suitable choice. The BIF method largely outperformed the data fusion algorithms of CDFF, NLRF and LRF, with the largest correlation coefficients and smallest root mean square error. Moreover, the BIF results can capture the high Chla concentrations in the northwest and the low Chla concentrations in the east of Lake Taihu.

Understanding the relation between landscape pattern and water quality is essential to making a master plan for restoration of regional lake and wetland clusters, which has not yet been well resolved. Here, we studied the impacts of landscape pattern changes on water quality over lake clusters, taking the aquaculture area in the Lixia River hinterland of China as a case. Multi-temporal Landsat series of remote sensing data from 1985 to 2018 was used and space-for-time substitution (SFTS) method was applied to explore the relationship between landscape pattern and water quality. Results showed that wetland and free water surface were the dominant classes of the lake cluster in 1985 and 1990, but they began to rapidly decrease from 1995 to 2000. The enclosure aquaculture increased rapidly since 1995 and became the dominant class between 1995 and 2018. The patch density of aquaculture water (PD_A) increased from 0.09n/km2 in 1985 to 0.34n/km2 in 2018, with the largest degree of fragmentation in 2000. However, the growth rate of PD_A declined significantly after the enactment of the lake ecological protection policies. The SFTS results showed that PD_A had positive correlation with total nitrogen (TN) (r = 0.26), ammonia nitrogen (NH3-N) (r = 0.21), and Chlorophyta (r = 0.33), and the water quality degraded with increasing PD_A. Hence, PD_A could be a water quality indicator of lakes in the Lixia River hinterland. The study is expected to provide a viable method to design regional restoration plan for degraded and over-developed wetland areas.

To investigate the effect of recurrent sediment resuspension-deposition events (RSRDEs) on bioavailability of polycyclic aromatic hydrocarbons (PAHs) in aquatic environments, a modified device was used to simulate three resuspension-deposition events with the sediment collected from the Yellow River. The results showed that the dissolved organic carbon (DOC)-water distribution coefficients of PAHs decreased with time during the first resuspension-deposition period. It indicates that some PAHs associated with organic carbon (OC) in suspended sediment (SPS) desorbed with the release of OC and became DOC-associated PAHs in the overlying water, then the PAHs desorbed from the DOC and became freely dissolved. After first 2-h suspension, only 1.90% of phenanthrene, 2.98% of pyrene, and 0.33% of chrysene in the overlying water came from pore-water; at least 61.6%, 89.6%, and 95.3% came from DOC-associated PAHs in SPS and the rests were released from the insoluble OC in SPS. The maximum desorption ratios in the original sediment were 20%, 12%, and 14% for phenanthrene, pyrene, and chrysene, respectively during the first resuspension-deposition event. The SPS concentration followed the sequence of the third > second > first resuspension event. This was because RSRDEs changed the SPS particle size and enhanced floc formation. There was no significant difference in the total dissolved PAH concentrations among the three resuspension events, while their freely dissolved concentrations followed the sequence of the third > second > first resuspension event. During deposition periods, more than half of the total/freely dissolved PAHs released during suspension still existed in the overlying water after 70-h deposition. This study suggests that the RSRDEs will increase the bioavailability of PAHs in aquatic environments, especially near the sediment-water interface, and the potential effects of PAHs during RSRDEs on fish/human in rivers and lakes should be considered in future management.

The water–sediment regulation of the Xiaolangdi Reservoir is conducted to control the relationship between riverine runoff and sediment transport of the Yellow River; however, there is no research about the effect of water–sediment regulation on the bioavailability and fluxes of hydrophobic organic compounds (HOCs). In this study, water and suspended sediment (SPS) samples were collected downstream of the Xiaolangdi Reservoir before, during, and after the water–sediment regulation in 2013. The 16 priority polycyclic aromatic hydrocarbon (PAH) concentrations of freely dissolved, total dissolved, and SPS-associated were determined. During water regulation, water discharged from the reservoir at a high flow rate led to the resuspension of downstream sediment. During sediment regulation, the sediment ejected from the reservoir resulted in higher SPS concentrations than that during water regulation. Both the freely and total dissolved PAH concentrations in river water during sediment regulation were the highest, followed by the concentrations during water regulation and before regulation. The freely dissolved PAH concentrations in river water during the water–sediment regulation were 2–11 times higher than those before water–sediment regulation. This was due to the fact that the resuspended sediment during water–sediment regulation could release PAHs into water phase, and more contaminants were released from the SPS during sediment regulation than during water regulation. The fluxes of sediment and the 16 priority PAHs (Σ16PAHs) during water–sediment regulation contributed to 32.4% and 35.7% of their annual fluxes, respectively, which were higher than the contribution (22.6%) of water discharge. This study suggested that the water–sediment regulation might reduce the long-term retention of sediment and PAHs in the reservoir. However, the environmental risk of PAHs as well as other contaminants downstream of the reservoir and in the estuary might increase during that period. Therefore, the effect of water–sediment regulation on the bioavailability and environmental risk of HOCs should be considered in the operation and management of the Xiaolangdi Reservoir in the future.

