Soil sampling technology (2)

3.

According to the types of soil pollution and monitoring items, the types of samples are divided into individual samples, mixed samples, profile samples, and layered samples

(1) Separate sample

It is suitable for the monitoring of atmospheric deposition polluted and solid waste polluted soil, as well as the determination of volatile and semi-volatile pollutants

Figure 2-6 Example of separate sample collection

(2) Mixed samples

It is suitable for irrigation water pollution type, agricultural chemical substance pollution type, macro-regional soil environmental monitoring (soil census), and the determination of soil inorganic and pesticide samples

①Plum Blossom Point Method

②Diagonal method

③Snake-shaped method (S-shaped)

④ Checkerboard method

The layout of sampling points for mixed soil is shown in Figure 2-7

After the sampling point is determined, collect the split-point samples in the sampling area

After mixing the samples of each sub-point with equal mass, discard them by the quarter method, and keep the soil sample equivalent to 1.

Figure 2-8 Sample collection of mixed samples

(3) Profile sample

When specific investigation, research and monitoring need to understand the vertical distribution of pollutants in the soil, soil profile samples are collected

The profile specifications are generally 1.

Generally, three layers of soil samples A, B, and C are collected for each section

For mountain soils where layer B is not fully developed (underdeveloped), only two layers A and C are used;

In arid areas, samples with imperfectly-developed soils were sampled at about 5-20 cm in the surface layer, 50 cm in the core soil layer, and 100 cm in the subsoil layer

The A layer is extremely thick, the sedimentary layer is not very developed, and the parent material is not visible within 1m.
The soil is collected according to the A layer 5-20cm, the A/B layer 60-90cm, and the B layer 100-200cm
.
Meadow soil and fluvo-aquic soil are generally sampled at 5-20cm in the A layer, 50cm in the Cl layer (or B), and 100-120cm in the C2 layer
.

The paddy soil is sampled in layers according to the A tillage layer, P plough bottom layer, and C parent material layer (or W fertile layer, G gyle layer).
For the section where the P layer is too thin, only the A and C layers (or A, G Layer or A, W layer)
.
The schematic diagram of the paddy soil profile is shown in Figure 2-9
.

Figure 2-9 Schematic diagram of the section of paddy soil

The sampling sequence is from bottom to top.
The bottom layer of the profile is sampled first, then the middle layer samples, and finally the upper layer samples
.
For heavy metal samples, try to use bamboo chips or a bamboo knife to remove part of the soil in contact with the metal sampler, and then use it to sample (Figure 2-10)
.

Figure 2-10 Example of soil profile collection

Collect about 1kg of samples for each layer of the profile and put them into sample bags
.
The sample bag is generally sewn from cotton cloth
.
Such as wet samples can be lined with plastic bags (for the determination of inorganic compounds) or put the sample in a glass bottle (for the determination of organic compounds)
.

(4) Layered samples

It is suitable for soil monitoring in key areas, and the number of layers and depth of collection are determined according to the type of pollution and the specific pollution situation
.
Sampling is collected from bottom to top at different depths, each layer is collected in the middle of the soil according to the plum pattern method, and after mixing, it is discarded by the quarter method, and the soil sample equivalent to 1kg of air-dried soil is retained
.
The samples are divided into packages according to the analysis requirements
.

Related Links: Soil Sampling Technology (1)