GB/T 35523-2017 in English

Standard Background and Technology Evolution

This standard is equivalent to OECD 309 Guidelines (2004), developed in combination with ISO 14592 series standards, and together with GB/T 27853 and GB/T 27856, it constitutes a water-sediment system degradation test system. The 2017 version first introduced radioisotope tracer technology and semi-continuous operation methods, solving the problem of low-concentration organic matter degradation monitoring.

Core Test Principles

Use Centrifuge for Separation

Key operating procedures

1. Water sample collection: Avoid water bodies affected by similar pollutants within 4 years, and store them in the dark at 4℃ during transportation
2. Concentration design: At least 2 gradients (5-10 times difference), 1-10μg/L is recommended
3. Quality control:
   • Sterile control group (F_S): Sterilize at 121℃ for 20min
   • Reference group: aniline/sodium benzoate (10μg/L)
4. 14CO₂ determination:

   Direct method	Alkali absorption after acidification	Applicable to volatile products
   Indirect method	Liquid scintillation counting after air stripping	Conventional preferred method

Degradation kinetic analysis

Calculate the first-order degradation rate constant k (d^-1) through a semi-logarithmic coordinate graph, requirements:

• At least 5 sampling points after the stagnation period
• Linear correlation coefficient R²≥0.9
• Half-life t_0.5=ln2/k

Typical case: Aniline at 20℃ k=0.3-1.7d^-1 (t_0.5=0.9d)

Implementation suggestions

The test report must include phase distribution data (DOA/POA ratio) and mass balance calculation (recovery rate 90-110%)