Antibiotics and antibiotic resistance genes in the water sources of the Wuhan stretch of the Yangtze River: Occurrence, distribution, and ecological risks.

Given the ubiquitous detection of antibiotics and antibiotic resistance genes (ARGs) in waterbodies worldwide and increasing public attention to water resource safety, this study investigated the presence of antibiotics and ARGs in the water sources of the Wuhan stretch of the Yangtze River (YR) as well as potential ecological risks. In this study, 15 antibiotics and 10 ARGs in a source of drinking water were analyzed using solid-phase extraction-ultra performance liquid chromatography-mass spectrometry technology (SPE-UPLC-MS/MS) and real-time fluorescence quantitative polymerase chain reaction (qPCR). Fourteen antibiotics were detected in the samples from 18 water sources, with the highest concentration detected for tetracycline, reaching up to 1708.33 ng/L. The detection rates of norfloxacin, enrofloxacin, ofloxacin, tetracycline, and roxithromycin were 100%. The concentrations of antibiotics were highest in She Shui, followed by the Wuhan stretch of the lower reaches of the YR, whereas the lowest concentrations were found in the Wuhan stretch of the upper reaches of the YR which were approximately equal to those in the Han River (HR). Ofloxacin and roxithromycin presented a substantial threat to aquatic organisms with high sensitivity at the majority of the sampling sites. The overall abundance of ARGs was notably greater in the lower reaches of the YR compared with the upper reaches and the HR. The highest absolute abundance was observed for sulfa ARGs. Integron intl1 strongly correlated with sul1, sul2, ermB, and qnrS, and antibiotics, strongly correlated with multiple ARGs, suggesting that antibiotics and ARGs are present in water sources in Wuhan and may present a plausible hazard to both human and ecological well-being. Hence, regulating the spread and dissemination of antibiotics and ARGs in the environment is imperative. The findings of this research offer significant insights into the stewardship and safeguarding of aquatic reserves in the Wuhan stretch of the YR.

Analysis and Risk Assessment of Organic Pollutants in Surface Water from Xujiahe Basin, China.

In this study, organic compounds were screened in surface water collected from Xujiahe basin, China by gas chromatography-mass spectrometry (GC-MS). A total of 51 compounds were identified including 14 organochlorine pesticides (OCPs), 9 organophosphorus pesticides (OPs), 16 polycyclic aromatic hydrocarbons (PAHs) and 12 chlorobenzene (CBs). The concentrations of OCPs, PAHs and CBs were generally low. The concentrations of OCPs in Xujiahe reservoir ranged from N.D. to 35.6 ng/L, the concentrations of PAHs ranged from N.D. to 19.8 ng/L and the concentrations of CBs ranged from 10.3 to 124.6 ng/L. The Ecological Structure Activity Relationships (ECOSAR) model was employed to directly predict the integrated toxicity indexes of 51 organic pollutants. The risk quotient (RQ) values of most of the organic compounds in the water samples were acceptable for their ecological risk.

Research on partition of phosphorus in the Three Gorges Reservoir on the Yangtze River.

Partition of phosphorus (P) plays an essential role in its ecological effect in surface waters. Yet limited river sampling hinders our understanding for it. P partition between suspended sediments (SS) and aqueous phase in the mainstem of the Three Gorges Reservoir (TGR) on the Yangtze River were studied based on data during 2004-2019. The results reveal that the percentage of DP (dissolved phosphorus) in TP (total phosphorus) (i.e, λ (DP/TP)) decreased remarkably with increasing concentrations of SS, and the empirical equation by nonlinear fitting is λ (DP/TP) = (SS/50 + 80)/(SS + 98) (SS: mg/L, Model I). When SS increased from several mg/L to 180 mg/L, λ (DP/TP) decreased sharply from averagely 0.80 to 0.25. In the range of SSï¹¥ ~ 400 mg/L, λ (DP/TP) tended to be relatively steady remaining between 0.05 and 0.20 with an average of 0.12. The partition coefficient (Kp) of P between SS and aqueous phase was found to decrease with rising SS and Ce (aqueous concentration of P, i.e., DP).The empirical equation based on SS is Kp (L/g) = 1000 × (49 × SS + 900)/(SS2 + 4000 × SS) (SS: mg/L, Model II). When SS increased from <3 mg/L to ~50 mg/L, Kp decreased rapidly from averagely 88 to 23 L/g, and when SS exceeded 50 mg/L, the pace of decreasing of Kp slowed down. The equation based on Ce is Kp (L/g) = 45.88-194.44 × Ce (mg/L) (Model III). When Ce increased from 0.025 to 0.25 mg/L, the average Kp decreased from 50 to 7.0 L/g. Compared with the influence of variation in SS and Ce, the influence of temperature change on Kp can be ignored. New models are advantageous over previously reported ones, and they can be used to better predict P partition and determine whether SS is a sink or a source.

