[Effect of Aging on Adsorption of Tetracycline by Microplastics and the Mechanisms].

As new pollutants, microplastics (MPs) can adsorb antibiotics in the water environment and migrate together as carriers. However, microplastics will age continuously in the environment, and their adsorption capacity and adsorption mechanism will change accordingly. With polyethylene (PE) and polystyrene (PS) as the target MPs, which were irradiated by ultraviolet (UV-254), the changes in the physical and chemical properties of MPs before and after aging, such as the color, surface morphology, and functional groups, were compared, and their effects on the adsorption of tetracycline (TC) as well as the related mechanism were explored. The results showed that the pseudo-second-order model could better fit the adsorption process, the adsorption equilibrium was reached within 24 hours, the adsorption capacity of aged MPs for TC was significantly higher than that of original MPs, and the adsorption capacity of PS was higher than that of PE. Langmuir and Freundlich isothermal adsorption equations could both describe the adsorption isothermal test data, and the adsorption of TC on MPs was a spontaneous and endothermic physical adsorption process, whereas aging had no obvious effect on the adsorption thermodynamic characteristics of MPs. With the increase in pH value, the adsorption capacity first increased and then decreased. The maximum adsorption capacity of MPs before and after aging was reached at pH=5. UV aging increased the specific surface area of MPs, generating oxygen-containing functional groups such as -C＝O, -OH, and O＝C＝O, changing the physical and chemical properties of MPs, and thus changing the adsorption mechanism of MPs for TC. Compared with the original PE MPs, in addition to hydrophobic distribution, van der Waals forces, and electrostatic interactions, pore filling was also an important adsorption mechanism of aged PE. The main adsorption mechanisms of original PS microplastics were hydrophobic distribution, van der Waals forces, electrostatic interaction, and π-π interaction, whereas there was hydrogen bonding for aged PS.

[Analysis of Nitrate Sources in Different Waters of a Karst Basin].

To identify the sources and transformation processes of nitrate in surface water and groundwater in a karst basin, water samples were collected in the Songbai Mountain Reservoir basin during the normal and dry seasons. The spatio-temporal distribution, sources, and transformation processes of nitrate in the waters were analyed using a hydrochemical and stable isotopic (δ15N-NO3-, δ18O-NO3-, and δ18O-H2O) multi-tracing approach. The contribution rates of different nitrate sources in surface and groundwater were estimated based on the SIAR model. The results showed that NO3--N and NH4+-N were the main species of dissolved inorganic nitrogen in the waters. The over standard rate of NO3--N in groundwater was 7.89% in the normal season and 16.67% in the dry season. Temporally, the nitrate concentrations of waters in the dry season were higher than those in the normal season. Spatially, the nitrate concentrations of groundwater around dryland areas (from the Kailun River to the Songbai Mountain Reservoir) were higher than those of paddy fields (Ganhe River), and the nitrate concentrations of surface water in dryland and construction sites (Kailun River) were generally high. Nitrification was the dominant process in the waters. The nitrate in the waters mainly came from soil organic nitrogen, manure/sewage, and chemical fertilizers; their contribution rates to nitrate were 36.7%, 34.7%, and 28.6% for surface water and 39.9%, 34.9%, and 25.2% for groundwater, respectively. Nitrate pollution in the waters was mainly affected by agricultural activities and the discharge of sewage; appropriate control measures such as water and fertilizer regulation for farmland and treatment of rural sewage should be strengthened.

Levels and distribution of synthetic musks and polycyclic aromatic hydrocarbons in sludge collected from Guangdong Province.

The levels and distribution of six polycyclic musks, three nitromusks and 15 polycyclic aromatic hydrocarbons (PAHs) were investigated in sludge collected from 19 municipal wastewater treatment plants (WWTPs) in six cities in Guangdong Province, China. PAHs were detected in all of the sludge samples, and the levels of the total 15 PAHs ranged from 177.2-4421.8 µg/kg dry weight (dw). Four polycyclic musks, 4-acetyl-1,1-dimethyl-6-tert-butylindan (ADBI), 6-acetyl-1,1,2,3,3,5-hexamethylindan (AHMI), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta (g) -2-benzopyran (HHCB) and 7-acetyl -1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydro naphthalene (AHTN), were found in these samples. The total concentrations of polycyclic musks varied from 794.4-12960.3 µg/kg dw, with HHCB and AHTN being the main components. Of the three nitromusks, 2,6-dinitro-3-methoxy-4-tert- butyl - toluene (MA) was only found in one sludge sample at the limit of detection (LOD) level, while 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (Musk xylene, MX) and 4-acetyl-1-tert-butyl-3,5-dimethyl-2,6-dinitrobenzene (Musk ketone, MK) were found at levels ranging from the LOD to 65.8 µg/kg dw and LOD to 172.7 µg/kg dw, respectively, in most of the sludge samples. The PAHs, polycyclic musks and nitro musks were also shown to have various distribution patterns, possibly due to their different wastewater sources and wastewater treatment technology.

[Method of ecological risk assessment for risk pollutants under short-term and high dose exposure in water pollution accident].

In recent years, water pollution accidents resulting in acute aquatic ecological risk and security issues become a research focus. However, in our country, the surface water quality standards and drinking water health standards were used to determine the safety of waters or not in pollution incidents due to lacking safety effect threshold or risk value for protection of aquatic life. In foreign countries, although predicted no effect concentration (PNEC) or risk value (R) of pollutants were provided for protection of aquatic organisms, the PNECs or risk values were derived based on long-term exposure toxicity data NOECs (no observed effect concentrations) and lack of short-term exposure risk or threshold values. For the short-term and high dose exposure in pollution incident, ecological risk assessment methods were discussed according to the procedures of the conventional ecological risk assessment and the water quality criteria establishment of the U.S. EPA for the protection of aquatic organisms in short-term exposure, and had a case study. At the same time, we provide some suggestions for the establishment of ecological risk assessment system in water pollution incidents.