Abstract:Based on analysis of the variation of ²¹⁰Pb_ex inventory in soil of cultivated land in response to changes in soil erosion rate, mistakes in calculation of soil erosion rate of cultivated land using the ²¹⁰Pb_ex method are discussed. A model is established to fit response of ²¹⁰Pb_ex inventory to variation of soil erosion rate in soil of cultivated land, based on the principle of mass balance, demonstrating that the long-commonly-held assumption that what is determined with the ¹³⁷Cs method is the mean soil erosion rate of the past 40 a or 50 a and with the ²¹⁰Pb_ex method the mean of a longer past of 100 a or 200 a is incorrect. The model is used to fit response of ²¹⁰Pb_ex inventory to the variation of soil erosion rate from 0.06 cm a^-1 to 0.6 cm a^-1 and from 0.6 cm a^-1 to 0.06 cm a^-1. The results indicate that ²¹⁰Pb_ex inventory responds quickly, which rises or reduce exponentially with time, but negatively with soil erosion rate. Consequently, ²¹⁰Pb_ex can replace ¹³⁷Cs in determining soil erosion rate in cultivated land not only 100 years old, but also just a few years old due to change in land use.

Abstract:Soil samples were collected from the north of Taipusiqi County，Inner Mongolia for lab analysis to explore content and distribution of ¹³⁷Cs in surface soils different in land use (grassland，cropland and nabkha). Results show that in the soil layers 0~30 cm in depth, the activity of ¹³⁷Cs averaged 4.97±0.31 Bq kg^-1, following an order of Grassland>cropland>nabkha, and its content 2 149±133.8 Bq m^-2, following an order of nabkha>Grassland>cropland; The variance coefficients of ¹³⁷Cs activity and content were 146.1% and 142.1%, respectively, in nabkha, 63.90% and 74.67%, in grassland and 62.98% and 55.61% in cropland. The distribution of ¹³⁷Cs in soil profiles at a typical sampling site showed that it accorded with that of the erosion-sediment profile in nabkha, fitted negative exponential in grassland and was relatively wellproportioned in cropland.

Abstract:It is a frontier in the field of soil erosion control and soil-water conservation to establish a model of extensive applicability for prediction of soil erosion and sediment yield on a watershed scale. With Chabagou Watershed of the Loess Plateau as a case for study, an artificial neural network model was established for sediment yield; analysis was done of various factors for their sensitivities to sediment yielding with the default factor method; and then based upon sensitiveness factors and fractal information dimension, a piecewise prediction model for erosion and sediment yield of individual rainfall events was established and verified. Results show that the artificial neural network model demonstrated capability of describing quantitatively the coupling relationship between runoff and sediment with sufficient high accuracy. The sensitivity of sediment yielding of individual rainfall events to runoff depth and runoff erosion power is related to complexity of the landform. With fractal information dimension as boundary, runoff depth and runoff erosion power were introduced piecewise into the prediction model. The prediction based on runoff erosion power was higher than that based on runoff depth in accuracy, when D_i＞0.8308, and it was the other way round when D_i＜0.8140. The findings demonstrate that the establishment of the piecewise prediction model and the proposition of the method for prediction of erosion and sediment yield are reasonable and reliable, and of some value as reference for establishment of other models for prediction of erosion and sediment yield.

Abstract:Effects of soil bulk density on soil water-holding capacity were explored through simulated experiments designed to have soils different in soil texture by artificially altering composition of soil particle fractions. (1) Water holding capacity and specific water capacity of the experimental soils decreased along with increasing soil bulk density. (2) Soil saturated water content, field moisture capacity and wilting coefficient showed the same trend, and negative correlation of power, exponent and exponential function, respectively, with soil bulk density. (3)Soil available water, readily available water and slowly available water contents were also significantly affected. The three water parameters decreased along with increasing soil bulk density, too, showing negative correlation of exponential, power and logarithmic function, respectively, with soil bulk density.

