Northwest River Research Articles

Developing an Integrated Flood Management Plan under climate change for Grand River North West River basin, Mauritius

Developing an Integrated Flood Management Plan under climate change for Grand River North West River basin, Mauritius

Spatial Analysis for Geometric Parameters of Badush dam Reservoir, Mosul, Northern Iraq

The Iraqi government planned to complete the building of partially constructed Badush dam to protect against the collapse of Mosul Dam on Tigris River northwest of Mosul. The study aimed to derive the ge‎ometric parameters that compatible with the levels ranged 226.5-312 m (a.s.l.) such as reservoir volume, reservoir area, reservoir submerged area, perimeter, and average depth of the water column, which values ranges are 68039-12354976139 m3, 130074-407943574 m2, 130078-410538707 m2, 2.32-594.27 km, and 0.52-30.29 m respectively. These parameters were analyzed against the raising of the level, the spatial analysis of the geometric criteria and its relations with the levels of Badush reservoir showed that the relations between the volume of the positive bodies (islands), the undulated areas above water level which indicate the islands, and the planer areas (projections) of the islands with the level, fluctuates between increase and decrease with an increase in the level, as for the volume of reservoir, the submerged undulated area, the exposed planer area of the water pond, and the average water column depth they increased with the level increasing, unlike the thickness of the islands with the level, which fluctuates in increase and decrease with the level, the geometric analysis of the reservoir showed that Badush Dam is able to absorb the flood wave resulting from the collapse of Mosul Dam, at a level much lower than the level suggested in the preliminary studies that were adopted in the designs, because a large part of the water of Mosul Dam reservoir will remain in the same reservoir when the level is balanced after the collapse. between the two reservoirs, and that the results of this analysis represent a database that will be used in subsequent modifications in the designs.

Urbanization influenced the interactions between dissolved organic matter and bacterial communities in rivers

Increased urbanization and anthropogenic activities can alter dissolved organic matter (DOM) and complicate its interaction with bacteria in rivers' ecosystems, however, there is limited information about how bacterial communities respond to DOM components in rivers with different urbanization levels. Here, we combined spectroscopy-based DOM analysis and 16S rRNA gene amplicon sequencing to investigate the associations of bacterial taxa and DOM properties as well as the impacts of DOM on bacterial niche breadth in North River (NR) and West River (WR) of Jiulong River watershed, southern China, which had low and high urbanization levels, respectively. Spectroscopy analysis showed that hydrophilic DOM was predominant in both rivers whereas chromophoric DOM was higher in WR. Network analysis indicated that only seven bacterial genera (i.e., hg clade, chthoniobacter, Geobacter, Acidibacter, Alphal Cluster, Fluviicola, and Lacunisphaera) showed strong associations with DOM optical variables in both rivers, whereas more than 85% of DOM-bacterial genera associations were different between rivers. These results suggest that the relationship between DOM and bacterial communities had different responses in rivers with different urbanization levels. The partial least square path model indicated that the total standardized effect of physico-chemicals on bacterial niche breadth was higher in NR (0.62) than in WR (0.35), whereas humic substances showed an opposite pattern (NR: −0.42; WR: 1.67). The distinct effects of physico-chemicals and DOM on bacterial niche breadths between rivers could be due to the different effects of urbanization and human activities on the environmental conditions of riverine ecosystems. Our findings revealed a huge dissimilarity in the bacteria-DOM co-occurrence networks between rivers with different urbanization levels and provide a novel insight that urbanization may enhance DOM's importance to bacterial niche breadths.

Analysis of Change and Driving Factors of River Environmental Quality in China from 2002 to 2020

