Effect of Temperature, pH and Salt on Fluorescent Quality of Water Extractable Organic Matter in Black Soil

Water erosion is the major reason for the loss of soil organic carbon in the Northeast China, which leads to the soil quality deterioration and adjacent water pollution. In this study, the effect of extraction temperature, pH value, and salt on the water extractable organic matter （WEOM） was determined by means of the UV absorbance, fluorescence excitation-emission matrix, and derived fluorescence indexes. In general, the carbon content and aromaticity of WEOM increased with the increasing of extraction temperature, with the exception that there was no significant difference in the amount at 0 and 20℃. More fluorophores, especially microbially-derived organic matter were extracted at high temperature. The pH values of extractant, including 5, 7, and 10, showed no effect on the carbon amount of WEOM, whereas the aromaticity and microbially-derived component gradually increased with the increasing of pH values. The fluorescence intensity of humic acid-like fluorophore was stronger in neutral and alkali condition than that in acidic condition. The addition of 10 mmol L-1 CaCl2 significantly decreased the carbon amount of recovered WEOM. Moreover, it significantly decreased the aromaticity of WEOM and the quantity of fulvic acid-like and humic acid-like fluorophores, whereas increased the percentage of tyrosine-like and tryptophan-like fluorophores in the total fluorophores and the amount of microbially-derived organic matter. Generally, 10 mmol L-1 KCl showed the same influence trend, but with low influence degree.

Organic matter and pH affect the analysis efficiency of (31)P-NMR

Solution ^（31）P nuclear magnetic resonance spectroscopy（ ^（31）P-NMR） is a useful method to analyze organic phosphorus（Po）, but a general procedure for the analysis method is lacking.The authors used solution ^（31）P-NMR, which was found to be an effective method for analysis of Po in Haihe River sediment, to analyze the Po in the surface sediment in Eastern China at the regional scale, and found that the Na OH-ethylenediaminetetraacetic acid（EDTA）extraction rate was affected by environmental factors. At the regional scale, the extraction rate showed a positive relationship with loss on ignition, when the extraction rate was lower than 60%. The extraction rate had no relationship with the loss on ignition when the extraction rate was higher than 60%. The extraction rate showed a negative relationship with p H, which means that the extraction rate was higher in acidic sediment and lower in alkaline sediment. The ratio of TC/TN（the ratio of total carbon to total nitrogen） was considered to represent the origin of organic matter in the sediment. The extraction rate was high when the TC/TN ratio was lower than 20, meanwhile the extraction rate decreased as the TC/TN ratio increased. The results show that the origin of organic matter in sediment significantly affects the Na OH-EDTA extraction rate. This study will give theoretical support for building an effective and general solution ^（31）P-NMR analysis method.

Influencing factors and significance of organic and inorganic nitrogen isotopic compositions in lacustrine sedimentary rocks

Comprehensive nitrogen biogeochemical cycle has been reconstructed for representative lacustrine organic-rich sedimentary rock in China,namely the Triassic Yanchang Formation(YF,199–230 Ma)in Ordos and the Cretaceous Qingshankou Formation(QF,86–92 Ma)in Songliao basins,by evaluating the organic and inorganic nitrogen isotopic compositions rather than only organic or bulk nitrogen isotopic compositions.The results indicate that the nitrogen isotope values of bulk rock(δ^(15)N_(bulk))in the non-metamorphic stage are significantly different from that of kerogen,which challenge the conceptual framework of sedimentary nitrogen isotope interpretation.Theδ^(15)N_(bulk)from the YF and QF were lower than their respective the nitrogen isotope values of kerogen(δ^(15)N_(ker)),with offsets up to5.1‰,which have the inverse relationship for the metamorphosed rock.Thermal evolution did not significantly modify the d15N of bulk rock and kerogen.The d15N of sediments from the YF(δ^(15)N_(bulk),1.6‰–5.6‰)were lower than that of rock from the QF(δ^(15)N_(bulk),10.2‰–15.3‰).The nitrogen isotope values of silicate incorporated nitrogen(δ^(15)N_(sil))were slightly lower than those of the d15Nker in the YF and obviously lower for the QF.The fact that different nitrogen cycles occur in the YF and QF due to the different depositional redox conditions leads to different isotopic results.The YF water environment dominated by oxic conditions is not conducive to the occurrence of denitrification and anammox,and no abundant N2 loss leads to the relatively lightδ^(15)N_(bulk).In the stratified water for the QF,redox transition zone promotes denitrification and anammox,resulting in the heavyδ^(15)N_(bulk)of rock and promotes the DNRA,resulting in heavyδ^(15)N_(ker)and lowδ^(15)N_(sil).

Aromatic Moieties from Matured Chicken Manure and Agriculture Residues Compost Suppress Growth of Lepidium sativum L. and Trichoderma harzianum

To better understand the role of organic matter(OM)prepared from chicken manure and agriculture residues compost on the growth of plants(Lepidium sativum L.)and antagonistic fungi(Trichoderma harzianum),we analyzed the structure and composition of extracted OM using fluorescence excitation-emission matrix(EEM)spectroscopy and solid-state13C cross-polarization magic-anglespinning nuclear magnetic resonance(13C CPMAS NMR)spectroscopy.The results showed that the EEM contours of water-extracted OM(WEOM)and alkali-extracted OM(AEOM)were similar.Furthermore,solid-state13C CPMAS NMR spectroscopy demonstrated that water extraction could not proportionally pull out aromatic moieties(112–145 ppm)from compost,but the alkali method in proportion extracted both carbohydrates(65–85 ppm)and aromatic moieties.The results suggest that AEOM may better reflect the bulk OM composition of compost,and one should be cautious when applying WEOM as an alternative indicator of total compost OM.Further investigations demonstrated that,compared to carbohydrates,aromatic moieties played a predominant role in growth suppression of Lepidium sativum L.seeds and Trichoderma harzianum.