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The risk of a cyanobacterial bloom was judged based on the 75th percentile of chlorophyll-a concentration readings. A low risk of cyanobacterial bloom outbreak was indicated when the probability of chlorophyll-a concentrations being lower than the threshold exceeded 75%. The data suggests a spring average temperature-to-wind speed ratio of 667 sm⁻¹ and a probability of high chlorophyll-a levels less than 75% under total phosphorus concentrations lower than 0.130 mg L⁻¹. Summer saw an average temperature-wind ratio of 1052 sm⁻¹; the probability of high chlorophyll-a levels dipped below 75% when the total phosphorus concentration fell below 0.257 mg L⁻¹. In autumn, the average total phosphorus concentration measured 0.154 mg/L, and the likelihood of high chlorophyll-a levels remained below 75% when wind speeds, relative to temperature, were less than 630 sm⁻¹. Leveraging the insights gained from the preceding study, a chlorophyll-a model, generated via a Bayesian network incorporating continuous variables, was subsequently utilized for simulating nutrient control targets under various climate change scenarios. Maintaining low-risk cyanoHAB levels in Lake Taihu required adjusting chlorophyll-a control by setting specific total phosphorus concentration targets, factoring in climate conditions across three periods: 1992-2000, 2001-2010, and 2011-2020. During the timeframe between 1992 and 2000, the spring threshold of total phosphorus concentration was 0.135 mg/L, whereas summer had a threshold of 0.174 mg/L, and autumn had a threshold of 0.171 mg/L. Throughout the decade of 2001 to 2010, the spring threshold for total phosphorus concentration was pegged at 0.115 mg/L, while the summer and autumn thresholds were 0.164 mg/L and 0.162 mg/L respectively. The total phosphorus concentration threshold varied across the seasons between 2011 and 2020, with a spring value of 0.059 mg/L and a summer and autumn value of 0.145 mg/L. The study’s results indicated a need for enhanced nutrient management policies, specifically targeting cyanoHABs, in eutrophic lakes in the face of global warming. Lake Taihu benefited from a reference point, enabling the prevention and control of cyanoHABs and eutrophication. Previous research has incorporated multiple regression modeling, numerical hydrodynamic simulations, and various alternative approaches to predict chlorophyll-a levels and cyanobacteria proliferation in lakes. No prior research has explored the prediction of cyanoHABs in lakes using a Bayesian network model that considers continuous variables and dynamically assesses nutrient thresholds. Consequently, the chlorophyll-a model for Lake Taihu was initially formulated using a Bayesian network approach with continuous variables. This model, constructed from 1992 to 2020 seasonal meteorological, water quality, and biological data, simulates chlorophyll-a concentrations in response to diverse climate indicators and total phosphorus levels. The impact of influencing factors’ weight was also investigated, alongside a dynamic evaluation of nutrient control targets under different climate situations.

A study on the spatial distribution and contamination characteristics of nutrients in the surface sediments of Chengxi and Chengdong Lakes, Huoqiu County, involved determining total nitrogen (TN), total phosphorus (TP), and organic matter (OM) in 30 samples from each lake, followed by an analysis of their contamination levels and source identification. The content of total nitrogen (TN), total phosphorus (TP), and organic matter (OM) was considerably greater in Chengxi Lake than in Chengdong Lake. The average amounts for Chengxi Lake were 74623 mg/kg TN, 53838 mg/kg TP, and 117% OM, whereas Chengdong Lake had 47080 mg/kg TN, 49208 mg/kg TP, and 068% OM. In the north and northwest of Chengxi Lake, the spatial distribution was considerably greater than elsewhere and showed a reduction from north to south. Analysis of the C/N ratio revealed that the organic matter in Chengxi Lake and Chengdong Lake is largely derived from unbundled plants and phytoplankton. Homologous patterns were observed in the concentrations of total nitrogen (TN), total phosphorus (TP), and organic matter (OM) between Chengxi Lake and Chengdong Lake, according to correlation analysis. Sediment samples from Chengxi and Chengdong Lakes revealed average total nitrogen (TN) single indices (STN) of 0.67 and 0.42, and average total phosphorus (TP) single indices (STP) of 1.18 and 1.08, respectively. This indicates clean TN levels and moderately polluted TP levels in both lakes. The average comprehensive pollution index (FF) was 1.51 for Chengxi Lake and 1.31 for Chengdong Lake. The organic index and the organic nitrogen index measurements demonstrated that the water quality of both Chengxi Lake and Chengdong Lake is clean.

