不同前处理方法对紫色土粒度测试的影响

Influence of Different Pretreatment Methods on the Particle Size Distribution Measurement of Purple Soil

[目的]厘清不同前处理方法对土壤颗粒组成(PSD)测定结果的影响,对土壤水分运移、养分迁移、土壤侵蚀和泥沙搬运过程研究有重要意义。[方法]选择典型紫色土人工林地剖面土壤(0—110 cm)为研究对象,采用浸泡、振荡的物理方式,H_(2)O_(2),HCl处理的化学方式等9种前处理方式,然后用Mastersizer2000激光粒度仪进行颗粒分析。[结果](1)各物理前处理中值粒径较干测(对照)平均减小33.79μm,其中浸泡、振荡2 h、振荡10 h中值粒径依次减小,但其对黏粒的释放作用较弱,不同振荡时间之间黏粒含量无显著差异(p>0.05)。各化学处理中值粒径较对照平均减小32.72μm,其中H_(2)O_(2)处理总体比HCl处理分散作用更强,该处理下黏粒含量为所有处理中最大,平均>4%。(2)各物理前处理方式下,不同土层间颗粒含量总体无显著差异。对不同H_(2)O_(2)用量的敏感性中土层(30—70 cm)>下土层(70—110 cm)>上土层(0—30 cm),其中20—90 cm土层在足量H_(2)O_(2)处理下砂粒含量比10 ml H_(2)O_(2)处理平均增多9.5%,粉粒含量平均减少9.7%;对不同HCl处理的敏感性上,中土层>下土层,其中0—90 cm土层在10 ml HCl+洗酸处理下砂粒含量比10 ml HCl处理平均增多6.2%,粉粒含量平均减少5.4%,黏粒含量则无明显土层分异。(3)足量H_(2)O_(2)处理下砂粒和粉粒含量与剖面有机质含量呈显著线性相关(r>0.8),而HCl处理下剖面碳酸钙含量则与各级颗粒含量无显著相关性。[结论]物理和化学前处理方法之间PSD差异显著,且化学处理中试剂用量不同对PSD有显著影响,研究可为不同研究目的下紫色土颗粒组成分析提供参考。

[Objective]It is of great significance for clarifying the influence of different pretreatment methods on the measurement of soil particle composition(PSD),which is the basis of studies on water transport,nutrient transport,soil erosion and sediment transport processes.Soil particle composition(PSD)is the basis of soil physical properties and has important implications for[Methods]Typical purple soil natural woodland profile soil(0—110 cm)was selected,and 9 pretreatment methods were adopted,including physical methods of soaking and shaking,and chemical methods of H_(2)O_(2) and HCl treatment,and then particle analysis was carried out with a Mastersizer 2000 laser particle size analyzer.[Results](1)The median particle size of each physical pretreatment decreased by 33.79μm on average compared with the direct measurement without any pretreatment(control).The median particle size under pretreatments of soaking,shaking for 2 h,and shaking for 10 h decreased sequentially,but their release effects on clay were weak.There was no significant difference in clay content between different shaking times(p>0.05).The median particle size of each chemical treatment could be reduced by 32.72μm on average compared with control.Among them,the H_(2)O_(2) treatments had a stronger dispersing effect than the HCl treatments,and the clay contents of H_(2)O_(2) treatments were the highest among all treatments,which were greater than 4%.(2)Each physical pretreatment method had a uniform dispersion effect among soil layers.Sensitivity to different H_(2)O_(2) dosage of different layer of soil was middle(30—70 cm)>lower(70—110 cm)>upper(0—30 cm).Specifically,sand content in the 20—90 cm soil layer under sufficient H_(2)O_(2) pretreatment increased by 9.5%and silt content decreased by 9.7%compared with 10 ml H_(2)O_(2) pretreatment.Sensitivity to different HCl pretreatments of different layer of soil was upper and middle>lower,specifically the sand content of the upper and middle soil(0—90 cm)increased by 6.2%on average under the treatment of 10 ml HCl plus acid washing compared with the treatment without acid washing.The silt content reduced by an average of 5.4%.There was no significant difference in clay content among soil layers under these treatments.(3)There was a significant linear correlation(r>0.8)between the content of sand and silt and the content of organic matter in the profile under the treatment of sufficient H_(2)O_(2),but there was no significant correlation between the content of calcium carbonate and any particles under the treatment of HCl.[Conclusion]There are significant differences in PSD between different pretreatment methods,and the amount of reagent in chemical pretreatments affects the PSD obviously,too.This study can provide a reference for the analysis of purple soil particle composition under different research purposes.