[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.

[Effects of conservation tillage measures on soil water and NO3--N leaching in dryland maize cropland]. / 保护性耕作措施对旱地春玉米土壤水分和硝态氮淋溶累积的影响.

Based on a field experiment on conservation tillage over 15 years in Weibei Highland maize cropland, six conservation tillage patterns, i.e., conventional tillage (CT), no-tillage (NT), no-tillage plus biochar (NB), no-tillage and straw mulching (NS), no-tillage and plastic film mulching (NF), and no-tillage and straw-plastic film mulching (NSF), were investigated for their effects on soil water and nitrate nitrogen(NO3--N) leaching, to seek sustainable agricultural cultivation measures suitable for the region. Results showed that, compared with NT treatment in the first water recharge period, CT had no effect on water recharge in 0-100 cm soil layer, and NS, NB, NSF and NF significantly reduced soil water recharge. In 100-300 cm soil layer, NS, NB, NF and NSF significantly increased soil water recharge, but CT significantly reduced soil water recharge. During the second water recharge period, water recharge depth was mainly concentrated in 0-100 cm soil layer, and there was no significant difference between each treatment and NT. During the water depletion period, compared with NT treatment, other treatments had no significant effect on water depletion in 0-100 cm soil layer, but NF and NSF increased soil water depletion by 33.9% and 59.9% in 100-300 cm soil layer, respectively. In 0-200 cm soil layer, compared to NT, CT significantly increased the accumulation of NO3--N by 2.2 fold, NS, NB, NF and NSF reduced soil NO3--N accumulation by 44.6%, 61.5%, 69.2% and 69.8%, respectively. In 200-300 cm soil layer, NS significantly reduced the accumulation amount of NO3--N, but CT had no significant effect on the accumulation amount of NO3--N, and NS, NB, and NSF all had negative effects on NO3--N accumulation. Soil water movement had significant effect on the distribution of NO3--N in soil profile. Soil NO3--N was mainly distributed in 0-40 cm soil layer for NB, NF and NSF treatments, in 0-100 cm and 200-300 cm soil layers for NS treatment, and over the entire profile for NT and CT, and NS, NT and CT treatments had two NO3--N accumulation peaks in soil profile. Different agricultural cultivation measures could reduce soil NO3--N leaching by regulating soil water content, and subsequently improve nitrogen utilization efficiency. Among those measures, NSF could effectively control soil water movement to reduce the NO3--N leaching and accumulation, and thus is a feasible measure to improve soil water and fertility conditions and increase dryland maize yields.

High symmetry superoctahedron cluster [Mn(III)18O14]26+ from the use of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine.

The use of flexible N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine has provided one new high symmetry superoctahedron with unprecedented aesthetically-pleasing Mn(III)18 clusters, which exhibits out-of-phase signals indicative of the slow magnetic relaxation.