Eutrophication in the reservoir’s tributary bays is aggravated by the accelerated migration and transformation of phosphorus in the water-level fluctuation zone (WLFZ) following repeated wetting-drying cycles. Samples of soils from the WLFZ of a typical tributary of the Three Gorges Reservoir were collected, and subsequent analysis of phosphorus forms and the degree of phosphorus saturation (DPS) was conducted to estimate the potential for phosphorus to be released. Soil analysis in the WLFZ revealed the average levels of total phosphorus (TP), inorganic phosphorus (IP), and organic phosphorus (OP) as 77180, 48533, and 16630 mg/kg, respectively. Speciation patterns, in IP and OP, were primarily defined by the dominance of the non-labile IP and the non-labile OP, respectively. Wetting-drying cycles impacted the spatial arrangement of P forms within the soils of the WLFZ. In the soils of the WLFZ, the concentrations of Ex-P and NaHCO3-Po were notably higher than in contrasted soils, in contrast, the levels of Fe-P, HCl-Po, and Fulvic-Po saw a substantial decline along the altitudinal gradient (P < 0.05). her2 signaling The soils of the WLFZ responded to the repeated wetting and drying cycles by generating labile phosphorus and subsequently releasing and accumulating a quantity of moderately labile phosphorus. Soil bioavailable phosphorus (Bio-P), both in content (4919-14878 mg/kg) and proportion (717%-2478%), and the degree of phosphorus sorption (DPS, 585%-2200%), in the WLFZ displayed considerable variability. Currently, the soils in the WLFZ have a low risk of releasing phosphorus. The soil situated at an altitude of 170 meters warrants further scrutiny. The factors Fe-P, HCl-Po, and Fulvic-Po collectively prompted a considerable release of phosphorus. A rise in pH triggered the release of Fe-P. Alkaline phosphomonoesterase (ALP) was indispensable in the alteration and transformation of OP. Moreover, organic matter (OM) served as the primary source of OP.

The Lanzhou reach of the Yellow River was selected as the study area to investigate the contamination characteristics and possible origins of heavy metals present in the surface sediments of urban rivers in the Yellow River Basin. Forty-six surface sediment samples from the Lanzhou section of the Yellow River were collected, and the concentrations of eight heavy metals—chromium, nickel, copper, zinc, arsenic, cadmium, mercury, and lead—were determined using inductively coupled plasma mass spectrometry and atomic fluorescence spectrometry. In the Lanzhou reach of the Yellow River, the characteristics of heavy metal pollution and ecological risk in urban river surface sediments were determined by applying contamination indexes, including the single factor pollution index (Pi), geo-accumulation index (Igeo), and sediment pollution index (SPI). To quantitatively analyze the origin of heavy metal pollution, a combined approach incorporating Pearson’s correlation analysis (CA), positive matrix factorization (PMF), and principal component analysis/absolute principal component score (PCA/APCS) was used. Measurements demonstrated that the average levels of the majority of heavy metals exceeded the background values for both Gansu Province and Lanzhou City, with the sole exception being arsenic; a significant concentration of these metals was predominantly observed in the river’s edge. Pollution of the Yellow River near Lanzhou, measured using single-factor and geo-accumulation indexes for eight heavy metals, showcased chromium (Cr) as the dominant contaminant in urban riverbed sediments, alongside elevated levels of cadmium (Cd) and nickel (Ni). Surface sediment samples demonstrated SPI values for the eight heavy metals spanning from 0.48 to 8.56, thus indicating a risk level that progressed from natural to a low ecological risk. Moreover, source apportionment analysis indicated that a combination of industrial and agricultural activities (776%) was the primary contributor of Cr, Ni, Zn, As, Cd, and Pb in the surface sediments of the urban river, surpassing natural sources (114%) and a combined source from industry and traffic (11%).

Microplastic (MP) and metal pollution are frequently concentrated in urban rivers, where they serve as pathways for pollution migration. However, despite the significance of microplastics as important sources and sinks for resistance genes, the exploration of their links with metal contamination and related metal resistance genes has been limited. In situ, ten water samples were collected from the Huangpu River, and analyses were performed on both metal elements and MPs characteristics. Through the application of metagenomic technology, the presence of metal resistance genes and mobile genetic elements (MGEs) in water and microplastics (MPs) was established. Subsequently, the most prominent metal concentration in surface water was Sb, at a level of 3160419 gL-1. In industrial and densely populated areas, the average abundance of MPs reached 178,084 nL⁻¹, exceeding the levels observed in agricultural and sparsely populated areas significantly. Transparent polyethylene terephthalate (PET), fibrous and measuring less than 0.5 mm in size, contributed the most to the microplastic load. In all the examined samples, eighteen MRGs were identified. Regarding the relative abundance of MRGs in water, the figure was 168021. MRG subtypes merR and ruvB, resistant to mercury and multi-metal exposure, were the most prevalent forms.