Abstract:Field-scale bioremediation of oily sludge on prepared beds was studied at the Shengli Oilfield in North China. Effects of addition of manure or soil conditioners (coarse sand and sawdust), inoculation of hydrocarbon degrading bacteria, and setting up greenhouses on oil and grease removal rate were evaluated. After 230 days of bioremediation, oil and grease content fell by 31.5~41.8 g kg^-1 dry sludge in treated plots, indicating a removal rate ranging from of 27.5% to 46.3% compared with that in the control plot, being only 15.1%. Addition of manure or soil conditioners and setting up of greenhouses significantly increased the removal rate (p < 0.05）. Moreover, the physic-chemical properties of the sludge in all treatment plots improved significantly after bioremediation. Microbial biomass in sludge and community-level physiological profiling (CLPP） analyzed using BIOLOG microplates were also studied. Total petroleum hydrocarbon（TPH）degraders and polycyclic aromatic hydrocarbon (PAH) degraders increased in all treated oily sludge. The activity of sludge microbial communities, characterized by average well color development (AWCD) value and Shannon diversity index, increased markedly in the treatment plots compared with that in the control.

Abstract:Based on data collected from literatures on cropland contamination of China, relationship between cadmium contents in soil and in crops was explored and human health risk of cadmium through soil-crop-human pathway analyzed. The data used in this paper partly come from published data in the last 3 decades in China and unpublished data in our own laboratory. The data for model parameterization were distinguished between field studies and salt-added pot experiments. Uptake factors and single-variable regression models were developed based on soil Cd content and used to predict cadmium content in edible parts of rice, wheat and vegetables, while multiple regression models based on soil Cd content and soil pH were to predict Cd content in those parts. Results show that the regression models are much better than the median of the uptake factors in predicting Cd content in those parts. Generally, the upper 95% prediction intervals of regression models provided a better conservative prediction than the 90 percentile uptake factors did. Soil pH as a variable generally contributed significantly to model fit. The main factors which restricted model development and model predictive utility were uneven distribution and inadequacy of data. Finally, soil environmental benchmarks of Cd content in agricultural land were derived by applying multiple-regression model based on Cd content limits for crops as human food.

Abstract:Contents and geochemical fractionation of rear earth elements (REE) in soil both have important impacts on distribution，migration，transformation and fate of the REE in the environment. The surface functions of iron/manganese oxide minerals on elements have been thought to be one of the important mechanisms of activation，migration and pollution of the elements in the biotic and abiotic environment. Typical soil profiles of paddy soil and Chao soil were selected in the Yangtze River Delta region and the Pearl River Delta region，representing the northern tip and southern tip of the sub-tropical zone in China，respectively，for analysis of effects of iron/manganese oxides on contents and geochemical fractionation of REEs. Results show that among the iron/manganese oxides，crystalline iron oxides bind REEs in the soils，which is more significant in Chao soil than in paddy soil.Free iron oxides in paddy soil have a positive effect on accumulation of Ce and depletion of Eu，while manganese oxides reduce the extent of Eu deficiency probably through oxidation of Eu from bivalent cation to trivalent cation. Moreover，the content of iron/manganese oxides also affect REE fractionation in the soil profiles，that is，the lower the content of iron/manganese oxides，the bigger the difference of REE fractionation between soil layers.In paddy soils high in free iron，in the southern subtropical zone，Eu is readily reduced and leached with Sr from the soils，which is contrary to the paddy soils in the northern subtropical zone.

Abstract:A microcosmic experiment was set to investigate effects of controlling measures like adding carbon sources，plowing and mulching，on bioremediation of polychlorinated biphenyls (PCBs) polluted soils and changes in soil microbial ecology. Results showed that soil stirring was the most effective method，being 29.3% in depletion rate，and adding starch and mulching with plastic film came the next，similar in effect to each other，PCBs degradation was significantly enhanced in all these treatments. Compared to the control，the treatments of addition of starch and cultivation of soil showed much higher density of soil microbiology，but lower-utilization ability of communities for carbon(AWCD) and lower functional diversity. In the treatment of mulching，the density of soil microbiology，the utilization ability of communities for carbon and the functional diversity all decreased. The results indicate that the controlling measures could not only influence the depletion rate of PCBs，but also alter the structure and affect activity and function of the soil microorganism.

