Monitoring and dietary exposure assessment of pesticide residues in strawberry in Beijing, China.

In this study, 142 pesticide residues in 245 strawberry samples, gathered from farmers markets or supermarkets in Beijing from June 2017 to May 2018, were investigated. The samples were analysed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). According to the validation data, including linearity, recovery, precision and measurement uncertainty, the method performed well in monitoring pesticide residues and complied with the requirements of the European Guideline SANTE/11813/2017. Among the strawberry samples, 26.0% contained at least one pesticide residue, four of which contained pesticide residues that exceeded the maximum residue limit of China. Carbendazim, pyrimethanil and azoxystrobin were the most frequently detected pesticides in the strawberry samples. Lower bound, middle bound and upper bound values were used to replace left-censored results. In the worst-case scenario, the hazard index (HI) for adults and children was 0.91% and 3.62%, respectively. Carbofuran, bifenazate and pyraclostrobin were identified as the top three contributors to HI.

Nanoselenium transformation and inhibition of cadmium accumulation by regulating the lignin biosynthetic pathway and plant hormone signal transduction in pepper plants.

Selenium (Se) can promote the growth and resistance of agricultural crops as fertilizers, while the role of nano-selenium (nano-Se) against Cd remains unclear in pepper plants (Capsicum annuum L.). Biofortification with nano-Se observably restored Cd stress by decreasing the level of Cd in plant tissues and boosting the accumulation in biomass. The Se compounds transformed by nano-Se were primarily in the form of SeMet and MeSeCys in pepper tissues. Differential metabolites and the genes of plant signal transduction and lignin biosynthesis were measured by employing transcriptomics and determining target metabolites. The number of lignin-related genes (PAL, CAD, 4CL, and COMT) and contents of metabolites (sinapyl alcohol, phenylalanine, p-coumaryl alcohol, caffeyl alcohol, and coniferaldehyde) were remarkably enhanced by treatment with Cd1Se0.2, thus, maintaining the integrity of cell walls in the roots. It also enhanced signal transduction by plant hormones and responsive resistance by inducing the biosynthesis of genes (BZR1, LOX3, and NCDE1) and metabolites (brassinolide, abscisic acid, and jasmonic acid) in the roots and leaves. In general, this study can enable a better understanding of the protective mechanism of nano-Se in improving the capacity of plants to resist environmental stress.

Diagnostic performances of the KWAK-TIRADS classification, elasticity score, and Bethesda System for Reporting Thyroid Cytopathology of TI-RADS category 4 thyroid nodules.

OBJECTIVE: To explore the value of the KWAK Thyroid Imaging Reporting and Data System (KWAK-TIRADS), elasticity score (ES), and Bethesda System for Reporting Thyroid Cytopathology (BSRTC) in the diagnosis of suspicious thyroid nodules. MATERIALS AND METHODS: The study included 392 cases of TI-RADS category 4 thyroid nodules that underwent thyroidectomy between January 2017 and October 2019. All patients underwent ultrasonography, ultrasound elastography, and fine-needle aspiration cytology (FNAC) before surgery. The nodules were classified into different categories based on the KWAK-TIRADS, ES, and BSRTC. Patients were divided into two groups based on postoperative pathological characteristics. The sensitivity (Se), specificity (Sp), and area under the receiver operating characteristic (ROC) curve were calculated. Student's t-test and Pearson chi-square test were used to compare diagnostic performance. RESULTS: There were 159 patients in the benign group and 233 in the malignant group. The percentage of malignant nodules in KWAK-TIRADS categories 4a, 4b, and 4c were 44.3%, 64.8%, and 92.9%, respectively. The percentages of malignant nodules in ES 2, 3, 4, and 5 were 0%, 37.1%, 93.8%, and 100%, respectively. The percentage of malignant nodules in BSRTC levels I, II, III, IV, V and VI were 57.1%, 2.8%, 9.9%, 76.6%, 99.1%, and 100%, respectively. Among those methods, the BSRTC had better diagnostic efficiency than the KWAK-TIRADS and ES (Sp 81.1%, Se 93.6%, and AUC 0.918, P<0.01). Among the combined methods, KWAK-TIRADS+ES+BSRTC was more effective than KWAK-TIRADS+ES, KWAK-TIRADS+BSRTC, and ES+BSRTC (Sp 93.7%, Se 91.4%, and AUC 0.967, P<0.01). CONCLUSION: The combination of KWAK-TIRADS, ES, and BSRTC can improve the accuracy of identifying category 4 thyroid nodules.

