Microplastics are widely found in oceans and rivers. In China, the research on microplastic pollution in inland urban fresh waters of China is insufficient. We studied microplastics in the surface waters of urban rivers in Chengdu, which is the largest city in western China. The concentration of microplastics in the analysis environment ranged from 5.00 to 10.5 items/L, and the average quantity was 8.82 items/L. The majority of the microplastics were transparent and took the form of fragments, particles, and fibers. Polyethylene terephthalate (PET) and polyamide (PA) were the dominant polymer types of the microplastics analyzed. Plastic particles ≤ 500 μm accounted for 69.8% of the total. This large proportion of small transparent microplastics in urban rivers in Chengdu is a potential threat to the growth of aquatic organisms and birds foraging from the river and may pose hazards to human health. Additionally, the correlation of microplastic content with population quantity and economic level was calculated by the Pearson coefficient method (p < 0.05), and the results showed that both have an important effect on the number of microplastics in rivers. This research provides a reference for understanding the level of microplastics in urban rivers in Chengdu and pollution control.

Phosphogypsum (PG) is an acid by-product from the production phosphate fertilizers that is produced in large amounts all over the world. However, it is challenging to reuse this waste due to the quantities of various impurities in PG and technical restrictions, resulting in PG accumulation, which threatens adjacent environments. To reduce PG storage and safely utilize PG, the aim of our study was to define the leaching characteristics of the impurities present in PG under different conditions. We found that (1) different leaching experiments showed different leachate profiles (including pH and electrical conductivity values of leachate), which indicated that the liquid/solid (L/S) ratio, temperature, oscillation strength, particle size, and pH have remarkable effects on the concentration of leached impurities; (2) all leachate (i.e. soluble P, fluoride, Zn, Pb, As, and Hg) extraction concentrations were significantly more sensitive to the effect of the L/S ratio and pH than the effect of the other conditions; and (3) the leaching concentration was strongly influenced by pH, and a strong correlation among soluble P, F, As, and Hg concentrations in the leachate was demonstrated by a correlation analysis. In the present study, we revealed a systematic leaching mechanism of potential toxic elements in PG and have provided guidance and a reference for PG resource comprehensive utilization and surrounding environment treatment. Supplementary material: Chemical compositions of the phosphogypsum and pairwise Wilcoxon test results are available at https://doi.org/10.6084/m9.figshare.c.5088187

The coastal area is a major area of socio-economic development and the most active zone for human activities. With the rapid development of the economy and the strengthening of urban construction, the groundwater environmental problems in coastal areas are increasingly prominent. It is significant to investigate the groundwater chemical characteristics, hydrochemical types, and the factors that influence groundwater chemistry for water resources protection and groundwater resources development. In this paper, 48 groundwater samples and 5 surface water samples from the study area were analyzed with statistical analysis, Piper diagram, Gibbs diagram, mineral saturation index method, and the ionic scale factor, and explored the factors that influence groundwater chemistry. The modified Nemerow index method was also applied to evaluate the groundwater. The results show that the groundwater in the study area is neutral to weakly alkaline (average pH = 7.0~8.0). The groundwater chemical types are mainly Cl·SO₄-Na and SO₄·Cl-Ca·Mg. Hydrochemistry is mainly influenced by rock weathering and evaporative concentration. TDS was strongly correlated with TDS, Na+, Mg²⁺, K⁺, Ca²⁺, Cl⁻, SO₄²⁻, and the saturation index showed a gradual increase along the groundwater drainage flow path, it indicates that the main groundwater ions originate from the dissolution of halite, sulfate, and carbonate. Combining GIS technology and the kriging spatial interpolation method, we obtained the current situation map of groundwater quality in Laoshan District. The groundwater quality is mainly III water, and the overall water quality is good; IV and V water is mainly distributed in the middle and lower reaches of rivers, distributed in a belt pattern along the coastline. It is mainly influenced by both the human factor and seawater intrusion. It is significant for the utilization of groundwater resources and the management of seawater intrusion in the Laoshan District. In addition, the proposed research ideas and methods provide a reference for the study of groundwater genesis in other coastal areas in the world.