Abstract:Chemical forms and availabilities of soil Cu，Ni，Pb and Zn in Kunshan City of Jiangsu Province were studied. In terms of content soil Cu，Ni，Pb and Zn of various forms followed the order of residue form > organic-matter-bound form > Fe-Mn-oxide-bound forms > carbonate-bound form and exchangeable form. Residue form was obviously higher than the others in content. Of Cu and Pb，the organicmatterbound form accounted for a quite high proportion，being 3609% and 28.30% respectively. Among the heavy metals，Zn was the highest in exchangeable，carbonate-bound，Fe-Mn-oxide-bound and residue forms，and Cu was in organic-matter-bound form. Ni was the highest in variation coefficient of exchangeable，carbonate-bound and Fe-Mn-oxide-bound forms，Zn was of organic-matter-bound form，and Pb was of residue form. Among the various forms，Fe-Mn-oxide-bound Cu and soil exchangeable Cu showed the biggest impact on availability of soil Cu；exchangeable Ni did on availability of soil Ni；Fe-Mn-oxide-bound Pb and organic-matter-bound Pb did on availability of soil Pb；and exchangeable Zn and carbonate-bound Zn did on availability of soil Zn.

Abstract:With the aid of the DeNitrification–DeComposition (DNDC) model，the total CH₄ emission from of paddy fields in the period from 1982 to 2000 in the Taihu Lake region，as was affected by grid size，was estimated and variation of the total emission with grid size characterized A total of 7 grid sizes，i.e.1 km，2 km，4 km，8 km，16 km，32 km and 64 km，were designed，based on the 1∶50 000 soil database. Results showed that an apparent turning point was observed with the grid size of 16 km，and displayed as a limited range of the estimation of the total CH₄ emission being only 0.27 Tg C and low variation of the simulation of grid sizes from 1 km to 16 km.However，the range of the estimation expanded to 2.96 Tg C due to errors in area calculation in grid sizes from 16 km to 64 km，and the variation increased rapidly. Taking into account the amount of spatial data and computing cycle of the model，16 km was the optimal grid size for estimating emission of greenhouse gas from the farmlands.

Abstract:Sixteen different soils，representative of the soils of China，were selected and sampled for an experiment on toxicity of extraneous copper to tomato growth. The samples were amended with CuCl₂ to obtain a range of eight concentrations. Tomato shoot growth (21 d) test was performed in unleached and leached soils under controlled environment conditions. The results showed that the values of EC₅₀，which were the concentrations of Cu added to soils that made tomato shoot biomass down to 50%，were increased significantly in leached soils，especially the three soils high in organic carbon and the two soils high in salinity. Partial correlation analysis showed that soil pH was the most important factor controlling Cu toxicity to tomato growth. Stepwise multiple regressions showed that soil pH and organic carbon content could explain more than 80% of the variance for EC₅₀ values in both leached and unleached soils. When taking into account the effect of soil clay content in unleached soils or the effect of cation exchange capacity in leached soils on EC₅₀ values，determination coefficients (R²) of the regression models were increased up to 0.862 and 0.891，respectively. Findings of the experiment demonstrate that it is proper to use some soil properties，like pH，organic carbon content，clay content or cation exchange capacity as indicators to predict the toxicity of extraneous copper in the soil to tomato growth.

Abstract:An in-situ field experiment was carried on to study nitrogen leaching from farmlands typical of the Three-Gorges Reservoir Region of Chongqing for three successive years (from 2005 to 2007)，using modified apparatuses packed with ion exchange resin and buried into the soil at the depth of 20 cm，30 cm and 40 cm，separately to adsorb NO₃^--N and NH₄⁺-N and hence to monitor nitrogen leaching from the two soils monthly and after each moderate and heavy rainfall event. It was found that nitrogen leaching from vegetable field (74.58 kg hm^-2 a^-1) was higher but that from on slope farmland (46.01 kg hm^-2 a^-1) was lower than nitrogen input (56.9 kg hm^-2 a^-1) with rainfall into the fields，which indicates that nitrogen leaching from vegetable fields may partially affect the local water environment，but the farmland as a whole may not be the major cause of eutrophication of the local water system.Of the total nitrate leached from the soil more than 90% was NO₃^--N and its leaching occurred mainly during the first moderate or heavy rainfall event after fertilization.And NO₃^--N leaching from soil layers followed the sequence of cultivated layer > subsoil layer > bottom layer，and the former was much higher than the latter two.Moreover，it concentrated mainly in the early part of the rainy season，peaking in May，and stayed low in the later part，rendering limited impact on waterbody.A positive exponent correlation was observed between nitrate leaching and soil alkalyzed N. Therefore，it seems that vegetable fields are the major object for control of soil N leaching and effective measures may include control of nitrogen fertilization rate，reduction of soil available nitrogen pool and suppression of nitrification in the soil.