Preferential deposition of buoyant small microplastics in surface sediments of the Three Gorges Reservoir, China: Insights from biomineralization.

Sediments act as sinks of microplastics (MPs) derived from terrestrial ecosystems. However, the fate and transport of MPs at the zone of sediment-overlying water in reservoir environment are poorly understood. Here, the MPs distribution patterns in surface sediments of the Three Gorges Reservoir (TGR) and dominant mechanisms responsible for the sinking of MPs at the zone of sediment-overlying water were comprehensively investigated. The predominant occurrence of small microplastics (<300 µm, SMPs) in surface sediments of the TGR was found, with buoyant polyethene (PE) was dominant polymer types. Interestingly, the high abundance of SMPs in sediments correlated well with the Ca2+/Mg2+ in overlying water, suggesting that divalent cations in overlying water may enhance the preferential deposition of SMPs. Simulation sinking experiments under the presence of Microcystis aeruginosa and two divalent cations using different-sized PE MPs demonstrated that the greater deposition of SMPs was mainly the result of the formation of biogenic calcite on the surface of MPs rather than magnesium minerals, which provides stronger ballasting effects for SMPs than for large MPs. This study first highlights that the impact of biomineralization on preferential sinking of SMPs and enhances the understanding of the transport behaviour of MPs in aquatic environment.

Geochemical characteristics and environmental implication of rare earth elements in sediments from the Three Gorges Reservoir, China.

The construction and operation of the Three Gorges Dam occluded sediment transportation in the Yangtze River. However, the sources, transport processes, and environmental impacts of these sediments on the Three Gorges Reservoir (TGR) remain unclear. Here, we used rare earth elements (REEs) to trace the transport pathways of sediments in the TGR, China. Geochemical characteristics including the chemical composition and fractionation, temporal and spatial distribution, and potential sources of REEs were also evaluated in this study. The individual REEs concentration in the TGR sediments followed the Oddo-Harkins rule, with the mean REEs value of 207.33 µg/g. REEs concentrations in the midstream were higher than those in the upstream and downstream of the TGR. Statistical analysis showed that water impoundment phase had no significant influence on the distribution of REEs. TGR sediments are mainly derived from terrigenous detrital particulates, characterized by a distinctive enrichment in light REEs, with its percentage higher than 90 % of the total REEs. The significant positive correlation among the REEs confirmed that they are co-existed and shared the similar sources. Multiple provenance analysis approaches using discriminant function analyses, provenance indices, and La/Yb-La/Sm-Gd/Yb ternary diagrams further indicated that the REEs in sediments originated from the weathering of mudstone in the basin of TGR. After periodic water level fluctuation for more than six years, the chemical compositions of REEs in TGR sediments slightly differed from those of the Yangtze River sediments before TGR construction, but were similar to those of the downstream of the Yangtze River. Therefore, this study indicated that the construction and operation of the TGR changed the chemical compositions and the origin of the sediments in the Yangtze River, which can provide useful insights into the transport pathways of TGR sediments and their impacts on the fluvial environment.

Hydrological regimes and water quality variations in the Yangtze River basin from 1998 to 2018.

Understanding the long-term variations in basins that undergo large-scale hydroelectric projects is crucial for effective dam operation and watershed management. In this study, comprehensive analyses were conducted on a dataset spanning over 20 years (1998-2018) of hydrological regime and physicochemical parameters from the Yangtze River basin to evaluate the potential impacts of the Three Gorges Dam. Water level significantly increased from 128.75±58.18 m in 2002 to 136.78±55.05 m in 2005, and the mean flow velocity significantly decreased from 2004 to 2010. However, no significant change in the flow was observed in the basin. Meanwhile, remarkable fluctuations in physicochemical parameters, including dissolved oxygen, chemical oxygen demand, conductivity, hardness, and alkalinity, were mainly observed during impoundment (2003-2009). After that, the above parameters tended to stabilize, and some even returned to their original levels. The dam's retention effect significantly reduced the suspended solids (SS) in both up- and downstream, to only one-third of the pre-operation level. And total phosphorus and chemical oxygen demand also significantly decreased with the decline of SS. Particularly, ammonium also showed a significant downward trend, with the up- and downstream of the dam falling by 36.8 % and 26.1 %, respectively. However, the increasing total nitrogen (7.5 % and 20.0 % up- and downstream of the dam, respectively) still threatened the water quality of the basin, especially in the estuaries. Additionally, the significant decline in dissolved oxygen downstream (from 8.53±1.08 mg/L to 8.11±1.36 mg/L) also exacerbated the hypoxia in the Yangtze River estuary. The results demonstrated the long-term impact of the construction of the Three Gorges Dam on the environmental elements of the Yangtze River basin, which provides reference data and guidance for the construction of big dams in major rivers in the future.

