Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubi...Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubiquitously occur in nature.Humic substances represent the largest stable organic carbon pool in terrestrial environments and are the central characteristic of the soil.However,the validity of the HS concept and the justification of their extraction procedure have been recently debated.Here,we argue that the traditional humic paradigm is still relevant.Humic substances are distinctive and complex because the extracted HS formed during the humification are chemically distinct from their precursors and are heterogeneous among soils.By reviewing the concept,formation pathways,and stabilization of HS,we propose that the key question facing soil scientists is whether HS are soil microbial residues or unique synthesized compounds.Without revealing the distinctiveness of HS,it is impossible to address this question,as the structure,composition,and reactivity of HS are still poorly known owing to the heterogeneity and geographical variability of HS and the limits of the currently available analytical techniques.In our view,the distinctiveness of HS is fundamental to the soil,and thus further studies should be focused on revealing the distinctiveness of HS and explaining why HS hold this distinctiveness.展开更多
Biogas slurry is not suitable for liquid fertilizer due to its high amounts of volatile materials being of complicated composition and peculiar smell. In order to remove volatiles from biogas slurry efficiently, the d...Biogas slurry is not suitable for liquid fertilizer due to its high amounts of volatile materials being of complicated composition and peculiar smell. In order to remove volatiles from biogas slurry efficiently, the dynamic headspace and gas chromatography-mass spectrometry were used to clear the composition of volatiles. Nitrogen stripping and superfluous ozone were also used to remove volatiles from biogas slurry. The results showed that there were 21 kinds of volatile compounds in the biogas slurry, including sulfur compounds, organic amines, benzene, halogen generation of hydrocarbons and alkanes, some of which had strong peculiar smell. The volatile compounds in biogas slurry can be removed with the rate of 53.0% by nitrogen stripping and with rate of 81.7% by the oxidization and stripping of the superfluous ozone. On this basis, the removal rate of the volatile compounds reached 99.2% by chloroform and n-hexane extraction, and almost all of odor was eliminated. The contents of some dissolved organic compounds decreased obviously and however main plant nutrients had no significant change in the biogas slurry after being treated.展开更多
Corn straw is an important source of carbon(C),and when applied to soil,it alters the accumulation and distribution of organic C.However,the mechanistic pathways by which newly added C is stored and stabilized in soil...Corn straw is an important source of carbon(C),and when applied to soil,it alters the accumulation and distribution of organic C.However,the mechanistic pathways by which newly added C is stored and stabilized in soil remain a subject of interest and debate among scholars.In this study,we investigated the chemistry of organic matter in different density fractions of Haplic Cambisol(sandy clay loam)in a field experiment with corn straw at8900 kg ha^(-1)year^(-1)under no tillage(NT),minimum tillage(MT),and conventional tillage(CT).After five years of corn(Zea mays L.)monocropping,soils were collected from the 0-20 and 20-40 cm depths and processed to obtain the organic matter in light fraction(LFOM),occluded particulate(oPOM),and heavy fraction(HFOM)in the order.The results showed that compared with conventional tillage without corn straw return(CT0),corn straw return(i.e.,NT,MT,and CT)increased soil organic C content by 11.55%-16.58%.Thermogravimetric and Fourier transform infrared analyses demonstrated that the HFOM was characterized by a greater proportion of easily biodegradable substances,which may be due to the deposition of microbially processed materials on the surface of soil minerals.The LFOM and o POM were distinguished by greater phenolic,aromatic C,and thermally stable compounds.Compared with CT0,the NT and MT fields showed higher abundances of hydrophobic,aliphatic,and thermally unstable organic compounds,which increased soil C content and stability in the HFOM.Therefore,NT and MT may be ideal practices to increase soil organic C content.展开更多
Soil organic matter(SOM)is crucial for ecosystem carbon cycling,soil fertility,and environmental quality.As the main component of SOM,humic substances(HS)are considered a unique category of nonuniformly assembled subs...Soil organic matter(SOM)is crucial for ecosystem carbon cycling,soil fertility,and environmental quality.As the main component of SOM,humic substances(HS)are considered a unique category of nonuniformly assembled substances.展开更多
