Status of different anthropogenic organic pollutants accumulated in sediments from Olt River Basin, Romania: From distribution and sources to risk assessment

Spatiotemporal evolution of environmental factors in representative tributaries of the Yellow River: insights from a decade of monitoring data

The Yellow River, recognized as the cradle of Chinese civilization, has experienced significant environmental transformations due to rapid urbanization, which has substantially increased wastewater discharge into its basin, thereby altering its hydrological and water quality dynamics. Based on nearly a decade of monitoring data from over 20 sections within the Dahei River basin, a pivotal tributary at the upper reaches of the Yellow River, this study analyzed the variations in seven key water quality parameters (TN, TP, NH3-N, COD, BOD5, DO, and CODMn) across regions influenced by varying degrees of human activity and differing climatic conditions over wet, normal, and dry years. The results indicated that the most suitable model for fitting the 'hydrological frequency-water quality' relationship over time was linear. The R2 values ranging from 0.82 to 0.99, suggesting strong reliability of the model. Generally, the water quality concentrations exhibited gradual changes over time. Spatially, the preferred model for the 'hydrological frequency-water quality' relationship was exponential, with a greater likelihood of sudden increases in water quality concentrations, supported by R2 values ranging from 0.85 to 0.99, indicating dependable fitting. During various periods, the water quality in high-activity areas consistently exhibited poorer water quality compared to the low-activity areas. Indicators negatively impacting water quality were 1.66-63.25 times higher in high-activity areas than in low-activity areas. Water quality was generally poorer during wet years. For example, total nitrogen (TN) concentrations exceeded the Class V water standard (2 mg/L) in all river sections during wet years, with 81.05% of sections surpassing this threshold in normal years and 90.36% in dry years. These findings offer valuable insights for basin managers, highlighting the need for targeted interventions to mitigate water quality deterioration and enhance pollution control strategies.

Unveiling polycyclic aromatic hydrocarbon pollution dynamics in river-lake sediments: Insights for energy transition

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants primarily emitted by heavy industry, while their relationship with light industry has remained largely overlooked. This study quantified 16 priority PAHs in sediments from an urbanized river and its tributaries using gas chromatography coupled with triple quadrupole mass spectrometry, assessing the impact of local light industries. The total sedimentary PAH concentrations ranged from 244 to 24,616 ng/g dw (mean: 2097 ± 2673 ng/g dw), with high molecular weight PAHs predominating. PAH concentrations closely mirrored the operational footprint of the textile and shipping industries, including significantly higher PAH concentrations in the midstream compared to the upstream and downstream areas with fewer industrial activities. Additionally, PAH concentrations were significantly higher in the rainy season in the semi-closed lakes than in the dry season and normal season, likely due to increased industrial production and shipping activity, combined with the periodical closure of sluice gates that restricts the outflow of PAHs from connected lakes to the main watercourse. Multiple statistical analyses revealed that coal and petroleum combustions, primarily from these local industries, contributed 88% to the sedimentary PAH load, while vehicle exhausts and oil leakages accounted for the remaining 12%. According to sediment quality guidelines, PAHs exhibited pervasive ecological risks, even near drinking water sources. This study highlights the substantial influence of industrial activities on PAH distribution in urbanized rivers and provides a robust theoretical foundation for energy transition and drinking water protection strategies.

Distribution and sources of polycyclic aromatic hydrocarbons in cascade reservoir sediments: influence of anthropogenic activities and reservoir hydrology

The construction of dams has caused disruptions to river connectivity, leading to alterations in the deposition of hydrophobic organic contaminants in reservoir sediments. Further investigation is warranted to explore the impact of cascade reservoirs with differing hydrological characteristics on polycyclic aromatic hydrocarbons (PAHs) distribution in sediment. This study examines the presence of 30 PAHs in the sediments collected from six cascade reservoirs situated in the Wujiang River basin during January and July 2017. The results showed that Σ30 PAHs ranged from 455-3000 ng/g dw (mean 1030 ng/g dw). Anthropogenic activities and reservoir hydrology determined the distribution trend of PAHs in sediments, with an overall increase from upstream to midstream and then a decrease downstream. The PAH levels were highly linked to the secondary industry (P < 0.05). This was further supported by the relationship between the PAH emissions from coal combustion and traffic sources analyzed by the positive matrix factorization model and economic parameters in the wet season (P < 0.01). At the same time, reservoir age (RA) showed a positive correlation with PAH concentrations (P < 0.05), while hydraulic retention time (HRT) exhibited a negative correlation with PAH levels (P = 0.03). The relationship between total organic carbon (TOC) and PAHs in stream sediments worldwide was nonlinear (P < 0.01), with PAH concentrations initially rising and then falling as TOC levels increased. Concerns regarding carcinogenic risk were raised due to contributions from coal and vehicular sources, with the risk increasing with RA.

Ecotoxicological risk assessments and components of persistent organic pollutants and metals in the historical settlement area (Iznik (Nicea) lake) large water resource sediments

The main objectives of this study are to measure permanent organic and inorganic pollutants in detail in an area that hosts historical structures underneath and feeds the huge ecosystem with water, to reveal risk values. Total PAH concentrations in the samples ranged from 43.41 to 202.7 ng/g. Total OCP concentration ranged from 5.15 to 17.98 ng/g, while total PCB concentration ranged from 0.179 to 0.921 ng/g. PCB 28/31, 138, and 153 are the highest detected PCBs. It was found that the lake sediment reached toxic equivalent quotient (TEQ) values of 29.21 for total PAHs and 28.90 for carcinogenic PAHs. Negligible concentration risk quotient had a low to moderate ecological and toxicological risk between 12.91 and 64.42. Highest pollution index value was found 3.81 and the risk index value reached 417.4. It has been revealed that toxicologically risky components accumulate over many years even in the best-protected water resources.