[Water Quality Change Trend and Risk Analysis of Wuhan Hanjiang River Water Source].

Hanjiang River is closely related to the middle route of the South-to-North Water Diversion Project, the Water Diversion Project from the Hanjiang River to the Wei River, and the Water Diversion Project in Northern Hubei. The Wuhan Hanjiang River water source is one of the important drinking water sources in China; its water quality safety is significant to living and production for millions of residents in Wuhan. Based on data from 2004 to 2021, the water quality variation trend and risk of Wuhan Hanjiang River water source were studied. The results showed that a certain gap existed between the concentrations of some pollutants such as total phosphorus, permanganate index, ammonia nitrogen, and correspondent water quality target, especially for the total phosphorus. The growth of algae in the water source was marginally limited by the concentrations of nitrogen, phosphorus, and silicon. When other factors remained unchanged, diatoms tended to grow rapidly when the water temperature was appropriate (6-12℃). The quality of water upstream had a great impact on the water quality of the Hanjiang water source. There may have been pollutants entering into the reach during the West Lake Water Plant and Zongguan Water Plant. There were differences in the temporal and spatial variation trend of concentrations between permanganate index, total nitrogen, total phosphorus, and ammonia nitrogen. Significant changes in the ratio of nitrogen and phosphorus in the water body will affect the population structure and quantity of planktonic algae and ultimately affect the safety of water quality. The water body in the water source area was generally in the state of medium nutrition to mild eutrophication, and middle eutrophication may have occurred in a few periods. In recent years, the nutritional level of the water source has been on the decline. It is necessary to make an in-depth investigation on the source, quantity, and change trend of pollutants in water sources in order to eliminate potential risks.

Spatiotemporal Patterns in pCO2 and Nutrient Concentration: Implications for the CO2 Variations in a Eutrophic Lake.

Lakes are considered sentinels of terrestrial environmental change. Nevertheless, our understanding of the impact of catchment anthropogenic activities on nutrients and the partial pressure of carbon dioxide (pCO2, an important parameter in evaluating CO2 levels in water) is still restrained by the scarcity of long-term observations. In this study, spatiotemporal variations in nutrient concentrations (total nitrogen: TN, total phosphorus: TP, nitrate: NO3--N, and ammonium: NH4+-N) pCO2 in Taihu Lake were analyzed from 1992 to 2006, along with the gross domestic product (GDP) and wastewater discharge (WD) of its catchment. The study area was divided into three zones to characterize spatial heterogeneity in water quality: the inflow river mouth zone (Liangxi River and Zhihugang River), transition zone (Meiliang Bay), and central Taihu Lake, respectively. It is abundantly obvious that external nutrient inputs from the catchment have a notable impact on the water parameters in Taihu Lake, because nutrient concentrations and pCO2 were substantially higher in the inflow river mouth zone than in the open water of Meiliang Bay and central Taihu Lake. The GDP and WD of Taihu Lake's catchment were significantly and positively correlated with the temporal variation in nutrient concentrations and pCO2, indicating that catchment development activities had an impact on Taihu Lake's water quality. In addition, pCO2 was negatively correlated with chlorophyll a and the saturation of dissolved oxygen, but positively correlated with nutrient concentrations (e.g., TN, TP, and NH4+-N) in inflow river mouth zone of Taihu Lake. The findings of this study reveal that the anthropogenic activities of the catchment not only affect the water quality of Taihu Lake but also the CO2 concentrations. Consequently, catchment effects require consideration when modeling and estimating CO2 emissions from the extensively human-impacted eutrophic lakes.

Source, Distribution and Potential Risk of Antimony in Water and Sediments of Danjiangkou Reservoir: Impact from Dam.

