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HJ 746-2015 English PDF

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HJ 746-2015: Soil. Determination of redov potential. Potential method
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Basic data

Standard ID HJ 746-2015 (HJ746-2015)
Description (Translated English) Soil. Determination of redov potential. Potential method
Sector / Industry Environmental Protection Industry Standard
Word Count Estimation 11,126
Date of Issue 2015-06-04
Date of Implementation 2015-07-01
Quoted Standard GB/T 6682; HJ/T 166; ISO 11271-2002
Adopted Standard ISO 11271-2002, MOD
Regulation (derived from) Ministry of Environment Announcement 2015 No.39
Issuing agency(ies) Ministry of Ecology and Environment
Summary This standard specifies the soil redox potential field testing method. This standard applies to the state of fresh water or moist soil is given in Appendix A of the measured redox potential.

HJ 746-2015: Soil. Determination of redov potential. Potential method

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Soil.Determination of redov potential.Potential method National Environmental Protection Standard of the People 's Republic of China Determination of soil oxidation - reduction potential Soil-Determination of redox potential-Potential method 2015-06-04 released 2015-07-01 implementation Issued by the Ministry of Environmental Protection Directory Preface ii 1 Scope of application 1

2 normative reference documents

3 Terms and definitions 1 Principle of Method 1 5 reagents and materials 1 6 instruments and equipment 2 7 live .3 8 Analysis Step 3 The results are calculated and expressed 10 Precautions 5 Appendix A (normative) Evaluation of soil moisture status Appendix B (informative) Standard oxidation - reduction buffer solution potential value Appendix C (informative) Reference electrode potential value

Foreword

To carry out the "People's Republic of China Environmental Protection Law" to protect the environment, protect human health, regulate soil oxidation and reduction potential of the test Set this standard. This standard specifies the field test method for the determination of redox potential in soils. This standard is modified using the "Field Test Method for Determination of Reducing Potentials of Soil Mass" (ISO 11271..2002). The main changes are as follows. - modified standard name; - the original reference standard ISO 3696. 1987 to GB/T 6682; - simplifies the formulation of the principle of the method; - refinement of instruments and equipment terms; - modified the analysis steps; - Added caution. This standard is the first release. Appendix A to this standard is a normative appendix, Appendix B and Appendix C are informative appendices. This standard is organized by the Ministry of Environmental Protection Science and Technology Standards Division. The main drafting unit of this standard. Jinzhou City Environmental Monitoring Center Station. This standard is approved by the Ministry of Environmental Protection on June 4,.2015. This standard is implemented as of July 1,.2015. This standard is explained by the Ministry of Environmental Protection. Determination of soil oxidation - reduction potential

1 Scope of application

This standard specifies the soil oxidation-reduction potential of the field test method. This standard applies to the determination of the redox potential of fresh or moist soils given in Annex A for the water state.

2 normative reference documents

The contents of this standard refer to the following documents or their terms. For undated references, the valid version applies to this standard quasi. GB/T 6682 Analytical laboratory water specifications and test methods Technical specification for soil environmental monitoring ISO 11271..2002 Determination of soil mass oxidation and reduction potential Field test method (Soil quality-Determination of redox Potential-field method

3 terms and definitions

The following terms and definitions apply to this standard. Soil Oxidation - Reduction Potential EhSoil Redoxpotential Refers to the soil oxidation state substances and the reduction of the relative concentration of substances generated by the potential, expressed by Eh.

4 principle of the method

The platinum electrode and the reference electrode are inserted into fresh or moist soil, and the soluble oxidant or reducing agent in the soil is accepted from the platinum electrode Or give electrons until a potential is established on the surface of the electrode to measure the difference between the potential and the potential of the reference electrode, The electrode is added to the potential of the hydrogen standard electrode to obtain the redox potential of the soil.

