Abstract We investigated 14 antibiotic residues in 8 marketed freshwater fish species from southeast China and estimated the associated health risks to local consumers. The antibiotic residues were determined by UPLC-MS/MS. Our findings revealed widespread distribution of quinolones (QNs), tetracyclines (TCs), and chloramphenicols (CAPs) in the freshwater fish. Notably, the average concentrations of enrofloxacin and ciprofloxacin reached levels as high as 62.5 µg/kg wet weight (ww) and 11.7 µg/kg ww, respectively, and detection frequencies were 68.7% for enrofloxacin and 31.6% for ciprofloxacin. Additionally, we detected chloramphenicol, a prohibited antibiotic, in samples with a detection frequency of 0.76%. Among the fish species, the mean concentration of total antibiotic residues was highest in bluntnose black bream (263.3 µg/kg), followed by English perch (52.4 µg/kg), crucian carp (46.3 µg/kg), black carp (28.6 µg/kg), yellowcheek carp (21.0 µg/kg), grass carp (15.3 µg/kg), bighead carp (3.78 µg/kg), and mandarin fish (3.69 µg/kg). We estimated the daily intake values of these antibiotic residues which were lower than the acceptable daily intake values and hazard indexes were much less than 1. It indicates there is very low direct health risk to consumers. Despite that, investigation on the chronic impact, such as antibiotic-resistant bacteria, gut microbiota disruption and allergic reactions is urgently needed.
A sensitive and rapid analytical method based on alkaline diatomaceous earth extraction followed by GC/MS was developed for the quantitative determination of the toxic contaminant ethyl carbamate (EC) in yellow rice wines. The optimal extraction conditions were investigated. With the application of diatomaceous earth extraction, the damage of organic acids to the capillary column was greatly reduced. By using d5-EC as an internal standard for quantitative analysis of EC, the linearity of the calibration curves was good between 10 and 1000 ng/mL. The LOD and LOQ were 1.7 and 5.0 μg/kg, respectively. The spiked level of EC was 5.0-300 μg/kg, and the average recovery of the spikes was between 78.4 and 98.2%, with an RSD between 4.3 and 8.3%. Upon validation by five laboratories when spiked with 50, 100, and 300 μg/kg, the average respective recoveries were 102.9, 102.2, and 98.7% with a RSD between 0.7 and 8.1%. The validation results demonstrated that the method is fast, simple, selective, and suitable for the determination of EC in yellow rice wines.
Environmental pollution with toxic heavy metals can lead to the possible contamination of the rice. Selected metals (As, Cd, Hg and Pb) and their accumulation in rice collected from Zhejiang, China were analyzed to evaluate the potential health risk to the local adults and children. The mean levels found in rice were as follows: As, 0.080 mg/kg; Cd, 0.037 mg/kg; Hg, 0.005 mg/kg; Pb, 0.060 mg/kg. The estimated daily intakes (EDIs) were calculated in combination of the rice consumption data. The mean intakes of As, Cd, Hg and Pb through rice were estimated to be 0.49, 0.23, 0.03 and 0.37 µg/kg bw/day for adults, and 0.34, 0.29, 0.04 and 0.47 µg/kg bw/day for children. The 97.5th percentile (P97.5) daily intakes of As, Cd, Hg and Pb were 1.02, 0.64, 0.37 and 1.26 µg/kg bw/day for adults, and 0.63, 0.83, 0.47 and 1.63 µg/kg bw/day for children. The risk assessment in mean levels showed that health risk associated with these elements through consumption of rice was absent. However, estimates in P97.5 level of Cd and Pb for children, and Hg for adults have exceeded the respective safe limits.
Cadmium (Cd) pollution of food safety is a prominent food safety concern worldwide. The concentration of Cd in six aquatic food categories collected from 2018 to 2022 was analyzed using inductively coupled plasma mass spectrometry, and the Cd exposure levels were calculated by combining the Cd concentration and food consumption data of 18913 urban and rural residents in Zhejiang Province in 2015–2016. The mean Cd concentration was 0.699 mg/kg and the mean Cd exposure of aquatic foods was 0.00951 mg/kg BW/month for the general population. Marine crustaceans were the largest Cd contributor, corresponding to 82.7%. The regional distribution results showed that the average Cd exposure levels of 11 cities did not exceed the provisional tolerable monthly intake (PTMI). According to the subgroups, the Cd mean exposure level of 2–3-year-old children was significantly higher than that of the other age groups but did not exceed the PTMI. Health risk classification assessment demonstrated that the final risk score was six, and the health risk level of Cd exposure in aquatic products in the Zhejiang population was medium. These results demonstrated that the risk of Cd exposure in certain food types or age groups should be given more concern.
