Distribution characteristics, influencing factors, and ecological and environmental effects of soil sulfur in Huai'an agricultural land

Objective The study area is located in the core area of the Northern Jiangsu Plain, characterized by complex geological settings. Under the combined influences of geological processes and anthropogenic activities, the spatial variability of soil sulfur exhibits significant heterogeneity. However, the key factors influencing its spatial distribution and its corresponding ecological environmental effects remain poorly understood.

Methods The paper compares soil sulfur content under varying depths, soil types, landforms, and land uses, evaluates sulfur balance, identifies distribution patterns and driving factors, and preliminarily explores ecological environmental effects.

Results The mean concentration of sulfur in topsoil is 388×10⁻⁶ and distinctly elevated compared with the mean background level of soil in Jiangsu province. The overall spatial distribution suggests that the southern part is higher than the northern one, and the vertical distribution gradually decreases with depth. The concentration of sulfur in different soil types is the highest in marsh soil, the second in paddy soil, and the lowest in fluvoaquic soil. Among different types of landforms, the fan edge lake marsh plain area is the highest, and the alluvial sand dam highland is the lowest. Based on the comparison of land use patterns, the concentration of soil sulfur is the highest in irrigated land and lowest in woodland. The concentrations of soil sulfur exhibit a significant positive relationship with the contents of organic matter(P＜0.01). The evaluation results of soil sulfur balance in agricultural soil show that the net increase will be 58.21 kg/hm² annually. Compared with the multi-target data in 2004, the content of sulfur in agricultural soil in the study area has been accumulated to some extent in the last 15 years.

Conclusions The distribution characteristics of soil sulfur are closely related to soil depth, soil type, land use patterns, and organic matter content. Hotspots of sulfur accumulation correspond to areas with greenhouse agriculture (e.g., red pepper cultivation), primarily due to the extensive application of sulfur-containing fertilizers such as potassium sulfate compound fertilizers and organic fertilizers. These regions have shown a trend of soil acidification, contributing to sulfur loading in surrounding water bodies. Therefore, ecological risk monitoring is recommended.