Effects of ant nesting on seasonal dynamics of soil N2O emission in a secondary tropical forest.

We assessed the seasonal dynamics of N2O emission in ant nests soils in secondary tropical Millettia leptobotrya forest of Xishuangbanna by using the static chamber-gas chromatography method, and determined the lin-kages between ant-mediated changes in soil properties (e.g., carbon pool, nitrogen pool, and temperature and humidity) and N2O emission. The results showed that ant nesting significantly affected soil N2O emission. The ave-rage soil N2O emission (0.67 mg·m-2·h-1) in ant nests was 40.2% higher than that in the control (0.48 mg·m-2·h-1). N2O emission in ant nests and the control showed substantial seasonal variation, with higher rate in June (0.90 and 0.83 mg·m-2·h-1, respectively) than that in March (0.38 and 0.19 mg·m-2·h-1, respectively). Ant nesting significantly increased the values (7.1%-74.1%) of moisture, temperature, organic carbon, total nitrogen, hydrolytic nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass carbon, but decreased pH (9.9%) compared with the control. Results of structural equation model showed that soil N2O emission was promoted by soil C and N pool, temperature, and humidity, but was inhibited by soil pH. The explained extents of soil nitrogen pool, carbon pool, temperature and humidity, and pH for N2O emission changes were 37.2%, 27.7%, 22.9% and 9.4%, respectively. Therefore, ant nesting regulated N2O emission dynamics by changing nitrification and denitrification substrates (e.g., nitrate and ammoniacal nitrogen), carbon pool, and micro-habitat (temperature and moisture) of soil in the secondary tropical forest.

[Spatiotemporal Distribution and Pollution Risk Assessment of Heavy Metals in Sediments of Main Water Supply Reservoirs in Central Zhuhai City].

The Modaomen and Hongwan waterways are the main estuaries of the Pearl River system. Affected by tides, the Fenghuangshan Reservoir, Dajingshan Reservoir, and Zhuxiandong Reservoir, which are subject to water transfer along the river line, are important drinking water sources in the central part of Zhuhai City in the Guangdong-Hong Kong-Macao Greater Bay Area. Eight heavy metals in 15 sampling points in the reservoir area were monitored in the two seasons (August and October) of 2019. The environmental quality of the surface sediments of the three water supply reservoirs was surveyed using correlation analysis, geoaccumulation index evaluation, ecological risk assessment, and traceability analysis in the present study. The results showed that the order of the average content of the eight heavy metals in the three reservoirs was as follows: Zhuxiandong Reservoir>Dajingshan Reservoir>Fenghuangshan Reservoir. The contents of Hg, Zn, and Pb in Fenghuangshan Reservoir; Hg, As, Mn, Ni, Cu, Zn, and Pb in Dajingshan Reservoir; and Zhuxiandong Reservoir exceeded the background values of soil heavy metals in Guangdong province by 1.88-2.75, 1.05-2.32, and 1.69-6.45 times. Except for As in Fenghuangshan Reservoir, As and Cu in Dajingshan Reservoir and Cr and Ni in Zhuxiandong Reservoir, the other heavy metals elements showed the content characteristics of dry season>wet season. The evaluation results of the geoaccumulation index method indicated that the pollution degree of the three reservoirs was in the order of: Zhuxiandong Reservoir>Dajingshan Reservoir>Fenghuangshan Reservoir. Among them, the Fenghuangshan Reservoir and the Dajingshan Reservoir were only slightly polluted by Hg, Zn, and Pb elements, and the Zhuxiandong Reservoir as a whole was slightly or moderately polluted. The evaluation results of the potential ecological risk index showed that the overall ecological risk of Fenghuangshan Reservoir and Dajingshan Reservoir was low, and Zhuxiandong Reservoir was at a medium ecological risk level. Hg was the main ecological risk-contributing factor of the three reservoirs, with contribution rates of 78.8%, 64.4%, and 51.0%, respectively.

[Structural Characteristics of Phytoplankton Communities and Its Relationship with Environmental Factors in a Group of Drinking Water Reservoirs by Water Transmission from Modaomen Waterway in Zhuhai].

