| BackgroundAntibiotics is a new environmental pollutant, they can pollute different environment mediums in a variety of ways, and then pose a threat to microbial activity, the growth of animal and plant and human health. Soil is the main destination of antibiotics, antibiotics in the environment will eventually accumulate in the soil or sediment, and vegetables can uptake antibiotics from soils. Quinolones(FQs) was detected in higher levels in soils, and the adsorption capacity of FQs in soils is higher than macrolides and sulfonamides. So the research of quinolones in the soil become a hot issue. Currently, studies of the dissipation of quinolones in soils and quinolones research of antibiotics on soil ecology and human health are less. Therefore, we deeply explore the dynamics and health risks of quinolones in soils.ObjectiveTo investigate the residue levels and spatial pattern of the FQs distribution in soil in a large number of samples from Shouguang City, the largest vegetable cultivation base in Northern China. To study the dissipation dynamics of the FQs in the two types of soil in the study region by the laboratory simulation experiment. To evaluate and forecast ecological risk to the soil ecology and risk to human health of FQs.Methods(1)100vegetable greenhouses were selected from the study area, Five sampling sites were distributed along an S-shaped path within each greenhouse and were then fully mixed to form a single sample. The concentration of FQs in soil was analyzed using high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS).(2) Cinnamonicsoil and fluvo-aquic soils samples which were texted without antibiotics were collected in the parterre of the study area. The concentration of mixed standards1000μg/kg were added to the samples artificially according to the design. All the samples were incubated in darkness at25℃. Samples from each treatment were sacrificed at given time intervals, and the concentrations of FQs in the soil samples were analyzed by HPLC-MS/MS. The same concentration of mixed standards were added to the steriled fluvo-aquic soils, the last concentration of the samples were compared with the non-sterile samples.(3) The concentrations of the FQs in soils in the harvest time were forecasted using the content of the FQs in samples in November,2012and the degradation dynamics of the antibiotics targeted. Then the ecological risks to the soil biology were evaluated. On the other hand, the contents of FQs in vegetables were acquired using the accumulation factor (AF) and the forecasted concentration of FQs, then the health risks were forecasted.Results(1) The detection frequency of norfloxacin, ciprofloxacin and enrofloxacin were100%,100%, and85%, respectively, and the concentrations were0.39-288.33μg/kg,2.39-651.57μg/kg and ND-166.96μg/kg.(2)when the adsorption equilibrium is reached, the mean concentrations of norfloxacin, ciprofloxacin and enrofloxacin in Cinnamonicsoil were:218.23μg/kg,223.06μg/kg and235.80μg/kg, three antibiotic concentrations were degraded to80.52μg/kg,63.64μg/kg and104.00μg/kg at the end of the experiment. The initial concentrations of norfloxacin, ciprofloxacin and enrofloxacin in fluvo-aquic soils were:273.43μg/kg,210.62μg/kg and224.37μg/kg, the antibiotics concentrations were:107.22μg/kg,68.26μg/kg and86.22μg/kg at the end of the experiment. The initial concentrations of three antibiotics in steriled fluvo-aquic soils were278.55μg/kg,221.82μg/kg and228.30μg/kg, the concentration decreased to165.27μg/kg, 130.51μg/kg and142.20μg/kg at the end of the experiment.(3) According to the experiments of soil degradation, the degradation rates of norfloxacin, ciprofloxacin and enrofloxacin after three months were48.60%,54.51%,42.14%, respectively, the maximum predicted reduced to148.20μg/kg,296.40μg/kg and96.60μg/kg. Experimental results show that the degradation rate of norfloxacin, ciprofloxacin, enrofloxacin in the soil after six months were respectively62.22%,70.93%and54.32%, then the corresponding predicted maximum values were108.93μg/kg,189.41μg/kg and76.27μg/kg, the predicted value of the maximum daily intake of various types of vegetables range0.07to0.38μg/kg body weight/day.Conclutions(1) The concentration of ciprofloxacin is higher than norfloxacin and enrofloxacin in the intensive vegetable cultivation, it exhibit high ecological risk. FQs in soil revealed that FQ concentration shows a spatial stratification pattern, the samples with higher concentration were in the northwest.(2)The half-lives of the degradation of norfloxacin, ciprofloxacin and enrofloxacin in the cinnamonicsoil samples were95.26days,77.14days and146.61days respectively, and the half-lives of the degradation of the FQs in fluvo-aquic soils were83.20days,81.34days and92.38days in sequence. The dissipation behavior of the FQs in one type of soil showed diversity, the degradation trend of one antibiotic also show different in different types of soil. In the whole experiment, the contribution rates of microorganisms to the dissipation of norfloxacin, ciprofloxacin, and enrofloxacin were33.11%,39.10%and38.75%.(3) Six months after sampling, the risks of norfloxacin and ciprofloxacin on soil ecology are still existed. The antibiotics intaked from vegetables is low. |
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