Search Results (180)

Riparian land use and land cover (LULC) exerts scale- and season-dependent controls on surface water quality, yet its influence in regulated agricultural–urban rivers is poorly characterized. We combined seasonal t-tests, one-way ANOVA, and redundancy analysis (RDA) at three riparian buffer scales (500, 1000, and 2000 m) to examine discharge, dissolved oxygen (DO), temperature, turbidity, and pH at four USGS stations along the Kansas River mainstem (2019–2026). DO and temperature showed the strongest seasonal contrasts: DO was 3.1–3.7 mg/L higher in the dry season and temperature 13–15 °C higher in the wet season, a coupling central to aquatic habitat suitability. Turbidity rose significantly in the wet season, consistent with agricultural runoff and sediment mobilization, whereas discharge showed no significant seasonal difference at three of four stations, reflecting upstream reservoir regulation. Spatial ANOVA detected station-level differences only for wet-season DO ($F_{3,28}=4.91$, $p=0.007$), which was lowest at the downstream urbanized station. RDA linked agricultural cover to turbidity and urban cover to reduced wet-season DO, although permutation tests were non-significant ($p\ge 0.42$) at $n=4$ replicates. Seasonality and riparian LULC jointly shape water quality along this regulated river, and the 500 m buffer is the most spatially discriminating scale for land-cover assessment. Full article

The middle–lower Huaihe River Basin faces persistent flood and waterlogging threats, with river–lake interactions being a critical yet underexplored factor constraining flood discharge capacity. This study investigates the flood discharge capacity and erosion–deposition dynamics in the Bengbu–Hongze Lake reach and proposes sustainable management solutions. By analyzing long-term hydrological data (1954–2020) and cross-sectional measurements (1971–2025), we quantified changes in channel morphology and flood behavior. The results reveal that while upstream inflow has remained stable (annual runoff 20.5–33.3 billion m³), sediment concentration has continuously declined by approximately 80%—from 0.474 kg/m³ in the 1950s to 0.094 kg/m³ in the 2020s. The main channel exhibits persistent incision totaling 135.7 × 10⁶ m³, while floodplains have undergone progressive aggradation of 35.1 × 10⁶ m³, reflecting a sediment-starved river system in geomorphic disequilibrium. Critically, the riverbed leading to Hongze Lake exhibits an adverse slope, rising from –10 m at Fushan to over +9 m at Laozishan, while the lake’s sedimentation has reduced its storage capacity by 29% since the 1980s (from 31.27 × 10⁸ m³ to 22.15 × 10⁸ m³). Despite extensive engineering interventions, significant issues persist—including the backwater effect of Hongze Lake, prolonged high water levels during moderate floods (in 2020, water level at Fushan reached 18.34 m at only 61% of the design discharge), and exacerbated waterlogging in riparian lowlands. Therefore, we advocate for a paradigm shift towards a river–lake separation scheme, specifically, an inner-lake embankment approach. This nature-based solution aims to restore the river’s physical structure and harness its self-shaping morphological function for long-term flood management and ecological sustainability. Our findings provide a quantitative basis for re-evaluating the river–lake relationship and offer a strategic direction for sustainable flood management in highly altered alluvial river systems. Full article

Pharmaceuticals and personal care products (PPCPs) are contaminants of emerging global concern, yet their long-term fate and distribution in strategic trans-boundary water source areas remain underexplored. This study conducted a comprehensive monitoring campaign spanning from 2018 to 2020, with six sampling campaigns carried out in August 2018, December 2018, May 2019, August 2019, December 2019, and May 2020, to investigate the occurrence, spatiotemporal dynamics, source apportionment, and ecological risks of 54 PPCPs in the surface water and sediments of the Taipu River in eastern China. Utilizing non-target screening via liquid chromatography high-resolution mass spectrometry (LC-HRMS), 54 PPCPs across 15 categories were detected, with average total concentrations of 28.60 ng/L in surface water and 13.01 ng/g in sediments. Sulfonamides, quinolones, and non-steroidal anti-inflammatory drugs (NSAIDs) dominated the aqueous phase (with bisphenol A and sulfamethoxazole highly prevalent), while hormones (e.g., estriol) and quinolones (e.g., ciprofloxacin (CIP)) exhibited significant accumulation in the benthic zone. Spatiotemporal analysis revealed a seasonal pattern where PPCP concentrations were higher in the dry season than in the wet season, primarily driven by hydrological dilution and climate-induced degradation. Furthermore, Positive Matrix Factorization (EPA PMF 5.0) extracted five distinct source factors for each matrix. Specifically, surface water pollution was primarily driven by domestic wastewater, municipal effluents, medical discharges, and localized pharmaceutical emissions, whereas sediments acted as a long-term sink predominantly for domestic wastewater, agricultural/veterinary runoff, and municipal/industrial emissions. Ecological risk assessment indicated that while most of the nine high-frequency contaminants posed low risks, specific compounds such as CIP, SM2, and E3 presented medium risks in surface water, whereas ENR, CIP, and SPI posed medium risks in sediments. These findings emphasize that the continuous multi-source input and the resulting pseudo-persistence of PPCPs in sediments warrant prioritized continuous attention and targeted pollution control strategies in the Taipu River Basin. Full article

