Zhihong Ma

Occurrence of antibiotics in soils and manures from greenhouse vegetable production bases of Beijing, China and an associated risk assessment.

The occurrence of 15 antibiotics in soil and manure samples from 11 large-scale greenhouse vegetable production (GVP) bases in Beijing, China was investigated. Results showed that the greenhouse soils were ubiquitously contaminated with antibiotics, and that antibiotic concentrations were significantly higher in greenhouses than in open field soils. The mean concentrations of four antibiotic classes decreased in the following order: tetracyclines (102μg/kg)>quinolones (86μg/kg)>sulfonamides (1.1μg/kg)>macrolides (0.62μg/kg). This investigation also indicated that fertilization with manure and especially animal feces might be the primary source of antibiotics. A risk assessment based on the calculated risk quotients (RQs) demonstrated that oxytetracycline, chlortetracycline, norfloxacin, ciprofloxacin and enrofloxacin could pose a high risk to soil organisms. These results suggested that the ecological effects of antibiotic contamination in GVP bases and their potential adverse risks on human health need to be given special attention.

Accumulation status, sources and phytoavailability of metals in greenhouse vegetable production systems in Beijing, China.

The accumulation status, sources and phytoavailability of selected metals in greenhouse vegetable production systems in peri-urban areas of Beijing were investigated. The mean concentrations of As, Cd, Cr, Hg and Pb in greenhouse soils were 8.44, 0.25, 69.0, 0.09 and 22.0 mg kg(-1), dw, respectively. According to principal component analysis, As, Cd, Cr and Hg are mainly from anthropogenic source, but Pb is likely from natural source. Metal concentrations in all vegetable samples were decreased in the order of Cr>As>Pb>Cd>Hg. Compared with root and fruit vegetables, leaf vegetables had relatively high concentrations and transfer factors of heavy metals, except for Cd. By including soil pH, OM and greenhouse soil metals, 10 empirical models were derived using stepwise multiple linear regression analysis to predict heavy metal concentrations in the edible parts of different vegetables. Among the different vegetable groups, the highest intakes of metals occurred through consumption of leaf vegetables for the two age groups, except for Cd. The HI value of the studied metals were all below 1, indicating that consumption of vegetables grown in greenhouse soils was of low risk to consumers in our study area.

Highly Sensitive Colorimetric Detection of Ochratoxin A by a Label-Free Aptamer and Gold Nanoparticles

A label-free aptamer-based assay for the highly sensitive and specific detection of Ochratoxin A (OTA) was developed using a cationic polymer and gold nanoparticles (AuNPs). The OTA aptamer was used as a recognition element for the colorimetric detection of OTA based on the aggregation of AuNPs by the cationic polymer. By spectroscopic quantitative analysis, the colorimetric assay could detect OTA down to 0.009 ng/mL with high selectivity in the presence of other interfering toxins. This study offers a new alternative in visual detection methods that is rapid and sensitive for OTA detection.

Effect of land use type on metals accumulation and risk assessment in soil in the peri-urban area of Beijing, China

ABSTRACT Heavy metal concentrations of As, Cd, Cu, Hg, Ni, Pb, and Zn were investigated for 107 soil samples collected from crop land, orchard land, greenhouse land, and wood land in the peri-urban area of Beijing, China. The mean concentrations of As, Cd, Cu, Hg, Ni, Pb, and Zn in all soil samples were 8.40, 0.20, 24.7, 0.08, 25.0, 23.0, and 77.1 mg/kg, dw, respectively. Among the four land use types, the Cd concentration in greenhouse land was significantly higher than the other three kinds of land uses (p < .05), and Cu and Zn concentrations in greenhouse land were significantly higher than in crop land and wood land (p < .05). Based on principal component analysis, elevated Cu, Zn, and Cd concentrations in greenhouse land might have originated from high application rates of manure and fertilizer. According to an ecological risk analysis, the four land use types can be ranked in the following order: greenhouse land > orchard land > crop land > wood land. However, the degree of non-cancer risk for both adults and children in different land uses decreased in the order of greenhouse land > orchard land > wood land > crop land.

Determination of Aflatoxins in Rice and Maize by Ultra-High Performance Liquid Chromatography–Tandem Mass Spectrometry with Accelerated Solvent Extraction and Solid-Phase Extraction

A fast and reliable ultra-high performance liquid chromatography–tandem mass spectrometry method was developed for the determination of aflatoxins B1, B2, G1, and G2 in cereal. The analytes were extracted by accelerated solvent extraction with methanol/water (80:20). A polymeric solid-phase extraction column was used for sample preparation. Under optimum conditions, the analyte recoveries for samples spiked at different concentration levels in rice and maize ranged from 71.2 to 94.0%, with relative standard deviations less than 16.4%. Limits of detection (signal-to-noise ratio, 3:1) for the aflatoxins ranged from 0.25 to 0.93 ng/g. The developed method was applied to the determination of aflatoxins in ten rice and maize samples. One maize sample tested positive with an aflatoxin B1 concentration of 2.7 ng/g.

