GB/T 36783-2018 in English

Interpretation of the safety threshold standard for heavy metals in dryland soil for growing root vegetables

The National Standard of the People's Republic of China GB/T 36783-2018 "Safety thresholds for cadmium, lead, chromium, mercury and arsenic in dryland soil for growing root vegetables" is an important standard formulated to ensure the quality and safety of agricultural products and guide agricultural producers to scientifically evaluate and manage soil heavy metal pollution.

Background of standard formulation

With the acceleration of industrialization and unreasonable farming practices, the problem of heavy metal pollution in soil has become increasingly prominent. Due to their growth characteristics, root vegetables are prone to absorb and accumulate heavy metal pollutants, which directly threatens food safety. This standard is based on a large number of scientific research and practical verification, and provides a scientific basis for the evaluation of soil environmental quality for growing rootstalk vegetables.

Technical evolution analysis

The formulation of this standard follows GB/T1.1-2009 "Guidelines for Standardization Work Part 1: Structure and Writing Rules of Standards", and refers to a number of advanced domestic and foreign standards. Compared with the previous soil heavy metal limit standards, this standard has the following characteristics:

• For the first time, a special safety threshold is set for rootstalk vegetables
• Comprehensive consideration of influencing factors such as soil pH and organic carbon content
• Detailed monitoring and analysis method requirements to ensure data accuracy
• Increased guidance on risk assessment and response measures for exceeding the standard

Standard Framework Comparison Table

Detailed explanation of safety thresholds

Cadmium (Cd)

Table 1 specifies the safety thresholds of cadmium under different pH values and organic carbon contents, ranging from 0.20 mg/kg to 0.70 mg/kg.

Lead (Pb)

Table 2 lists the safety threshold range of lead based on soil cation exchange capacity (CEC), ranging from 40 mg/kg to 290 mg/kg.

Chromium (Cr), mercury (Hg), arsenic (As)

Table 3 specifies the safety thresholds of these three heavy metals, with the upper limit of total arsenic being 75 mg/kg and the upper limit of total mercury being 3.0 mg/kg.

Monitoring and analysis requirements

Sample collection

In accordance with NY/T395 "Technical Specifications for Monitoring of Agricultural Soil Environmental Quality", monitoring points shall be set up to ensure that the samples are representative.

1. Determine the sampling area and depth (usually 0-20cm)
2. Avoid sampling on ridges and special parts
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3. Mix multiple samples to make standards for analysis

Test method

Result analysis

When the content of heavy metals in the soil is lower than the threshold value in the table, the cultivation of rootstalk vegetables can be carried out normally; if it exceeds the standard, risk assessment must be carried out and corresponding measures must be taken.

Implementation suggestions

1. Strengthen publicity:Popularize the content of the standards through training and manuals to improve farmers' awareness.
2. Improve the monitoring network:Establish a regular monitoring mechanism in major vegetable producing areas.
3. Promote technology application:Encourage the use of rapid testing equipment such as mobile soil testers.
4. Develop emergency plans:Plan treatment plans in advance for areas where the standards are exceeded.