According to the river environmental quality, pollutant emission, and investment in environmental pollution control from 2002-2020, the change law and driving factors of river environmental quality in China were evaluated using canonical correlation analysis and the Spearman correlation coefficient to analyze the influence between environmental and pollutant emission/investment in environmental pollution control. The results indicated that the river environmental quality was improved significantly based on the proportion of Class Ⅰ-Ⅲ increasing from 29.1% to 87.4% and the proportion of inferior Class Ⅴ decreasing from 40.9% to 0.2% from 2002-2020. The emission of wastewater and domestic wastewater increased from 4.395×1010 tons and 2.323×1010 tons to 8.491×1010 tons and 6.598×1010 tons, respectively. However, emissions of industrial wastewater decreased from 2.072×1010 tons to 1.680×1010 tons. Investment in environmental pollution control increased from 110.66 billion yuan to 1063.89 billion yuan. The proportion of Class Ⅰ-Ⅲ in seven major river basins, river basins in Zhejiang and Fujian, southwest river basins, and northwest river basins showed a negative correlation for industrial pollutant emissions and a positive correlation for investment in environmental pollution control. The primary measure for the seven major river basins, river basins in Zhejiang and Fujian, and northwest river basins cut down the industrial pollutant emissions, in the order of COD>NH4+-N>total wastewater. The primary measure for southwest river basins increased the investment in environmental pollution control, in the order of industrial investment in environmental pollution control>urban environmental infrastructure construction investment and environmental protection investment in construction projects. These results can provide theoretical and policy suggestions for the improvement of river environmental quality during the "14th Five-Year Plan" period.

Relationship between sediment load and climate extremes in the major Chinese rivers

Global warming has led to increase in climate extremes, which altered both hydrological cycles and soil erosion processes. However, the responses of river sediment load to climate change, especially climate extremes have not been well understood due to a lack of comprehensive assessment. This study investigated the temporal trends and spatial patterns of sediment load at 70 hydrological stations during the period of 1956–2019 in ten major river basins in China. Both the partial linear square regression model and the double mass curve method were used to quantify the contribution of key climatic indices and anthropogenic driving forces. Overall, the annual total sediment load exhibited a significant negative trend (P < 0.01), decreasing from 1842.18 Mt/yr in 1960 s to 322.72 Mt/yr in 2010 s (82.48 %). The significant decline of sediment load was particularly obvious in the Yangtze River basin and the Yellow River basin. The abrupt changes of sediment load mostly occurred in 1985–2000. Human activities were primarily response for sediment load changes in most basins. The sediment load in mainstream was mainly regulated by reservoirs, while the tributaries were largely affected by soil and water conservation measures. Intensive human activities have led to substantial changes in land surface and resulted in weakened correlation between sediment load and climate extremes. Generally, precipitation, erosive rainfall and precipitation amount in flood period were closely related to sediment load. In the Southwest River basin and Northwest River basin, the sediment load had a relatively good relationship with extreme temperature, which was related to alpine snowmelt and permafrost degradation due to climate warming. This study provides good insights for a better understanding of the interaction between river sediment load and climate extremes variables, which will be valuable for decision-making in river basin management.

Future water security in the major basins of China under the 1.5 °C and 2.0 °C global warming scenarios

Freshwater is an essential resource for human lives, agriculture, industry, and ecology. Future water supply, water withdrawal, and water security under the impacts of climate change and human interventions have been of key concern. Numerous studies have projected future changes in river runoff and surface water resources under climate change. However, the changes in the major water withdrawal components including agricultural irrigation water, industrial, domestic and ecological water withdrawal, as well as the balance between water supply and withdrawal, under the joint impacts of climate change and socio-economic development have been seldom investigated, especially at the basin and national scales. In this study, changes in surface water resources, agricultural irrigation water, industrial, domestic and ecological water withdrawal, as well as the balances between water supply and withdrawal, under the baseline climate (2006–2015), 1.5 °C and 2.0 °C warming scenarios (2106–2115) in the 10 major basins across China, were investigated by combining modelling and local census data. The results showed that water withdrawal exceeded water supply in the basins of Liao River, Northwest River, Hai River, Yellow River and Huai River in the baseline period. Under the 1.5 °C and 2.0 °C warming scenarios, the shortage of water resources would aggravate in the above-mentioned basins and the Songhua River basin. And the surplus of water resources would reduce substantially in the basins of Yangtze River, Southeast River and Pearl River. Overall, the difference between water supply and water withdrawal was 435.88 billion m3 during the baseline period, and would be 261.84 and 218.39 billion m3, respectively, under the 1.5 °C and 2.0 °C warming scenarios. This study provides a comprehensive perspective on future water security in the 10 major basins across China, has important implications for water resources management and climate change adaptation.

