Untapped policy avenues to protect coral reef ecosystems.

Coral reefs are experiencing severe decline, and urgent action is required at local and global scales to curb ecosystem loss. Establishing new regulations to protect corals, however, can be time consuming and costly, and it is therefore necessary to leverage existing legal instruments, such as policies originally designed to address terrestrial rather than marine activities, to prevent coral reef degradation. Focusing on the United States, but drawing on successful examples worldwide, we present actionable pathways to increase coral protections under legislation that was originally designed to advance clean freshwater, safe drinking water, and emergency management. We identify specific legal policies and procedures (e.g., industrial permit limits, nonpoint source management incentives, and floodplain restoration programs) that can curb coral reef pollution and can be extended to other countries with similar regulations in place. Coral reef practitioners should consider a broad array of currently underused, actionable, and intersecting environmental policies that can be applied to mitigate coral stress.

Atmospheric Nitrogen Pollution Control Benefits the Coastal Environment.

Nitrogen is an essential nutrient and a major limiting element for the ocean ecosystem. Since the preindustrial era, substantial amounts of nitrogen from terrestrial sources have entered the ocean via rivers, groundwater, and atmospheric deposition. China serves as a key hub in the global nitrogen cycle, but the pathways, sources, and potential mitigation strategies for land-ocean nitrogen transport are unclear. By combining the CHANS, WRF-Chem, and WNF models, we estimated that 8 million tonnes (Tg) of nitrogen was transferred into the ocean in 2017 in China, with atmospheric deposition contributing 1/3. About half variation of the offshore chlorophyll concentration was explained by atmospheric deposition. The Bohai Sea was the hot spot of nitrogen input, estimated at 214 kg N ha-1, while other areas were around 25-51 kg N ha-1. The largest contributors are agricultural systems (4 Tg, 55%), followed by domestic sewage (2 Tg, 21%). Abatement measures could reduce nitrogen export to the ocean by 43%, and mitigating ammonia and nitrogen oxide emissions accounts for 33% of this reduction, highlighting the importance of addressing air pollution in resolving ocean pollution. The cost-benefit analysis suggests the priority of nitrogen reduction in cropland and transport systems for the ocean environment.

Fate and Transport of Mercury through Waterflows in a Tropical Rainforest.

Knowledge gaps of mercury (Hg) biogeochemical processes in the tropical rainforest limit our understanding of the global Hg mass budget. In this study, we applied Hg stable isotope tracing techniques to quantitatively understand the Hg fate and transport during the waterflows in a tropical rainforest including open-field precipitation, throughfall, and runoff. Hg concentrations in throughfall are 1.5-2 times of the levels in open-field rainfall. However, Hg deposition contributed by throughfall and open-field rainfall is comparable due to the water interception by vegetative biomasses. Runoff from the forest shows nearly one order of magnitude lower Hg concentration than those in throughfall. In contrast to the positive Δ199Hg and Δ200Hg signatures in open-field rainfall, throughfall water exhibits nearly zero signals of Δ199Hg and Δ200Hg, while runoff shows negative Δ199Hg and Δ200Hg signals. Using a binary mixing model, Hg in throughfall and runoff is primarily derived from atmospheric Hg0 inputs, with average contributions of 65 ± 18 and 91 ± 6%, respectively. The combination of flux and isotopic modeling suggests that two-thirds of atmospheric Hg2+ input is intercepted by vegetative biomass, with the remaining atmospheric Hg2+ input captured by the forest floor. Overall, these findings shed light on simulation of Hg cycle in tropical forests.

Occurrence, Concentration, and Distribution of 35 PFASs and Their Precursors Retained in 20 Stormwater Biofilters.