Baseflow separation was performed for 42 small catchments completely built up of either crystalline rocks or folded/unfolded Paleogene flysch rocks. Three different methods were applied—Local minimum (BFI), Kille’s and Rambert’s. Mean total annual runoff in individual catchments varied from 179 to 1132 mm, with an average of 498 mm. Taking into account results for the whole dataset, baseflow participated in 45% ± 15% ratio of the total runoff. Local minimum and Kille’s method results were quite similar: both showed average baseflow participating on 39%/40% of total runoff in unfolded Paleogene catchments, on 29%/29% in folded flysch and 44%/45% in catchments with crystalline basement. Rambert’s method results were 10% to 12% higher from the previous two, reaching 50% in unfolded flysch Paleogene catchments, 41% in folded flysch and 56% in crystalline catchments. Differences might be caused by the nature of Rambert’s method, which is based on recession curves analyses, while the previous two result from discharge statistics. Still, usually only less than 50% of unevaporated precipitation is able to infiltrate and recharge groundwater resources in crystalline rocks and flysch sediments, and folded flysch rocks are sometimes able to absorb only 10–20% of unevaporated precipitation. Full article

This study evaluates the performance of natural plant-derived coagulants as sustainable alternatives to conventional chemical coagulants in water treatment. Surface water samples were collected from the Meda Ela stream in Karadiyana, Sri Lanka, which is an urban water body impacted by leachate from the Karadiyana dumpsite, industrial discharges, and urban runoff. Grab samples were analyzed for key water quality parameters, including pH, conductivity, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), settleable solids, total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), total nitrogen, and total phosphorus. Several parameters exceeded permissible standards established by the Central Environmental Authority (CEA) of Sri Lanka, including turbidity (35 NTU; limit: 20 NTU), COD (80 mg/L; limit: 15 mg/L), TDS (1000 mg/L; limit: 500 mg/L), and TSS (100 mg/L; limit: 40 mg/L), indicating significant pollution levels. Jar test experiments were conducted to compare the coagulation efficiency of cowpea seeds (75.8%), fenugreek seeds (69.2%), papaya seeds (72.5%), okra pods (84.6%), and Moringa oleifera (drumstick) leaves (87%) with conventional alum (94.2%) at an optimum dosage of 12 mL/L. Among the tested plant-derived coagulants, Moringa oleifera leaves demonstrated the highest turbidity removal efficiency, reducing residual turbidity to 4.54 NTU. A low-cost integrated treatment system incorporating coagulation, flocculation, sedimentation, and filtration using sawdust and cotton wool was developed, achieving average removal efficiencies of 90.13% for turbidity, 88.57% for COD, 83.46% for TDS, and 74.83% for TSS, with all effluent parameters maintained within CEA permissible limits. The results confirm that locally available plant-derived coagulants, particularly Moringa oleifera leaves, offer an effective, environmentally friendly, and economically viable approach for sustainable water treatment, highlighting the potential of nature-based solutions in strengthening climate-resilient water management strategies. Full article