We developed a new method, based on alkaline diatomite solid-phase extraction followed by gas chromatography with mass spectrometry, for the simultaneous determination of the toxic contaminants ethyl carbamate (EC) and 4-(5-)methylimidazole (4-MEI) in yellow rice wine and soy sauce. The optimal extraction conditions were defined. With the application of alkaline diatomite solid-phase extraction, damage to the capillary column by organic acids was greatly reduced. With deuterated EC used as the internal standard, the linearity of the calibration curves for EC and 4-MEI was good with correlation coefficient above 0.99. In a spiked experiment with EC and 4-MEI in yellow rice wine and soy sauce, recovery of the added EC was 80.5-102.5% and that of 4-MEI was 78.3-92.8%. The limit of quantification and limit of detection for EC were 6.0 and 2.0 μg/kg, respectively, and for 4-MEI were 15.0 and 5.0 μg/kg, respectively. The validation results demonstrate that the method is fast, simple, and selective, and therefore is suitable for simultaneously determining the presence of EC and 4-MEI in fermented food.
To consider dynamic load while equivalent standard axle load conversion is carried out,two degree of freedom vehicle model is built to calculate power spectral density of dynamic load coefficient,and then distribution of dynamic load coefficient is calculated.Increasing degree of equivalent standard axles is calculated in theory while dynamic load is considered.The results of examples show that equivalent standard axle load shall be increased when dynamic load is considered for various kind of pavement: for asphalt pavement,while design deflection and tensile stress at the bottom of asphalt pavement is taken as index,1%-2% shall be increased for expressway and first class highway,2%-5% shall be increased for other classes highway;while tensile stress at the bottom of semi-rigid base is taken as checking index,3%-6% shall be increased for expressway and first class highway,7%-17% shall be increased for other classes highway;for cement concrete pavements,15%-25% shall be increased for expressway and first class highway,35%-80% shall be increased for other classes highway.
Delft-3D software system was designed by the water power academe of Netherlands(Delft Hydraulics).And it could be used to simulate the changes of hydraulics and water quality in two directions or three directions.The models not only think of complicated hydrodynamics questions and transportation process,but also think of many physical chemical and biological reciprocity,which makes the results more credibility and reliable.By using Delft-3D,the water quality of the first three years in Huadao Reservoir was simulated the time to irrigate and drink was defined.And some suggestions were given for local decision-making departments.
Light spot centroid detection is one of the key technologies in optical measurement. In order to overcome the poor stability caused by small scale spot, we proposed an extract method by using saturated light spot in this paper. By increasing the input voltage of LED and adjusting the exposure time of CCD, the image of LED which projected in the image plane become larger, it can help enhancing the stability of light spot centroid extracting. The experiment results showed that the extract stability of saturated light spot has improved obviously compared with small scale spot. This method can be adopted in close range measurement; it reflected the sub-pixel coordinate of spot in image plane coordinate more accurately after calibrating the distorted image.
Large-scale space simulation of high field intensity electromagnetic environment is difficult to test radiation effects, and there are gaps in the application of existing BCI (bulk current injection) technology to nonlinear system tests. The research on the equivalent alternative radiation test method of the shielded cable coupling channel is carried out. Taking the equal response of the tested equipment as the equivalent basis, an analysis model of the response of the EUT (equipment under test) under the two conditions of radiation method and injection method is established. The equivalent corresponding relationship between the injection excitation source voltage and the radiation field intensity is deduced, and the conditions and test methods for the equivalent replacement of radiation with BCI are proposed and verified by experiments. The research results show that the BCI method can be accurately equivalent to the radiation effect test of the EUT, and the test error does not exceed 2 dB, which can meet the actual needs of the project.
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