Current knowledge about the fate and transport behaviors of per- and polyfluoroalkyl substances (PFASs) in urban stormwater biofilter facilities is very limited. C5-14,16 perfluoroalkyl carboxylic acids [perfluorinated carboxylic acids (PFCAs)], C4,8,10 perfluoroalkanesulfonic acids (PFSAs), methyl-perfluorooctane sulfonamide acetic acid (MeFOSAA, a PFSA precursor), and unknown C6-8 PFCA and perfluorooctanesulfonic acid precursors were frequently found in bioretention media and forebay sediments at Σ35PFAS concentrations of <0.03-19 and 0.064-16 µg/kg-DW, respectively. Unknown C6-8 PFCA precursor concentrations were up to ten times higher than the corresponding PFCAs, especially at forebays and biofilters' top layer. No significant trend could be attributed to PFAS and precursor concentrations versus depth of filter media, though PFAS concentrations were 2-3 times higher in the upper layers on average (significant difference between the upper (0-5 cm) and deepest (35-50 cm) layer). PFASs had a similar spatial concentration distribution in each filter media (no clear difference between short- and long-chain PFASs). Commercial land use and organic matter were important factors explaining the concentration variations among the biofilters and between the sampling depths, respectively. Given the comparable PFAS accumulations in deeper and superficial layers and possible increased mobility after precursor biotransformation, designing shallow-depth, nonamended sand biofilters or maintaining only the top layer may be insufficient for stormwater PFAS management.

Small-Intensity Rainfall Triggers Greater Contamination of Rubber-Derived Chemicals in Road Stormwater Runoff from Various Functional Areas in Megalopolis Cities.

Rubber-derived chemicals (RDCs) originating from tire and road wear particles are transported into road stormwater runoff, potentially threatening organisms in receiving watersheds. However, there is a lack of knowledge on time variation of novel RDCs in runoff, limiting initial rainwater treatment and subsequent rainwater resource utilization. In this study, we investigated the levels and time-concentration profiles of 35 target RDCs in road stormwater runoff from eight functional areas in the Greater Bay Area, South China. The results showed that the total concentrations of RDCs were the highest on the expressway compared with other seven functional areas. N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), 6PPD-quinone, benzothiazole, and 1,3-diphenylguanidine were the top four highlighted RDCs (ND-228840 ng/L). Seasonal and spatial differences revealed higher RDC concentrations in the dry season as well as in less-developed regions. A lag effect of reaching RDC peak concentrations in road stormwater runoff was revealed, with a lag time of 10-90 min on expressways. Small-intensity rainfall triggers greater contamination of rubber-derived chemicals in road stormwater runoff. Environmental risk assessment indicated that 35% of the RDCs posed a high risk, especially PPD-quinones (risk quotient up to 2663). Our findings contribute to a better understanding of managing road stormwater runoff for RDC pollution.

Inter-event and intra-event dynamics of microplastic emissions in an urban river during rainfall episodes.

Urban rivers represent the major conduits for land-sourced microplastics in the global oceans, yet the real-time dynamics of their emissions in rivers during rainfall (and runoff) events are poorly understood. Herein, we report the results of high-frequency sampling of microplastic particles (MPs) and fibers (MPFs) in the surface water of an urban river in Japan over the course of three rainfall events (i.e., light, moderate, and heavy rainfalls). The event mean concentrations (EMCs) of MPs amounted to 35,000 items/m3, 929,000 items/m3, and 331,000 items/m3; and the corresponding total loads were 0.5 kg, 19.8 kg, and 35.0 kg for light, moderate and heavy rainfalls, respectively. The inter-event total loads of MPs correlate well with the total rainfall, while the concentrations were linked with the number of antecedent dry days. The dynamic trends show that <2000 µm MPs displayed first flush effects during light to moderate rainfall events (>50% mass discharged with the initial 20-40% of flow). Small-sized MPs (10-40 µm) mobilized rapidly at lower rainfall intensities, whereas MPs over 2000 µm discharged immediately after the peak rainfall intensity. Moreover, <70 µm MPs depicted a surge following heavy rainfall events due to turbulent flow conditions reverting the deposited MPs into suspension. Overall, the three events increased the loads by 4-110 folds, and EMCs by 10-350 folds compared to the concentrations during dry weather while portraying a significant impact on 300-1000 µm MPs. The dynamics of MPs were correlated with those of suspended solids in river water, and the characteristics were comparable to the same of road dust sampled in Japan. Although the dynamic trends between MPs and MPFs in river water were comparable, MPFs were relatively less impacted by rain, likely due to the intervention of separate sewer systems in the study area.

Modeling the effects of land use/land cover changes on river runoff using SWAT models: A case study of the Danjiang River source area, China.