Storm-driven turbidity is a major water-quality concern in urban watersheds, reflecting the mobilization and transport of fine sediment during runoff events. This study examines how seasonal storm characteristics influence turbidity and associated sediment transport responses in the Middle Fork of Beargrass Creek, Louisville, Kentucky, over a two-year period. Forty-one erosive storm events were identified and characterized using high-resolution rainfall data to capture storm magnitude and structure. Study objectives were to: (1) quantify event-scale turbidity responses to erosive storms, (2) compare upstream and downstream turbidity behavior to assess spatial variability, (3) evaluate seasonal variation in these relationships, and (4) assess implications for sediment-focused best management practice (BMP) design. Event-based regression models related downstream turbidity to lagged upstream turbidity and downstream erosivity. Turbidity ratios and turbidity–discharge hysteresis characterized spatial and temporal sediment transport dynamics. Results showed that winter and spring storms exhibited longer durations, stronger upstream–downstream turbidity coupling, and more stable lag relationships, indicating integrated sediment transport. Short-duration, high-intensity summer storms produced elevated turbidity ratios, pronounced clockwise hysteresis, and greater model sensitivity, consistent with localized sediment mobilization. Findings support seasonally adaptive BMP strategies, with volume-reduction approaches most effective during winter–spring and source control measures critical during summer-fall. Full article

A remote analysis of coastal sedimentation in northern KwaZulu-Natal (KZN), South Africa, describes how summer runoff and winter wave-action operate within a highly variable climate. Despite rising sea levels, the sediment flux can sustain beaches under certain conditions. Daily satellite red-band reflectivity and ocean–atmosphere reanalysis datasets were studied over the period of 2018–2025. Statistical results indicate that streamflow discharges are spread northward by oblique wave-driven currents. Sediment concentrations peak during late winter (>1 mg/L, May–October) when deep turbulent mixing (>40 m) mobilizes sand from the seabed. A case study from September 2021 revealed that ridging high-pressure/cut-off low weather patterns can simultaneously increase streamflow, wave energy, and wind power, creating a surf-zone sediment conveyor along the coast of northern KZN. Long-term climate diagnostics from 1981 to 2025 reveal upward trends in coastal runoff, vegetation, and turbidity (0.29 σ/yr) that point to an increasingly vigorous water cycle. The warming of the southeast Atlantic intensifies the sub-tropical upper-level westerlies and late winter storms over southeast Africa. These processes occur in 5–8 year cycles and drive shoreline advance and retreat, from accretion ~1 T/m and storm surge inundations up to 5.5 m. Using Digital Earth, it was noted that ~1/4 of beaches around Africa are gaining sediment while ~1/3 are eroding. Although remote information could not close the sediment budget, realistic estimates of long-shore transport in the surf-zone (>10⁴ kg/yr/m) and on the beach (>10³ kg/yr/m) were calculated. These provide an emerging explanation for the resilience of northern KZN beaches, as sea levels rise at a rate of 0.6 cm/yr. Full article

Flood events are major drivers of soil erosion and sediment yield on the Loess Plateau, where extensive ecological restoration has been implemented. This study investigates runoff–sediment dynamics by analyzing 215 flood events recorded in the Chabagou watershed (1959–2022), with a focus on changes under intensifying restoration efforts. Using long-term hydrological and rainfall data, we applied cluster and discriminant analyses to classify flood events based on sediment hysteresis loops and evaluated variations across three management periods (1959–1979, 1980–1999, and 2000–2022), characterized by progressive increases in check dam construction and vegetation recovery. The results show that the floods characterized by short duration, low peak flow, and low sediment concentration were predominant, accounting for 77.7% of the recorded 215 events. A clear decreasing trend was observed, with average sediment yield and peak discharge declining by approximately 68% and 52%, respectively. Anticlockwise hysteresis loops were most common (45.6%), followed by complex (27.9%) and figure-of-eight loops (23.7%). The proportion of figure-of-eight loops increased notably from 17% to 39%, indicating reduced sediment connectivity due to large-scale ecological restoration. Extreme rainfall events consistently produced complex hysteresis patterns, influenced mainly by rainfall intensity but increasingly modulated by human interventions. These results highlight adaptive watershed management strategies that target figure-of-eight and complex flood events to mitigate erosion and flood risks. Full article

