The effect of biomass on the microbiodiversity of cadmium-contaminated soil.

Microbial Technology Channel News: Research reports that at present, China has more than 130,000 km2 of cultivated land is Cd pollution, including 11 provinces and cities, 25 regions, wide-ranging pollution, large-scale, the ecosystem security poses a great threatAccording to recent surveys, the soil Cd pollutant content shows the geographical distribution trend from northwest to southeast, from northeast to southwest gradually increased, and the southwest region of heavy metals exceed the standard range is wideObviously, heavy metal Cd pollution makes the southern red soil ecosystem has a risk, the treatment of Cd pollution red soil is imminentBiological, physical and chemical conventional methods are applied to soil remediation of contaminated soilForeign studies reported that the use of biomass carbon to contaminate soil, Cd biological effectiveness was greatly reduced, Cd concentration decreased to 10%the early study of this research group also showed that after biomass carbon was imported into the soil, the cd effective state decreased, the residue state increased, and the biological effectiveness of rice decreasedIt is shown that biomass carbon is a chemical passivation repair agent with potential application value, but the repair mechanism has not yet been unified and clearly statedhas shown that biomass carbon relieves the negative environmental effects of heavy metals by its own porosity, surface area, oxygen-containing organ groups and other characteristics, but also with biomass carbon to improve soil pH, organic content and other factors, in addition to subject to biomass carbon type, addition to the amount of factorsmicrobe is an indispensable part of soil vitality, is one of the sensitivity measures of soil fertility, quality and health, it is sensitive to heavy metal pollution, when the weight of gold exceeds the critical value of microbial quantity, activity, population structure and diversity are stressed downHowever, some population sized microorganisms can still survive in heavy metal-contaminated soil for a long time, it can be seen that microbes revolt against heavy metals by means of absorption, enrichment, dissolution and precipitationCitric acid bacteria can fix the Cd2 plus in the soilBiomass carbon can improve the abundance, activity and change of community structure and composition of soil microorganismsstudies have confirmed that two kinds of biomass carbon added to the soil can be added to increase the content of various types of bacteria, change the microbial structure of the soilIt has also been shown that the community structure of nitrogen fixation bacteria in soil is significantbefore before and after the addition of biomass carbonReunions are the basic structural units and components of the soilHeavy metal Cd, micro-organism 2 in different grain-level soil reuniting body showed different spatial behaviorEarly studies have shown that bacterial biomass in large reunions is significantly lower than fungi, and the number of large reunions constrains the biomass of fungi, and the microbial mass of large reunions is high compared to small reunions The interaction between biomass carbon-soil-microorganism s3 is complicated, and the mechanism of biomass carbon passivating heavy metal Cd is still stuck in two directions, the physical and chemical properties of biomass carbon itself and soil, but the microbial factor is rarely studied the following , materials and methods experimental materials experimental materials the experimental soil for testing the experimental soil for the mountain red soil of Yunnan Agricultural University, typical red soil in Yunnan, is non-rice soil that can be grown rice, because the heavy metal content is close to the base value, it is easy to explore the role of Cd cd this factor on the red soil microbial system and the restoration mechanism of carbon biomass pH of 5.35, conductivity of 420 s/cm, containing machine quality 44.26g/kg, effective phosphorus 64.55mg/kg, alkali nitrogen denitrogen 99.05mg/kg biomass carbon this study selected the wheat commodity straw biomass carbon produced by Henan Sanli Company pH of 9.03, organic carbon 543.7g/kg, total nitrogen 1.98g/kg, total phosphorus 3.2g/kg, full potassium 28.65g/kg, 23.26m2/g ratio, asunous exchange of 185.56mol/kg experimental design experiment for potted simulation experiments, the use of ordinary plastic barrels, 8 kg of soil per barrel The CdCl2 mother liquor is prepared and mixed evenly with the soil the biomass carbon of straw was added to the above-mentioned mixed soil according to the quality ratio of 0%, 2.5%, 10% (because there was no significant change in Cd form and soil enzyme activity under 5% biomass carbon addition in the previous project experiment, so the experiment did not set biomass increase according to the gradient, selected a significant change of 2.5%, 10% biomass carbon addition amount) and set up no addition of blank control group, both Cd addition is 2.5mg/kg and biomass carbon addition is 0% (B0 for short); Cd addition is 2.5 mg/kg and biomass carbon addition is 2.5% (B2.5 for short); Cd addition is 2.5mg/kg and biomass carbon addition is 10% (B10 for short) set up 3 parallel control groups for each treatment, placed in a greenhouse shed and planted rice, adjusted and maintained soil moisture to 70% of the field water holding, and collected the soil when the rice grows to the stage (5 points method) for the next step the separation method of soil reuniting using Elliott's wet sieve method to separate the reunion of different particle sizes Place the soil that clears the stone and rice roots into a sieve with apertures of 5, 2, 1, 0.5, 0.25mm The set of sieve poured into the sterilized water, so that the water just did not pass the upper most sieve, and then the uniform speed up and down the set of sieve 15min, then get the 5mm, 5 to 2mm, 2 to 1mm, 1 to 0.5mm, 0.5 to 0.25mm, .25mm 6 different particle size reuniting Among them, the 0.25mm particle size is classified as the boundary, which is larger than it is a large reunion body, and smaller than it is a micro-reunion body the soil microbial community functional diversity measurement method this study used Biolog-ECO board to analyze the metabolic functional characteristics of the