5 reagents and materials

Unless otherwise stated, analytical pure chemical reagents conforming to national standards are used in the analysis, and the test water meets the requirements of GB/T 6682. 5.1 quinone hydroquinone (C12H10O4). 5.2 potassium ferricyanide (K3 [Fe (CN) 6]). 5.3 Potassium ferrocyanide (K4Fe (CN) 6 · 3H2O). 5.4 agar. ω = 0.5%. 5.5 Potassium chloride. KCl. 5.6 Redox Buffer Solution. Adding the appropriate amount of powdered quinone hydroquinone (5.1) to the pH buffer to obtain a suspension; or equimolar potassium potassium ferricyanide (5.2) Potassium cyanide (5.3) (mol/mol). Refer to Appendix B for the potential values of the standard redox buffer solution. 5.7 Potassium chloride solution. c (KCl) = 1.00 mol/L. Weigh 74.55 g potassium chloride (5.5) in 1000 ml volumetric flask, diluted with water to the mark, mix. 5.8 Potassium chloride solution. c (KCl) = 3.00 mol/L. Weigh 223.65 g potassium chloride (5.5) in 1000 ml volumetric flask, diluted with water to the mark, mix. 5.9 Electrode cleaning materials. fine sandpaper, decontamination powder, cotton cloth.

6 instruments and equipment

6.1 potentiometer. input impedance of not less than 10 GΩ, sensitivity of 1 mV. 6.2 Redox electrode. Platinum electrode, need to be stored in the air and keep clean. The structure of the two different types of platinum electrodes is shown in Fig. A) redox electrode b) spike redox electrode 1 insulating material; 2 copper rod; 3 platinum wire; 4 handle; 5 jack; 6 steel rod; 7 epoxy resin; 8 exposed platinum wire bundle Fig.1 Structure of redox electrode 6.3 Reference electrode. Silver-silver chloride electrode, other electrodes such as calomel electrodes can also be used. The potential of the reference electrode relative to the standard hydrogen electrode is given in the Appendix C. Silver-silver chloride electrode should be stored in 1.00 mol/L or 3.00 mol/L potassium chloride solution (5.7 or 5.8), the concentration of potassium chloride and The electrodes are of the same concentration or are stored directly in a salt bridge containing the same concentration of potassium chloride solution. 6.4 stainless steel hollow rod. diameter greater than the redox electrode 2 mm, the length should meet the redox electrode inserted into the soil required depth. 6.5 salt bridge. connecting the reference electrode and soil, salt bridge structure shown in Figure 2. 1 silver-silver chloride electrode; 2 agar potassium chloride solution (ω = 0.5%); 3 ceramic sleeve Fig.2 Salt bridge structure in redox potential measurement 6.6 Hand drill. diameter greater than the salt bridge reference electrode 3 mm ~ 5 mm. 6.7 Thermometer. Sensitivity ± 1 ℃.

7 scene

According to the relevant requirements of HJ/T 166, according to the background data and field investigation results, the spatial diversity of pollutants and the degree of soil pollution The basic judgment selects the measurement site. In the selected measurement point, should be removed rubble, gravel and other large particles of impurities.

8 Analysis steps

8.1 Field layout of electrodes and salt bridges The field arrangement of the redox electrode and the salt bridge is shown in Fig. The distance between the redox electrode and the salt bridge should be between 0.1 and 1 m, The oxidative reduction electrodes are inserted into soils of different depths, respectively. The state of the soil layer of the electrode inserted into the soil shall be classified according to the classification in Appendix A. Fresh or damp. If the surface soil is dry, the salt bridge should be placed in the pores of fresh or humid soils, and the reference electrode should avoid direct sunlight. Unit. cm 1 redox electrode; 2 soil; 3 salt bridge Figure 3 Arrangement of redox electrode and salt bridge 8.2 Determination At each measurement point, first use a stainless steel hollow rod (6.4) to drill two holes in the soil with a depth of 2 to 3 cm smaller than the depth Quickly insert the platinum electrode to the depth to be measured. At least two electrodes are placed at each measurement depth, and the distance between the two electrodes is 0.1 to 1 m, The platinum electrode is placed in the soil for at least 30 minutes and then connected to the potentiometer. The salt bridge is installed in the soil at 0.1 ~ 1 m from the redox electrode, and the ceramic sleeve of the salt bridge should be in good contact with the soil. After 1 h, the measurement of the potentiometer (Em) is recorded. If 10 min continuous measurement of the adjacent two measured values of the difference ≤ 2 mV, Can shorten the measurement time, but at least 30 minutes. While reading the potential, measure the temperature at the reference electrode. Note 1. The platinum electrode is disconnected from the millivolt meter during the reading interval because the potassium chloride leaks from the salt bridge to the soil and reaches the most Large leaks. If the break can not solve the problem, remove the salt bridge from the soil and re-install it before the next measurement.

