CN104280512A - Method for determining organic matters in soil - Google Patents

Abstract

The invention relates to pedology and ecology, in particular to a method for determining organic matters in soil. The method comprises the steps of levigating and sieving air-dried soil, then placing the soil into a conical flask, sequentially adding a potassium dichromate solution and sulfuric acid into the conical flask, placing the conical flask into a drying box which is already preheated to 100 to 125 DEG C for 30 to 90 minutes, taking out the conical flask, cooling the conical flask to room temperature, performing titration, and calculating the content of organic matters. The heating of the drying box is used for substituting the traditional oil-bath heating, and the conical flask is used for substituting a sterilizing tube. When the heating temperature of 115 DEG C and the heating time of 30 minutes are determined, compared with the organic matter result determined by existing precise element analyzers, the standard deviation and deviation ratio are respectively 2.18 and less than 6 percent; and the correlation of the content of organic matters determined in two methods reaches up to 0.998; compared with the traditional oil-bath heating method, the precision is improved by about 12 percent. By adopting the method, in the determining process of the soil organic matters, uniformity in heating is achieved, the temperature fluctuation range is small, and the precision of a test result is high.

Description

A kind of method measuring soil with organic matter

Technical field

The present invention relates to pedology with ecological, specifically a kind of assay method for soil with organic matter, be suitable for the soil organism in enormous quantities and measure.

Background technology

Soil organic matter content level is one of important indicator weighing soil fertility and soil quality, and thus, measuring the soil organism is quickly and accurately the key obtaining change of soil fertility, has great importance in fertility evaluation.

In mensuration soil organism method, instrument analytical method mainly contains carbon nitrogen elemental analyzer method and near infrared spectroscopic method.Carbon nitrogen elemental analyzer method utilizes in sample heater to make sample decompose release CO up to the high temperature of 1100 ° of C ₂, then utilize detecting device to collect CO ₂signal is also converted into a total organic carbon value; be multiplied by organic reduction coefficient (1.724) again and obtain soil organic matter content; the method can make the soil organism all decompose; not by the impact of reducing substances in soil; the result obtained accurately, reliably, is used when can be used as standard method check and correction; And near infrared spectroscopic method adopts pellet technique, have according near infrared spectrum region and can roll into a ball with the soil organism palace method that (as C=O, COO-and C-H) carrys out semiquantitative determination soil organic matter content, the method of these two kinds of Instrument measuring organic matters be all fast, the analytical technology of efficient, test favorable reproducibility, but because analytical instrument is expensive, operative technique require high, analysis cost is higher, be not suitable for the analysis nearby on sample ground, field and not use by some analysts.

In manual assay method, utilize oil bath to heat, with the excessive potassium bichromate solution oxidation soil organism in acid medium, then be the method that each experimental determination soil organic matter content often adopts by the outer hot potassium dichromate oxidation-volumetric method of the high temperature of ferrous sulphate titration residual gravity potassium chromate, also be a kind of generally acknowledged classical way, this method mainly adopts oil bath pan (in-built glycerine or vegetable oil) heating to disappear and boils the mode of pipe, in control pot, oil bath temperature is at 170-180 ° of C, solution seethes with excitement 5 minutes, makes the oxidation of coal in the soil organism become CO ₂, and the hexavalent chromium (Cr in potassium bichromate solution ⁶⁺) be reduced into trivalent chromic ion (Cr ³⁺), remaining potassium dichromate standard copperas solution residual titration, the potassium dichromate calculated by the soil organism consumes by the amount of remaining potassium bichromate solution calculates soil organic matter content, and concrete chemical reaction is as follows:

2K ₂CrO ₇+3C+8H ₂SO ₄→2K ₂SO ₄+2Cr ₂(SO ₄) ₃+3CO ₂↑+8H ₂O

Remaining potassium dichromate ferrous sulphate reduces, and chemical reaction is as follows:

K ₂CfO ₇+6FeSO ₄+7H ₂SO ₄→K ₂SO ₄+Cr ₂(SO ₄) ₃+3Fe ₂(SO ₄) ₂+7H ₂O

The method is to the noiseless effect of the carbonate in soil, and the carbon of various form, also without impact, is applicable to the analysis of a large amount of sample.But this method also exists following deficiency: (1) finding speed is slow, and Parallel errors is larger; (2) test temperature required higher, heating-up temperature undulatory property more greatly, not easy-regulating, affect sample oxidation speed; (3) disappear boil pipe outer wall attachment greasy dirt be difficult to cleaning and in cleaning process, affect measurement result by grease lead-in tube.Therefore, it is very necessary for designing quick, accurate, simple soil organism analytical approach.

