| Soil humic substances(HS) is one kind of special pseudo-high molecule compound of soil, which plays important role in adjusting soil fertility. So it is significant for agriculture produce and environmental protection to research HS. HS was divided into three fractions by the traditional method, including humic acid(HA), Fulvic acid(FA) and Humin(HM). Previously, most studies focused on solvable humus fractions(HA and FA), but the study on unsolvable humus faction(HM) was little.In this paper, laboratory simulated method was used to study the influence of different O2 and CO2 concentrations on the mutative regulation of composition and optical property of HM extracted from soil with corn stalk. The treatments of O2 concentrations included 0％, 4-7％, 18-23％and 82-87％; the treatment of CO2 concentrations included＜2％, 8-12％and 48-52％. The time of taking sample was at day 0, 35, 70, 105, 140, 210, 360 and 540 (0-210 days was completed by LiKai), respectively. Firstly, modified humus composition method was adopted to divide HS into Water floating substance(WFS), Water soluble substance (WSS), HA, FA and HM; then, modified Pallo method was used to separate HM to three HM fractions which include Humin linked to iron(HMi), Humin linked to clay(HMc), Indissoluble humin(HMr). At the same time, the character of HMi and HMc was measured by FTIR and DTA.The results of test are as following:(1) After adding certain amount of corn stalk to soil, the amounts of HM were higher than CK, which increased form 54％to 78％. Under different concentrations of gas incubation, high O2 can decrease the amounts of HM; high CO2 can increase the amounts of HM.(2) After adding certain amount of com stalk to soil, the absolute amounts of C in HMi was higher than CK, and it increased from 0.61g.kg-1 to 1.06g.kg-1, increased 73％; Under different concentrations of gas incubation, high O2 can accelerate HMi decomposition, decrease the amounts of HMi; high CO2 can increase the amounts of HMi. The gas concentrations did not play an important role for HMi.(3) After adding certain amount of com stalk to soil, the absolute amounts of HMc was increasing. Under different concentrations of gas incubation, high O2 can decrease the amounts of HMc; high CO2 can increase the amounts of HMi.(4) After adding certain amount of com stalk to soil, HMi/HMc increased from 1.66 to 1.88, increased 13％. With the gas concentrations increased, HMi/HMc increased 20％, it said that, HMc decomposition was faster than HMi. With the gas concentrations increasing, HMi/HMc increased 10％, it said that, the formation rate of HMi was faster than HMc.(5) After adding certain amount of corn stalk to soil, (HMi+HMc)/HM decreased 40％. (HMi+HMc)/HM increased 34％after 360 days.(HMi+HMc)/HM increased 63％after 540 days. It said that, HM changed into solubility with corn stalk breaking down.(6) After adding corn stalk, the absolute carbon of HMr increased from 5.6g.kg-1 to 15.9g.kg-1, nearly 2 times. With prolonging of incubation time, the absolute carbon of HMr increased firstly and then decreased. Under different gas concentrations, high CO2 was beneficial to accumulate the amounts of HMr.(7) After adding certain amount of corn stalk to soil,△logK of HMi and HMc increased 17％and 6％, respectively. At the same time, the molecule structure became simple. Under different gas concentrations, high O2 was beneficial to increase△logK of HMi and HMc, which increased 29％and 12％, respectively. It said that, high O2 can make the molecule structure more simple.(8) By elemental analysis, after adding certain amount of corn stalk to soil, the mole ratio of C/H increased, the treatment of high O2 increased 58％. The condensation of HMi and HMc of paddy soil and Aeolian soil increased, and the structure was becoming complicated. Under different gas concentrations, high O2 and low CO2 were beneficial to decrease the mole ratio of C/H in HMi to paddy soils from 0.57 to 0.44, and decreased 40％, and made the structure of molecule simple; high O2 was beneficial to increase the C/H of HMc to paddy soils, and made the structure of molecule complicated.(9) By DTA analysis, with O2 concentrations increased, decalescence peak in low temperature decreased from 69℃to 32℃, decreased 37℃. The temperature of middling increased 6℃. The loss weight of HMi was main in high temperature region, but the loss weight in middling was little. It said that, the molecule structure of HMi became simplify with O2 concentrations increasing.(10) By IR analysis, the absorption peak intensity became strong with O2 concentrations increasing, which increased from 0.245 to 0.280 in the range of 2920 cm-1--2930 cm-1. The absorption peak intensity of 1630 cm-1 was 0.530, it said that, high O2 increased aliphatic chain of HMc in paddy soil, and decreased the aromaticity of HMc. With CO2 concentrations increased, the absorption peak intensity of 2930 cm-1 decreased, and the absorption peak intensity of 1630 cm-1 increased. It said that, high CO2 makes the amount of aliphatic chain of HMc decreased in paddy soil, and the aromaticity increased. With prolonging of incubation time, the fractions of HM changed gradually. After adding certain amount of corn stalk to soil, the structure of HMi became complicate. High O2 makes the structure of HMi simplified and the structure of HMc complicated. |
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