Danjiangkou Reservoir is the water source of the mid-route of the South-to-North Water Transfer Project. The source, distribution and potential risk of antimony in its water and sediments are rarely reported. In this study, symmetrical investigation results demonstrated that the concentration of antimony in the Han sub-reservoir and water in front of the dam fluctuated at about 0.9 mg L-1, while it was relatively higher and increased with the distance from the dam in Dan sub-reservoir water, with an annual average of 0.93~3.15 mg L-1. In recent years, the concentration of antimony in the Danjiangkou Reservoir showed a downward trend, and the difference between the Han and Dan sub-reservoirs decreased significantly. The antimony in the sediments in the reservoir was primarily derived from the inflowing rivers, and it was higher in the Dan sub-reservoir than in the Han sub-reservoir. The concentration of antimony in the water in the reservoir was considerably higher than the background value in the watersheds, indicating that there is an external input with decreasing input intensity. The content of antimony in the sediments in the reservoir and its inflow rivers was substantially higher than the background value of watersheds, indicating that there is a certain degree of enrichment. In addition, the antimony mining industry in the water source area poses a risk to the water safety of the reservoir. Antimony is not a conventional pollutant. Consequently, the collection of antimony monitoring results is a challenging task. Additionally, this study fills the gap in regional antimony research. Furthermore, the ecological risk assessment of antimony in China is still in its infancy. Unquestionably, the study of the temporal and spatial distribution of antimony concentration will be beneficial for the protection of water sources in relevant regions.

Hydrochloric acid corrosion induced bifunctional free-standing NiFe hydroxide nanosheets towards high-performance alkaline seawater splitting.

We report a facile route to fabricate free-standing NiFe hydroxides by corrosion engineering as high-performance bifunctional electrocatalysts for seawater splitting. Compared with H2SO4 and HNO3, HCl can promote the dissolution of Ni2+ from NiFe foam and the in situ formation of active NiFe hydroxides due to the strong interaction between Cl- and metal. In situ Raman spectroscopic characterization reveals that HCl corrosion induced NiFe hydroxides (HCl-c-NiFe) can generate oxygen evolution reaction (OER) active NiOOH species at a low potential of 1.4 V vs. reversible hydrogen electrode (RHE) and exhibits equally respectable activity for the hydrogen evolution reaction (HER). During a 1000 h test in an alkaline electrolyte or a 300 h test in an alkaline seawater electrolyte within a two-electrode system at 100 mA cm-2, the cell exhibits outstanding stability and high Cl- tolerance with a low working voltage of 1.62 V, outperforming benchmark Pt/IrO2 and most of the reported bifunctional catalysts.

[Temporal and Spatial Characteristics of Total Phosphorus in the Middle and Lower Yangtze River Mainstem Under New Water and Sediment Conditions].

After the completion of the Three Gorges Reservoir and the upstream reservoir group of the Yangtze River, new water and sediment conditions appeared in the middle and lower reaches of the Yangtze River, and its influence on the phosphorus concentrations in water has attracted much attention. Therefore, the spatial and temporal distributions of total phosphorus (TP) concentrations in the middle and lower reaches of the mainstem under the new water and sediment conditions were studied. The results show that:① after the construction of the Three Gorges Reservoir, the concentrations of TCP (samples were allowed to settle for 30 min) in the middle and lower reaches of the Yangtze River fluctuates between 0.10 and 0.15 mg·L-1, and generally increased during 2004-2010 and then decreased during 2014-2019, and increases along the flow direction. The concentrations of dissolved total phosphorus (TDP) have slowly increased with time. ② The settleable solids influence the phosphorus content to varying degrees. The median values of TCP/TP ratio in Nanjinguan, Hankou, and 23 km below Wusongkou, are 0.900, 0.720, and 0.609, respectively, which decreases successively from upstream to downstream. The proportion of TPP (total particulate phosphorus)/TP shows an increasing trend along the flow direction. The median values of TPP/TP ratios in Nanjinguan, Hankou, and 23 km below Wusongkou were 0.439, 0.567, and 0.738, respectively. ③ According to the "Environmental quality standard for surface water GB 3838-2002", the water quality was assessed using TCP concentrations, and the assessment results showed that the water quality of the middle and lower reaches of the Yangtze River was generally good. However, considering the influence of settleable solids, the water quality categories assessed based on TP concentrations would be worse, especially near estuaries. ④ In the middle and lower reaches of Yangtze River, there is little difference in the phosphorus concentration of different monitoring sites in the upper section of main stream; however, the difference is obvious near the estuary. ⑤ The concentration of TCP in the coastal waters of the urban river section of the middle and lower reaches of the Yangtze River is significantly higher than that of the main channel, and there are obvious coastal pollution zones in the coastal waters of the urban river section.

[Evaluation of Temporal and Spatial Variation Characteristics of Nutrients in Surface Sediment in the Three Gorges Reservoir Area].

