In this study, the characteristics and distribution of the organic phosphorus (Po) fractions in the surface sediments of seven inflow rivers around Hongze Lake in China were analyzed with a soil Po fraction method, as used by Ivanoff. The relationships between the Po fractions and physiochemical features of sediments were also discussed. The results showed that, the sediments of the rivers had been moderately pollution with certain ecological risk effects except the Waste Yellow River. The relative contribution order of the Po fractions in the sediments was residual Po > HCl-Po > fulvic acid-Po > humic acid-Po > labile organic phosphorus (LOP). Moderately labile organic phosphorus (MLOP) was the main part of the Po forms in the whole sediments. The risk of phosphorus released from river sediments was the highest in the western region, followed by the southwestern region, and finally the northwestern region. There were significant correlations between Po forms and total phosphorus (TP), inorganic phosphorus (Pi), and Po. Non labile organic phosphorus (NLOP) had the strongest correlation with TP. The distribution of Po forms in each region was different due to the impact of human activities, industrial and agricultural production and the land types; the heaver polluted sediments with higher Po fractions. It is suggested that most of the sediments of the inflow rivers in the regions have certain ecological risk effects and P of them have an important contributions on the eutrophication of Hongze Lake. Po forms can provide a reliable theoretical basis for dealing with the change of water quality and should be paid more attention in the lake eutrophication investigation. There was reciprocal transformation between different Po forms, especially non-bioavailable fraction can change into bio-available ones. The results can provide a basis for the earth cycle of phosphorus and a new perspective of eutrophication control of shallow lakes.

Non-point source pollution is widely considered a serious threat to drinking water. Eutrophication in Chinese watershed is mainly due to nitrogen and phosphorus output from agricultural source. Taihu Lake is a typical eutrophic lake in China, a basin representative for the study of the temporal-spatial characteristics of pollution loading of nitrogen and phosphorus to provide scientific basis for reasonable estimation and targeted control measures of nitrogen and phosphorus loss. Based on data from nitrogen and phosphorus loss in agricultural land, livestock breeding, domestic discharge and aquaculture, this study calculated the levels of nitrogen and phosphorus comprehensive loss risk for each pollution source. Using the superposition of ArcGIS raster data, we also described the spatial distribution of nitrogen and phosphorus comprehensive loss risk by the formula of comprehensive loss risk. The results showed that critical risk areas of nitrogen and phosphorus loss mainly originated from livestock breeding and agricultural land during flood period in Tiaoxi watershed. Agricultural land and livestock breeding sources formed major parts of nitrogen loss, accounting for 30.85% and 36.18%, respectively, while phosphorus loss mainly originated from livestock breeding (56.28%). During non-flood period, integrated management of livestock breeding and domestic discharge requires much attention to control nitrogen and phosphorus loss in the critical risk area. Finally, it is of great practical significance to propose spatial-temporal targeted measurements to control nitrogen and phosphorus pollution in watershed for various periods and different areas.

Unlike conventional energy-intensive physical/chemical soil remediation, dietary regulation of As oral bioavailability represents a cost-effective, sustainable downstream intervention in environmental risk management and control. However, how distinct dietary structures regulate As bioavailability remains unelucidated, hindering a holistic understanding of corresponding exposure and health risks. To address this, a mouse bioassay was conducted to evaluate the relative bioavailability (RBA) of As in two soils with four typical diet structures (high-fat, high-protein, high-carbohydrate, and high-dietary fiber diets). The results showed that although the four diets promoted the gastrointestinal As dissolution by 1.1–1.7-fold, the high-dietary fiber diet decreased As-RBA by 9.49–13.2% and lowered the health risk by 0.50–0.70-fold, which was more effective than high-protein and high-carbohydrate diets. The decrease was associated with lower intestinal permeability, which correlated with a significant increase in the relative abundance of Roseburia and Lachnospiraceae, and a decrease in the apoptosis rate of mouse intestinal epithelial cells. In contrast, a high-fat diet increased As-RBA by 8.72–11.9% and raised the health risk by 1.33–1.38-fold, which was associated with a significant proliferation of Dubosiella and a significant inhibition of Roseburia. This study shows that a high-dietary fiber diet is associated with reduced As exposure and potential health risks, in parallel with favorable changes in gut microbiota, oxidative status, and intestinal permeability.

Urban road dust is an important way for people to contact potentially toxic elements (PTEs). However, the correlation between the bioaccessibility of PTEs in road dust and the contribution rate of pollution sources has not yet reached a consensus. Road dust was divided into three particle sizes (<63, 63–125, and 125–250 μm). Then, the Mantel test was used to analyze the correlation between the contributions of the four pollution sources (composite sources, traffic sources, industrial sources, and fuel combustion) and the bioaccessibility of PTEs. Finally, by incorporating bioaccessibility into the health risk assessment system, Ni was identified as the priority lifetime carcinogenic risk element and fossil fuel combustion as the priority pollution source. The remediation target obtained by the probabilistic risk assessment of bioaccessibility guidance is 3.91 times the target value based on the total content and reduces carbon emissions by 22.6%. Overall, this study not only enhances the precision of identifying pollution sources and pollutants in complex urban environments by integrating PMF with the bioaccessibility of PTEs but also highlights the potential value of bioaccessibility in urban environmental management for carbon emission reduction. This facilitates the implementation of precise risk assessments and low-carbon sustainable development.

While increasing dietary calcium (Ca) intake can reduce the oral bioavailability of heavy metal(loid)s, it remains unclear whether a series of Ca compounds can simultaneously reduce the oral bioavailability of As and Pb from soil. The influence of eight Ca compounds on As and Pb bioaccessibility in soils was determined using an in vitro gastrointestinal model, following which an in vivo bioassay was used to determine the most effective Ca compounds on As and Pb bioavailability. The results showed that, while CaHPO₄ was the most effective in reducing Pb bioaccessibility in gastric (from 19.0 to 92.3% to 14.3‒66.4%) and intestinal (from 0.18 to 17.5% to 0.00‒3.53%) phases, it conversely exhibited the strongest capacity to enhance As bioaccessibility. However, the addition of Ca acetate reduced the Pb bioaccessibility in the gastric phase and As bioaccessibility in the intestinal phase. More importantly, the Ca acetate (~ 200 mg Ca kg^-1) was the most effective in reducing relative bioavailability of As and Pb based on mouse bioassay. Our finding verify the efficacy of Ca acetate in mitigating the oral bioavailability of As and Pb. This study lays a theoretical foundation for the targeted use of optimal Ca compounds to mitigate human exposure risks to environmental As and Pb.