[Effects of Earthworms/Biochar on Bacterial Diversity and Community in As-contaminated Red Soil].

Cerium-manganese modified biochar (MBC) combined with earthworms (Eisenia foetida) can immobilize arsenic (As) in red soils. In this study, high-throughput sequencing technology was used to explore the combined effects of MBC and E. foetida on bacterial diversity and community structure in As-contaminated red soils. The results showed that the single earthworm treatment had the highest diversity index, whereas the diversity index decreased in the single biochar or MBC treatment, indicating that earthworms can boost the growth of bacteria in the soil, and the addition of biochar/MBC all decreased the bacterial diversity of soils. When biochar/MBC was combined with earthworms, the diversity index increased to some degree. In terms of bacterial community structure, the relative abundance of Proteobacteria and Bacteroidetes increased significantly in each treatment, especially for MBC-earthworm treated soil, in which the relative abundance was increased by 17.08% and 329.47% for Proteobacteria and Bacteroidetes, respectively, compared to that in the control (CK). Otherwise, those abundances were decreased by 19.18% and 48.76%, respectively, for Acidobacteria and Chloroflexi. Correlation analysis results showed that the soil water-soluble As (WSAs) was negatively correlated with the relative abundances of Proteobacteria and Bacteroides (P<0.05) but was positively correlated with Acidobacteria and Chloroflexi (P<0.05), which indicated that with the decrease in WSAs in soils, the bacteria of Proteobacteria and Bacteroides reproduced rapidly, whereas the Acidobacteria and Chloroflexi were inhibited. Moreover, different treatments induced selective changes in the bacterial community, in which earthworms significantly promoted the proliferation of γ-Proteobacteria, Flavobacteriales, Aeromonadales, and Variovorax and earthworms improved the immobilization effect of As by promoting the growth of these bacteria.

[Effect of Manure from Different Sources on the Leaching of Antibiotics in Soil].

Antibiotic residues in farmland soils resulting from the application of livestock manure poses risks to the soil and water ecology associated with the spread of antibiotic resistance, thereby threatening environmental safety and human health. Here, a leaching experiment was carried out using soil(CK-T), pig manure(PM-T), cow manure(CM-T), and chicken manure(CHM-T) with the addition of tetracyclines(tetracycline, oxytetracycline, and chlortetracycline) and a control group(without antibiotics). The effects of different sources of manure on soil physical and chemical indicators and bacterial abundance under simulated leaching conditions were studied, while the migration of tetracyclines in the different treatments were also determined. The results showed that compared with the CHM-T and CM-T treatments, the tetracyclines in the PM-T treatment were more easily accumulated in the soil(residual amounts=0.90-6.91 mg·kg-1 compared to the other treatments=0.33-4.42 mg·kg-1). Compared with the surface soil(0-4 cm), higher concentrations of tetracyclines were detected at soil depths of 16-24 cm. Consistent with the residues of antibiotics, the concentrations of TN and NH4+-N in the soil with the PM-T treatment were increased by 0.044 g·kg-1 and 14.11 mg·kg-1, respectively, which were significantly higher than other treatments. The abundance of bacteria in the soil was reduced due to the bactericidal effect of antibiotics, by 39.66% in the PM-T treatment, which was significantly higher than in the other treatments(12.38%-35.26%). Compared with other treatments, the antibiotics in the CHM-T treatment were more easily leached from the soil, with 9.91 mg of antibiotics in the leachate, which was significantly higher than the other treatments(P<0.05). TN, NH4+-N, tetracycline, oxytetracycline, and chlortetracycline were the first principal component factors, accounting for 54.55% of the variation, and corresponding concentrations increased with soil depth. Based on these results, tetracyclines in pig manure tended to accumulate in soil and transfer vertically along with variations in the soil microbial community. For chicken manure, relatively high concentrations of tetracyclines were detected in the soil leachate, increasing the risk of water pollution.

[Situation Analysis and Trend Prediction of the Prevention and Control Technologies for Planting Non-Point Source Pollution].

The contribution of crop planting to agricultural non-point source pollution should not be underestimated in China. Although many modern technologies have been developed to prevent non-point source pollution in recent decades, their impacts on pollution control in farmland are far from expectation. The application of technologies for non-point source pollution control for crop farming has been delayed due to unclear technical parameters and application effectiveness. Therefore, based on studies of the non-point source pollution control for crop farming in China and abroad that were published in the last 20 years, the present research was carried out to determine the development process of planting non-point source pollution control technologies and to illuminate the framework construction. The technologies in different fields and directions were compared by their effects on fertilizer input,yield, and pollutant emission. The development trend in the field of prevention and control technologies for planting non-point source pollution was subsequently predicted. In addition, a technical framework was developed with 3 fields (pollutant source reduction, pollutant interception in the migration process, and nutrient recycling) and 14 directions. The analysis showed that the technologies for reducing pollutants from the source have attracted the most (and increasing) concern with many research directions, and that many of the studies in this field have focused on the regulation of fertilizer application. On the contrary, there is a lack of technologies in the fields of pollutant process interception and nutrient recycling. Promoting nutrient-use efficiency, regulating nutrient transformation, and using soil supplements will be the main entry points for non-point source pollution control for crop farming. Furthermore, technologies will operate better with the help of farmland infrastructure and downstream purification systems.