Abstract:A batch experiment was carried out to study adsorption kinetics of aniline on clay-layer (CL) of Lou soil modified with cetyltrimethylammonium bromide (CTMAB, CB) at varying ratio (100CB and 50CB) and cetyltrimethylammonium bromide + sodium dodecylsulphonate (CTMAB+SDS, CS) mixture and its mechanism. Results show that the modification of the CL of Lou soil increased significantly the adsorption velocity of aniline; a rising temperature sped up its initial velocity (V_0.5) only, but did not have any significant effect on the other adsorption velocity parameters. Aniline adsorption velocity increased with increasing aniline concentration. At the two experimental temperatures, 20℃ and 40℃, all the three aniline adsorption velocity parameters, i.e. total adsorption velocity (V_t), initial adsorption velocity (V_0.5) and fast adsorption velocity (V_f), did not vary much with the modification ratio when aniline was added at a low rate, 50μg•mL^-1, but displayed a decreasing order of 100CB > 50CB ≈120CS > CK at 5% level when the addition was at 200μg•mL^-1. The aniline adsorption process appeared to have two phases, fast adsorption and slow adsorption, of which the former dominated the total adsorption, and turned into the latter within 3h (t_c). Lyophobic proportional adsorption was the major mechanism dominating the fast adsorption and demonstrating the feature of a concentration driving force. However, slow adsorption generally occurred on the surface of unmodified soil with a complex mechanism.

Abstract:In-lab simulation of low molecular weight organic acids, i.e. oxalic acid, citric acid, tartaric acid and malic acid, activating inorganic phosphorus (P) in red soil was performed. When the same in concentration, organic acids followed an order of citric acid > tartaric acid > malic acid in capability of activating soil phosphorus. When their concentrations were < 0.5 mmol L^-1, oxalic acid was the lowest and when ≥ 5 mmol L^-1, it is still oxalic acid that was the highest in the capability. The P activating capability of the organic acids declined with rising pH. When they were the same in pH, they activated Al-P the most, Fe-P and Ca-P the next, and O-P the least. It is suggested that P release from phosphates in soils induced by organic acid should be attributed to the joint effect of acidity effect of proton and complex effect of organic anion, and closely related to solubility product constant of inorganic phosphate. The findings are of important significance to the study on cycling of inorganic P in the rhizospheric soil.

Abstract:Flocculation and settlement of fine sediments play an important role in silt transportation, soil penetrability and pollutant translocation in the Three-Gorges Reservoir. Surface charge properties of fine particles of the purplish soil in the Three Gorges Reservoir Region were determined and effects of Mg²⁺ and K⁺ on deposition of fine sediments in static water were studied with the pipette technique. Results show that (1) the surface potential of the fine particles of acidic, neutral, and calcareous purplish soils was -0.156, -0.171 and -0.192 V, respectively, in the 2:1-type electrolyte system, and varied in the range of -0.310~0.390 V in the 1:1-type electrolyte system; (2) when the concentration of Mg²⁺ and K⁺ was 0.1 mol m^-3 in the systems, settling velocity of the silts of the three different purplish soils reached 1.56 cm min^-1, 1.47 cm min^-1, and 1.35 cm min^-1and 1.05 cm min^-1, 1.01 cm min^-1 and 0.99 cm min^-1, respectively, showing that the higher the surface potential, the lower the settling velocity; and (3) the mean settling velocity of the fine silts of the three purplish soils increased with the concentration of the electrolyte of the Mg²⁺ and Na⁺ ystems. Besides, a concentration threshold was observed in either Mg²⁺ or K⁺ system for flocculation and settlement of fine silts, being about 0.1 mol m^-3 in the 2:1-type electrolyte system and 0.25 mol m^-3 in the 1:1-type electrolyte system.