The Role of Surface Termination in Halide Perovskites for Efficient Photocatalytic Synthesis.

Halide perovskites have received attention in the field of photocatalysis owing to their excellent optoelectronic properties. However, the semiconductor properties of halide perovskite surfaces and the influence on photocatalytic performance have not been systematically clarified. Now, the conversion of triose (such as 1,3-dihydroxyacetone (DHA)) is employed as a model reaction to explore the surface termination of MAPbI3 . By rational design of the surface termination for MAPbI3 , the production rate of butyl lactate is substantially improved to 7719 µg g-1 cat. h-1 under visible-light illumination. The MAI-terminated MAPbI3 surface governs the photocatalytic performance. Specially, MAI-terminated surface is susceptible to iodide oxidation, which thus promotes the exposure of PbII as active sites for this photocatalysis process. Moreover, MAI-termination induces a p-doping effect near the surface for MAPbI3 , which facilitates carrier transport and thus photosynthesis.

Remediation of 1-Nitropyrene in Soil: A Comparative Study with Pyrene.

Nitrated polycyclic aromatic hydrocarbons (nPAHs) are ubiquitous environmental pollutants, which exhibits higher toxicity than their corresponding parent PAHs (pPAHs). Recent studies demonstrated that the nPAHs could represent major soil pollution, however the remediation of nPAHs has been rarely reported. In this study, biological, physical, and chemical methods have been applied to remove 1-nitropyrene, the model nPAH, in contaminated soil. A comparative study with pyrene has also been investigated and evaluated. The results suggest that the physical method with activated carbon is an efficient and economical approach, removing 88.1% and 78.0% of 1-nitropyrene and pyrene respectively, within one day. The zero-valent ion has a similar removal performance on 1-nitropyrene (83.1%), converting 1-nitropyrene to 1-aminopyrene in soil via chemical reduction and decreasing the mutagenicity and carcinogenicity of 1-nitropyrene. Biological remediation that employs scallion as a plant model can reduce 55.0% of 1-nitropyrene in soil (from 39.6 to 17.8 µg/kg), while 77.9% of pyrene can be removed by plant. This indicates that nPAHs might be more persistent than corresponding pPAHs in soil. It is anticipated that this study could draw public awareness of nitro-derivatives of pPAHs and provide remediation technologies of carcinogenic nPAHs in soil.

Development of a QuEChERS-Based Method for Determination of Carcinogenic 2-Nitrofluorene and 1-Nitropyrene in Rice Grains and Vegetables: A Comparative Study with Benzo[a]pyrene.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are ubiquitous environmental pollutants attracting increasing attention because of their potent mutagenicity to humans. Previous studies of nitro-PAHs focused on investigating their formation mechanisms and detecting them in atmospheric environment; however, few studies have reported their occurrence in food samples, and regulations on nitro-PAHs are still lacking. We report in this study the development and application of a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for determination of nitro-PAHs in rice and vegetable samples. Analysis of the collected samples by the validated method revealed 1-nitropyrene and 2-nitrofluorene were widespread food contaminants. A comparative study with benzo[a]pyrene, the commonly used marker for PAH exposure, showed that carcinogenic nitro-PAHs existed in rice and vegetables at similar concentrations. Dietary exposure risk, which was estimated based on the surveillance data, suggested 3.28-5.03 ng/kg/day of nitro-PAHs exposure for Hong Kong citizens from rice grains and vegetables.