Land use/land cover (LULC) is a crucial factor that directly influences the hydrology and water resources of a watershed. In order to assess the impacts of LULC changes on river runoff in the Danjiang River source area, we analyzed the characteristics of LULC data for three time periods (2000, 2010, and 2020). The LULC changes during these periods were quantified, and three Soil and Water Assessment Tool (SWAT) models were established and combined with eight LULC scenarios to quantitatively analyze the effects of LULC changes on river runoff. The results revealed a decrease in the cropland area and an increase in the forest, grassland, and urban land areas from 2000 to 2020. Grassland, forest, and cropland collectively accounted for over 94% of the total area, and conversions among these land types were frequent. The SWAT models constructed based on the LULC data demonstrated good calibration and validation results. Based on the LULC data in three periods, the area of each LULC type changed slightly, so the simulation results were not significantly different. In the subsequent LULC scenarios, we found that the expansion of cropland, grassland, and urban areas was associated with increased river runoff, while an increase in forest area led to a decrease in river runoff. Among the various LULC types, urban land exerted the greatest influence on changes in river runoff. This study establishes three SWAT models and combines multiple LULC scenarios, which is novel and innovative. It can provide scientific basis for the rational allocation of water resources and the optimization of LULC structure in the Danjiang River source area.

Assessment of seasonal and annual patterns in phosphorus content in a monitored catchment through a partitioning approach based on hydrometeorological data.

High amounts of phosphorus (P) in rivers come mainly from two sources: fertilizers washed off from agricultural and urban areas by runoff water (non-point sources) and urban and industrial development which are translated in P discharges from wastewater treatment plants (WWTP). This work analyses the content of P in water for nearly 40 years inquiring into the origin of the sources, based on the hypothesis of runoff generation from the detection of river streamflow increases during the P contribution episode and the previous precipitation. For this purpose, the Guadaira River, which is located in the South of Spain and has a drainage surface of 1524 km2, was selected. In this watershed agricultural land use converges with numerous human activities resulting in high pressures on water quality. We found 40% of the P contribution episodes found seem to come from the runoff generated after the heaviest rainfall events, which normally occur between November and May. The remaining 60% of the P contribution episodes were found to be linked to point sources, which become more relevant from June to September, reaching the highest concentration values (6-17 mg/L). The results highlight that the target phosphate concentration value of 0.34 mg PO4/L imposed by the national legislation for a good state following the Water Framework Directive 2000/60/EC is exceeded by 96% of the measurements during the period from 1981 to 2022. On a monthly basis, PO4 loads showed a linear relationship with river streamflow (R2 = 0.94). However, on field measurements scale, a potential relationship between both variables was found, which changed according to the improvement in the wastewater treatment and facilities for 1982-1994, 1995-2017 and 2018-2022. In these three periods, different significant decreasing trends of the P content were found, mainly marked by the setup of each individual WWTP.

Optimizing stormwater runoff treatment: The role of two-stage tandem rain gardens.

Regarded as a superior urban stormwater management solution, rain gardens can effectively store rainfall runoff and purify water quality. However, the efficiency of traditional rain gardens (TRG) in regulating runoff and removing nitrogen and phosphorus varies under different hydrological conditions. In this study, the TRG was retrofitted to construct a two-stage tandem rain garden (TTRG). Based on the experimental monitoring of rain gardens under natural rainfall from 2011 to 2013, results indicated a significantly higher runoff reduction capacity for the TTRG compared to the traditional garden (p < 0.05), with average runoff and peak flow reduction rates increasing by 42.8% and 36.2%, respectively. Rainfall characteristics significantly impacted the runoff reduction of the TRG (p < 0.05), but not the TTRG (p > 0.05), demonstrating the enhanced control and stability of the TTRG in managing rainfall runoff. The concentration removal efficiency of nitrate nitrogen (NO3--N) was significantly improved (p < 0.05), whereas the total phosphorus (TP), ammonium nitrogen (NH3-N) and total nitrogen (TN) were not significantly changed (p > 0.05). The first-order kinetic model was used to fit the removal effect of different pollutants before and after retrofitting the rain garden, and the removal of NO3--N by the TTRG was better than that of the TRG. The TTRG showed significantly higher load removal efficiencies for TP, NO3--N, and NH3-N compared to TRG (p < 0.05), with average load removal rates increasing by 49.92%, 75.02%, and 14.81%, respectively. The TTRG can regulate urban rainfall runoff more efficiently and stably. By changing the water flow path in the rain garden, the TTRG has a better runoff reduction ability and pollutant purification effect.

Effects of storm events on nutrient characteristics in a stratified drinking water reservoir: Behavior, transmission pathways and management strategy.

