[Occurrence Characteristic and Risk Assessment of Microplastics in Sishui River (Xingyang Section)].

Urban rivers are the main receptors and transporters of microplastic pollution. Understanding the occurrence and environmental risk of microplastics in urban rivers can provide theoretical basis for further control of microplastic pollution. The Sishui River, a tributary of the Yellow River, was selected as the research object. A total of nine water samples were collected from sewage outlets of the Sishui River (Xingyang section). The microplastics in the collected samples were characterized by their sizes, shapes, and colors using a microscope. It was found that microplastics were mostly in the form of transparent fibers and fragments in the water body of sewage outlets, of which the size below 500 µm was relatively high. In addition, PET and PE polymers were identified as the main types using a laser infrared imager. The correlation analysis showed that there was a significant correlation between the PET and PE, indicating that they were similar in origin. The results of the environmental risk assessment showed that the type of microplastics was the main factor affecting the assessment results, whereas the risk values of six sewage samples containing PVC were high. However, the value of pollution load index revealed a low risk level of pollutants in the study area.

[Characteristics of Secondary Inorganic Ions in PM2.5 and Its Influencing Factors in Summer in Zhengzhou].

Nitrate (NO3-), sulfate (SO42-), and ammonium (NH4+) are important components of PM2.5, and studying their characteristics and influencing factors is essential for the continuous improvement of air quality. A series of online instruments were used to analyze the chemical components of PM2.5 in Zhengzhou in the summer of 2020. The results showed that the average ρ(PM2.5) was (28 ±13) µg·m-3, showing a daily variation characteristic of high at night and low during the day. The main concentrations of NO3-, SO42-, and NH4+ were (7.8 ±6.7), (7.2 ±3.7), and (5.5 ±3.1) µg·m-3, accounting for 22%, 21%, and 16% in PM2.5, respectively. The proportions of NO3- (27%) and SO42- (23%) in PM2.5, respectively, increased with the increase in PM2.5 and O3 concentration. In addition, the proportions of NO3- and NH4+ increased under low wind speed, high humidity, low temperature, and rainfall conditions. Moreover, the proportion of NO3- showed a daily variation characteristic of high at night and low during the day, whereas the opposite was true for SO42-. The gas-particle partitioning process of NH4NO3 was the main factor affecting the concentrations of NO3- and NH4+ in PM2.5. Low temperature, high humidity, and high aerosol water content concentrations favored the partitioning of HNO3 and NH3 to the particulate phase. High pH also favored the partitioning of gas-phase HNO3 to NO3-; however, it was not conducive to the partition of NH3 to NH4+. These trends partially explained the increase in the concentration and proportion of NO3- in PM2.5 under different scenarios.

[Stabilization of Heavy Metals in Municipal Sludge Using a Slag-Based Modifying Agent].

Taking urban domestic sludge as the research object, a slag-based modifying agent was used to modify sludge under different dosages and curing times, and the solidification effect of six heavy metals in the sludge, namely Zn, Cr, Cu, Pb, As, and Cd, were evaluated by analyzing stability efficiency and morphological changes. The results showed that the stability efficiency improved as curing time and dosage increased, reaching the maximum when the curing time was 14 d and the dosage was 50%. Under these conditions, Cu reached the maximum of 69.62%, and the most rapid growth was observed when dosages were 5%-20%. Through the regression analysis of adding amount, maintenance time and stability efficiency, it was found that the fitting correlation coefficient Cu was the highest 0.97, with a strong degree of fitting and a strong interaction between adding amount and maintenance time, which had a significant influence on the stability efficiency. In addition, Pb and As were the residual state, Cu and Cr were oxidizable state and residue state, Zn and Cd were reducible and extractable state as the main forms in the sludge after modifying, respectively. With the increase of curing time or dosage, the residual state of each heavy metal increased by 7%-86%. The results showed that the slag-based modifying agent could effectively solidify heavy metals in sludge and reused solid wastes such as sludge.