9 Results calculation and representation

9.1 Results calculation The soil redox potential (mV) is calculated according to the formula (1). Eh = Em Er (1) Where. Eh - soil oxidation and reduction potential, mV; Em - instrument readings, mV; Er - the potential value of the reference electrode relative to the standard hydrogen electrode at the test temperature, mV (see Appendix C). 9.2 The result is shown Keep integer bits. 10 Precautions 10.1 The use of the same platinum electrode continuous testing of different types of soil, the instrument readings often lag phenomenon, this time should be measured in each After the sample is measured, the electrode is cleaned and cleaned. If necessary, the electrode is placed in saturated KCl solution soak, until the reference electrode to restore the original state Can be used. 10.2 If the soil moisture content is less than 5%, the distance between the platinum electrode and the reference electrode should be minimized to reduce the resistance in the circuit. 10.3 Platinum electrodes are used within one year and check whether the platinum electrodes are damaged or contaminated before each use. If the platinum electrode is contaminated, it is available Wipe the cotton cloth and rinse it with distilled water. 10.4 Platinum Electrode Before use, apply the redox buffer solution (5.6) to check its response value if its measured potential value is proportional to the oxidation reduction The difference between the potential values of the solution (5.6) is greater than 10 mV and should be purged or replaced. Also check the reference electrode. Reference electrode available To detect each other, but at least three reference electrodes need to be connected in turns, when the reading of an electrode and other electrodes read the difference of more than 10 MV, the electrode can be regarded as defective and should be discarded.

Appendix A

(Normative appendix) Evaluation of soil water status Table A Soil water status assessment Soil identification soil evaluation nature > 17% clay < 17% clay Dry moisture content below the wilting point of solid, hard, not plastic, wet after a serious dark color, wet after a serious black Shrinkage limit The fresh water content is between the soil moisture content and the wilting point Semi-solid, plastic, hand into 3 mm fine The article will break and broken, moist after the light color Slightly deepened After moistening the color slightly deepened Wet moisture content close to the field moisture content, there is no free water Plastic, crushed into 3 mm thin strip without rupture, After wetting the color remains the same The touch finger is slightly moistened when squeezed No water appears, moist after the color to keep constant There is free water in the wet, part of the soil pore space saturation soft, can be crushed into < 3 mm thin Contact fingers quickly wet, squeeze when There is water Saturation All porosity is saturated, there is free water All pore saturation, there is free water All pore saturation, presence of free water Filling the surface soil contains moisture The surface soil contains water. The surface soil contains water

Appendix B

(Informative) Standard redox buffer solution potential value Table B.1 Standard Oxidation Reduction Buffer Solution Potential (quinone hydroquinone) PH = 4 (mV) pH = 7 (mV) Reference electrode 20 ° C 25 ° C 30 ° C 20 ° C 25 ° C 30 ° C Saturated silver - silver chloride 268 263 258 92 86 79 Saturated calomel electrode 223 218 213 47 41 34 Saturated hydrogen electrode 471 462 454 295 285 275 Table B.2 Standard oxidation-reduction buffer solution potential (potassium ferricyanide-potassium ferrocyanide) PH Eh (mV) pH Eh (mV) 2 750 10 -150 3 710 11 -320 4 620 12 -480 5 500 13 -560 6 390 14 -620 Table B.3 Standard Redox Buffer Solution Potential Values (Standard Hydrogen Electrode) Mol/L Eh (mV) 0.01 415 0.007 409 0.004 401 0.002 391 0.001 383 Note. with 0.001 mol/L potassium ferricyanide and potassium ferrocyanide solution measured the most accurate. A potassium ferricyanide and potassium ferrocyanide solution concentrations are equal.

Appendix C

(Informative) Reference electrode potential value Table C Potential value of the reference electrode corresponding to the standard hydrogen electrode at different temperatures Unit. mV Calomel electrode 0.1mol/L KCl Calomel electrode 1mol/L KCl Calomel electrode Saturated KCl Silver - silver chloride 1mol/L KCl Silver - silver chloride 3mol/L KCl Silver - silver chloride Saturated KCl 50 331 274 227 221 188 174 45 333 273 231 224 192 182 40 335 275 234 227 196 186 35 335 277 238 230.200 191 30 335 280 241 233 203 194 25 336 283 244 236 205 198 20 336 284 248 239 211 202 15 336 286 251 242 214 207 10 336 287 254 244 217 211 5 335 285 257 247 221 219 0 337 288 260 249 224 222

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