GB/T 42629.2-2023 in English

As an important part of the supporting environmental survey technology system for deep-sea resource exploration, this standard systematically regulates the survey methods for seawater chemical elements, sediment chemical characteristics and trace elements in the international seabed area and the high seas environment. Its technical framework is synchronized with the environmental guidelines of the International Seabed Authority (ISA), reflecting the standardization level of my country in the field of deep-sea environmental survey.

1. Low-concentration phosphate detection technology

For the low-nutrient environment in the deep sea, the standard innovatively proposes the magnesium hydroxide co-precipitation-phosphomolybdenum blue method, which reduces the detection limit to 0.8nmol/dm³ through Mg(OH)₂ adsorption enrichment, which is 25 times more sensitive than conventional methods.

2. Clean laboratory system

Trace element analysis must be carried out in an ISO 5 clean environment, and the sampling bottles must undergo six levels of purification: including acid leaching, ultrapure water cleaning, trace acid preservation and other steps to ensure that the blank value of heavy metal analysis meets the standard.

Sampling design principles

• Grid station layout: latitude and longitude grids are used in combination with the seabed topography. When the water depth is greater than 3000m, additional sampling from the bottom layer is required.
• Stratified sampling: 13 standard layers are set from 0 to 3000m, including the near-bottom layer (10m from the bottom) with special requirements.
• Quality control: Each batch of samples must contain 15% parallel samples, and the qualified rate must be greater than 90%.

Typical application cases

In the investigation of polymetallic nodules, the GO-FLO water sampling bottle and Kevlar cable sampling, the measured deep water Cu background value is 1.2±0.3nmol/dm³, and the data quality meets the ISA report requirements.

Compared with the 2007 version of the marine survey specification, the main breakthroughs of this version are:

1. New analysis methods for biogeochemical indicators such as methane and amino acids
2. Introduction of the element analyzer method to determine the total organic carbon in sediments (replacing the traditional potassium dichromate oxidation method)
3. Clarify the sample storage time in special deep-sea environments (e.g. fixed dissolved oxygen samples can only be stored for 24h)