Spatial distribution, pollution degree and hazard assessment of heavy metals in black soil layer of five counties in Eastern Qiqihar, Heilongjiang Province

Objective To understand the spatial distribution characteristics and pollution degree of heavy metals in cultivated black soil of five counties in the east of Qiqihar (Fuyu County, Yi'an County, Baiquan County, Keshan County and Kedong County), so as to provide scientific basis for regional land development and utilization and ecological risk management.

Methods 157 black soil samples were collected to determine the contents of as, CD, Cr, Cu, Ni and Zn; Kriging interpolation method was used to study the spatial distribution of heavy metal content; Single factor index method, Nemerow comprehensive index method, geoaccumulation index method and ecological risk index method were used to evaluate the pollution degree.

Results The average contents of as, Cd, Cr, Cu, Ni and Zn were 11.3×10⁻⁶, 0.07×10⁻⁶, 59.1×10⁻⁶, 22.4×10⁻⁶, 31.2×10⁻⁶ and 60×10⁻⁶, respectively. Except for Cd, the average contents of other elements were higher than the background value of Songnen plain soil; Kriging interpolation results showed that the spatial distribution characteristics of other elements were relatively consistent (high content in the middle and low content on both sides), except that the high value area of Cd was mainly located in the central and southern part of the study area; The results of the four evaluation methods show that the study area belongs to non pollution level and low potential risk level as a whole.

Conclusions The overall pollution level of heavy metals in the black soil layer of cultivated land in the five counties in the east of Qiqihar is low, non hazardous, and in a clean and safe state. The relevant research results can provide data support for regional cultivated land protection and agricultural planting, and help the ecological risk management and scientific planning in land development and utilization.