**4. Mitigation methods**

#### **4.1. Soil structure reforms**

Soil is an important medium for salt and water transport. Its structure directly determines the hydraulic conductivity. The capillary effect is the major force driving water rise, whether the water table located on the capillary rise zone has an obvious effect on the amount of evapora‐ tion. Once the capillary is destroyed if a multilayered structure is designed in the land reclamation zone, the salt accumulation process will be prevented. Therefore, it is meaningful to design multilevel backfilling technology based on the mechanism of salt movement in the reclamation area. Hornbuckle et al. [13] introduced that multilevel drainage system could provide faster leaching rate in the root zone, without increase in salt loads.

#### **4.2. Sediment property modifications**

In the reclamation regions, coastal sediment is often used to improve the physical and chemical properties of soil and construct grassy areas, because the organic matter content in offshore and river areas is high and acidic. Containing abundant microbes, sediment can increase the number of microorganisms and soil microbial population structure and improve the fertility of soil enzyme activity and content of humus. However, coastal sediment is rich in salt and heavy metal pollutants, and the soil particle size is small, which is easy to harden after dehydration. Therefore, coastal sediment needs to be modified before its application on the reclamation soil.

#### **4.3. Rainwater utilization and desalination**

countermeasures such as recharge wells are suggested to promote salt water discharge into

Soil is an important medium for salt and water transport. Its structure directly determines the hydraulic conductivity. The capillary effect is the major force driving water rise, whether the water table located on the capillary rise zone has an obvious effect on the amount of evapora‐ tion. Once the capillary is destroyed if a multilayered structure is designed in the land reclamation zone, the salt accumulation process will be prevented. Therefore, it is meaningful to design multilevel backfilling technology based on the mechanism of salt movement in the reclamation area. Hornbuckle et al. [13] introduced that multilevel drainage system could

In the reclamation regions, coastal sediment is often used to improve the physical and chemical properties of soil and construct grassy areas, because the organic matter content in offshore and river areas is high and acidic. Containing abundant microbes, sediment can increase the number of microorganisms and soil microbial population structure and improve the fertility

provide faster leaching rate in the root zone, without increase in salt loads.

the sea and inhibit seawater intrusion.

172 Soil Contamination - Current Consequences and Further Solutions

**Figure 9.** Groundwater chloride concentration in model area.

**4. Mitigation methods**

**4.1. Soil structure reforms**

**4.2. Sediment property modifications**

Phreatic water is a sensitive element of the environment. Due to the shallow depth and high salinity of groundwater, efficient desalination system for reclaimed land is necessary. Many scholars used drainage system in salt elimination, but well‐canal combined method is the main desalination technology recently [14, 15]. For coastal saline soil, desalination technology based on hydraulics was proposed. The freshwater resources in semi‐humid regions are limited, and the groundwater discharge is not enough to push the fresh‐salt water downwards to the sea. In the sea reclamation region, rainwater is infiltrated into soil by engineering measures, which could remedy the seasonal distribution defect of precipitation and adjust the groundwater environment. For example, rainwater is collected to construct the layer of salt leaching, and the soil drainage system is improved to control the underground water level and the salt content. Both methods above prove that it is feasible to build the long‐term desalination mechanism of rain. Xu et al. [16] found that rainwater infiltration through pervious pavements can effectively resist seawater intrusion and the interface of fresh‐salt water is pushed to the coastline. It is helpful to combat the salinization using rainwater infilling method in urban area.

#### **4.4. Conservation tillage**

Although the parent material under the reclaimed soil is complicated, the clay layer contains little organic matter due to lacking of supply. Soil and water loss will damage ecological resources and lead to ecological degradation. Conservation tillage has been used in the northeast of China to protect soil and water resources by preventing soil erosion. For example, straw return is an efficient strategy to enhance soil fertility, which provides a buffer for raindrops to transfer energy and promotes the infiltration rates of salt leaching. In the long term, conservation tillage will be an efficient method for saline soil restoration and ecosystem restoration.