With the construction of the Three Gorges Dam, the river flow pattern and sediment dynamics are expected to be affected. As a consequence, the sediment traits could be impacted by these changes. The temporal and spatial variation characteristics of the nutrient content from 2000 to 2015 in surface sediment were analyzed in the main stream from Jiangjin to the dam site section of the Yangtze River and in the estuaries of the representative input tributaries of the Three Gorges Reservoir, such as the Jialing River, Yulin River, Wujiang River, Xiaojiang River, Daning River, and Xiangxi River. Then, the state of the pollution was assessed. Results revealed that the average concentrations of total phosphorus (TP) in the surface sediments of the main stream ranged from 678.2 to 928.6 mg·kg-1, the average contents of total nitrogen (TN) ranged from 0.203% to 0.362%, the average contents of potassium ranged from 1.74% to 2.37%, and the average contents of organic matter ranged from 0.94% to 1.54%. The average concentrations of TP in the estuaries of the representative input tributaries ranged from 490.1 to 832.3 mg·kg-1, the average contents of TN ranged from 0.257% to 0.495%, the average contents of potassium ranged from 1.69% to 2.32%, and the average contents of organic matter ranged from 1.21% to 2.27%. The concentrations of TP and potassium in the study sections were generally within background concentration ranges, while the concentrations of TN were obviously above background levels, and the concentrations of organic matter were obviously below background levels. The nutrient contents in the surface sediment did not display significant differences among the study sites; however, the distributions of different nutrient contents along the river varied widely. Although the nutrient contents in the surface sediments fluctuated somewhat during different flow periods, they were seemingly unaffected by the impoundment, since no obvious enrichment was observed throughout the impoundment. The evaluation of organic index indicated a clean state for the surface sediments in the majority of the study area, while there was a moderately polluted state in some local sections. The evaluation of nitrogen pollution indicated a polluted state for most sections. Overall, the nutrients in the surface sediments of the Three Gorges Reservoir showed moderate ecological risks, possibly caused by TP and TN.

[Temporal and Spatial Variation Characteristics of the Heavy Metals Content in the Surface Sediment and the Potential Ecological Risk Trends in the Three Gorges Reservoir Area].

With the construction progress of the Three Gorges Project, the hydrological situation of Three Gorges Reservoir changes greatly, which causes the changes of suspended solids precipitation conditions and surface sediment traits. This research analyzed the temporal and spatial variation of the heavy metal pollution in the surface sediment and the potential ecological risk trends during the years from 2000 to 2015 in the trunk stream of the Yangtze River from Jiangjin to the Three Gorges Dam area and some major tributaries, such as Jialing River, Yulin River, Wujiang River, Xiaojiang River, Xiangxi River. The results showed that the average content ranges of heavy metals (including Cu, Pb, Mn, As, Hg etc.) in surface sediments at the main stream monitoring sections during the study period were 46.5-85.7 mg·kg-1(Cu), 43.8-65.1 mg·kg-1(Pb), 784.2-910.6 mg·kg-1(Mn), 8.44-11.91 mg·kg-1(As), 0.193-0.236 mg·kg-1(Hg) respectively; The average content ranges of the heavy metals in surface sediments at the main stream monitoring sections during the study period were 16.5-85.6 mg·kg-1(Cu), 25.8-74.8 mg·kg-1(Pb), 573.7-996.3 mg·kg-1 (Mn), 6.96-13.31 mg·kg-1 (As), 0.160-0.232 mg·kg-1 (Hg) respectively. The results also showed that there were obvious differences of the heavy metals content in some areas between the left and right bank of the trunk stream of the Yangtze River in the Three Gorges Reservoir area. The results also showed that the concentration variation trends of the heavy metals were different in the surface sediments, such as Cu, Pb, Mn, As and Hg. The content of Hg was the most influenced element by the water period effect. The concentration variation trends of these elements were different at different monitoring sections during the construction and water harvesting progress of the Three Gorges project. The contents of Cu, Pb, Mn and As in sediment from the Three Gorges Reservoir area showed strong positive correlations between each other. But there was a low correlation between the content of As and those of other elements. There was no significant correlation between the content of Hg and those of other heavy metal elements. According to the geoaccumulation index analytical method, the contents of the heavy metals in surface sediments in the Three Gorges Reservoir area were generally at low enrichment level. But the pollution caused by Hg should be paid attention. The change of potential ecological risk index was small in the main stream and the major tributaries of the Yangtze River (except Wujiang River) in most of the time. It should also be noted that the change of potential ecological risk index fluctuated obviously at a high level before the year of 2008, and then the change fluctuations trends descended with time and tended to be stable.