[Cerium-manganese Modified Biochar Immobilizes Arsenic in Farmland Soils].

Loaded cerium and manganese modified biochar (MBC) was prepared by high temperature pyrolysis at 600℃, and three kinds of arsenic (As) contaminated soils were selected for remediation, including red soil, yellow soil, and purple soil with different basic properties. During the soil incubation experiment, the goal of this research was to investigate the influence of MBC as a stabilizer of the mobility of arsenic in these three soils after treated by biochar (BC) and MBC. The results revealed that the application of MBC resulted in a significant decrease of water soluble arsenic content in the three different kinds of soils. With the additional amount increasing, the stabilization efficiency of soil arsenic increased continuously. When the applied amount of MBC ranged from 1% to 10%, the stabilization efficiency of arsenic was in the range of 70%-99%. The corresponding stabilizing efficiencies of the red, yellow, and purple soils were 70.59%-94.72%, 75.24%-98.35%, and 76.53%-99.61%, respectively, after being treated by MBC at 1%-10%. At a higher addition of 10% MBC, the efficiency of stabilization reached 95%. On the contrary, the addition of unmodified biochar caused the activation and dissipation of As in soils. Comparatively speaking, according to the stabilization efficiency, the three soils ranked in this decreasing order:purple soil > yellow soil > red soil. It also illustrated that the addition of MBC into soils led to the conversion of active arsenic to stable ones in soil, indicating the conversion from non-specifically sorbed (F1) and specifically sorbed (F2) to well-crystallized hydrous oxides of Fe and Al (F4) and residual phases (F5), which reduced the mobility of arsenic in these soils. According to the analysis of scanning electron microscopy (SEM) and X-ray diffraction analysis, the immobilization of arsenic by MBC was strongly related to the successful loading of cerium-manganese oxide onto biochar. Therefore, MBC can be used to make suitable amendments to immobilize As in soils for remediation of arsenic-contaminated farmland soils.

[Accumulation Characteristics of Heavy Metals in Greenhouse Soil and Vegetables in Siping City, Jilin Province].

Based on the typical greenhouse vegetable production system in Siping City, Jilin Province, 124 soil samples were collected from greenhouse soils growing vegetables (GSGV), fields growing maize (FGM), and forest soil (FS) under different land utilization patterns. In addition, other samples including greenhouse vegetables (81), fertilizers (50), and irrigation water (10) were also collected in the studied region. To illustrate the accumulation characteristics of heavy metals in GSGV and greenhouse vegetables, the heavy metal content of different samples was measured using inductively coupled plasma mass spectrometry (ICP-MS) technology. The results indicated that the heavy metal content in GSGV was much higher than that in FGM and FS except for lead (Pb). Heavy metals including cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) in GSGV presented with various degrees of accumulation. The mean value of Cd content in the soils in the investigation region was 0.45 mg·kg-1, with about 42.8% of all the soil samples exceeding the Cd content criterion of the Environmental Quality Evaluation Standard for Farmland in Greenhouse Vegetable Production (HJ 333-2006). The content of the other heavy metals was in the normal range, and all met the regulations of the standard. In comparison with different vegetable categories, leafy vegetables showed much higher heavy metal concentrations (Cd 0.033 mg·kg-1 fresh weight) than did fruity ones. In total, about 2.5% and 1.2% of vegetable samples exceeded the regulated values of Cd and Pb recommended by the Standard of Food limits, respectively. With the cultivation time prolonged, heavy metal concentration in soils and vegetables all increased synchronously as the pH value decreased. The content of heavy metals in greenhouse vegetables was significantly influenced by soil pH and organic matter. It can be concluded that the health risk of greenhouse vegetables increased with GSGV accumulating more heavy metals due to the substantial application of chemical fertilizer and manure containing high level of heavy metals.

[Microbial source tracking of water fecal pollution: a review].

Livestock feces and domestic sewage are the one of the main factors inducing water pollution, while the identification of the pollution source is particularly important in pollution control and management. Because of this, microbial source tracking (MST) has recently been paid more and more attention by the related researchers around the world. In this paper, the research progress of two types of MST methods, their advantages and disadvantages, and existing problems in application were reviewed and discussed. It was considered that in the library- and culture-dependent MST methods, PCR genotyping based on repetitive sequences was most practicable, while in the library- and culture-independent MST methods, PCR-DGGE based on the gene of specificity in Escherichia coli had a very glaring sight. Future researches should be more focused on the library- and culture-independent MST, and the combination of library- and culture-dependent MST with library- and culture-independent MST could make the tracking results more credible.