Nitrogen(N)deposition has a profound influence on forest soil carbon(C)and N pools,but there was no consensus on the responses of different C and N components in different forest types.In this study,a two-year simulat...Nitrogen(N)deposition has a profound influence on forest soil carbon(C)and N pools,but there was no consensus on the responses of different C and N components in different forest types.In this study,a two-year simulated N deposition experiment with four levels of N(NH4NO3)-addition treatments(0,50,100,and 150 kg N/hm^(2)·a)were conducted in Larix gmelinii(LG)and Quercus mongolica(QM)plantation in Northeast China,in order to investigate the C and N pool dynamics under continuously enhanced N deposition.Soil organic carbon(SOC),soil total N(STN)and their active components(readily oxidizable C,ROC;dissolved organic C,DOC;microbial biomass C,MBC,dissolved organic N,DON;microbial biomass N,MBN)of the forest soil were measured monthly from May to October 2017.C and N contents in LG were observed higher than in QM.N addition had no effect on SOC and STN of LG,but significantly increased SOC and STN of QM at low N addition level.Low N addition generally raised active C components(ROC,DOC,and MBC)in both plantations,whereas high N addition did not significantly affect these components,or even decreased ROC in LG soil.Low N addition also increased STN and MBN of QM,while no significant change in STN and MBN of LG was observed.DON was directly affected by N addition and increased significantly with elevated N addition levels.The results indicated that N addition,especially of low rate,might enhance the C sequestration capacity of the forest soils and mitigate climate change.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41571231 and 41201221)the National Key Research and Development Program of China(No.2016YFD0200304)+3 种基金the Scientific Instrument and Equipment Development Project of Chinese Academy Sciences(CAS)(No.YJKYYQ20170058)the Natural Science Foundation of Jiangsu Province,China(No.BK2012496)the Youth Innovation Promotion Association,CAS(No.2017362)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB180010)。
文摘Humic substances(HS),which are defined as a series of highly acidic,relatively high-molecular-weight,and yellow to black colored substances formed during the decay and transformation of plant and microbial remains,ubiquitously occur in nature.Humic substances represent the largest stable organic carbon pool in terrestrial environments and are the central characteristic of the soil.However,the validity of the HS concept and the justification of their extraction procedure have been recently debated.Here,we argue that the traditional humic paradigm is still relevant.Humic substances are distinctive and complex because the extracted HS formed during the humification are chemically distinct from their precursors and are heterogeneous among soils.By reviewing the concept,formation pathways,and stabilization of HS,we propose that the key question facing soil scientists is whether HS are soil microbial residues or unique synthesized compounds.Without revealing the distinctiveness of HS,it is impossible to address this question,as the structure,composition,and reactivity of HS are still poorly known owing to the heterogeneity and geographical variability of HS and the limits of the currently available analytical techniques.In our view,the distinctiveness of HS is fundamental to the soil,and thus further studies should be focused on revealing the distinctiveness of HS and explaining why HS hold this distinctiveness.
基金supported by the National Basic Research Program (973) of China (No. 2011CB100503)the National Natural Science Foundation of China (No. 40971141)the Science and Technology Development Project of Jilin Province (No. 201105012)
文摘Biogas slurry is not suitable for liquid fertilizer due to its high amounts of volatile materials being of complicated composition and peculiar smell. In order to remove volatiles from biogas slurry efficiently, the dynamic headspace and gas chromatography-mass spectrometry were used to clear the composition of volatiles. Nitrogen stripping and superfluous ozone were also used to remove volatiles from biogas slurry. The results showed that there were 21 kinds of volatile compounds in the biogas slurry, including sulfur compounds, organic amines, benzene, halogen generation of hydrocarbons and alkanes, some of which had strong peculiar smell. The volatile compounds in biogas slurry can be removed with the rate of 53.0% by nitrogen stripping and with rate of 81.7% by the oxidization and stripping of the superfluous ozone. On this basis, the removal rate of the volatile compounds reached 99.2% by chloroform and n-hexane extraction, and almost all of odor was eliminated. The contents of some dissolved organic compounds decreased obviously and however main plant nutrients had no significant change in the biogas slurry after being treated.