Evaluation of water quality at national scale from 2011 to 2021: Advances and challenges

More environmental policies and larger investments in protecting the aquatic environment in China have been made in the last decade than previously. It is important to assess how this will affect river water quality. Here, changes in water quality in China between 2011 and 2021 are assessed. Water bodies meeting class III or better defined in the Chinese Environmental Quality Standards for Surface Water (GB3838-2002) were labeled WQI, water bodies meeting class V or better but below class III were labeled WQII, and water bodies below class V were labeled WQIII. The percentage of WQI water bodies increased from 66.1 % in 2011 to 81.0 % in 2021, and the percentages of WQII and WQIII water bodies decreased between 2011 and 2021. The percentage of WQI water bodies increased more quickly and the percentage WQIII water bodies decreased more quickly after 2017 than between 2011 and 2016. The percentages of WQI water bodies in the Northwest River Basin (RB), Pearl RB, Southeast RB, Southwest RB, and Yangtze RB were >80 %, and were higher than the percentages of WQI water bodies in the other five RBs. The percentages of WQI and WQII water bodies increased but the percentage of WQIII water bodies decreased in the Hai RB. The percentage of WQI water bodies increased but the percentages of WQII and WQIII water bodies decreased in the Huai RB, Liao RB, Yangtze RB, and Yellow RB. The river monitoring capacity increased and pollution sources, particularly point sources, became more controlled, and this improved river water quality. River management in China has passed the first stage of controlling pollution sources after 10 years of centralized management. The next stage should be focused on strengthening control of non-point sources of pollution and rehabilitating ecological systems to improve river health.

Runoff changes in the major river basins of China and their responses to potential driving forces

Identifying the effect of climate variability and human activities on runoff changes is scientifically essential for understanding hydrological processes and sustainable water resources management. This study selected 64 catchments located in the mainland of China to quantify the effects of different driving forces on runoff changes. Results showed that annual runoff in the Haihe river basin, Liaohe river basin, and Yellow river basin exhibited significantly decreasing trends from 1965 to 2018 (P < 0.05), whereas the Northwest river basin had positive trends in the annual runoff. Meanwhile, the Pettitt test method was applied to detect abrupt changes in annual runoff. Compared to the rivers in Southern China, the northern rivers had significant abrupt changes in annual runoff and mostly occurred in the 1990 s. The Choudhury-Yang equation based on the Budyko hypothesis was used to assess the sensitivity of runoff to precipitation (P), potential evapotranspiration (ET0), and the land surface (n) changes. The results showed that runoff was more sensitive to P and n, compared to ET0. Attribution analysis revealed that P was the dominant factor in the Northwest river basin, Southwest river basin, Yangtze river basin, Southeast river basin, and Pearl river basin, whereas the changes in n were responsible for runoff changes in the Liaohe river basin, Haihe river basin, Yellow river Basin, Songhuajiang river basin, and Huaihe river basin. The land surface changes (n) were resulted from vegetation restoration, urbanization expansion, construction of reservoirs/check dams, and surface water withdrawals, leading to significant changes in river runoff in recent years. The findings can provide good insight for water resources management across China.

Reduction in Precipitation Seasonality in China from 1960 to 2018

AbstractChanges in precipitation seasonality or the distribution of precipitation have important impacts on hydrological extremes (e.g., floods or droughts). Precipitation extremes have been widely reported to increase with global warming; however, the variability and mechanism of precipitation seasonality have not been well quantified in China. Here, we explore the multiscale variability in precipitation seasonality from 1960 to 2018 in China. A seasonality index of precipitation is defined to quantify the precipitation seasonality with a lower value indicating a more even distribution throughout a year. The seasonality index increases from southeastern to northwestern China, with a decrease in the annual mean precipitation, a later timing of the wet season, and a shorter wet season duration. The seasonality index decreases from 1960 to 2018 in China, accompanied by the increasing duration of wet season, especially in northern climate-sensitive basins, such as the Northwest River, Hai River, and Songliao River basins. In the Northwest River basin, for example, the observed significant decrease in the seasonality index (~0.02 decade−1) from 1960 to 2018 is consistent with a significant decrease in the ratio of annual maximum 10-day precipitation to annual precipitation, which is confirmed by their significant positive correlation (R= 0.72;p= 0). El Niño–Southern Oscillation (ENSO) dominates interannual fluctuations and spatial patterns of precipitation seasonality in China. In El Niño years, the precipitation seasonality index decreases across China except for the Yangtze River basin, with broad increases in annual precipitation.