Summary of the invention

For solving classic method-oil bath heating measuring the various problems existed in the organic process of pedotheque, the invention provides a kind of assay method of soil with organic matter,

It is specially:

A kind of method measuring soil with organic matter; triangular flask is put into by after levigate for air-dry soil sieving; potassium bichromate solution and sulfuric acid is added successively in triangular flask; triangular flask is put into taking out for baking oven 30-90 minute of being preheating to 100 ° of C-125 ° of C and is cooled to room temperature; carry out titration, calculate the content of organic matter; Wherein count in mass ratio, potassium bichromate solution: sulfuric acid: soil=50-100:50-100:1.

Described air-dry soil is levigate to sieve, and screen size is 0.149mm-0.25mm.

Described triangular flask puts into the baking oven of preheating, and wherein in baking oven, temperature is the suitableeest is 115 ° of C, and the timing heat time is the suitableeest is 30 minutes.

Triangular flask keeps temperature-resistant after putting into the baking oven of preheating until take out.

Described titration process drips for adding o-phenanthrolin indicator 2-3 in triangular flask, is titrated to solution changes color with ferrous sulphate, colourshifting process by orange through bluish-green to brownish red be terminal, record sulfuric acid Asia consumption.

The described calculating content of organic matter is according to formula: the soil organism (gkg ^-1)=(C × 5/V ₀), (V ₀-V) × 10 ^-3× 3.0 × 1.724 × 1.08 × 10 ³/ m

In formula: C is K ₂cr ₂o ₇the concentration of solution;

5 for adding the volume of potassium bichromate solution;

V ₀for blank titration consumes the volume of ferrous sulphate;

V is the volume that sample titration consumes ferrous sulphate;

M is soil sample weight;

3.0 is the molal weight of 1/4 carbon atom;

1.08 be oxidation adjusting coefficient;

1.724 change organic reduction coefficient into for organic carbon.

Potassium bichromate solution concentration is 0.8000mol L ^-1sulfuric acid concentration is 18mol L ^-1; Ferrous sulphate concentration is 0.2mol L ^-1.

When every batch sample (have 24 for examination soil samples, every batch sample analysis refers to by 24 samples under different temperatures and time often kind combination) is analyzed, do 3 blank titrations; The present invention makes homogeneous heating in soil organism mensuration process, temperature fluctuation range is little, test findings degree of accuracy is high; Simplify experimental procedure, decreasing pollution, shorten test duration of single sample, labour intensity is decreased for large batch of sample determination; Compared with " elemental analyser " of costliness, while guarantee estimating precision, save overspending.

Advantage of the present invention:

Soil organism assay method of the present invention, provides a kind of and saves time, the analytical approach that laborsaving, result reliability is high, greatly improves the analytical test speed of the soil organism.

1) save time: a collection of mensuration 10-30 sample when measuring the soil organism with bath oiling, whole Digestion time is 20-30 minute, needs the boiling situation of close observation sample in the process and timing; And adopt a collection of 100-150 the sample (according to baking oven size) that measure of this method (baking oven heating); the whole heat time is 40-45 minute; only need observe the steady temperature (115 ° of C) of baking oven and timing in this process, this process only needs about 10 minutes;

2) laborsaving: need to use hard test tube when measuring with bath oiling, the solution after need boiling disappearing is poured into triangular flask from hard test tube, and hard test tube flushing repeatedly, maintenance liquor capacity is 60-70ml; Method of the present invention only need use triangular flask, disappears to boil to add water to 60-70ml toward triangular flask afterwards, and shake up i.e. available ferrous sulphate titration and survey organic carbon, this process decreases labour intensity;