Abstract:Macroarray and Real-time quantitative polymerase chain reaction (Real-time PCR) methods were used to perform quick check and quick quantification of Fusarium oxysporum in soils infected with watermelon wilt disease, and their usage was optimized and studied in lab. Results show that in rhizospheric soils of Treatments N^-+ P^-and N^-+ P⁺ severely infected with the disease, the Macroarray System detected strong positive signals, indicating that Fusarium oxysporum existed in these soils in large quantity. The real-time PCR method also found that the number of Fusarium oxysporum in treatments N^-+P^- and N^-+ P⁺ was the largest, being up to 8.89×10⁵ dRn g^-1 soil and 2.24×10⁵dRn g^- soil, respectively, while in other two treatments not infected with the disease, the number was 6.23×10³dRn g^-soil and 3.28×10³ dRn g^-1soil. While in bulk soils of all the four treatments, the number of Fusarium oxysporum varied between 10²~10³ dRn g^-1 soil, and the Macroarray System didn’t detect any strong positive signals. Compared to the traditional isolation, culture, plate screening and counting method for identification and detection of pathogens, the two above described methods are accurate, instant, and time-and-labor saving.

Abstract:A field experiment was carried out on mudflat along the coast of Yancheng, Jiangsu Province to study coupling effect of salt and fertilizer application on growth and yield of Helianthus tuberosus in soils different in salt concentration in 2008. Results show (1) the plant decreased significantly in plant height with rising salt concentration of the soils and a similar trend was observed with diameter of its stem, and yields of its tuber and shoot, and however, it displayed a reverse trend in plant height and yields of tuber and shoot, with higher N and P application, but remained almost unchanged in diameter of the stem; (2) the positive effects of N and P additions on plant height was significant in all treatments and became more with rising salt concentration in the soils, and so were the effects on stem diameter, and yields of tuber and shoot; and (3) variance analysis revealed extremely significant correlations at the lever of F _0.05 and F _0.01 among soil salt concentration, application rate of N and P fertilizers, interaction between salt and fertilizer application and interaction between N and P applied. Through analysis of effects of soil salt, nitrogen and phosphorus in various treatments, the main factor that affected tuber yield was salt concentration of the soil, which was followed by fertilizers of N and P. And the yield of tuber was the highest in Treatment S1N2P3, of which the soil salt concentration was 0.9～1.5 g kg^-1, and the N and P application rate 60 kg hm^-2 and 60 kg hm^-2, respectively.

Abstract:Structure and stability of soil aggregates in upland red soil were studied in a long-term fertilization experiment. Results show that in treatments of mixed application of organic and inorganic fertilizers, bulk density of the soil decreased and porosity of the soil increased to some extent as was compared with that of blank treatment (CK).The percentage of mechanical-stable macroaggregates (>5 mm), increased by 2%〖KG-*3〗~42% as a result of application of organic manure.In terms of percentage of water-stable aggregates (>0.25 mm) the treatments followed a decreasing order of Stable manure>Rice straw>Green straw>incorporation of aerial parts>CKThe treatments of organic manure increased the contents of organic matter, amorphous Fe, and amorphous Al by 9%~54%, 8.5%~21.7% and 10.9%~26.8%, respectively over the treatments of application of chemical fertilizer alone.Statistic results show that the content of water-stable aggregates (> 0.25 mm) was significantly and positively correlated to content of organic matter (p<0.01), but soil aggregate destruction rate was significantly but negatively correlated to it (p<0.01). Application of organic manure in addition to inorganic fertilizer was not only favorable to formation of macro-aggregates in upland red soil, but also beneficial to improve structure and stability of the aggregates in the soil.

Abstract:Properties of humus and contents of aggregates in the soils on the Gaoligong Mountains were studied in the lab and through field survey as well to gain a better knowledge about characteristics of the soils in the Gaoligong Eco-system and provide a scientific basis for soil erosion controlResults show that composition of the soil humus therein demonstrated apparent zonality, and its contents of organic matter, humic acid, HA/FA increased first and then decreased with declining elevation. Humic acid and fulvic acid in A₁ layer followed a decreasing order of dark brown＞brown＞brown coniferous forest soil＞subalpine meadow soil＞yellow brown＞yellow＞yellow red soil in content, while those in A₂ layer did one of dark brown＞brown＞brown coniferous forest soil＞yellow brown＞yellow＞sub-alpine meadow soil＞yellow red soil. The HA and FA in A₂ horizon was higher than those in A₂ horizon in molecular complexity and chemical stabilitySoil aggregates, 1～0.5mm and＜0.25mm in particle size, occupied an overwhelming majority, accounting for about 60%~70% of the soil, and decreased in particle size with declining elevation, displaying a pattern of lognormal distribution. Negative correlations were observed of their geometric mean diameter with geometric standard deviation and soil erodibility K-factor, while a positive correlation was between geometric standard deviation and soil erodibility K-factor. Moreover, the soil also demonstrated some fractal features. Subalpine meadow soil was the highest among the soils in Dg and MWD but the lowest in δg, soil erodibility K-factor and CFD, and its soil structure stability and resistance to erosion was relatively stronger. The content of humic acid is believed to be an important factor, influencing soil stability.