GIS-based multi-criteria modelling of flood risk susceptibility in Port Louis, Mauritius: Towards resilient flood management

Economic growth and population expansion in Mauritius have driven unprecedented rates of development. Most notably, increased urbanization of flood-prone regions has exacerbated challenges around resilience and vulnerability to recurrent flooding. We implement a multi-criteria model consisting of a physical-oriented, a social-oriented and an economic-oriented scenario to identify highly vulnerable sites to flooding in the capital city, Port Louis. Social, technical, economic and legal perspectives are incorporated to propose comprehensive flood management strategies. The aim is to minimize the physical impacts of floods while also addressing the broader social and economic risks. Location-based flood management strategies are thereafter proposed to increase the resilience of the city to flooding. Measures include, inter alia, the construction of an underground stormwater storage tank at Champ de Mars, establishment of flood refugee camps at Vallée Pitot and Cité La Cure, reviewing building regulations and urban planning, replacement of the Caudan Underpass by an Overhead Bridge, green renaturing of rivers in downstream areas, construction of a retention pond on the downhill slope of the mountain at Bell Village, and the setting up of a diversion tunnel linking St Louis River to Grand River North West. The approach adopted will allow an understanding of the geography of flooding in Port Louis and support management decisions for limiting its impacts.

Land-based Nitrogen Pollution Source Structure and Spatial Distribution in Guangdong-Hong Kong-Macao Greater Bay Area

Total nitrogen pollution from land-based sources carried by rivers is the main source of inorganic nitrogen entering the sea. Inorganic nitrogen pollution in the coastal waters of Guangdong-Hong Kong-Macao Greater Bay Area(GBA) is a serious problem. The water quality of an adjacent large area of the sea is classified as poor-category Ⅳ. Therefore, clarification of the scale, structure, and discharge pressure of nitrogen emissions from the land area of the GBA is needed to manage marine nitrogen pollution. Based on multi-source data, including land use, socio-economic statistics, and pollution source census information, the scale, source structure, and regional differences of total nitrogen discharge in GBA and surrounding cities were evaluated using administrative and watershed units. The results show that:①The total nitrogen emissions from the study area are approximately 332500 t. Residential waste is the main source of pollution, accounting for 55.4%, followed by cultivation, with 28.18%, while the contribution from animal husbandry and industrial production is relatively limited. ②The regional differences of total nitrogen emissions are obvious, and the total emissions from GBA(231400 t) are significantly higher than those from neighboring cities(101100 t). ③The distribution of marine pollution and intensity of land-based nitrogen pollution emissions are spatially consistent, which indicates that there is a large number of pollution emissions in the East River Basin, Northwest River Delta Basin, and Tan River Basin; the shoreline sections belonging to the basins carry the greatest emission pressure, lead to serious pollution in the Lingding Sea, Jin Bay, and Huangmao Sea.

Anthropogenic activities and seasonal properties jointly drive the assemblage of bacterial communities in subtropical river basins

Anthropogenic activities have inevitably impacted riverine ecosystems, yet their overall contribution to the assemblage of bacterial communities at a large river basin scale remains unclear. In this study, 16S amplicon sequencing was implemented to investigate the bacterial ecosystems in paired water and sediment of North River and West River basins in South China., which contains various anthropogenic environments (e.g., rural/urban area, mining area and livestock area). Subsequently, the links between bacterial community and various types of emerging pollutants in river water were analyzed. The results show that the bacterial assemblage of water and sediment had their own properties that the bacterial community of sediment were mainly affected by seasonal properties, while the bacterial community of water were affected by both seasons and anthropogenic activities. Therein, the aquatic bacterial compositions and abundances were driven by changes in temperature, dissolved oxygen and the emerging pollutants. The dominant phyla Proteobacteria and Firmicutes exhibited adaptability to the mining-affected regions, therein many clades (e.g., Beijerinckiaceae, Acetobacteraceae and Mycobacteriaceae) were also prevalent in the livestock-affected and densely-populated regions. In addition, these two phyla presented associations to the antibiotic resistance in water. The levels of antibiotics, relative antibiotic resistance gens (ARGs) and non-antibiotic pharmaceuticals (NAPs) were closely related to bacterial community composition, diversity and functional diversity, indicating their drive in shifting bacterial communities. Collectively, this work provides a basis for understanding the contribution of anthropogenic activities in shifting bacterial community at a large river basin scale. Further, the results provide new insights for expansion of ecological assessment.

