[Effect of Manure Application on the Adsorption of Antibiotics to Soil].

Sulfonamide antibiotics and florfenicol(FFC) are commonly used antibiotics in Zhejiang Province. They have weak adsorption on soil and are easy to migrate, with high environmental risks. In recent years, most of the studies on the potential risk of fecal-derived antibiotics to farmland soil were conducted by adding manure under laboratory conditions; therefore, it is impossible to assess the risk of antibiotic pollution under natural fertilization. Therefore, batch balance experiments were conducted to explore the effects of different soil types and manure types on the adsorption of antibiotics in the soil, in which five types of dryland farmland soils[Lin'an(LA), Jiashan(JS), Longyou(LY), Kaihua(KH), and Jinhua(JH)]in Zhejiang Province that have been used with different fertilizers(chicken manure, pig manure, and chemical fertilizer) for a long time were chosen, and four types of commonly used antibiotics[sulfadiazine(SD), sulfamethazine(SMT), sulfamethoxazole(SMZ), and FFC]were selected. The results showed that the adsorption of the four antibiotics in the experimental soil was weak, and the adsorption capacity decreased in the order of:SMT(1.44-13.23 mg1-(1/n)·L1/n·kg-1)>SMZ(0.73-6.05 mg1-(1/n)·L1/n·kg-1)>SD(0.16-5.57 mg1-(1/n)·L1/n·kg-1)>FFC(0.27-3.81 mg1-(1/n)·L1/n·kg-1). The Freundlich model was superior to the linear model in fitting the isotherm adsorption of SD, SMT, and FFC, in which SD and FFC belonged to "S" type adsorption, and SMT belonged to "L" type adsorption. For SMZ, the fitting effect of the linear model was better than that of the Freundlich model. The contents of total organic carbon(TOC) and dissolved organic carbon(DOC) could better predict the adsorption capacity of the four antibiotics(r=0.548-0.808), and the values of cation exchange capacity(CEC) and electrical conductivity(EC) could better predict the adsorption capacity of SMT and FFC(r=0.758-0.841). Compared with the application of chemical fertilizer, manure application increased the values of TOC, DOC, CEC, and EC in acidic and neutral soils, which was conducive to the adsorption of antibiotics on the soil. Meanwhile, manure application also increased pH in acidic and neutral soils, which was not conducive to the adsorption of antibiotics on the soil. In addition, manure application reduced the values of TOC, DOC, CEC, EC, and pH in alkaline soils. The lower pH was conducive to antibiotic adsorption on the soil, whereas the lower content of the other four was not conducive to antibiotic adsorption on the soil. For the acidic soil with low fertility, the application of manure increased soil fertility and thus increased the adsorption of antibiotics on the soil, such as the LA soil with chicken manure, the LY(1) soil with pig manure, and the JH soil with chicken manure and pig manure. However, for the acidic and neutral soils with high fertility, the application of manure had significantly increased soil pH and thus reduced the adsorption of antibiotics on the soil, such as the JS soil with chicken manure and pig manure and the LY(2) soil with chicken manure. For calcareous soil with high fertility and pH(such as KH soil), the adsorption profiles of the four types of antibiotics on the soil showed diversity after the application of manure:the adsorption capacity of SD increased significantly after the application of chicken manure and pig manure, whereas the adsorption capacity of SMT and SMZ decreased significantly, and the adsorption capacity of FFC declined significantly after the application of chicken manure. Therefore, manure application according to soil fertility could effectively control the environmental risk of fecal antibiotics.

[Application of solidification technology in ecological protection of rural riverbank].

A self-developed binder was used for the solidification of construction refuse piles and whole soil matrix, and a technology of this solidification combining with grass-planting was adopted to ecologically protect the rural riverbanks at Tianshan Village of Shanghai. This technology and other ecological engineering techniques were also employed to reconstruct the ecological environment of a sewage pond at the Village. The results showed that the solidified piles had an anti-compression strength of up to 7.3 MPa, with good hydraulic permeability, fast hardening rate, and low drying shrinkage, which met the requirements for ecological safety. The solidified stakes could be used at a low temperature of above -18 degrees C with addition of certain anti-freezing agents. The riverbank underpinned with the solidified stakes had higher anti-compressive strength, higher ability of anti-soil erosion, and better hydraulic permeability; and its soil had the similar moisture content to bare riverbank soil, with no detrimental effects on the root growth of planted grass. After soil solidification, the shearing strength of the riverbank increased by 50 times, and its soil loss was only 5% of the bare riverbank. In the first 10 days after adopting this technology, parts of Cynodon dactylon roots on the surface of solidified soil matrix began to extend into soil; after one month, 60% of the roots penetrated into deeper soil layer; and 11 months later, the grass roots completely grew in-depth in the soil. The combination of our solidification technique with vegetation reconstruction satisfied the requirements of both stabilizing riverbank and improving riparian habitat.