Molecular Methods of Studying Microbial Diversity in Soil Environments

Microorganisms live in all parts of the biosphere and are critical to nutrient recycling in ecosystems. In recent years, the development of methodologies for the analysis of microorganisms and microbial ecology, at the molecular level, has progressed phenomenally. This review introduces and compares the various molecular methods for studying microbial diversity in soil environments, and the advantages and disadvantages of current methods are proposed as well.

An Identification of the Growing Area of Longjing Tea Based on the Fisher's Discriminant Analysis with the Combination of Principal Components Analysis

In recent years, the fake Xihu Longjing Tea has damaged its brand image and reputation. This paper based on the Fishers discriminant analysis using the fixed-size moving window evolving factor analysis to find characteristic spectra through analyzing the near infrared spectroscopy of Xihu Longjing Tea and Zhejiang Longjing Tea. The Fishers discriminant analysis was used to reduce the data dimension combined with the principal component analysis. A discrimination model was set up for the identification of the Xihu Longjing Tea and Zhejiang Longjing Tea. The models accuracy is 97.3%. The results proved that this model is feasible to identify the differences between the Xihu Longjing Tea and Zhejiang Longjing Tea. Unlike other methods, the tea does not need to be made into a powder. It also lays out a theoretical foundation for developing an identification instrument for Xihu Longjing Tea.

The detection of chlorophyll content for salt stress of the wheat seedling by hyperspectral imaging

An auto-development pushbroom imaging spectrometer (PIS) with wavelength range of 400-1000 nm was applied to measure the chlorophyll content of wheat seedling. It showed that according to images of spectral imaging for leaves of Chinese Spring (Salt-sensitive), Zhouyuan 9369(common and high-yield) and Changwu 134(salt-tolerant) wheat seedling under salt stress, growth of salt-sensitive Chinese Spring wheat seedling was inhibited and it was feasible to carry out qualitative analysis. Images could intuitively reflect morphological information of growth status of wheat seedling and could show spectral differences of different leaves and different locations of one leave. Also, it was feasible to identify green and yellow locations of leaf and to carry out qualitative analysis. The tested sites of spectrum and the chlorophyll content measured sites were on the same area of single leaf. After measuring the hyperspectral image of leaf, the mean reflectance spectra of each leaf was calculated Totally, 126 samples were collected, which were then divided into a calibration set and a prediction set. Partial least square regression (PLSR) method was used to build the calibration model. Results showed that the extracted hyperspectral spectra had high correlation with chlorophyll content. The correlation coefficient of the calibration model is R=0.8138, the standard error of prediction is SEP=4.75. The results indicated that hyperspectral imaging were suitable for the non-invasive detection of chlorophyll content of wheat seedling.

Application research on enhancing near-infrared micro-imaging quality by 2nd derivative

Near-infrared micro-imaging will not only provide the sample’s spatial distribution information, but also the spectroscopic information of each pixel. In this thesis, it took the artificial sample of wheat flour and formaldehyde sodium sulfoxylate distribution given for example to research the data processing method for enhancing the quality of near-infrared micro-imaging. Near-infrared spectroscopic feature of wheat flour and formaldehyde sodium sulfoxylate being studied on, compare correlation imaging and 2nd derivative imaging were applied in the imaging processing of the near-infrared micro-image of the artificial sample. Furthermore, the two methods were combined, i.e. 2nd derivative compare correlation imaging was acquired. The result indicated that the difference of the correlation coefficients between the two substances, i.e. wheat flour and formaldehyde sodium sulfoxylate, and the reference spectrum has been increased from 0.001 in compare correlation image to 0.796 in 2nd derivative compare correlation image respectively, which enhances the imaging quality efficiently. This study will, to some extent, be of important reference significance to near-infrared micro-imaging method research of agricultural products and foods.

A rapid instrument designed for identifying the authenticity of agricultural products

Abstract. This paper introduced a development idea of prototype instrument which would be used to fast identify the authenticity of agricultural products. The instrument used the trait of near-infrared spectroscopy can quickly extract characteristic information of agricultural products, near infrared spectroscopy of agricultural products before going out the factory, was used algorithm processing to write two-dimensional code. When the agricultural products need to identify, we can quickly extract near infrared spectroscopy of agricultural products and read information of two-dimensional code label. Comparing above information from two parts, the authenticity of agricultural products finally can be identified.