Grading Effects on Growth and Size Variation of Common Carp Cyprinus carpio Cultivated in Floating Cages

The present study aimed to investigate the effect of fish grading on the growth performance of common carp Cyprinus carpio cultivated in floating cages located in the Al-Mashab River northwest of Basrah. A total of 4896 fishes were transferred from storage cages to culture cages (3×4×2 m), and distributed at a rate of 816 fishes per cage with a culture density of 34 fishes/m3 into six cages, three of which were classified into large (GL), middle (GM) and small (GS) individuals, whereas three cages were left without grading (UG). The graded and ungraded cages were chosen depending on the standard deviation for each cage. The fishes were fed for both treatments on a standardized, locally made diet. The results of the study were evaluated according to the criteria for total weight gain (WG), daily growth rate and specific growth rate. In the first grading process, significant differences (P&lt;0.05) were recorded between graded (GL) and ungraded in final weight and specific growth rate (SGR) but not in weight gain and daily growth rate (DGR), while in the second grading, significant differences (P&lt;0.05) were recorded between graded (GL) and ungraded in final weight and weight gain but not in SGR and DGR. At the end of the second grading period, the daily and specific growth rate of graded fishes were ranged between 3.26-4.73 g/day and 0.22-0.46%/day, respectively, while for ungraded fishes there were 2.35 g/day and 0.23%/day, respectively. The survival rate (SR) was not different very much in all treatments and ranged between 94.34 to 95.49% in small graded and ungraded fishes, respectively. The study results recommend at least two grading processes should be established during the culture season in two or three months intervals.

Comparison of characteristics, water quality and health risk assessment of trace elements in surface water and groundwater in China

Water quality is closely associated with human health and socio-economic sustainable development. With the increasingly intensive anthropogenic activities, pollutants especially trace elements, enter water aquatic system and cause harm to humans. This study conducted the first systematic comparison on the pollution status of surface water and groundwater in China. Water quality and health risk assessment of 12 trace elements were evaluated according to the water quality index (WQI), hazard quotient (HQ), hazard index (HI), and carcinogenic risk (CR). The results showed that the average values of trace elements in the majority of surface water were higher than those in groundwater. The WQI values demonstrated that 86.02% of surface water and 83.11% of groundwater were suitable for drinking water. Arsenic served as the predominant pollutant and contributed significantly to cause the non‑carcinogenic risk on human health in both surface water and groundwater, children were more vulnerable to the adverse effects than adults. In surface water, the priority non-carcinogenic risk sites were mainly distributed in Anning River, Taizi River, Middle reaches of Huai River and Jilin section of Songhua River. For groundwater, the high-risk sites were located in Huhhot Basin, Kuitun, Jianghan Plain, Datong Basin and Yucheng County. Arsenic posed potential carcinogenic risk to local resident in some water sites, and it presented higher in groundwater than surface water. More concerns should be paid on Songhua, Yangtze and Huai River Basins, in addition, Pearl, Southeast Coastal, Southwest and Northwest River Basins still need attention. The future work should be carried out more extensive range of the water sites and long-term monitoring in China. In particular, more attention should be dedicated to assess high As water bodies.