Modaomen Waterway is the main outlet of the Pear River system and an important water source for Zhuhai and Macao. The water quality of 13 sampling sites in Modaomen Waterway, phytoplankton, and environmental factors were investigated at 21 sampling sites in 4 drinking water source groups, which transport water from Modaomen Waterway and connect with each other, in August and October of 2021. A total of 73 genera of phytoplankton in eight phyla were identified, with a total of 150 species, most of them belonging to Cyanophyta, Chlorophyta, and Bacillariophyta. The relative abundance of Cyanophyta was higher than 90% in the DJS and YL reservoirs during flood and dry seasons; Cyanophyta, Chlorophyta, and Bacillariophyta were dominant phyla during different seasons; and their distribution was balanced in the ZXD and ZY reservoirs. The Shannon-Wiener index, Pielous uniformity index, and Margalef richness index showed that the ZY reservoir had the most abundant biodiversity, which indicated the best water quality, followed by the ZXD and YL reservoirs. Conversely, the DJS was the least diverse reservoir for phytoplankton. The PCoA analysis indicated significant differences in plankton structures in ZXD and ZY with the other two reservoirs (P<0.05), respectively. Redundancy analysis (RDA) showed that the main environmental factors affecting the distribution of the phytoplankton community were NO3-, TOC, TP, Cl-, and NH4+-N. These results indicated that the phytoplankton community of the four reservoirs were greatly affected by the nutrient salt caused by water transport, which suggested that the water quality of Modaomen Waterway should be improved to increase reservoir water nutrition to ensure the safety of drinking water sources.

[Pollution Characteristics and Risks of Polycyclic Aromatic Hydrocarbons in Underground and Surface Drinking Water Sources in Northeast Inner Mongolia].

Polycyclic aromatic hydrocarbons (PAHs) are hazardous and ubiquitous pollutants in the aquatic environment, and understanding the pollution characteristics and risk levels of PAHs is of great significance to the sustainable development of drinking water sources and drinking water safety. Hence, PAHs residues were measured qualitatively and quantitatively with solid-phase extraction-gas chromatography-mass spectrometry (SPE-GC-MS) in 33 water samples (including 22 groundwater and 11 surface water samples) of the drinking water sources in the Manzhouli and Xinyouqi areas of northeast Inner Mongolia, and assessments of the pollution level of PAHs and the health and ecological risks were carried out. The results showed that PAHs were detected in all 33 sampling points of Manzhouli drinking water sources, except for benzo[k] fluoranthene, benzo[a] pyrene, and dibenzo[a,h] anthracene, with detection rates ranging from 36.36% to 95.45%; the detection rates of the other 13 PAHs monomers were 100%. The detection range of ρ（ΣPAHs） was 42.76-164.50 ng·L-1, and the mean value was 90.82 ng·L-1. The detection ranges of ρ（ΣPAHs） in surface water and groundwater were 66.39-164.50 ng·L-1 and 42.76-147.70 ng·L-1, respectively. The concentration of the detected naphthalene was the highest, with a mean value of 36.91 ng·L-1, and the concentration of anthracene was the lowest, with a mean value of 0.81 ng·L-1; there were no significant differences among the concentrations of all the PAHs monomers of the surface and groundwater (P>0.05). The pollution of PAHs was at a median level in China and abroad, mainly in the middle and low loops (3-4 loops). The analysis of the sources of PAHs in groundwater and surface water in Manzhouli using the ratio feature method and principal component analysis showed that the PAHs in the drinking water source water bodies in the Manzhouli area were mainly affected by the combustion of coal and biomass and oil, and some surface water sources were affected by the oil source. The human health and ecological risk assessment results showed that the water body of drinking water would not cause health risks to the human body, and the ecological risk was at a medium level; however, the high risk of benzo[b] fluoranthene (BbF) monomer production should be continuous cause for concern. From the perspective of the sustainable development of drinking water sources and drinking water safety, the necessary supervision and protection measures should be considered to prevent further pollution. The results of this research provide a scientific basis for the pollution control and prevention and control of PAHs in drinking water sources.

[Pollution Characteristics and Risk Assessment of DBPs in Typical Drinking Water Sources in Wuhan Under the COVID-19 Pandemic].

