[Pollution Characteristics and Source Apportionment of Heavy Metals in Vegetable Field in the Three Gorges Reservoir Area (Chongqing Section)].

To explore the pollution characteristics, ecological risks, and sources of heavy metals, soil surface samples of vegetable fields in 14 typical districts of the Three Gorges Reservoir area (Chongqing section) were collected in October 2021. The contents of seven types of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were analyzed. Based on the single-factor pollution index, the Nemerow integrated pollution index and potential ecological risk coefficient of heavy metals were evaluated. Additionally, the effects of different planting years and methods (open-field and greenhouse planting) on soil heavy metal accumulation were analyzed. The results indicated that the mean concentrations of heavy metals in vegetable soils in the area were lower than the national risk screening values for soil contamination of agricultural land (GB 15618-2018) but higher than their background values in Chongqing. According to the single-factor pollution index method, Pb, Zn, Cu, and Cd showed negligible slight hazards. The Nemerow pollution index showed that the study area was at a slight hazard level, and the main factors were Ni and Cd. Heavy metal pollution was found in 91.4% of the soil samples (PN>1) with different degrees, and 9.19% of them were severely polluted. The potential ecological risk coefficient showed that the vegetable lands were polluted slightly, and 9.77% of soil samples polluted by Cd were at moderate ecological risk. According to cluster analysis, the sources of Cd-Cu-Pb-Zn and As-Cr-Ni were similar. The content of heavy metals in the open field and greenhouse showed an increasing trend with the increase in planting years, and the content of heavy metals in greenhouse soil were generally higher than that in open field soil.

[Pollution Characteristics and Ecological Risk Assessment of Antibiotics in Vegetable Field in Kaizhou, Chongqing].

The accumulation of antibiotics in farmland and its ecological risk have become a research hotspot at home and abroad. The objective of this study was to investigate the occurrence and accumulation of antibiotics and their potential environmental and ecological risks in vegetable fields in Kaizhou district of Chongqing country. The occurrence characteristics of antibiotics including tetracyclines, sulfonamides, quinolones, macrolides, and chloramphenicols were detected using experimental analysis. The results showed that there was an accumulation of antibiotics in the vegetable soil, and 18 antibiotics in five categories were detected (0-42.88 µg·kg-1), mainly for tetracyclines and quinolones. The detection rate of quinolone antibiotics was the highest (15.38%-100%), especially for norfloxacin and ofloxacin (100%), whereas the tetracyclines presented the highest concentration (0-42.88 µg·kg-1). The amount of total antibiotics in the vegetable soil was 1.64-233.11 µg·kg-1, whereas different vegetable soils showed the following trend:water spinach soil (89.73 µg·kg-1)>cabbage soil (32.53 µg·kg-1)>pepper soil (32.16 µg·kg-1)>tomato soil (32.13 µg·kg-1)>cucumber soil (26.46 µg·kg-1)>grassland (7.32 µg·kg-1). The correlation results showed that there was a significantly positive correlation between total antibiotic residues and organic fertilizer application (P<0.05) but a significantly negative correlation with soil pH (P<0.05). Quinolones and sulfonamides were negatively correlated with soil water content (P<0.05), whereas quinolones positively correlated with soil available phosphorus and organic matter content (P<0.05). The potential eco-environmental risk assessment results showed that tetracyclines and quinolones in vegetable soil in Kaizhou district had certain ecological risks, of which 62%-92% and 62%-100% of soil samples with quinolones had potential toxicity to soil animals and microorganisms.

A Novel Bristle-Shaped Semi-Dry Electrode With Low Contact Impedance and Ease of Use Features for EEG Signal Measurements.

OBJECTIVE: In this paper, we present a novel soft bristle-shaped semi-dry electrode for electroencephalography (EEG) recording. Because the bristle-shaped structure with electric conductivity could overcome the obstacle of hair and enable direct connection to scalp, the semi-dry electrode could work with drinking water instead of saline water that was widely used in previous semi-dry or water electrodes to improve its convenience. The electrode consisted of conductive bristles and a 3D-printed casing. Carbon-coated nylon conductive bristles could achieve low impedance and soft properties of the semi-dry electrode. The bristles could spread on skin and realize a larger contact area. The carbon-coated conductive bristles could also continuously penetrate water into the corneum of skin to reduce contact impedance. The contact impedance of the bristle-shaped semi-dry electrode was similar to the traditional wet electrode, but much lower than dry electrode. Although the saline water had much lower impedance than drinking water, our electrode still achieved even lower skin-electrode contact impedance than previous semi-dry or water electrode with saline water. The alpha rhythms, P300 visual evoked potential, and steady-state visual evoked potential were, respectively, measured to evaluate the electrode performance for EEG recording.