A novel method based on multiset canonical correlation analysis (mCCA) and linear discriminant analysis (LDA) is presented to identify the major depressive disorder (MDD). The new method comprises two parts, namely, the mCCA-rreg and sparse LDA models. The mCCA-rreg model extends the classical canonical correlation model to calculate functional connections by restricting the references to a reference space and adding a spatial regularization term. The reference space is used to ensure that the model extracts important components first from several datasets simultaneously by decreasing the importance of the components in which we are uninterested. The spatial regularization term helps in avoiding the multicollinearity and overfitting problems under the low signal-to-noise ratio circumstance. The sparse LDA model extends the classical LDA model to extract a small subset of discriminative classification features by fusing clinical scores. In the real data experiment, we extract two functional connection modes from 45 subjects by the mCCA-rreg model. Then, we construct classifiers to identify the patients with MDD based on the connections selected by the sparse LDA model. The best accuracy is higher than 95%. The results show that the mCCA-rreg model can retrieve the important components characterized by a preassigned reference space and exclude the noise or components of no interest. The sparse LDA model can extract discriminative classification features related to clinical scores.

In the present work, the influences of suspended sediment (SPS) on the toxic effects of phenanthrene (PHE), one kind of polycyclic aromatic hydrocarbons, to Daphnia magna was studied using a dialysis bag simulation system, which equalized the freely dissolved concentration of PHE between outside the dialysis bag in the presence of SPS and inside the dialysis bag in the absence of SPS. The immobilization and total superoxide dismutase (T-SOD) activity of Daphnia magna caused by PHE (0-0.8 mg L(-1)) were investigated under the influence of different SPS concentrations (0, 1, 3, 5 g L(-1)) during a 96 h-exposure. The results showed that, compared to the absence of SPS, the presence of SPS (1-5 g L(-1)) increased the immobilization of Daphnia magna by 1.6-2.7 times when the freely dissolved concentration of PHE was identical in both systems. The inhibition of T-SOD activity of Daphnia magna by PHE was significantly greater in the presence of SPS than in the absence of SPS (p0.01). This infers that the PHE sorbed on SPS might be bioavailable and enhanced the toxic effect of PHE to Daphnia magna. The bioavailable fraction of PHE sorbed on SPS ranged from 10.1% to 22.7%, and the contribution of PHE sorbed on SPS to the immobilization caused by total PHE in the exposure system increased with SPS concentration, with the contribution ratio increasing from 36.7% to 57.7% when SPS concentration increased from 1 to 5 g L(-1). This study suggests that only considering the concentrations of hydrophobic organic compounds in the water phase may underestimate their toxicity; and the hydrophobic organic compounds sorbed on SPS should not be ignored in assessment of water quality and the establishment of water quality standard in the future.