Quantitation of Aristolochic Acids in Corn, Wheat Grain, and Soil Samples Collected in Serbia: Identifying a Novel Exposure Pathway in the Etiology of Balkan Endemic Nephropathy.

While to date investigations provided convincing evidence on the role of aristolochic acids (AAs) in the etiology of Balkan endemic nephropathy (BEN) and upper urothelial cancer (UUC), the exposure pathways by which AAs enter human bodies to cause BEN and UUC remain obscure. The goal of this study is to test the hypothesis that environmental pollution by AAs and root uptake of AAs in the polluted soil may be one of the pathways by which AAs enter the human food chain. The hypothesis driving this study was that the decay of Aristolochia clematitis L., a AA-containing herbaceous plant that is found growing widespread in the endemic regions, could release free AAs to the soil, which could be taken up by food crops growing nearby, thereby transferring this potent human nephrotoxin and carcinogen into their edible parts. Using the highly sensitive and selective high-performance liquid chromatography coupled with fluorescence detection method, we identified and quantitated in this study for the first time AAs in corn, wheat grain, and soil samples collected from the endemic village Kutles in Serbia. Our results provide the first direct evidence that food crops and soil in the Balkans are contaminated with AAs. It is possible that the presence of AAs in edible parts of crops originating from the AA-contaminated soil could be one of the major pathways by which humans become exposed to AAs.

Determination of DNA adducts by combining acid-catalyzed hydrolysis and chromatographic analysis of the carcinogen-modified nucleobases.

The commonly used method of analyzing carcinogen-induced DNA adducts involves the hydrolysis of carcinogen-modified DNA samples by using a mixture of enzymes, followed by (32)P-postlabeling or liquid chromatography (LC)-based analyses of carcinogen-modified mononucleotides/nucleosides. In the present study, we report the development and application of a new approach to DNA adduct analysis by combining the H(+)/heat-catalyzed release of carcinogen-modified nucleobases and the use of LC-based methods to analyze DNA adducts. Results showed that heating the carcinogen-modified DNA samples at 70 °C for an extended period of 4 to 6 h in the presence of 0.05% HCl can efficiently induce DNA depurination, releasing the intact carcinogen-modified nucleobases for LC analyses. After optimizing the hydrolysis conditions, DNA samples with C8- and N (2) -modified 2'-deoxyguanosine, as well as N (6) -modified 2'-deoxyadenosine, were synthesized by reacting DNA with 1-nitropyrene, acetaldehyde, and aristolochic acids, respectively. These samples were then hydrolyzed, and the released nucleobase adducts were analyzed using LC-based analytical methods. Analysis results demonstrated a dose-dependent release of target DNA adducts from carcinogen-modified DNA samples, indicating that the developed H(+)/heat-catalyzed hydrolysis method was quantitative. Comparative studies with enzymatic digestion method on carcinogen-modified DNA samples revealed that the two hydrolysis methods did not yield systematically different results.

Combination of precolumn nitro-reduction and ultraperformance liquid chromatography with fluorescence detection for the sensitive quantification of 1-nitronaphthalene, 2-nitrofluorene, and 1-nitropyrene in meat products.

Carcinogenic nitropolycyclic aromatic hydrocarbons (nitro-PAHs) are ubiquitous in the ambient environment. They are emitted predominantly from internal combustion engines and by reacting polycyclic aromatic hydrocarbons with nitrogen oxide. The emerging evidence that nitro-PAHs are taken up by plants and bioaccumulatd in the food chain has aroused worldwide concerns for the potential of chronic poisoning through dietary intake. Therefore, analytical methods of high sensitivity are extremely important for assessing the risk of human exposure to nitro-PAHs. This paper describes the development of a simple and robust ultraperformance liquid chromatography coupled fluorescence detector (UPLC-FLD) method for the sensitive determination of nitro-PAHs in meat products. The method entails precolumn reduction of the otherwise nonfluorescent nitro-PAHs to amino-PAHs which strongly fluoresce for their determination by UPLC-FLD analysis. The developed method was validated for extraction efficiency, accuracy, precision, and detection limit and has been successfully applied in quantifying 1-nitronaphthalene (1-NN), 2-nitrofluorene (2-NF), and 1-nitropyrene (1-NP) in fresh and cured meat products. The results showed that the combination of Fe/H(+)-induced nitro-reduction and UPLC-FLD analysis allows sensitive quantification of 1-NN, 2-NF, and 1-NP at detection limits of 0.59, 0.51, and 0.31 µg/kg, respectively, which is at least 10 times lower than those of the existing analytical methods.

