Fertilization intensities at the buffer zones of ponds regulate nitrogen and phosphorus pollution in an agricultural watershed.

The sudden increase in water nutrients caused by environmental factors have always been a focus of attention for ecologists. Fertilizer inputs with spatio-temporal characteristics are the main contributors to water pollution in agricultural watersheds. However, there are few studies on the thresholds of nitrogen (N) and phosphorus (P) fertilization rates that affect the abrupt deterioration of water quality. This study aims to investigate 28 ponds in Central China in 2019 to reveal the relationships of basal and topdressing fertilization intensities in surrounding agricultural land with pond water N and P concentrations, including total N (TN), nitrate (NO3--N), ammonium (NH4+-N), total P (TP), and dissolved P (DP). Abrupt change analysis was used to determine the thresholds of fertilization intensities causing sharp increases in the pond water N and P concentrations. Generally, the observed pond water N and P concentrations during the high-runoff period were higher than those during the low-runoff period. The TN, NO3--N, TP, DP concentrations showed stronger positive correlations with topdressing intensities, while the NH4+-N concentrations exhibited a higher positive correlation with basal intensities. On the other hand, the NO3--N concentrations had a significant positive correlation with the topdressing N, basal N, and catchment slope interactions. Significant negative correlations were observed between all water quality parameters and pond area. Spatial scale analysis indicated that fertilization practices at the 50 m and 100 m buffer zone scales exhibited greater independent effects on the variations in the N and P concentrations than those at the catchment scale. The thresholds analysis results of fertilization intensities indicated that pond water N concentrations increased sharply when topdressing and basal N intensities exceeded 163 and 115 kg/ha at the 100 and 50 m buffer zone scales, respectively. Similarly, pond water P concentrations rose significantly when topdressing and basal P intensities exceeded 117 and 78 kg/ha at the 50 m buffer zone scale, respectively. These findings suggest that fertilization management should incorporate thresholds and spatio-temporal scales to effectively mitigate pond water pollution.

[Census of pesticide residues and suggestions for control in traditional Chinese medicine].

In our study, 198 types of pesticides in 120 types 333 lots of traditional Chinese medicine (TCM), which were reasonably classified according to its matrix property, were determined by using the pretreatment platform and gas chromatography-mass spectrometry method. As a result, 158 were contaminated with pesticides. However, the content of pesticides in most TCM was very low. In addition, types of pesticides were different in different part of materia medica. In conclusion, the current status of pesticide residues pollutants in TCM was summarized, and the result can provide proof for the formulation of maximum residue limit. The new species of herbs and the new detecting index should be electively monitored in Chinese Pharmacopeia.

[Purification of EGCG monomer from the extracts of tea by high speed countercurrent chromatography].

OBJECTIVE: To investigate the feasibility and techniques for purifying epigallocatechin-3-gallate (EGCG) by high speed countercurrent chromatography (HSCCC). METHODS: A HSCCC unit was used for the purification of EGCG from the extracts of tea. RESULTS: The preferable solvent system was composed of Ether-Ethyl Acetate-H2O (4:10: 25, V/V), and the preferable technical conditions were as follows: the temperature was 35 degrees C, the rotation speed was 800 r/min and the mobile phase flow-rate was 2.5 mL/min. CONCLUSION: The purity of the obtained EGCG sample determined by high performance liquid chromatography (HPLC) is 95%.

[Study on isolation of Chlorogenic acid from Eucommia ulmoides leaves by ultrafiltration technique].

OBJECTIVE: To isolate and purify Chlorogenic acid from Eucommia ulmoides leaves by ultrafiltration technique. METHODS: Chlorogenic acid transferring ratio was investigated by temperature, pressure, time, cut-off molecular mass. RESULTS: The optimal conditions for the ultrafiltration technique were finally determined. It was found that, for the membrane with a cut-off molecular mass of 20000, when the temperature, pressure, time were respectively 40 degrees C, 0.36 MPa, 20 minutes and adding 24L water, yield of Chlorogenic acid was 99.38%. CONCLUSION: High Chlorogenic acid transfering ratio can be gotten by ultrafiltration technique, which is helpful to the further isolation and purification of Chlorogenic acid in the subsequent process.