3) process contamination is measured little, and measurement result precision improves greatly: use baking oven heating to replace oil bath heating, overcoming in bath oiling disappears boils pollution to air and sample, the whole spin manifold temperature of baking oven heating is even, and good heat insulating, the fluctuation range of temperature is little, and the temperature that this method heats bath oiling, time, the test tube position be in oil bath are difficult to the shortcoming such as accurately and improve, and the method estimating precision comparatively bath oiling improve about 12%;

4) determine to measure optimum temperature and time: this method is 115 ° of C in heating-up temperature, the heat time is 30 minutes is the optimum condition measuring soil (brown earth) content of organic matter.

Embodiment

In order to solve, classic method-oil bath heating is organic in pedotheque measures Problems existing; the invention provides a kind of assay method of soil with organic matter; simplify analytic process; hard test tube need be used when classical oil bath method measures; solution after need boiling disappearing is poured into triangular flask from hard test tube; and hard test tube flushing repeatedly, maintenance liquor capacity is 60-70ml; Process is very complicated, and only need use triangular flask in method of the present invention, disappears to boil to add water to 60-70m1 toward triangular flask afterwards, shakes up i.e. available ferrous sulphate titration and surveys organic carbon.

Its concrete steps following 1) to take air-dry soil levigate; put into triangular flask after being sieved by 0.149mm-0.25mm sieve aperture, accurately add potassium dichromate with transfer pipet, more slowly add sulfuric acid with transfer pipet; limit edged rotates and shakes up, and triangular flask is covered curved neck funnel afterwards; Prevent volatilization.

2) triangular flask puts into the baking oven being preheating to 100 ° of C-l25 ° of C, within timing 30-90 minute, takes out, is cooled to room temperature; Rinse curved neck funnel and triangular flask bottle wall with water, constant volume is to original volume;

3) add o-phenanthrolin indicator, ferrous sulphate is titrated to variable color, record ferrous sulphate consumption;

4) arrange blank titration, blank titration, for not add soil sample, adds 0.1-0.3g granular quartz sand, the same step of other step (1)-(3).

By formulae discovery soil organic matter content:

The soil organism (g kg ^-1)=(C × 5/V ₀) × (V ₀-V) × 10 ^-3× 3.0 × 1.724 × 1.08 × 10 ³in/m formula: C is 0.8000molL ^-1(1/6K ₂cr ₂o ₇) concentration of standard solution;

5 for adding the volume of potassium dichromate standard solution;

V ₀for blank titration consumes the volume of ferrous sulphate;

V is the volume that sample titration consumes ferrous sulphate;

M is soil sample weight;

3.0 is the molal weight of 1/4 carbon atom;

1.08 be oxidation adjusting coefficient;

1.724 change organic reduction coefficient into for organic carbon.

Be specially in the present embodiment

Get 24 kinds of brown earth soil samples in different location, Liaoning, 24 soil chosen to be soil sample that organic difference gradient is large be test sample (is 33.0 ~ 195.4g kg by 24 samples-soil content of organic matter scopes that elemental analyser measures ^-1), baking oven heating is adopted to measure soil organic matter content, determine to measure the optimum temperature of soil organic matter content and time, the content of organic matter simultaneously measured using elemental analyser ELEMENTAR (Vario EL III, Germany) is as test true value.

Concrete steps are as follows:

(1) sample: the air-dry soil sample (be accurate to 0.0001g) of 18 parts of 0.1g by 0.149mm (100 order) sieve aperture is taken to each pedotheque, [note: the soil high for the content of organic matter adopts Subtraction method, take 0.05g sample], put in 150ml triangular flask, accurately adding normal concentration with transfer pipet is 0.8000mol L ^-1(1/6K ₂cr ₂o ₇) potassium dichromate 5.0ml, then slowly adding 5m1 concentration with transfer pipet is 18mol L ^-1sulfuric acid, limit edged rotates and shakes up;

