盐碱化改良区农田排水沟水体与底泥界面微环境特征分析

深入探究农田排水沟水体与底泥界面微环境对界面间物质交换和迁移转化具有重要意义,为了明确不同水力联系的排水沟界面微环境特征,该研究利用微电极测量系统对陕西卤泊滩盐碱化改良区和盐荒地2种水力条件差异较大的排水沟水体与底泥界面微环境进行了研究.结果表明:改良区与盐荒地排水沟水体水质指标和底泥含水率、有机质、硫酸盐含量等方面均...

Characteristics analysis of micro-environment of sediment-water interface in drainage ditches in reclamation areas

Substance exchange and transfer depend mainly on the micro-environment of the interface between the water body and the underlying sediment in drainage ditches in Reclamation areas.In this study,the sediments were taken separately from two ditches that drain reclaimed and non-reclaimed fields in a salt impacted agricultural area in Shaanxi,China.A laboratory experiment was conducted to monitor physical and chemical properties at the sediment and water body interface using the Unisense micro-electrode system.The system consisted of microelectrode,four-channel host,motor controller,microelectrode thruster,the sensor trace PRO software,and lab support LS18.The tip diameter of Unisense DO microelectrode was 25μm,and the polarization voltage of DO microelectrode was-0.8 V,where the pre-polarization signal value was stable.Five parallel samples were set to separately measure DO values,and the average value was calculated.Each group in experiments was repeated three times.The measurement interval was 100μm,each DO concentration profile was measured for 30 min,and 120 DO profiles were observed.The Uniense H₂S microelectrode was a miniaturized picoamperometric microelectrode with a tip diameter of 25μm and a pre-polarization voltage of+0.08 V,including three electrodes for the measurement,protection,and reference.The pre-polarized signal was corrected after stabilizing.The temperature of the calibration solution was consistent with the test sample,and the calibration test was conducted in the same environment as the measurement.The measurement depth of H₂S profile was limited by the electrode length,where the maximum measurement depth was about 40 mm at 50μm measurement step.The measurement time was about 60 min for each setup of H₂S concentration profiles,and a total of 24 H₂S profiles were observed.The monitoring results showed that the maximum depth of oxygen penetration was 10.2 and 2.6 mm for sediment samples taken from the reclaimed and the non-reclaimed fields,whereas,the diffusion boundary-layer thicknesses were 0.4-0.8 mm and 0.2-0.4 mm,respectively.The observation results showed that the water content in the sediment decreased with the depth of sampling,due mainly to the compaction at the ditch bottom.Specifically,the measured water content ranged from 54%to 78%in the ditches of reclaimed field,and from 73%to 87%in ditch sediment of non-reclaimed field.The Electrical Conductivity(EC)was between 3.64 and 4.12 mS/cm in the ditch of the reclaimed field,while it ranged from 10.74 to 13.22 mS/cm in the ditch sediment of non-reclaimed field.There was a large difference(of 4 times)in EC between the two different sampling sites,indicating the salt accumulation in the drainage ditch from the non-reclaimed fields.The measured DO value remained stable at 8 mg/L for sediments from the ditch of the reclaimed field,while it varied from 3.21 mg/L to 5.44 mg/L in the ditch sediment of the non-reclaimed field.The concentration of hydrogen sulfide in the ditch sediment of reclaimed field less than 10μmol/L,while it was as high as 178μmol/L in the ditch sediment of non-reclaimed field.The findings can provide a sound reference for the design and application of ditches,and thereby to improving the ecological environment of farmland in similar areas.