Social–ecological management results in sustained recovery of an imperiled salmon population

When faced with the loss of a population, resource managers often feel compelled to choose restoration strategies perceived to have low risk, such as the management of the ecological components of the system or the application of regulatory measures. It can be counterintuitive to share decision‐making and resource management with those who want to harvest an imperiled population, yet this social–ecological strategy resulted in the recovery of a wild Atlantic salmon population in Newfoundland, Canada. Atlantic salmon supported widespread commercial, subsistence, and recreational fisheries but declines in abundance necessitated closures and other conservation strategies across many areas of Atlantic Canada in the 1990s. Recreational angling for Atlantic salmon was closed in Terra Nova National Park's Northwest River in 1995 when counts were below expectations based on available habitat. The population continued to decline, even though commercial and recreational fishing mortality had been eliminated, and by 2001, extirpation seemed imminent. Despite pressure to pursue conventional strategies such as catch and release fishing and stocking, public consultation and human dimensions research revealed that illegal fishing was likely contributing to declines and that distrust of resource managers created an environment conducive to poaching. Disrupting this dynamic could not be achieved with conventional strategies, so instead an adaptive management approach was implemented that incorporated local collaboration and improved transparency, and was responsive to positive changes in behavior. Adoption of social–ecological management led to a rapid and sustained recovery of the salmon population in Northwest River, out‐performing populations in adjacent rivers managed with conventional management strategies.

Projections of precipitation over China based on CMIP6 models

Precipitation fluctuations are continuously threatening the environment and may cause huge economic losses. In present study, the precipitation over China has been evaluated under five principal shared socioeconomic pathways (SSPs) scenarios during 2015–2099 based on eight CMIP6 models bias-corrected by the method of Equidistant Cumulative Distribution Functions. The results showed that (1) the simulated precipitation in China was in good agreement with observed precipitation for the eight CMIP6 models during 1961–2014, especially for the UKESM1-0-LL and MIROC6. However, the simulated annual mean precipitation has been significantly overvalued in the Southwest River basin (> 50%), while it was undervalued in the higher elevations of the Northwest River basin (< − 60%); (2) the annual mean precipitation will show a fluctuating upward trend during 2015–2099 over China under all the SSPs scenarios for the eight CMIP6 models. The rate of precipitation increase over north China will be higher than that in south China, especially in the Northwest River basin (reach 57.44% in the 2090s under the SSP5-8.5 for the ensemble mean). This increase of the precipitation in north China might alleviate the shortage of water there, but will not change the pattern of more rain in the south and less in the north; (3) in the southeastern basins, the precipitation of the multi-model ensemble (MME) and MIROC6 during 2011–2020 will be lower than that of 1961–2010 (− 6.53 to − 0.06%) under all SSPs scenarios. While the precipitation will increase obviously under all the SSPs scenarios, especially for the SSP5-8.5 scenario after the year of 2060; (4) the bias of the MME was much lower than that of individual CMIP6 models, and the bias of lower SSPs scenarios will be relatively lower. Generally, uncertainty ranges of precipitation fluctuations in north China (15.31–79.26%) will be higher than those in south China (16.06–7.55%). These findings revealed the projections and uncertainties of CMIP6 precipitation over China, which will be helpful for a better understanding of the future evolution of precipitation in China at large scale and in other regions of the world.

Insight from CMIP6 SSP-RCP scenarios for future drought characteristics in China

In this paper, future drought characteristics (frequency, duration and intensity) over China are analysed by using four climate models from CMIP6 under the seven SSP-RCP (shared socioeconomic pathway-representative concentration pathway) scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, SSP370, and SSP585) for three defined periods of 2021–2040 (near-term), 2041–2060 (mid-term) and 2081–2100 (long-term). The corresponding four climate models output from CMIP5 are also used to conduct a comparison analysis between CMIP5 and CMIP6 to address the improvements added to CMIP6 in terms of drought identification. The drought characteristics are identified by applying the standardized precipitation-evapotranspiration index (SPEI) at a 12-month timescale and run theory. The results show that CMIP6 has a robust capability to capture historical (1986–2005) drought characteristics. For the future period of 2021–2040, the decrease in precipitation and increase in potential evapotranspiration will lead to continuous dry conditions in the upper and middle Yangtze River basin and eastern Pearl River basin. Relative to the reference period, drought events will be more frequent and severe with longer durations in the Northwest River basins and middle Yangtze River basin. Furthermore, higher emissions signify a greater increase in drought frequency and intensity in the long-term period. Except for the SSP585 scenario, the lower emission scenario corresponds to the higher drought duration soon and in the mid-21st century (2021–2060). This finding is regarded as a “strange phenomenon”, which cannot be detected by the previous CMIP5-based emission scenarios (RCP2.6, RCP4.5 and the unlikely pathway RCP8.5). Therefore, additional “possible future”-based scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, and SSP370) should be included in extreme climate studies, especially for the near future and mid-21st century. Notably, compared with CMIP5, the reduced biases in drought characteristics are more likely associated with improvements in the representation of physical processes in climate models from CMIP6. The results of this study could provide a basis for the development of drought adaptation measures over China.