Abstract:Based on the knowledge of chemical composition and X ray analysis of <2 μm clays in agric horizon of the black soil in Northeast China, clay mineral composition and its spatial variation of 15 black soil samples collected from different latitudes was studied, and its affecting factors and evolution mechanisms explored. Results reveal that the clay minerals in agric horizon of the black soils in Northeast China are of the type of illite-Smectite/Illite mixed layer mineral, but their composition varies from region to region. At high latitude they are of the type of illite-Smectite/Illite mixed layer mineral, and at low latitude of the type of S/I mixture-illite-vermiculite. Factors causing spatial variation of their composition are mainly precipitation, temperature, and type of crops. As they vary sharply from region to region, clay minerals in the black soil of Northeast China evolve from illite toward S/I mixture or vermiculite, resulting in significant regional variation of clay mineral composition with latitude.

Abstract:As root exudates play an important role in mobilization of soil nutrients and mitigation of environmental stress, many scientists show great interests in root exudates, and have achieved some progresses in the research of those substances. However, it is still not an easy job to collect root exudates from plants growing in soil. Here, a new type of device and method is introduced for collecting root exudates from plants growing in soil. The device consists of a culture box and a collection box. During growth the plant in the culture box, affected by the oriented guidance technique, extends its roots through the agar medium into the collection box. When a certain amount of plant roots develop in the collection box, the medium in the box is leached for collection of root exudates. In this experiment, soybean was planted and cultured for 3 weeks. By then, more than 90% of the total root tips and 30% of the total root biomass were distributed in the collection box. In-situ recovery rate of organic acids reached over 70% in this system, it was found that secretion of organic acids from the roots of soybean under soil culture increased with its growth period. Soybean roots secreted more malate than citrate. Secretion of citrate and malate under soil culture were 11.4 and 6.7 times as much as under solution culture, respectively. The above findings suggest that this device is applicable to collecting organic acids secreted from plant roots under soil culture.

Abstract:In aim to understand the spatial variations of soil organic C (SOC) in the landscape scale in the redearth region of China, data obtained from a hilly landscape unit selected from the region were analyzed using geography-statistical methodology. The overall mean and variation coefficient of SOC content in the surface layer (0～20 cm) were 12.7 g kg^-1 and 31.3% for the landscape. The spatial distribution of SOC was highly self-correlated (nugget to sill was 6.3%) and land-use patterns in the landscape was strongly related (with a coefficient of 64.4%, p < 0.001) to topography factors (i.e. elevation and slope gradient), and its semi-variogram fitted well with an exponential model. The mean of SOC content for paddy soils in the landscape unit was 16.0 g kg^-1, which was significantly larger than that for soils from arable lands (11.2 g kg^-1), orchards (9.5 g kg^-1), and woodlands (8.4 g kg^-1). Surface visualization of SOC variations in the landscape unit demonstrates that the coefficient between SOC variations and landuse patterns was significantly larger that for SOC and elevation.

Abstract:Effect of application of NH₄⁺ and glucose on dynamics of three kinds of amino sugars (glucosamine, galactosamine and muramic acid) in mollisol was investigated through laboratory incubation. Relative contribution of microbial communities to nutrient immobilization was explored in relation to the ratio of glucosamine and muramic acid. Results show that contents of the soil amino sugars were influenced evidently to a various extent by the extraneous glucose and NH₄⁺. Concentration of muramic acid was significantly affected by the substrate added, regulating and balancing supply and demand of carbon or nitrogen to a certain extent. Glucosamine was more stable than muramic acid and subject to decomposition in the case of extreme carbon deficiency. No significant effect of soil nutrient status on galactosamine was observed. Carbon application was important to improve nitrogen fixation by soil microbes. In the presence of activated carbon sources, relatively rich nitrogen supply benefited rapid growth of bacteria, while relatively sufficient carbon sources did fast propagation of fungi.

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