Impacts of cultivated land landscape patterns on the risk of soil heavy metal pollution in economically developed areas

Landscape patterns indexes have widely been used to clarify the variation of landscape patterns under heavy metal accumulation in various ecological processes. One of the most important landscape types, cultivated land is profoundly disturbed by human activities in recent years, where the generation and evolution of heavy metal pollution are closely related to the landscape pattern. However, it is still lacking understanding of the relationship between landscape patterns and soil pollution in cultivated land. In this study, an attempt was made to explore the impact of landscape patterns on the risk of soil heavy metal pollution in cultivated land, thereby ensuring national food and ecological security. Taking an economically developed area in eastern China as an example, a Nemoro index model was employed to assess the level of soil heavy metal (Cd, Pb, and Hg) pollution using 93 point sampling laboratory data. Then, the landscape pattern indexes were selected from four aspects to evaluate the distribution of landscape patterns in cultivated land. Finally, the stepwise and spatial regression models were used to determine the relationship between landscape patterns and heavy metal pollution. The results showed that: 1) The average range of indexes was between 0.22 and 0.42 in the study area, including three indexes of soil heavy metal pollution, and Nemero comprehensive pollution index. The level of three heavy metal pollution was ranked in an order of Pcd>Ppb>Phg, indicating a relatively low risk of pollution. Furthermore, the variation coefficients of the single-factor pollution index were all greater than 0.5, indicating that the heavy metal pollution of farmland soil was significantly affected by external interference. 2) There was an obvious spatial differentiation on the comprehensive degree of heavy metal pollution in the cultivated land. The areas with higher pollution risks presented a clustering spatial distribution, where mainly concentrated in the southwestern and northern parts of the study area, as well as the surrounding areas of urban centers. The areas with lower pollution risks are mainly distributed in the northwestern basin. 3) There was a fluctuating downward for the level of cultivated land heavy metal pollution in the spatial gradient, especially in the urban-rural and road gradient. Meanwhile, the landscape pattern indexes in the cultivated land showed a trend of increasing first, and then decreasing in the urban-rural gradient, whereas, gradually downward trends in the river and road gradients. Correspondingly, cultivated land landscape patterns were found to be highly correlated with soil heavy metal pollution in spatial gradient. 4) There was a significant spatial autocorrelation in the heavy metal pollution, where landscape patterns profoundly affected both in local and adjacent areas. Specifically, the patch size, fragmentation, and landscape shape indexes were negatively correlated with three types of soil heavy metal pollution, whereas, there was a positive correlation between landscape aggregation and heavy metal pollution in the cultivated land. Anyway, this research can greatly contribute to determining the relationship between cultivated land landscape patterns and soil heavy metal pollution. The finding can provide insightful implications to control the soil heavy metal pollution from the perspective of landscape pattern optimization. © 2021, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.