Rainfall-runoff events can account for transferring a significant portion of agricultural nonpoint source (NPS) pollution loads to surface water bodies. Nevertheless, mechanistic understanding of intra- and inter-event characteristics and underlying controls are not sufficiently obtained especially under conditions of scarce monitoring data, which hampers the design of appropriate management strategies. This paper presented an approach for an increased understanding of NPS pollution characteristics and controls during events (intra-event) and between events (inter-event) by combining monitoring, modeling, and multivariate statistics. Event-based NPS modeling by the Hydrological Simulation Program-Fortran (HSPF) model was improved of its predictive ability by incorporating intra-event variability based on grab samplings during representative rainfall-runoff events. The validated model was then used to simulate the intra- and inter-event dynamics of flow, suspended sediment, total phosphorus (TP), and total nitrogen (TN) exports in 100 rainfall-runoff events with different event types. The simulation results suggested that the intra-event distribution (e.g., dispersion degree and maximum changing rate) varied between event types. A higher level of event types generally resulted in more sensitive and flashy catchment responses to rainfall-runoff events, while nutrient availability from fertilizer application, antecedent soil moisture, and precipitation intensity also drove the intra- and inter-event patterns. Load duration curves and flow-weighted concentrations showed that the TN pollution in the study area was extremely severe, especially for the high flow regime and V-E heavy (i.e. very heavy and extremely heavy) events which should be paid particular attention in designing vegetation- and storage-based conservation practices. The principal component analysis revealed that controlling factors varied among event types. Sediment and TP exports were transport-limited in medium and heavy events; TN export was transport-, pre-condition-, and source-limited in medium, heavy, and V-E heavy events, respectively. The combined framework offers insights into agricultural NPS pollution controls from an event-based prospective.

The existence of classical solutions to the one-dimensional stationary quantum drift–diffusion model for semiconductor devices is investigated. The proof is based on an exponential variable transformation and the Leray–Schauder fixed-point theorem. Furthermore, the uniqueness of solutions to the isothermal model is proved, if the current density and the Planck constant are sufficiently small.

A surface plasmon resonance (SPR) sensor that uses molecularly imprinted polymer (MIP) ultrathin film as sensing material was developed for detecting profenofos in tap water. The MIP ultrathin film was anchored on a gold chip by surface-initiated radical polymerization. The gold surface was first modified by 11-mercaptoundecanoic acid to form a self-assembled monolayer (SAM). To easily graft 2,2-azobis (2-amidinopropane) hydrochloride onto the SAM, the carboxyl of SAM was activated using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. Then, the MIP film was synthesized by thermal-initiated polymerization using methacrylic acid as functional monomer and trimethylolpropane trimethacrylate as cross-linker. On the basis of this principle, two methods for ultrathin film preparation were studied and the most suitable technique was adopted. The prepared ultrathin film was characterized by atomic force microscopy. The MIP-SPR sensor was used to detect profenofos in tap water spiked with 0.001–0.1 μg mL−1 of the insecticide. The sensor showed high sensitivity, selectivity and good stability. The recoveries and repeatability (RSD, n = 4) of the sensor were 89.81–100.99% and 3.69–5.76%, respectively, while the detection limit based on a signal-to-noise ratio of 3 (S/N = 3) was 3.6 × 10−4 μg mL−1.

In this work, we demonstrate the development of a highly sensitive and selective surface plasmon resonance (SPR) immunosensor for label-free detection of ractopamine (RCT) as low as 0.12 ppb (ng mL−1) direct from pork liver samples. RCT is a kind of the β-adrenergic agonist with N-alkylphenyl substituent, and the development of high performance sensing methods for RCT is a critical issue because of its vital role in human metabolism. To construct the immunosensor system, the biosensor surface was formed by immobilization of ractopamine–ovalbumin (RCT–OVA) conjugate onto an Au-thiolate self-assembled SPR sensor chip by covalent amide binding, and the detection of RCT was performed based on indirect competitive inhibition principle. Detailed works were carried out focusing on optimizing the conditions that affect immunosensitivity, including immobilization buffer, immunobinding buffer, RCT–OVA concentration, antibody concentration, activation time, regeneration buffer, etc. A preferable way to determine the optimal antibody concentration was performed comparing with that used in most other reported researches. Under the optimal conditions, the biosensor exhibits a linear detection range of 0.28–4.29 ng mL−1, LOD of 0.12 ng mL−1 and IC50 of 1.17 ng mL−1. It improved that the developed SPR immunosensor is more sensitive for detection of RCT against other reported ones.

The global-in-time existence of weak solutions to the barotropic compressible quantum Navier–Stokes equations has been proved very recently, by Jungel (2009) [1] , if the viscosity constant is smaller than the scaled Plank constant. This paper extends the results to the case that the viscosity constant equals the scaled Plank constant. By using a new estimate on the square root of the solution, apparently not available in [1] , the semiclassical limit for the viscous quantum Euler equations (which are equivalent to the barotropic compressible quantum Navier–Stokes equations) can be performed; then the results of this paper are obtained easily.