Storm events result in nutrient fluctuations and deterioration of reservoir water supply quality. Understanding of nutrient dynamics (e.g., concentration, composition, loads and transport pathways) and adoption of effective management strategies are critical for safeguarding water quality. A comprehensive monitoring was conducted for three storm events during the rainy season in 2023. Results showed nitrogen (N) and phosphorus (P) dynamics demonstrate a significant response to hydrological process. Rainfall resulted in the highest event mean concentrations (EMCs) of total nitrogen (TN), nitrate nitrogen (NO3--N), ammonia nitrogen (NH4+-N), total phosphorus (TP), and particulate phosphorus (PP) in the runoff being 1.97, 2.15, 2.30, 44.17, and 62.38 times higher than those observed in baseflow. On average, NO3--N/PP accounted for 82 %/96 % of N/P exports. Hysteresis analyses reveal that NH4+-N and PP were mainly transported by surface runoff from over-land sources, whereas TN and NO3--N were primarily delivered by subsurface runoff. Additionally, nutrient concentrations were significantly higher in the intrusive layer in reservoir compared to the pre-storm period, which gradually decreased from the tail to the head as particulate sedimentation and water column mixing occurred. Water-lifting-aerators (WLAs) were employed to alter the reservoir thermal stratification regime via artificial mixing to affect the intrusive layer of storm runoff. Comparison of the intrusive layer for three storms reveals that WLAs triggers the storm runoff to form an underflow via increasing the reservoir bottom water temperature above that the runoff, ensuring that water quality at the intake position remains unaffected by inflows. These findings serve as a reference for the response of reservoir eutrophication levels to storm events and present practical engineering experience for enhancing water quality safety during the rainy season.

Efficient dissipation of acetamiprid, metalaxyl, S-metolachlor and terbuthylazine in a full-scale free water surface constructed wetland in Bologna province, Italy: A kinetic modeling study.

The study investigated the dissipation ability of a vegetated free water surface (FWS) constructed wetland (CW) in treating pesticides-contaminated agricultural runoff/drainage water in a rural area belonging to Bologna province (Italy). The experiment simulated a 0.1% pesticide agricultural water runoff/drainage event from a 12.5-ha farm by dissolving acetamiprid, metalaxyl, S-metolachlor, and terbuthylazine in 1000 L of water and pumping it into the CW. Water and sediment samples from the CW were collected for 4 months at different time intervals to determine pesticide concentrations by multiresidue extraction and chromatography-mass spectrometry analyses. In parallel, no active compounds were detected in the CW sediments during the experimental period. Pesticides dissipation in the wetland water compartment was modeled according to best data practices by fitting the data to Single First Order (SFO), First Order Multi-Compartment (FOMC) and Double First Order in Parallel (DFOP) kinetic models. SFO (except for metalaxyl), FOMC and DFOP kinetic models adequately predicted the dissipation for the four investigated molecules, with the DFOP kinetic model that better fitted the observed data. The modeled distribution of each pesticide between biomass and water in the CW highly correlated with environmental indexes as Kow and bioconcentration factor. Computed DT50 by DFOP model were 2.169, 8.019, 1.551 and 2.047 days for acetamiprid, metalaxyl, S-metolachlor, and terbuthylazine, respectively. Although the exact degradation mechanisms of each pesticide require further study, the FWS CW was found to be effective in treating pesticides-contaminated agricultural runoff/drainage water within an acceptable time. Therefore, this technology proved to be a valuable tool for mitigating pesticides runoff occurring after intense rain events.

The hidden threat of heavy metal leaching in urban runoff: Investigating the long-term consequences of land use changes on human health risk exposure.

This study evaluated the potential effects of long-term land use and climate change on the quality of surface runoff and the health risks associated with it. The land use change projection 2030 was derived from the main changes in land use from 2009 to 2019, and rainfall data was obtained from the Long Ashton Research Station Weather Generator (LARS-WG) model. The Long-Term Hydrological Impact Assessment (L-THIA) model was then utilized to calculate the rate of runoff heavy metal (HM) pollutant loading from the urban catchment. It was found that areas with heavy development posed a significantly greater public health risk associated with runoff, with higher risks observed in high-development and traffic areas compared to industrial, residential, and commercial areas. Additionally, exposure to Lead (Pb), Mercury (Hg), and Arsenic (As) was found to contribute significantly to overall non-carcinogenic health risks for possible consumers of runoff. Carcinogenic risk values of As, Cadmium (Cd), and Pb were also observed to increase, particularly in high-development and traffic areas, by 2030. This investigation offers important insight into the health risks posed by metals present in surface runoff in urban catchment areas under different land use and climate change scenarios.