DNA damage of human derived liver cell line HL-7702 induced by organic extracts from surface water in Pearl River Delta, China.

Many organic pollutants attract public health concern due to their genotoxicity. To investigate the genotoxicity of organic matter in surface water of the Pearl River Delta (PRD). Organic substances of 24 samples (dry and wet season) from North River, West River and East River were extracted from 60 L source water by XAD-2 macroporous resin. DNA damage effect of organic extracts was tested in human derived liver cells (HL-7702), using single cell gel electrophoresis (SCGE) assay. The results showed that 100% organic extracts (24/24) could induce DNA damage in HL-7702 cells when the concentration was above 1.0 L surface water/ml culture, no significant difference of DNA damage between dry and wet seasons was observed. The organic substance-induced DNA damage in HL-7702 cells was significantly (P < 0.05) correlated with the contents of Dissolved Organic Carbon in both seasons and Total Suspended Solids in dry season. In conclusion, organic extracts induced genetic damage in HL-7702 cells, indicating potential genotoxicity of organic pollutants of surface water from PRD, South China.

Future river basin health assessment through reliability-resilience-vulnerability: Thresholds of multiple dryness conditions

Increasing dryness conditions under global warming are posing severe threats to water resources management in China. Projecting river basin responses to dryness conditions is beneficial to effectively managing water resources. However, existing studies have seldom considered the impact of multiple dryness conditions on future river basin health under global warming. Therefore, we combine the 3- and 12-month standard precipitation evapotranspiration index (SPEI) and reliability-resilience-vulnerability framework (RRV) to map future river basin health based on the responses of basins across China to different dryness conditions from 2021 to 2050. The calculation is based on downscaled outputs of 10 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for three future emission scenarios (i.e., RCP2.6, RCP4.5 and RCP8.5). The results show that water deficits are projected to occur in most areas of China and significantly increase in the basins located in the northern part of China in the next 30 years due to global warming effects. The conditions in parts of the basins located in the northern part of China (especially in the Northwest River basins and Yellow River basin) are projected to be unhealthy and deteriorate significantly in the future, while the basins located in the southern part of China are projected to be moderate. The health status is anticipated to be worse under the RCP8.5 scenario than the RCP2.6 and RCP4.5 scenarios. Integrated results from the three thresholds indicated that normal dryness is applicable to most areas of northeastern, northern and southern China, while abnormal dryness is applicable to the remaining areas. Our findings could help reduce the impact of future dryness conditions on water resources and provide insights into risk planning and management for river basins in China under global warming.

Homogeneous selection drives antibiotic resistome in two adjacent sub-watersheds, China

Rivers are a significant reservoir of antibiotic resistance genes (ARGs), yet the biogeographic pattern of riverine ARGs and its underlying driving forces remain poorly understood. Here, we used metagenomic approach to investigate the spatio-temporal variation of ARGs in two adjacent sub-watersheds viz. North River (NR) and West River (WR), China. The results demonstrated that Bacitracin (22.8 % of the total ARGs), multidrug (20.7 %), sulfonamide (15.2 %) and tetracycline (10.9 %) were the dominant ARG types. SourceTracker analysis indicated that sewage treatment plants as the main source of ARGs, while animal feces mainly contributed in spreading the ARGs in the upstream of NR. Random forest and network analyses confirmed that NR was under the influence of fecal pollution. PCoA analysis demonstrated that the composition of ARGs changed along with the anthropogenic gradients, while the Raup–Crick null model showed that homogenizing selection mediated by class 1 integron intI1 resulted in stable ARG communities at whole watershed scale. Structural equation models revealed that microbial community, grassland and several non-antibiotic micropollutants may also play certain roles in influencing the distribution of ARGs. Overall, the observed deterministic formation of ARGs in riverine systems calls effective management strategies to mitigate the risks of antibiotic resistance on public health.