(2) heat: curved neck funnel is put in triangular flask top; be respectively put into 100 ° of C, 105 ° of C, 110 ° of C, 115 ° of C, 120 ° of C, 125 ° of C as thermograde; with 30,60,90 minutes for time gradient; in the baking oven of totally 18 process (6 thermograde × 3 time gradients); in uniform temperature, take out triangular flask after the time (with 100 ° of C, 105 ° of C, 110 ° of C, 115 ° of C, 120 ° of C, 125 ° of C for heating-up temperature; with 30,60,90 minutes for after heat time combination; after each temperature, timing, take out triangular flask); After being cooled to room temperature, rinse curved neck funnel and triangular flask bottle wall with water, keep liquor capacity in triangular flask to be 60-70ml;

(3) titration: adding o-phenanthrolin indicator 2-3 and drip in triangular flask, is 0.2mo1 L by concentration ^-1ferrous sulphate be titrated to solution changes color process by orange through bluish-green to brownish red be terminal, record ferrous sulphate titration milliliter number.

During sample analysis, do 3 blank titrations; Blank titration does not add soil sample, adds 0.1-0.3g granular quartz sand, the same step of other step (1)-(3).

Computing formula:

The soil organism (g kg ^-1)=(C × 5/V ₀) × (V ₀-V) × 10 ^-3× 3.0 × 1.724 × 1.08 × 10 ³in/m formula: C is 0.8000molL ^-1(1/6K ₂cr ₂o ₇) concentration of standard solution;

5 for adding the volume of potassium dichromate standard solution;

V ₀for blank titration consumes the volume of ferrous sulphate;

V is the volume that sample titration consumes ferrous sulphate;

M is soil sample weight;

3.0 is the molal weight of 1/4 carbon atom;

1.08 be oxidation adjusting coefficient;

1.724 change organic reduction coefficient into for organic carbon.

(4) testing result is in table 1.Table 1 is the data of 24 samples for examination.

(5) table 2 is the correlationship between the measured value of baking oven heating and elemental analyser measured value.Related coefficient adopts Pearson linear correlative method to calculate (spss13.0 software)

Calculation of correlation factor formula is: $r=\frac{\mathrm{\ΣXY}-\frac{\mathrm{\ΣX\ΣY}}{N}}{\sqrt{(\mathrm{\Σ}{X}^2-\frac{{\left(\mathrm{\ΣX}\right)}^2}{N})(\mathrm{\Σ}{Y}^2-\left(\frac{{\left(\mathrm{\ΣY}\right)}^2}{N}\right))}}$

Wherein: r is related coefficient;

X and Y is respectively baking oven heating measured value and elemental analyser measured value;

N is sample number.

(6) table 3 is standard deviation between the measured value of baking oven heating and elemental analyser measured value and deviation ratio.

The computing formula of standard deviation is: $S=\sqrt{\frac{\mathrm{\Σ}{(x_i-\stackrel{\‾}{x})}^2}{N-1}}$

Wherein: S is standard deviation;

Xi is i-th sample value;

for the mean value of sample;

N is sample number.

The computing formula of deviation ratio is: T=(X-Y)/Y*100%

Wherein: T is deviation ratio;

X is baking oven heating measured value;

Y is elemental analyser measured value.

As can be seen from table 2 and table 3; the present invention is under the condition of 115 ° of C/30min; compared with the organic result that accurate " elemental analyser " measures at present; standard deviation and deviation ratio are only 2.18 and < 6% respectively, and the content of organic matter correlativity of two kinds of method mensuration is up to 0.998; Compared with traditional oil bath heating, improve precision about 12%.

Comparative example

With above-mentioned 24 soil for test sample, adopt conventional oil bath heating to measure soil organic matter content, concrete steps are as follows:

(1) sample: the air-dry soil sample (be accurate to 0.0001g) of 0.1g by 0.149mm (100 order) sieve aperture is taken to each pedotheque, [note: the soil high for the content of organic matter adopts Subtraction method, take 0.05g sample], put into 50ml to disappear and boil in pipe, accurately adding normal concentration with transfer pipet is 0.8000mol L ^-1(1/6K ₂cr ₂o ₇) potassium dichromate 5.0ml, then slowly adding 5m1 concentration with transfer pipet is 18mol L ^-1sulfuric acid, limit edged rotates and shakes up;

