Assessing the effect of potential water and salt intrusion on coastal wetland soil quality: simulation study

Abstract

Purpose

Faced with the increasing threat from seawater intrusion, it is of great importance to explore the effect of the increase of water and salt on the coastal wetland soil quality. A simulation experiment was designed in this study to identify the impact of water and salt on soil quality in the coastal wetland of Jiaozhou Bay, China.

Materials and methods

Three soil quality indices were applied to investigate the influence of different water and salt conditions on soil quality. Every index was computed by applying the total data set (TDS) and minimum data set (MDS) methods. The TDS included nine soil quality properties determined in 96 samples including pH, bulk density (BD), total organic matter (TOM), ammonium nitrogen (NH₄⁺-N), available phosphorus (AP), available potassium (AK), sucrase activity (SA), urease activity (UA), and alkaline phosphatase activity (APA). Principal component analysis (PCA) was applied to selected indicators for MDS.

Results and discussion

Soil quality decreased with the increase of salt content, and it increased first and then decreased with the increased water content. The soil samples with 60% water content had the lowest quality. Meanwhile, the nutrient indicators and enzyme activity in these soil samples were also lower than those in the other water gradients. The results of soil quality classification showed that the soil quality was mostly reckoned as moderate quality (grade III) and below and only a fraction of these samples was grade I based on all indices.

Conclusions

The results showed that too much water and salt in soil can decrease soil quality, and the effect of water was more obvious than salt. The results of match and kappa statistical analyses indicated that soil quality estimated by the weighted additive soil quality index was more accurate than those estimated by the additive soil quality index and Nemoro soil quality index. Besides, the agreement values of TDS were higher than those of MDS.

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