Combined sewer overflow (CSO) pollution has consequently become a critical challenge, yet its formation depends on tightly coupled dry- and wet-weather processes. This study aims to integrate high-resolution field monitoring with statistical analysis to characterize the full “accumulation–transport–discharge” cycle of CSO pollution in a representative combined sewer catchment located in the Yangtze River basin, China. A dynamic analytical framework was established, combining multiple pollution media and linking dry-weather accumulation with rainfall-driven transport, enabling quantitative source apportionment of pollutant contributions. Results indicated that during dry periods, domestic sewage exhibited strong enrichment, with concentrations of total inorganic nitrogen (TIN), chemical oxygen demand (COD), and total phosphorus (TP) being 2.1-, 2.3-, and 1.9-fold higher, respectively, than the Chinese secondary discharge standards (GB 18918-2002). Surface sediment showed pronounced spatial heterogeneity, with greater loads in residential than transportation areas and substantial fine-particle accumulation on roofs (particle size < 150 μm, accounting for 73% by mass). Sewer sediments, dominated by coarse inorganic particles (over 77% by mass), represented the main pollutant reservoir. Rainfall produced distinct hydrodynamic and water quality responses. Light rain following long antecedent dry periods generated a high-concentration but low-load regime with a strong first flush, whereas moderate rain yielded lower concentrations but higher loads. Overflow occurred when rainfall exceeded ~14 mm, with pollutant peaks lagging rainfall by 20–45 min in the studied area. TIN and TP peaked sharply at rainfall event onset, and first-flush intensities followed TIN > TP > COD > suspended solids (SS). Source apportionment identified sewer sediments as the dominant CSO source, followed by surface runoff and domestic sewage. These findings clarify the mechanisms linking dry-weather accumulation to wet-weather transport and support targeted CSO pollution control and urban water quality management. Full article

Coastal marine sediments and beach sands receive microbial and genetic inputs from wastewater discharge, urban runoff, aquaculture, wildlife, and recreational activity, yet their role as coupled microbial–genetic interfaces linking environmental processes and human exposure remains incompletely synthesized. This review integrates quantitative evidence from culture-based studies, qPCR surveys, metagenomic analyses, and multi-year monitoring investigations focused on coastal sediments and sands. Reported antibiotic resistance gene (ARG) concentrations in coastal sediments reach 2.2 × 10⁹ copies g⁻¹ (wet weight) for sul1 in wastewater-impacted systems, with total ARG abundances commonly ranging from 1.59 × 10⁷ to 2.88 × 10⁸ copies g⁻¹ in effluent-receiving zones and tetM reported at 1.43 × 10⁷ copies g⁻¹. Beach sands contain measurable resistance markers, including intI1 at 9–3823 copies g⁻¹ and blaTEM up to 14 copies g⁻¹ in wet sand. Viable fecal indicator bacteria and pathogens have been cultured directly from sands, including Staphylococcus aureus at 0–8710 CFU g⁻¹ and methicillin-resistant S. aureus at 0–605 CFU g⁻¹. Collectively, the evidence indicates that coastal sediments and sands function as structured microbial and genetic reservoirs requiring integrated assessment of benthic retention, hydrodynamic redistribution, and exposure-relevant interpretation. Full article

Riverbed siltation in estuaries affects ecosystem functioning, water quality, and navigation. This study investigates the flow-regulated Osellino Canal, a freshwater tributary of the Venice Lagoon that crosses a largely urbanized area and is undergoing progressive siltation. High-resolution measurements of discharge (Q) and suspended sediment concentration (SSC) were performed using hydroacoustic instrumentation from September 2019 to December 2021. The analysis examined discharge dynamics, sediment transport, and rainfall-runoff relationships. Results indicate a mean annual discharge of 2.1 m³ s⁻¹ and an average annual suspended sediment load of ~2900 ± 330 t. Discharge patterns were strongly influenced by water management, resulting in anomalous runoff coefficients (δ > 1) during dry periods. Sediment export proved to be strongly event-driven: episodic high-flow events accounted for about 23% of the total load despite representing only a small fraction of the study period. Furthermore, a strong linear relationship between runoff and sediment load (R² = 0.94) confirms an advection-dominated regime, where net export is regulated primarily by hydrodynamic volume rather than fluctuations in sediment supply. Bathymetric comparisons (2011–2019) reveal a mean annual sediment retention of 400 ± 100 t yr⁻¹, corresponding to a trapping efficiency of approximately 12 ± 3% relative to the gross sediment input. These findings, supported by SSL–runoff regression residuals, consistently indicate net sediment accumulation associated with the long-term malfunction of a miter-gate system that impedes efficient sediment export. This study provides a critical pre-rehabilitation baseline, establishing a benchmark to evaluate the effectiveness of ongoing restoration efforts initiated in March 2022 and the future hydromorphological recovery of the canal. Full article