基金supported by the National Natural Science Foundation of China(No.42077022)the Provincial Key Research and Development Program of Jilin,China(No.20200402098NC)。
文摘Corn straw is an important source of carbon(C),and when applied to soil,it alters the accumulation and distribution of organic C.However,the mechanistic pathways by which newly added C is stored and stabilized in soil remain a subject of interest and debate among scholars.In this study,we investigated the chemistry of organic matter in different density fractions of Haplic Cambisol(sandy clay loam)in a field experiment with corn straw at8900 kg ha^(-1)year^(-1)under no tillage(NT),minimum tillage(MT),and conventional tillage(CT).After five years of corn(Zea mays L.)monocropping,soils were collected from the 0-20 and 20-40 cm depths and processed to obtain the organic matter in light fraction(LFOM),occluded particulate(oPOM),and heavy fraction(HFOM)in the order.The results showed that compared with conventional tillage without corn straw return(CT0),corn straw return(i.e.,NT,MT,and CT)increased soil organic C content by 11.55%-16.58%.Thermogravimetric and Fourier transform infrared analyses demonstrated that the HFOM was characterized by a greater proportion of easily biodegradable substances,which may be due to the deposition of microbially processed materials on the surface of soil minerals.The LFOM and o POM were distinguished by greater phenolic,aromatic C,and thermally stable compounds.Compared with CT0,the NT and MT fields showed higher abundances of hydrophobic,aliphatic,and thermally unstable organic compounds,which increased soil C content and stability in the HFOM.Therefore,NT and MT may be ideal practices to increase soil organic C content.
基金financial support from the National Key Research and Development Program of China(No.2022YFD1500304)the Postdoctoral Fellowship Program of CPSF,China(No.GZC20232641)the Postdoctoral Science Foundation of China(No.2024M753215)。
文摘Soil organic matter(SOM)is crucial for ecosystem carbon cycling,soil fertility,and environmental quality.As the main component of SOM,humic substances(HS)are considered a unique category of nonuniformly assembled substances.
基金This work was supported by the National Key Research and Development Program of China(grant No.2016YFD0200304,2017YFC0504205).
文摘Nitrogen(N)deposition has a profound influence on forest soil carbon(C)and N pools,but there was no consensus on the responses of different C and N components in different forest types.In this study,a two-year simulated N deposition experiment with four levels of N(NH4NO3)-addition treatments(0,50,100,and 150 kg N/hm^(2)·a)were conducted in Larix gmelinii(LG)and Quercus mongolica(QM)plantation in Northeast China,in order to investigate the C and N pool dynamics under continuously enhanced N deposition.Soil organic carbon(SOC),soil total N(STN)and their active components(readily oxidizable C,ROC;dissolved organic C,DOC;microbial biomass C,MBC,dissolved organic N,DON;microbial biomass N,MBN)of the forest soil were measured monthly from May to October 2017.C and N contents in LG were observed higher than in QM.N addition had no effect on SOC and STN of LG,but significantly increased SOC and STN of QM at low N addition level.Low N addition generally raised active C components(ROC,DOC,and MBC)in both plantations,whereas high N addition did not significantly affect these components,or even decreased ROC in LG soil.Low N addition also increased STN and MBN of QM,while no significant change in STN and MBN of LG was observed.DON was directly affected by N addition and increased significantly with elevated N addition levels.The results indicated that N addition,especially of low rate,might enhance the C sequestration capacity of the forest soils and mitigate climate change.
