[Analysis of Pollution Characteristics and Sources of Rainfall Runoff from Roofs in the Central District of Beijing].

The rainwater and rainfall runoff of roofs in the central district of Beijing from June to September in 2019 were sampled and analyzed to study the characteristics of the water quality, the first flush effect, and the main influential factors and sources of pollutants. The results showed that the roof runoff was seriously polluted by total nitrogen, ammonia nitrogen, chemical oxygen demand, and total suspended solids whose event mean concentration (EMC) exceeded the fifth level of environmental quality standards for surface water (GB 3838-2002) (the EMC of suspended solids exceeded the second level of discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-2002)). The rainwater was relatively less polluted than the rainfall runoff, but the EMC of ammonia nitrogen and total nitrogen of the rainwater also exceeded the standard in some rainfall events. The first flush intensity of the rainfall runoffs was between weak and medium. The sequence of strength of the first flush of different pollutants was ammonia nitrogen>total suspended solids>chemical oxygen demand>total nitrogen>mercury>zinc>total phosphorus>lead. The concentration of total suspended solids, chemical oxygen demand, and total phosphorus in roof runoff were significantly positively correlated with the length of rainfall and the dry period and negatively correlated with the rainfall intensity. According to the results of principal component analysis, the main pollutant in rainwater was nitrogen emitted by vehicles, and the main pollutants in roof runoffs were suspended solids, organic matters, and phosphorus pollutants released from the aging of roofing materials and the corrosion of metal down pipes.

[Concentration and Carbon Isotope Composition of DOC and DIC in the Miyun Reservoir Watershed in Summer].

This study aims to complement existing research on the carbon cycle of water in reservoirs, for the effective control of nutrient input in drinking water. The content and isotopic compositions of water dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) from the Miyun Reservoir watershed in Beijing were studied, and water from the Jingmi diversion canal was also studied as a baseline reference. The results showed that the content of DOC in the Miyun Reservoir watershed in summer varied from 1.07 to 5.19 mg·L-1, with an average value of 2.61 mg·L-1. DOC in tributaries was lower than that of most rivers in China and globally, while DOC in reservoirs, particularly in Miyun Reservoir, was high. The high water level might be the main reason for the high DOC in the Miyun Reservoir. In summer, the δ13CDOC in the Miyun Reservoir watershed ranged from -27.4‰ to -24.3‰, with an average value of -25.8‰. Results from the isotopic analysis showed that the water in the Miyun Reservoir watershed was less affected by human sources, with the exception of some points. In summer, DOC in tributaries and in the Miyun Reservoir was mainly derived from soil organic matter and terrestrial C3 plants. In addition, endogenous substances also contributed to DOC in the watershed. DOC concentration increased along the Chao and Bai Rivers, and DOC from soil erosion and human sources was higher in the Chao River. The δ13CDIC in the study area varied from -12.6‰ to 5.75‰, with a mean value of -9.44‰. The weathering of carbonate rocks accounted for the major river DIC, and DIC had been clearly assimilated by the phytoplankton by photosynthesis. DOC and DIC in the Miyun Reservoir were significantly higher than in the Jingmi diversion canal (P<0.01), and the δ13CDIC in the Miyun Reservoir showed a clear positive deviation. This indicated that there were differences in carbon concentration and components in the two kinds of water, which might affect the denitrification capacity of the water in the Miyun Reservoir after mixing. In general, the dissolved carbon in the water of the Miyun Reservoir watershed is less affected by human sources. The conversion of DIC to DOC may also be a potential source of DOC in the study area.

Gas chromatography-mass spectrometry based metabolomics profile of hippocampus and cerebellum in mice after chronic arsenic exposure.

Intake of arsenic (As) via drinking water has been a serious threat to global public health. Though there are numerous reports of As neurotoxicity, its pathogenesis mechanisms remain vague especially its chronic effects on metabolic network. Hippocampus is a renowned area in relation to learning and memory, whilst recently, cerebellum is argued to be involved with process of cognition. Therefore, the study aimed to explore metabolomics alternations in these two areas after chronic As exposure, with the purpose of further illustrating details of As neurotoxicity. Twelve 3-week-old male C57BL/6J mice were divided into two groups, receiving deionized drinking water (control group) or 50 mg/L of sodium arsenite (via drinking water) for 24 weeks. Learning and memory abilities were tested by Morris water maze (MWM) test. Pathological and morphological changes of hippocampus and cerebellum were captured via transmission electron microscopy (TEM). Metabolic alterations were analyzed by gas chromatography-mass spectrometry (GC-MS). MWM test confirmed impairments of learning and memory abilities of mice after chronic As exposure. Metabolomics identifications indicated that tyrosine increased and aspartic acid (Asp) decreased simultaneously in both hippocampus and cerebellum. Intermediates (succinic acid) and indirect involved components of tricarboxylic acid cycle (proline, cysteine, and alanine) were found declined in cerebellum, indicating disordered energy metabolism. Our findings suggest that these metabolite alterations are related to As-induced disorders of amino acids and energy metabolism, which might therefore, play an important part in mechanisms of As neurotoxicity.

[Nitrous Oxide Production in Response to Oxygen in a Solar Greenhouse Vegetable Soil].

To explore the sources of peak nitrous oxide (N2O) flushes in solar greenhouse vegetable field, an experiment was conducted with two conventional vegetable soils under different initial volume fractions of oxygen (O2) (0%, 1%, 3%, 5%, and 10%). A robotized incubation system was employed to analyze the gas kinetics[O2, N2O, nitric oxide (NO), nitrogen (N2), and carbon dioxide (CO2)] every 6 or 8 h and calculate the N2O/(NO+N2O+N2) index. Sodium chlorate (NaClO3) was used to inhibit the oxidation of NO2- to further explore the relationship between N2O and nitrite (NO2-). A parallel off-line incubation in triplicates was conducted under similar conditions to measure the dynamic changes in inorganic nitrogen content[ammonia (NH4+), nitrate (NO3-), and NO2-]. The results showed that N2O production under anaerobic condition was significantly higher than that under aerobic condition. The peak value of N2O in the soil collected from a straw-added plot (DIS) was significantly higher than that in the soil from non-straw added plot (DI) (P<0.01) when the volume fraction of oxygen was ≤ 1%. Oxygen can directly affect N2O production by delaying or inhibiting N2O reduction, with significant increase in N2O production rate under oxygen-depleted condition. However, the N2production rate decreased significantly with increase in initial oxygen volume fraction (P<0.01). When the initial volume fraction of oxygen was between 1% and 5%, a continuous accumulation of NO2- was observed during the incubation period, resulting in the significantly higher N2O/(NO+N2O+N2) index than that in either anaerobic or 10% of oxygen treatments. Furthermore, a linear correlation was observed between NO2- and N2O at 5% and 10% of oxygen with the addition of NaClO3 (R2 ≥ 0.85). Incomplete denitrification and nitrifier denitrification from NO2- induction co-occurred in the range of 1% and 5% volume fractions of oxygen, significantly increasing the soil N2O production and N2O/(NO+N2O+N2) index. In addition, N2O production under anaerobic condition was significantly higher than that under aerobic condition (P<0.01).