Spatial distribution and correlation of heavy metals and carbon, nitrogen and phosphorus in forest soils and their effects on ecological environment in Honghe Prefecture, Yunnan Province

This paper is the result of ecological geological survey engineering.

Objective The study aims to clarify the spatial distribution characteristics of heavy metal pollution elements in soil, which is of great significance for the control and management of soil resources.

Methods Taking Honghe Prefecture, which is rich in mineral resources, as the research area, forest surface soil was sampled in 2021. The spatial distribution characteristics of 8 heavy metal elements and carbon, nitrogen, and phosphorus were analyzed. The pollution of heavy metals and the current status of carbon, nitrogen, and phosphorus nutrients were evaluated, and the intrinsic correlation between heavy metals and carbon, nitrogen, and phosphorus and their impact on the ecological environment were discussed.

Results The organic matter (57.96 g/kg) and total nitrogen (2.65 g/kg) in the forest soil of Honghe Prefecture belong to a very rich level, while total phosphorus is relatively lacking (0.98 g/kg), accounting for 27.78%. The distribution of heavy metals in the soil of the study area is uneven and exhibits strong variability. Overall, it belongs to mild pollution (Pc: 1.62), with a proportion of 37.50% being mild or above. It is mainly polluted by Cd, Cu, Cr, Ni, and As, with a proportion of 31.94%, 30.56%, 26.39%, 23.61%, and 20.83% being mild pollution or above. Among them, the high value areas of Cd are mainly distributed in Mile City and Luxi County, while the high value areas of Cu are mainly distributed in Luxi County Mile City and Kaiyuan City, the high-value areas of Cr are mainly distributed in the central region of the state. There is a highly significant positive correlation between soil total nitrogen and Hg (P<0.01), and a significant or highly significant positive correlation between total phosphorus and Cd, Pb, Zn, Ni, Hg, Cu, and Cr (P<0.05).

Conclusions More than one-third of the forest soil in Honghe Prefecture is contaminated with heavy metals, which urgently needs to be taken seriously. In view of this, relevant prevention and control suggestions are proposed to provide reference for soil ecological environment governance and sustainable development.