soil microbiome The preparation of ECO plate inoculation fluid is done using Classen and other methods Take the equivalent of 5g drying quality of fresh soil samples placed in sterile triangular bottles, add 45mL concentration of 0.85% sterile physiological saline, 200r/min oscillation 30min after sitting 15min, take 5mL above liquid to a triangular bottle containing 45mL sterile physiological salt water, repeated dilution 3 times, 1:1000 inoculation liquid Preheat the ECO plate to 25 degrees C in advance and grab 150 sl of inoculation fluid with eight pipettes in each hole ECO plate placed in the thermostatic incubator, 25 degrees C or so light-avoidance culture 7d, respectively, 4, 24, 48, 96, , results and analysis different treatment of soil reuniting microbial community activity changes AWCD is the average color change rate of each plate in the incubation period, can reflect the activity of soil microorganisms, physiological functional diversity, it can be the average change in the time dimension of microbial activity As shown in Figure 1, the AWCD values of soil microorganisms in different particle size reuniting bodies increased with the prolongation of the temperature, indicating that the utilization capacity of soil microbial carbon sources in the different granulated reuniting bodies increased over time from the perspective of time dimension, the AWCD value of each reunion body under different treatments is close to 0 before 4h, the carbon source is almost unused; the overall metabolic activity of soil microorganisms and the growth rate of AWCD value showed a significant positive proportion of the relationship between 24 to 120h, the carbon source utilization is strong, microbial activity is strong The utilization rate of carbon sources of 4 treatments in each granular reuniting body was B2.5, B10, CK, And B0, heavy metal Cd pollution caused soil microbial carbon source utilization to be single, weak utilization capacity, microbial metabolic activity decreased, carbon source utilization capacity of 2 treatment groups applied to biomass carbon was enhanced, microbial metabolic activity was increased and higher than the blank control group, especially B2.5 treatment material saitagens 6 different sizes and sizes of the carbon source utilization capacity from strong to weak in order: 5mm (10.55) reunion body, 2 mm (10.42) reunion body, .lt;25mm (10.18) reunion body, 5 to 2mm reunion body (8.50), 1 to 0.5mm (6.26) (5.00)The metabolic activity of soil microbial carbon sources in the micro-reunion body of 5 to 1mm is much higher than that of 1 to 0.25mm reuniting, especially in the 5mm, 2 to 1mm 2 particle size reuniting carbon metabolic activity peaked in .lt;0.25mm micro-reunion B0 treatment group AD value increased slowly compared with the remaining 3WC changes in soil reuniting microbiodiversity index under different treatments Shannon diversity index is a comprehensive index to study the richness of community species, Simpson index more reflects the most common species superiority in the community, and McIntosh index is a measure of the homogeneity of species in the community using 3 diversity indices, based on data of 120h, which has a stable wcwcd value during the culture period of each soil reuniting is shown in Table 2, first of all, the four treatments of Shannon, Simpson, and McIntosh 3 diversity index values of microorganisms in each granular-diameter reuniting body are all treated in the law of B2.5, B10, CK,B0 Anova analysis also showed that there were significant differences between the two treatment groups added biomass carbon and the single-plus Cd control treatment group, indicating that the toxic effect of heavy metal Cd forced the soil microbial abundance to decrease, the common species of the community was restricted, the homogeneity of the species was destroyed, and the application of biomass carbon had an enhanced effect on the diversity of microorganisms, and the effect of the B2.5 treatment group was particularly significant second, the three diversity index values under each treatment are high in 5 to 1mm, .lt;25mm particle size reuniting, 1 to 0.25mm particle size reuniting body low In 6 different granulated reuniting syllas, the Shannon index increased by 24.62 percent, 34.30%, 58.41%, 52.88%, 46.76%, 131.25%, compared with the B0 control group with a single-plus Cd The Simpson sofperby index rose 24.44%, 20.00%, 36.11%, 39.68%, 44.07%, 73.73%, respectively The McIntosh index rose 32.68 per cent, 35.74 per cent, 86.36 per cent, 87.15 per cent, 84.73 per cent and 135.52 per cent respectively it can be concluded that the promotion of biomass carbon to microbiodiversity in Cd-contaminated soil fluctuates with the decrease of the particle size of the reuniting body, and the promotion effect in the micro-reunion body is most prominent; different treatments of soil reuniting microbial carbon source utilization characteristics change according to the structure and chemical properties of 31 carbon sources on the ECO board, it is divided into 6 major carbon source compounds: sugar 7 kinds; The AWCD value of the 120h 6 carbon source compounds cultured was analyzed results show in Figure 2, first of all, the utilization of microorganisms in the soil reuniting of the particles of 6 carbon source compounds 4 treatments also show the law of B2.5, B10, CK,B0 It is obvious that heavy metal Cd inhibits the use of soil microorganisms on various carbon source compounds, biomass carbon has a recovery effect on the carbon source utilization capacity of Cd-contaminated soil microorganisms, 2.5% of biomass carbon addition swells up, and even has a certain effect of lifting This is consistent with the results of the analysis of the overall metabolic activity and functional diversity index of soil microorganisms second, the peak utilization intensity of 6 types of carbon sources of soil microorganisms under treatment is now in 5 to 1mm, lt;25mm particle size reuniting, and the valley value is now in the 1 to 0.25mm particle size reuniting body showed by Figure 3, 4 treatments in the soil reuniting body are distinct on the PC axis and the size of the reunion granulated is different 4 treatment coordinates are also different 5 to 0.25mm soil reuniting body B0 and CK2 treatment group discrete distance, available, single-application Cd treatment.