Phosphate (Pi) and arsenate uptake by two wheat (Triticum aestivum) cultivars and their doubled haploid lines.

BACKGROUND AND AIMS: Arsenic accumulation in cereal crops represents an important pathway for human exposure to arsenic from the environment. The objectives of the present work were to find whether the relationship between arsenate and phosphate (Pi) uptake rate differs among genotypes and to select genotypes with a low arsenate uptake rate with the aim of improving food safety and human health. METHODS: A hydroponic experiment was conducted using two wheat (Triticum aestivum) cultivars (Hanxuan 10 and Lumai 14) and ten doubled haploid (DH) lines derived from them to investigate Pi and arsenate uptake over 48 h. Ten plants were transferred to bottles containing 50 mL of pre-treatment solution containing 0.5 mM CaCl2 and 5 mM MES set at pH 6.0 with 330 microM Pi as KH2PO4 and 7.33 microM arsenate. The solutions were aerated continuously. At 8, 24 and 48 h after uptake, 1 mL of test solution was sampled for determination of Pi and arsenate concentrations. KEY RESULTS AND CONCLUSIONS: For each wheat line, Pi and arsenate concentrations in the test solution decreased with uptake time. Exponential (for Pi) or polynomial (for arsenate) regression plots fitted the data closely. For all genotypes, net Pi uptake rates decreased with time (from 0 to 48 h). However, net arsenate uptake rates decreased with time for D5, changed little with time for the male parent, D4 and D6, and increased with time for the others. An inflexion of about 25 microm Pi was observed for the relationship between arsenate and Pi concentrations in the test solution, indicating that 25 microm could be the point where the high-affinity uptake system 'switches on', or dominates over low-affinity uptake. In addition, the male parent, D1, D6 and D10 were considered ideal genotypes because they possess Pi transporters that discriminate strongly against arsenate and are expected to accumulate less arsenate in the field.

Arsenate (As) uptake by and distribution in two cultivars of winter wheat (Triticum aestivum L.).

Two cultivars of winter wheat (Triticum aestivum L.) (Jing 411 and Lovrin 10) were used to investigate arsenate (As) uptake and distribution in plants grown in hydroponic culture and in the soil. Results showed that without As addition, Lovrin 10 had higher biomass than Jing 411 in the soil pot experiment; in the hydroponic experiment Lovrin 10 had similar root biomass to and lower shoot biomass than Jing 411. Increasing P supply from 32 to 161 microM resulted in lower tissue As concentrations, and increasing As supply from 0 to 2,000 microM resulted in lower tissue P concentrations. Increasing P supply tended to increase shoot-to-root ratios of As concentrations, and increasing As supply tended to decrease shoot-to-root ratios of As concentrations. Both cultivars invested more in root production under P deficient conditions than under P sufficient conditions. Lovrin 10 invested more biomass production to roots than Jing 411, which might be partly responsible for higher shoot P and As concentrations and higher shoot-to-root ratios of As concentrations. Moreover, Lovrin 10 allocated less As to roots than Jing 411 and the difference disappeared with decreasing P supply.

Arsenate and phosphate interaction in Saccharomyces cerevisiae.

In the present study, arsenate (As(V)) and phosphate (P(V)) interactions were investigated in growth, uptake and RNA content in yeast (Saccharomyces cerevisiae). Yeast grew slowly with As(V) concentrations increasing in the medium. However, the maximal population density was almost the same among different As(V) treatments. It was in the late log phase that yeast growth was augmented by low As(V), which was maybe due to the fact that methionine metabolism was stressed by vitamin B6 deprivation, so As(V) treatments did not affect maximal population density. However, with P (V) concentrations increasing, the maximal population density increased. Therefore, the maximal population density was determined by P (V) concentrations in the medium but not by As (V) concentrations in the medium. Ycfl p(a tonoplast transpor) transports As(GS)3 into the vacuole, but arsenic(As) remaining in the thalli was 1.27% with As(V) exposure for 60 h, from which it can be speculated that the percentage of As transported into vacuole should be lower than 1.27%. However, the percentage of As pumped out of cell was 71.49% with As (V) exposure for 68 h. Although two pathways (extrusion and sequestration) were involved in As detoxification in yeast, the extrusion pathway played a major role in As detoxification. RNA content was the highest in the early-log phase and was reduced by As(V).