Comparison of the performance of SWAT and hybrid M5P tree models in rainfall-runoff simulation.

Stream flow forecasting is a crucial aspect of hydrology and water resource management. This study explores stream flow forecasting using two distinct models: the Soil and Water Assessment Tool (SWAT) and a hybrid M5P model tree. The research specifically targets the daily stream flow predictions at the MH Halli gauge stations, located along the Hemvati River in Karnataka, India. A 14-year dataset spanning from 2003 to 2017 is divided into two subsets for model calibration and validation. The SWAT model's performance is evaluated by comparing its predictions to observed stream flow data. Residual time series values resulting from this comparison are then resolved using the M5P model tree. The findings reveal that the hybrid M5P tree model surpasses the SWAT model in terms of various evaluation metrics, including root-mean-square error, coefficient of determination (R2), Nash-Sutcliffe efficiency, and degree of agreement (d) for the MH Halli stations. In conclusion, this study shows the effectiveness of the hybrid M5P tree model in stream flow forecasting. The research contributes valuable insights into improved water resource management and underscores the importance of selecting appropriate models based on their performance and suitability for specific hydrological forecasting tasks.

Freeze tolerance influenced forest cover and hydrology during the Pennsylvanian.

The distribution of forest cover alters Earth surface mass and energy exchange and is controlled by physiology, which determines plant environmental limits. Ancient plant physiology, therefore, likely affected vegetation-climate feedbacks. We combine climate modeling and ecosystem-process modeling to simulate arboreal vegetation in the late Paleozoic ice age. Using GENESIS V3 global climate model simulations, varying pCO2, pO2, and ice extent for the Pennsylvanian, and fossil-derived leaf C:N, maximum stomatal conductance, and specific conductivity for several major Carboniferous plant groups, we simulated global ecosystem processes at a 2° resolution with Paleo-BGC. Based on leaf water constraints, Pangaea could have supported widespread arboreal plant growth and forest cover. However, these models do not account for the impacts of freezing on plants. According to our interpretation, freezing would have affected plants in 59% of unglaciated land during peak glacial periods and 73% during interglacials, when more high-latitude land was unglaciated. Comparing forest cover, minimum temperatures, and paleo-locations of Pennsylvanian-aged plant fossils from the Paleobiology Database supports restriction of forest extent due to freezing. Many genera were limited to unglaciated land where temperatures remained above -4 °C. Freeze-intolerance of Pennsylvanian arboreal vegetation had the potential to alter surface runoff, silicate weathering, CO2 levels, and climate forcing. As a bounding case, we assume total plant mortality at -4 °C and estimate that contracting forest cover increased net global surface runoff by up to 6.1%. Repeated freezing likely influenced freeze- and drought-tolerance evolution in lineages like the coniferophytes, which became increasingly dominant in the Permian and early Mesozoic.

A Novel Diastolic Doppler Index Less Affected by Aortic Arch Anomalies Co-existing with Coarctation.

Severity assessment for coarctation of the aorta (CoA) is challenging due to concomitant morphological anomalies (complex CoA) and inaccurate Doppler-based indices. Promising diagnostic performance has been reported for the continuous flow pressure gradient (CFPG), but it has not been studied in complex CoA. Our objective was to characterize the effect of complex CoA and associated hemodynamics on CFPG in a clinical cohort. Retrospective analysis identified discrete juxtaductal (n = 25) and complex CoA (n = 43; transverse arch and/or isthmus hypoplasia) patients with arm-leg systolic blood pressure gradients (BPG) within 24 h of echocardiography for comparison to BPG by conventional Doppler indices (simplified Bernoulli equation and modified forms correcting for proximal kinetic energy and/or recovered pressure). Results were interpreted using the current CoA guideline (BPG ≥ 20 mmHg) to compare diagnostic performance indicators including receiver operating characteristic curves, sensitivity, specificity, and diagnostic accuracy, among others. Echocardiography Z-scored aortic diameters were applied with computational simulations from a preclinical CoA model to understand aspects of the CFPG driving performance differences. Diagnostic performance was substantially reduced from discrete to complex CoA for conventional Doppler indices calculated from patient data, and by hypoplasia and/or long segment stenosis in simulations. In contrast, diagnostic indicators for the CFPG only modestly dropped for complex vs discrete CoA. Simulations revealed differences in performance due to inclusion of the Doppler velocity index and diastolic pressure half-time in the CFPG calculation. CFPG is less affected by aortic arch anomalies co-existing with CoA when compared to conventional Doppler indices.

