Effects Of Cadium And Petroleum Contamination On The Quantity And Structural Characteristics Of Soil Humus

The purpose of this study on Cd and petroleum-contaminated soil under the conditions of the number of humus and structural characteristics were studied,mainly divided into two parts,the first through the indoor cultivation experiments on the effects of Cd,corn stalk in the soil decomposition and transformation law.The results show that:Adding Cd,and the decomposition of organic materials and Cd into the dosage. Experimental results are as follows:(1)In the topsoil,adding Cd after inhibited decomposition of soil organic carbon,and the promotion of water-soluble organic matter(WSS) and humic(HM) generation.When adding a lower concentration of Cd (50 mg/ kg) after promoting humic acid(HA) and fulvic acid(FA) generated,but when the concentration of Cd,promoting role gradually weakened.However,the addition of low concentration(50 mg / kg) of Cd after more conducive fulvic acid(FA) generation,but with the increasing concentration of Cd is more conducive to humic acid(HA) production.In the subsoil,add a lower concentration(50 mg / kg) of Cd inhibited decomposition of organic carbon in soil,and promote the humic acid(HA),fulvic acid(FA) and humic-(HM) generation.But with the increasing concentration of Cd,promote the decomposition of organic carbon in the soil,inhibiting the humic acid(HA), fulvic acid(FA) and humic-(HM) generation.And when added to soil at the end of Cd after more conducive fulvic acid(FA) formation,on the contrary,inhibited the formation of the HA.But water-soluble organic matters(WSS),after the addition of Cd promote its formation.(2) In the topsoil,add a lower concentration(50 mg / kg) of Cd can be made of water soluble(WSS),humic acid(HA) and fulvic acid(FA) of the molecular structure of simple,but with Cd concentration of molecular structure gradually change the complex.And a lower concentration(50 mg/ kg) of the Cd will humic acid (HA) and fulvic acid(FA) in the aliphatic carbon content increased,while the increase in Cd concentration of carbon content to aliphatic carbon and aromatic carbon gradually reduce the carbon content gradually increase.In the subsoil,after adding Cd,may cause water-soluble(WSS) and the fulvic acid(FA) the structure becomes complex,and along with the Cd density increases,then makes the molecular structure to be more complex.After adding Cd,also causes the fulvic acid(FA) the aliphatic carbon content to reduce gradually, the aromatic carbon content gradually increases.However,when after increasing Cd,may cause the humic acid(HA) the structure increases along with the Cd density becomes gradually simplifies,and makes the humic acid(HA) the aliphatic carbon content to increase along with the Cd density increases,but the aromatic carbon content gradually reduces. This study is the second part of long-term oil-contaminated soil humus composition and structural character -ristics of humic acid research.Petroleum hydrocarbon-contamination in soil decreases with increase in the dis -tance of soil to the drilling well.Accordingly,an abandoned petroleum well which had been exploited for abo -ut twenty years in Songyuan city of Jilin Province,China,was selected to study the compositions and charact -eristics of soil humus using revised humus composition method and Simon-Kumada method.Soil samples w -ere collected at 0.5,1.5,2.5,3.5,4.5,5.5,6.5,7.5 and 10.5m apart from the well head.Experimental results a -re as follows:(1) Results show that the petroleum contents increase from 0.08g/kg(10.5m to the well head) to 153.3g/kg (0.5m to the well head).With the increase in petroleum content,the contents of soil organic carbon and water soluble organic carbon increase;for total soil humus,the contents of extractable humus(HE) and humic acid (HA) decrease whereas that of humin(HM) increase;the percentage of HA/HE(PQ)(72.0%～8.05%) decree -se and HM/HE ratio(31.4～76.7) increase;for different combined humus,the contents of loosely combined humus(HⅠ) and stably combined humus(HⅡ) have a decrease tendency while that of tightly combined humus (HⅢ) increase;the HⅠ/HⅡratio(0.19～0.39) show an increase tendency,whereas HⅠ/HⅢratio(0.032～0.003) and HⅡ/HⅢratio(0.096～0.009) decrease;the PQs of HⅠ(3.21%～1.42%) and HⅢ(58.1%～35.5%) also decrease,and the range of PQ change is less in HⅠthan in HⅡ;the color coefficient(Δlogk) of water solu -ble organic matter(WSOM) decreases,whereas no obvious change for HA.The above results indicate that petroleum hydrocarbon promotes the formation of HM but not HA.The decrease in HA is mainly due to the restraining effect of petroleum hydrocarbon on the formation of stably combined HA.Petroleum hydrocarbon leads molecular structure of WSOM more complex but no effect on molecular structure of HA.(2) An abandoned petroleum well which had been exploited for about twenty years in Songyuan city of Jilin Province,China,was selected to investigate the structural characteristics of soil humic acids(HAs) using elem -ental analysis,Fourier transformed infrared spectroscopy(FTIR),differential thermal-thermogravimetric anal -ysis(DTA-TGA),solid-state(13)^C CPMAS nuclear magnetic resonance(NMR).With the decrease in the dista -nce of soil from well head,the atomic C/H,O/C and(N+O)/C ratio of HAs increased;the relative intensity at 2921cm^-1,2851cm^-1,1454cm^-1 from the FTIR spectra of HAs decreased;the reaction heat and weight loss at lower and higher temperature exothermic peaks from the DTA-TGA of HAs increased;the content of alkyl C decreased while that of O-alkyl C,aromatic C and carboxyl C increased in the(13)^C CPMAS NMR.These results showed that aliphaticity and hydrophobicity of HA decreased while aromaticity and polarity increased with increase in petroleum content.HA tended to become aged in structure.Thus,it is imperative to renew and activate the aged HAs by adopting appropriate measures for the remediation of petroleum-contaminated soil.