Research on the mechanism of plant root protection for soil slope stability.

In order to investigate the impact of herbaceous root development on soil slope stability in expansive soil areas, the research was conducted in the soil slope experimental area of Yaoshi Town, Shangzhou District, Shangluo City. Three types of herbaceous plants, namely Lolium perenne, Medicago, and Cynodon dactylon, were planted to examine their influence on slope stability. The results indicated that Lolium perenne had significantly higher root length density and root surface area density compared to Cynodon dactylon and Medicago. However, the root weight density of Cynodon dactylon was found to be highest. The roots of Lolium perenne, Cynodon dactylon, and Medicago were predominantly observed in diameter ranges of 0 < L ≤ 1.0 mm, 0 < L ≤ 2.5 mm, and 2.5 < L ≤ 3.0 mm, respectively. The roots of herbaceous plants have the ability to enhance water retention in soil, resist hydraulic erosion of slope soil, and reduce soil shrinkage and swelling. During the initial phase of herbaceous planting, there is an accelerated process of organic carbon mineralization in the soil. The roots of herbaceous plants play a crucial role in soil consolidation and slope protection. They achieve this by dispersing large clastic particles, binding small particles together, altering soil porosity, enhancing soil water retention, and reducing soil water infiltration. It was found that Lolium perenne and Medicago, which have well-developed roots, exhibited superior slope protection effects. These findings contribute to the theoretical understanding for the implementation of green ecological protection technology on soil slopes.

Analysis of rainwater storage and use recommendations: From the perspective of DBPs generation and their risks.

As a vital freshwater resource, rainwater is usually stored in water cellars in arid regions to solve the daily drinking water problems of the population. However, the status of disinfection by-products (DBPs) generation in cellar water under intermittent disinfection conditions is unclear. Therefore, we investigated the formation and distribution characteristics of DBPs in cellar water under intermittent disinfection conditions for the first time. The results demonstrated that six categories of DBPs were selected for detection after chlorination, including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs), haloacetonitriles (HANs), halonitromethanes (HNMs), and nitrosamines (NAs), among which HAAs, HKs, and HANs were the major DBPs. Only bromoacetic acid (MBAA), dichloroacetic acid (DCAA), and trichloroacetic acid (TCAA) showed an increasing trend of accumulation as the number of disinfections increased. Meanwhile, the precursor composition was gradually transformed from humic substances to amino acids, and both organic substances were the main precursors of HAAs. The health risk assessment showed that the main carcinogenic and non-carcinogenic risks of cellar water were contributed by NAs and HAAs, respectively, and children are more susceptible to the risks than adults. The best time to drink cellar water is after approximately 12 days of storage, when the total carcinogenic risk is the minimum.

Adsorption of Toxic Tetracycline, Thiamphenicol and Sulfamethoxazole by a Granular Activated Carbon (GAC) under Different Conditions.

Activated carbon can be applied to the treatment of wastewater loading with different types of pollutants. In this paper, a kind of activated carbon in granular form (GAC) was utilized to eliminate antibiotics from an aqueous solution, in which Tetracycline (TC), Thiamphenicol (THI), and Sulfamethoxazole (SMZ) were selected as the testing pollutants. The specific surface area, total pore volume, and micropore volume of GAC were 1059.011 m2/g, 0.625 cm3/g, and 0.488 cm3/g, respectively. The sorption capacity of GAC towards TC, THI, and SMZ was evaluated based on the adsorption kinetics and isotherm. It was found that the pseudo-second-order kinetic model described the sorption of TC, THI, and SMZ on GAC better than the pseudo-first-order kinetic model. According to the Langmuir isotherm model, the maximum adsorption capacity of GAC towards TC, THI, and SMZ was calculated to be 17.02, 30.40, and 26.77 mg/g, respectively. Thermodynamic parameters of ΔG0, ΔS0, and ΔH0 were obtained, indicating that all the sorptions were spontaneous and exothermic in nature. These results provided a knowledge base on using activated carbon to remove TC, THI, and SMZ from water.

Distribution characteristics and ecological risk assessment of heavy metals in sediments of Shahe reservoir.

Shahe Reservoir of Northern Canal Basin was selected as the study area. Nineteen surface (0~20 cm) sediment samples and three sediment core samples were collected to analyze the spatial distribution characteristics of As, Cd, Cu, Mn, Pb and Zn in the sediments. The geo-accumulation index, potential ecological risk index and risk assessment code were used to evaluate heavy metal pollution, as well as its potential risk was analyzed according to the speciation of heavy metals. Results showed that the average enrichment factors of heavy metals compared to the background value in soil of Beijing were ranked at the order as the point source pollution area > the central area of the reservoir > the downstream area of the reservoir > the Nansha River > the upstream area of the reservoir > the Beisha River, namely, 2.57 times, 2.06 times, 1.97 times, 1.95 times, 1.87 times and 1.85 times, respectively. The sediment core samples in the central area of the reservoir and the inlet of the Beisha River showed a trend of increasing firstly and then decreasing with the change of depth. Pollution assessment results showed that sediment was moderately contaminated or moderately to strongly contaminated by As, but the other heavy metals were not polluted or lightly polluted. The potential ecological risk index of all sampling sites was less than 150, showing a low ecological risk. As Cr and Cu were mainly in the speciation of residues, with low bioavailability. Although the content of Mn and Zn were low, they showed high bioavailability. Based on correlation analysis and principal component analysis, it was speculated that the sources of various heavy metal pollution in the sediment were similar, which were possibly input from the external wastewater. The heavy metals in sediment were positively related to nutrients and organic matter, indicating that all of them were mostly from the same point polluted sources.

The spatial distribution characteristics of typical pathogens and nitrogen and phosphorus in the sediments of Shahe Reservoir and their relationships.

Using samples collected in Shahe Reservoir in the upper North Canal in China, this research analyzes the structure of a microorganism group in sediment and the absolute abundance of two typical pathogenic bacteria (Escherichia coli and Enterococcus), and their relationship with environmental factors including total nitrogen (TN) and total phosphorus (TP). The study of samples collected from the surface (0-20 cm) and sediment cores shows that the absolute abundance of E. coli in horizontal distribution in the sediment is highest in downstream of the reservoir and point source pollution area. In vertical distribution, the absolute gene expression level of the two pathogenic bacteria in the sediment tends to decrease with increasing depth, although its highest value at 10-30 cm depth. The relative abundance the two pathogenic bacteria is much greater in the sediment of Shahe Reservoir with the structure of horizontal groups including Clortridium sensu stricto, unclassified Anaeroineaceae, and Povalibacter, while Anaeroineaceae is much more abundant in the group structure of the vertical distribution. Pearson correlation analysis suggests positive correlation in horizontal distribution for E. coli and TN and TP (P < 0.05) and for Enterococcus and TP (P < 0.05). The results clearly show that the amount of pathogenic bacteria in the sediment in Shahe Reservoir is most likely due to water eutrophication.