Altitude characteristics in the response of rain-on-snow flood risk to future climate change in a high-latitude water tower.

Global warming is profoundly impacting snowmelt runoff processes in seasonal freeze-thaw zones, thereby altering the risk of rain-on-snow (ROS) floods. These changes not only affect the frequency of floods but also alter the allocation of water resources, which has implications for agriculture and other key economic sectors. While these risks present a significant threat to our lives and economies, the risk of ROS floods triggered by climate change has not received the attention it deserves. Therefore, we chose Changbai Mountain, a water tower in a high-latitude cold zone, as a typical study area. The semi-distributed hydrological model SWAT is coupled with CMIP6 meteorological data, and four shared socioeconomic pathways (SSP126, SSP245, SSP370, and SSP585) are selected after bias correction, thus quantifying the impacts of climate change on hydrological processes in the Changbai Mountain region as well as future evolution of the ROS flood risk. The results indicate that: (1) Under future climate change scenarios, snowmelt in most areas of the Changbai Mountains decreases. The annual average snowmelt under SSP126, SSP245, SSP370, and SSP585 is projected to be 148.65 mm, 135.63 mm, 123.44 mm, and 116.5 mm, respectively. The onset of snowmelt is projected to advance in the future. Specifically, in the Songhua River (SR) and Yalu River (YR) regions, the start of snowmelt is expected to advance by 1-11 days. Spatially, significant reductions in snowmelt were observed in both the central part of the watershed and the lower reaches of the river under SSP585 scenario. (2) In 2021-2060, the frequency of ROS floods decreases sequentially for different scenarios, with SSP 126 > SSP 245 > SSP 370 > SSP 585. The frequency increments of ROS floods in the source area for the four scenarios were 0.12 days/year, 0.1 d/yr, 0.13 days/year, and 0.15 days/year, respectively. The frequency of high-elevation ROS events increases in the YR in the low emission scenario. Conversely, in high emission scenarios, YR high-elevation ROS events will only increase in 2061-2100. This phenomenon is more pronounced in the Tumen River (TR), where floods become more frequent with increasing elevation.

Nitrogen removal performance of bioretention cells under freeze-thaw cycles: Effects of filler structure and microbial community.

Cold climates have an adverse effect on the nitrogen-removal capacity of bioretention cells, especially during freeze-thaw cycles (FTCs). To explore the effects of FTCs on the nitrogen removal performance of bioretention cells, this research compared the effects of FTCs on the pore structure and microbial community composition of the filler, and analyzed the nitrogen removal performance of the bioretention cell before (RT), during (FTC) and after (RRT) FTCs. The results demonstrated that RRT filler had a much greater number of pores with equivalent diameter <500 µm than RT filler, and that RRT had a higher pore volume and pore density than RT. Microbial community analysis revealed that the diversity and richness of the microbial community in FTC were lower than in RT, and the relative abundance of Lacunisphaera, Pseudomonas, and Dokdonella decreased significantly. There was no significant difference in microbial community richness between RRT and RT, however RRT diversity was lower. RRT has a higher relative abundance of nitrifying bacteria (Subgroup_10, Bryobacter, etc.) than RT, but a lower relative abundance of denitrifying bacteria (Pseudomonas, Dokdonella, Arenimonas, etc.). The nitrogen removal efficiency of FTC was inhibited, resulting in a decrease of 13.0 ± 4.86%, 19.7 ± 9.17%, and 26.6 ± 1.74% in the removal rates of ammonia nitrogen(NH4+-N), nitrate nitrogen(NO3--N), and total nitrogen(TN) when compared to RT, respectively. RRT improved nitrification and increased NH4+-N removal rate by 10.3 ± 2.69% compared to RT. However, because of denitrification inhibition, the nitrogen removal performance of RRT was not able to reach RT levels, and its NO3--N and TN removal rates decreased by 100 ± 4.70% and 58.3 ± 3.71%, respectively. This study has demonstrated that FTCs can permanently harm the bioretention cell's filler structure and microbial community, resulting in a significant decrease in the nitrogen removal performance of the bioretention cell designed according to warm climate conditions after experiencing FTCs.

