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Polycyclic aromatic hydrocarbons (PAHs) in surface sediment from city catchment area were selected to research the environmental responses of PAHs contamination under an urban-suburb gradient. Total concentrations of 16 PAHs in the samples were found from 1.8 ng/g to 4 126.3 ng/g, with the average concentration of 403.2 ng/g. The total concentrations of 16 PAHs increased with urbanization levels, which were higher in the urban area than that in the suburban area. The composition of low molecular weight PAHs was higher in the suburban area than that in the urban area. These were probably because PAHs source differed during urbanization. The results of isomer ratios of PAHs and principal component analysis coupled with multiple stepwise linear regressions showed that PAHs in Ningbo were mainly from traffic emissions and coal combustion. The proportion of traffic emissions and coal combustion mixed sources was 78% in the urban area with high-level urbanization. In contrast, the proportion of diesel-power vehicular was 42%, and coal combustion was 33.9% in the suburban area with low-level urbanization. These showed a difference in PAHs sources with a gradient of urbanization. Ecological risk analysis by the sediment quality guidelines (SQGs) showed that the potential ecological risk of 16 PAHs in surface sediment from urban catchment area was low, and a significant difference was observed in the average of effect rang low (ERL) quotient between urban and suburban areas (P<0.05). The average of ERL quotient of H3 sampling site in the urban area exceeded 1, which might raise some ecological risk. While the average of ERL quotient of sampling sites in the suburban area did not exceed 1. The toxic benzo[a]pyrene equivalents (TEQBaP) of 16 PAHs (mean value) in urban area was 3 times higher than that in suburban area, and 7 carcinogenic PAHs were the main factors to the ecological risk. [ABSTRACT FROM AUTHOR]

Metal(loid)s can increase the spread and enrichment of antibiotic resistance in the environmental system by means of a co-selection effect. The effects of introducing antibiotics into the environment on the long-term resistance of microbial communities to metal(loid)s are largely unknown. Here, manure-fertilizers that contained either oxytetracycline (OTC) or sulfadiazine (SD) at four concentrations (0, 1, 10, and 100 mg kg−1) were incorporated into a maize cropping system in an area with a high arsenic geological background. The results showed that the introduction of exogenous antibiotics had a notable effect on the bacterial diversity of the maize rhizosphere soil, as evidenced by alterations in Chao1 and Shannon index values when compared to those of the control. Oxytetracycline exposure did not significantly alter the prevalence of most bacterial phyla, with the exception of Actinobacteria. However, sulfadiazine antibiotic exposure caused a decrease in prevalence as exposure concentrations increased, with the exception of Gemmatimonadetes. The same reaction pattern was observed in the five most prevalent genera, such as Gemmatimonas, Fulvimonas, Luteimonas, Massilia, and Streptomyces. It was observed that the abundance of tetC, tetG, and sul2 antibiotic resistance genes (ARGs) significantly increased in correlation with the concentration of antibiotic exposure, and a strong link was found between these genes and integrons (intl1). The abundance of microbial functional genes related to arsenic transformation (aioA and arsM) increased when there was an increase in oxytetracycline exposure concentrations, whereas a decrease in abundance was observed with increasing sulfadiazine exposure concentrations. Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Bacteroidota, Gemmatimonadota, Cyanobacteria and Planctomycetes were found to be important indicators of the introduction of antibiotics, and may be essential in the development of antibiotic resistance in soils with high arsenic geological background. Planctomycetacia (from Planctomycetes) was significantly negatively correlated with sul2 and intl1 genes, which might play a role in the development of resistance profiles to exogenous antibiotics. This study will expand our understanding of microbial resistance to antibiotic contamination in areas with a high geological background, as well as reveal the hidden ecological effects of combined contamination. [ABSTRACT FROM AUTHOR]

Information plays an important role in meeting the quantitative and qualitative goals of agriculture in the 21st century. As an emerging economy in a developing continent, China has already made many interventions to use information technology to support agricultural development. However, information service in some rural areas is still severely limited. The overall impact of the changing information environment on the farmers' information needs and access channels has not been fully studied. Thus, this study systematically investigates the characteristics of the information needs and channels of farmers in Guangdong, China. We have collected 4006 questionnaire samples and used correlation analysis to explore the relationships between farmers' information needs and access channel preferences. The results indicate that individual characteristic factors, social factors and family factors have different degrees of influence on farmers' information needs and access channel preferences. These findings can provide a reference for information construction in the rural areas of Guangdong Province and thus promote its economic development. This study can also provide useful insights for policy-makers and researchers from other developing countries to formulate implementation plans to promote agricultural development. [ABSTRACT FROM AUTHOR]