In order to reveal the pollution characteristics and risk levels of DBPs in typical drinking water sources in Wuhan under the COVID-19 pandemic, 26 sampling sites were selected in typical drinking water sources in Wuhan. N,N-diethyl-1,4-phenylenediamine spectrophotometry and gas chromatograph-micro-cell electron capture detector (GC-µECD) methods were used to detect residual chlorine disinfectants and DBPs in water, respectively, and their health and ecology risks were assessed. The results showed that free chlorine or total residual chlorine were detected in 16 of the 26 water samples, and the maximum concentration was 0.04 mg·L-1, which exceeded the limit of the surface water standard in China. The concentration of residual chlorine was higher in sampling sites near the outfall of a municipal sewage plant. There were 34 types of DBPs measured in 10 sampling sites, and 24 types of substances were detected with the detection rate of 10.00%-100.00%. The ρ (total DBPs) was in the range of 0.11-104.73 µg·L-1, with an average value of 7.26 µg·L-1. The concentration of chloroform was the highest among all the DBPs, ranging from 9.98 µg·L-1 to 11.15 µg·L-1, with an average value of 10.47 µg·L-1. The concentration of 2-bromo-2-iodoacetamide was the lowest, ranging from ND-0.11 µg·L-1, with an average value of 0.01 µg·L-1. The overall detection level of the DBPs area was low in this study area, and the result of the health risk assessment showed that the DBPs had no carcinogenic or non-carcinogenic health risks to human body. However, the results of the ecological risk assessment showed that chloroform presented a high ecological risk to aquatic organisms.

[Mechanism of "unification of drugs and excipients" for Chinese medicine semi-extract based on powder compression behavior analysis].

In this paper, five representative Chinese herbal decoction pieces of Scutellariae Radix, Paeoniae Radix Alba, vinegar-processed Corydalis Rhizoma, Polygoni Multiflori Radix Praeparata and Lonicerae Japonicae Flos were selected to prepare the corresponding fine powder of pieces, extract powder, semi-extract powder and physical mixed powder. The physical properties of 20 kinds of powders, such as related parameters of particle size, density, stability and flowability, were evaluated comprehensively. The compression curves of powder porosity and tensile strength changing with pressure were plotted, and the Heckel equation and the Kawakita equation were used to describe the powder compression behavior. The results showed that compared with the fine powder of pieces, the compressibility of the semi-extract powder and the extract powder was significantly improved. Compared with the extract powder, the particle size and relative uniformity of the semi-extract powder were increased, indicating that the uniformity of the powder was improved. Besides, the semi-extract powder could reduce the hygroscopicity of the powder. Particularly, the semi-extract powder of Scutellariae Radix, Paeoniae Radix Alba and vinegar-processed Corydalis Rhizoma could maintain the porous structure of the tablet even under a high tableting pressure, which was beneficial to tablet disintegration. For some traditional Chinese medicines(such as Lonicerae Japonicae Flos), the semi-extract powder could reduce the viscosity, which avoided the sticking in the die compression. The semi-extract powder and the physical mixture powder prepared by the same Chinese herbal decoction pieces had similar physical properties and compression behaviors. Principal component analysis(PCA) was carried out on the 17 physical attributes and 5 compression parameters of the powder. It was found that the first principal component mainly reflected the differences among the material sources, while the second principal component could reflect the differences among fine powder of pieces, extract powder, semi-extract powder and physical mixed powder originating from the same Chinese herbal decoction pieces. In this paper, the mechanism of "unification of drugs and excipients" of Chinese medicine semi-extract powder was explained in terms of physical properties and compression behavior of powders, which provided reference for the formulation design and process development of Chinese medicine tablets.

[Distribution characteristics of polycyclic aromatic hydrocarbons in runoff from the middle line source area of south-to-north water diversion project].

The distribution characteristics of polycyclic aromatic hydrocarbons in runoff from the middle line source area of south-to-north water diversion project were studied. Five groups of artificial runoff fields were established to collect runoff based on the different types of land-use, the contents of 16 USEPA priority PAHs in the runoff were determined using GC/MS method. The results showed that the average concentrations of PAHs of the aqueous phase in the collected runoff samples of different land-use types decreased in the order:cultivated land (26.53 ng x L(-1)) > oak forest (20.91 ng x L(-1)) > orchard (17.59 ng x L(-1)), and the average concentrations of PAHs of the particle phase were cultivated land (1 073.72 ng x g(-1)) > orchard (652.29 ng x g(-1)) > oak forest (385.46 ng x g(-1)). The high carcinogenic components Bap were detected in both run off of cultivated land and orchard with a detected rate of 30%. According to National Recommended Water Quality Standards of priority toxic pollutants (2006 USEPA), it was found that Chr exceed standard 40%, with a detected rate of 100%. It was also found that the runoff volume and the total PAHs content in runoff increase with the slope, and PAHs loss and slope were closely related in same land-use types. Based on the Molecular Markers Indicative Law, it can be concluded that the dominant source of PAHs in runoff of study area was combustion of coal, and a small amount came from vehicle exhaust emissions. There is a certain degree of ecological risk about runoff PAHs pollution in the study area, which is worth further attention.