Spatiotemporal convolutional long short-term memory for regional streamflow predictions.

Rainfall-runoff (RR) modelling is a challenging task in hydrology, especially at the regional scale. This work presents an approach to simultaneously predict daily streamflow in 86 catchments across the US using a sequential CNN-LSTM deep learning architecture. The model effectively incorporates both spatial and temporal information, leveraging the CNN to encode spatial patterns and the LSTM to learn their temporal relations. For training, a year-long spatially distributed input with precipitation, maximum temperature, and minimum temperature for each day was used to predict one-day streamflow. The trained CNN-LSTM model was further fine-tuned for three local sub-clusters of the 86 stations, assessing the significance of fine-tuning in model performance. The CNN-LSTM model, post fine-tuning, exhibited strong predictive capabilities with a median Nash-Sutcliffe efficiency (NSE) of 0.62 over the test period. Remarkably, 65% of the 86 stations achieved NSE values greater than 0.6. The performance of the model was also compared to different deep learning models trained using a similar setup (CNN, LSTM, ANN). An LSTM model was also developed and trained individually to predict for each of the stations using local data. The CNN-LSTM model outperformed all the models which was trained regionally, and achieved a comparable performance to the local LSTM model. Fine-tuning improved the performance of all models during the test period. The results highlight the potential of the CNN-LSTM approach for regional RR modelling by effectively capturing complex spatiotemporal patterns inherent in the RR process.

Uncovering the impact of climate and vegetation changes on runoff in karstic regions of southwest China.

The vegetation-runoff relationship remains unclear in karstic regions. The karst landform in southwest China is a focal area where significant changes in vegetation have occurred in the past few decades, which may substantially impact water resources. To date, the effects of these changes on runoff remain uncertain. This study employed statistical analysis, numerical simulation, and scenario analysis to investigate the temporal and spatial patterns of runoff, climate, and vegetation in 20 typical catchments. The study also evaluated the response of runoff to vegetation and climate changes and the underlying factors. The findings revealed precipitation changes dominated changes in runoff in these catchments (mean contribution of 53.03%), whereas the contributions of vegetation and potential evapotranspiration changes were 23.16% and 23.82%, respectively. The study also revealed that the impacts of vegetation changes on runoff were significantly dependent on vegetation and climate factors (R2 = 0.60, P < 0.01). Furthermore, under the same climate change conditions, a higher distribution of natural vegetation (such as forest) in the catchment resulted in a larger decreasing trend in runoff. The results provide guidelines for the prediction of runoff variation in southwest China, and benefits to decision-making on ecological restoration and water resources development.

Spatiotemporal geographically weighted regression analysis for runoff variations in the Weihe River Basin.

In order to investigate the effects of vegetation changes on runoff and to obtain recommendations for improving runoff in the Weihe River Basin (. In this study, a spatiotemporal geographic autocorrelation weighted regression analysis (SGAWRA) approach was newly developed based on previous studies. This approach investigates spatial non-stationarity of the dynamic response from vegetation variations to climatic change and human activity. Implications of spatial non-stationarity related to runoff variability were also discussed, which in turn yield the effect that vegetation changes have on runoff. The method systematically analysed the spatial non-stationarity of vegetation variations and its associated effects on runoff. Therefore, more closely related results with less error were produced at each step, and results with more accuracy were obtained. These results indicated that the average trend rates of NDVI in the annual average, each season, and the growing season (Growing season refers to April to September) exceeded 0. Areas where NDVI show a growing trend cover more than 50%, which is greater than the area with a decreasing trend. The GWR regression parameters of precipitation, average temperature, and NDVI are all greater than 0. The GWR regression parameters of human activities and NDVI also have more than 50% of the area greater than 0. Based on the visual analysis of the calculation results, it can be seen that there are obvious spatial trends in the data, and the spatial data are significantly different between different regions. Therefore, WRB can be regarded as spatio-temporally non-stationary. In the WRB, the underlying surface change with vegetation change as the prominent feature is the leading cause (about 60%) of the runoff attenuation. The results showed that WRB has spatial and temporal non-stationarity. The spatial non-stationarity of vegetation has a greater effect on runoff changes. The results of this study support recommendations for improving runoff in the WRB.