Eutrophication is a major threat to freshwater ecosystems, leading to harmful algal blooms, biodiversity loss, and hypoxia. Excessive nutrient loading, primarily from nitrates and phosphates, is driven by fertilizer runoff, sewage discharge, and agricultural practices. Sediment microbial fuel cells (sMFCs) have emerged as a potential bioremediation strategy for nutrient removal while generating electricity. Although various studies have explored ways to enhance sMFC performance, limited research has examined the relationship between external resistance, electricity generation, and nutrient removal efficiency. This study demonstrated effective nutrient removal from overlying water, with 1200 Ω achieving the highest nitrate and phosphate removal efficiency at 59.0% and 32.2%, respectively. The impact of external resistances (510 Ω and 1200 Ω) on sMFC performance was evaluated, with the 1200 Ω configuration generating a maximum voltage of 466.7 mV and the 510 Ω configuration generating a maximum current of 0.56 mA. These findings show that external resistance plays a major role in both electrochemical performance and nutrient-removal efficiency. Higher external resistance consistently resulted in greater voltage output and improved removal of nitrate and phosphate. The findings also indicate that sMFCs can serve as a dual-purpose technology for nutrient removal and electricity generation. The power output may be sufficient to support small, eco-friendly biosensing devices in remote aquatic environments while mitigating eutrophication. Full article

Aquatic ecosystems are currently facing anthropogenic pollution, mainly derived from agricultural, industrial, and urban runoff, including heavy metals, polycyclic aromatic hydrocarbons (PHAs), pesticides, fertilizers, and untreated wastewater discharges. To understand the impact of environmental contamination on fish, this research compared cytochrome P450 1A (CYP1A) gene expression in armored catfish across three locations in the lower Grijalva–Usumacinta River basin known for varying levels of pollution. Samples from the Ribera Alta, the Bitzales River, and the Chaschoc lagoon were collected during the dry and rainy seasons. We isolated RNA from liver samples, which were subsequently converted to cDNA. We used quantitative PCR to analyze CYP1A gene expression. Results showed that, of the three locations, Ribera Alta demonstrated the highest expression during the rainy season. Only in Chaschoc Lagoon did we observe significant differences between seasons (p = 0.03). This indicates that seasonal factors and the presence of pollutants in the water bodies and sediments likely play a role in regulating CYP1A gene expression in this fish species. Full article

Gully is the most visible sign of land degradation, but its effects on runoff and sediment dynamics during snowmelt conditions remain poorly understood. This study monitored a typical gully in the Mollisols region of Northeast China to investigate runoff and sediment transport at the Gully Head (GH) and Gully Tail (GT) during spring snowmelt. Results showed that gully significantly influenced snow distribution, with deeper snow accumulation than on slopes. Runoff at the GH lasted 9 days, while gully connectivity extended catchment runoff by 10 additional days. Runoff temporal variation at GH and GT was broadly consistent, with GH contributing 7.4% of the total runoff at GT. Peak runoff discharge and sediment concentration occurred on the sixth day after snowmelt onset, driven by snow cover and air temperature. Gully significantly increased the sediment concentration from the upslope runoff. Runoff responses to temperature varied by melt stage, with GT showing higher sensitivity, especially under high-runoff conditions. High sediment yield was linked not to snow depth, but to late-stage snowmelt and soil thawing, when erosion sensitivity peaked. Hysteresis analysis revealed dominant clockwise loops during this phase, contrasting with figure-eight and counterclockwise patterns in other stages. These findings highlight the importance of targeting erosion control during late snowmelt when runoff intensifies and soils thaw. Full article

The lower Yellow River, characterized by high sediment concentration and complex channel evolution, faces a persistent challenge of maintaining erosion–deposition balance. Using long-term hydrological and cross-sectional data (1950–2022) from seven key stations (Huayuankou–Lijin), this study established P-III frequency models for annual runoff (Q) and sediment discharge (S), introducing the flow–sediment frequency correlation coefficient (ζ) and the frequency relationship coefficient (λ) to quantify their synergy and erosion–deposition response. Results showed that (1) sediment discharge decreased by 91.4% at Huayuankou since the 1950s, while runoff decreased by 41.5%; (2) the flow–sediment synergy differed with river type—meandering (ζ ≈ 0, 69.23%) > transitional (64.39%) > wandering (59.26%); and (3) the equilibrium threshold of erosion and deposition was P(S) = (0.664–0.779) P(Q), corresponding to an incoming sediment coefficient of ~0.012 kg·s/m⁶. These findings quantitatively define the frequency-based synergy and threshold mechanism of flow and sediment in the lower Yellow River, providing a scientific basis for sediment regulation and channel stability management. Full article