Influence of different planting seasons of six leaf vegetables on residues of five pesticides.

To investigate the influence of different planting seasons on the dissipation of pesticides, field experiments of thiophanate-methyl, metalaxyl, fluazifop-P-butyl, chlorpyrifos, and λ-cyhalothrin on six crops including pakchoi, rape, crown daisy, amaranth, spinach, and lettuce were designed and conducted. In this study, a high-performance liquid chromatography and electrospray ionization-tandem mass spectrometer with multiple reaction monitoring was used to simultaneously determine thiophanate-methyl and its metabolite carbendazim, metalaxyl, and fluazifop-P-butyl in various samples; gas chromatography with an electron capture detector was used to detect chlorpyrifos and λ-cyhalothrin. The limits of quantitation (LOQs) of these six pesticides were in the range of 0.001-0.01 mg kg(-1) for all samples, and the average recoveries of all pesticides ranged from 60.1 to 119.1% at 0.01 and 0.1 mg kg(-1) spiked levels. The relative standard deviation (RSD) ranged from 1.1 to 13.9%. All maximal concentrations of the six pesticides in six leaf vegetables in autumn were higher than in summer in Beijing. For most pesticides half-lives in autumn were longer than in summer. The results showed that the initial concentration, maximal concentration, and half-lives of pesticides were influenced not only by environmental factors such as light, heat, moisture, and rainy climate but also by plant matrices.

Spinach or amaranth contains highest residue of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin on six leaf vegetables upon open field application.

To select representative leaf vegetables which may contain the highest residue, field experiments of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin on six crops including pakchoi, rape, crown daisy, amaranth, spinach, and lettuce were designed and conducted. In this study, a high-performance liquid chromatograph and electrospray ionization tandem mass spectrometer with multiple reaction monitoring was used to simultaneously determine metalaxyl and fluazifop-P-butyl residue in various samples, and a gas chromatograph with electron capture detector was used to detect chlorpyrifos and lambda-cyhalothrin. The limits of quantification (LOQ) of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin were in the range of 0.001-0.01 mg kg(-1) for all samples, and the average recoveries of all pesticides ranged from 67.6 to 119.1% at spiked levels of 0.01-0.1 mg kg(-1). In supervised field trials, the half-lives of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin were in the range of 1.11-3.79 days, 1.11-2.27 days, 1.13-5.17 days, and 1.77-6.24 days. It was also found that all pesticide residues in spinach and/or amaranth were higher than others after application. It is recommended that spinach or amaranth can be selected as a representative crop of leaf vegetables in studying systemic fungicide, insecticides, and herbicides with similarity as metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin.

Uniconazole residue and decline in wheat and soil under field application.

Uniconazole residue dynamics and final residues in supervised field trials at GAP conditions were studied. The residue levels and dissipation rate of uniconazole was detected by LC-MS. At fortification levels of 0.04, 0.2 and 2 mg kg(-1), recoveries ranged from 78.7 % to 100.9 % with RSDs of 0.1 %-4.6 % (n = 5). The dissipation experiments showed the half-lives (T1/2) of uniconazole in soil and wheat plants were 2.9-3.3 and 3.8-4.4 days, respectively. At pre-harvest intervals (PHI) of 45 and 60 days, uniconazole residue were no detectable or below the limit of quantification (LOQ) in soil, wheat plants and wheat.