(2) disappear and boil: oil bath pan is heated in advance 180 ° of C ~ 190 ° C; boil in pipe insertion iron wire cage by containing disappearing of soil sample; then put it in oil bath pan and heat; control kettle temperature at 170 ° of C ~ 180 ° C; and timing 5 minutes boil liquid in pipe boiling from disappearing; then take out iron wire cage, boiling pipe cooling wait disappearing after, cleaning to disappear with clean paper and boiling the fluid of pipe outside;

(3) shift: rinse curved neck funnel with water and disappear and boil phial wall, and will disappear and boil liquid in pipe and wash 150ml triangular flask, in maintenance triangular flask, liquor capacity is 60-70ml;

(4) titration: adding o-phenanthrolin indicator 2-3 and drip in triangular flask, is 0.2mol L by concentration ^-1ferrous sulphate be titrated to solution changes color process by orange through bluish-green to brownish red be terminal, record ferrous sulphate titration milliliter number.

When every batch sample is analyzed, do 3 blank titrations; Blank titration does not add soil sample, adds 0.1-0.3g granular quartz sand, the same step of other step (1)-(3).

Computing formula is the same.

(5) testing result is in table 1.

(6) table 2 is the correlationship between the measured value of bath oiling and elemental analyser measured value.

(7) table 3 is standard deviation between the measured value of bath oiling and elemental analyser measured value and deviation ratio.

(8) according to Oven Method (115 ° of C, 30 minutes) with the standard deviation of the standard deviation of elemental analyser measured value, bath oiling and elemental analyser measured value, calculate the precision that Oven Method improves compared with bath oiling as follows: (2.49-2.18)/2.49 × 100%=12.4%.

Claims (7)

1. one kind measures the method for soil with organic matter, it is characterized in that: put into triangular flask by after levigate for air-dry soil sieving, potassium bichromate solution and sulfuric acid is added successively in triangular flask, triangular flask is put into taking out for baking oven 30-90 minute of being preheating to 100 DEG C-125 DEG C and is cooled to room temperature, carry out titration, calculate the content of organic matter; Wherein count in mass ratio, potassium bichromate solution: sulfuric acid: soil=50-100:50-100:1.

2. by the method measuring soil with organic matter described in claim 1, it is characterized in that: described air-dry soil is levigate to sieve, and screen size is 0.149mm-0.25mm.

3. by the method measuring soil with organic matter described in claim 1, it is characterized in that: described triangular flask puts into the baking oven of preheating, wherein in baking oven, temperature is the suitableeest is 115 DEG C, and the timing heat time is the suitableeest is 30 minutes.

4. by the method measuring soil with organic matter described in claim 1, it is characterized in that: triangular flask keeps temperature-resistant after putting into the baking oven of preheating until take out.

5. by the method measuring soil with organic matter described in claim 1, it is characterized in that: described titration process drips for adding o-phenanthrolin indicator 2-3 in triangular flask, be titrated to solution changes color with ferrous sulphate, colourshifting process by orange through bluish-green to brownish red be terminal, record sulfuric acid Asia consumption.

6. by the method measuring soil with organic matter described in claim 1 or 5, it is characterized in that: the described calculating content of organic matter is according to formula: the soil organism (g kg ^-1)=(C × 5/V ₀) × (V ₀-V) × 10 ^-3× 3.0 × 1.724 × 1.08 × 10 ³/ m

In formula: C is K ₂cr ₂o ₇the concentration of solution;

5 for adding the volume of potassium bichromate solution;

V ₀for blank titration consumes the volume of ferrous sulphate;

V is the volume that sample titration consumes ferrous sulphate;

M is soil sample weight;

3.0 is the molal weight of 1/4 carbon atom;

1.08 be oxidation adjusting coefficient;

1.724 change organic reduction coefficient into for organic carbon.

7. by the method measuring soil with organic matter described in claim 1 or 5, it is characterized in that: potassium bichromate solution concentration is 0.8000mol L ^-1sulfuric acid concentration is 18mol L ^-1; Ferrous sulphate concentration is 0.2mol L ^-1.