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Based on nighttime light data and statistical data, this study calculated the level of urban-rural integration (URI) of Shandong province, researched spatial heterogeneity of URI levels by local spatial autocorrelation analysis, Geodetector, and geographically weighted regression, and analyzed its influencing factors and spatial heterogeneity. The results concluded that: (1) The spatial pattern of urban-rural integrated level is consistent with the level of regional economic development in Shandong province. The level of URI is higher along the Qingdao-Jinan railway and along the coast, whereas the level is lower in southwest Shandong and northwest Shandong. (2) The cities of Yantai and Weifang are High-High cluster areas of urban integration, and Jining is a Low-Low cluster area. The spatial agglomeration characteristics are not significant in other cities. (3) Among the main factors affecting URI, the explanatory power of the rural population with high school or technical secondary school education or above, the area of urban construction land, and the secondary and tertiary industry GDP to the spatial pattern of URI in Shandong province are 73.58%, 62.08%, and 58.66%, respectively. As the key factors, spatial heterogeneity, such as north-south differences, southwest-to-northeast differences, and east-west differences, is evident., (© 2022. The Author(s).)

The vegetable greenhouse soils in Yanglou Town, Ruzhou City, Henan Province were taken as the research object in the present study to explore the difference in soil physical and chemical properties and the total and fraction of heavy metals of different planting years. The potential ecological risks of heavy metals in greenhouse soils with different planting years were assessed by using single and comprehensive potential ecological risk index methods. The results showed that the soil pH of vegetable greenhouses increased, and fertility factors such as organic matter, available phosphorus, and alkali-hydrolyzable nitrogen accumulated to a certain extent compared to the control group, whereas catalase showed a decreasing trend. Correlation analysis showed that the planting years were significant positively correlated with pH ( P <0.05) and organic matter ( P <0.01) and significant negatively correlated with catalase ( P <0.01). The amount of heavy metals in the vegetable greenhouse soils increased with the increase in planting years, among which Cu, Zn, and Cd increased most obviously, with maximum increases of 129.14%, 204.17%, and 161.11%, respectively. The proportion of acid-soluble and reducible heavy metals in the vegetable greenhouse soils also increased gradually with the planting years, and the proportion of residual heavy metals decreased correspondingly, which resulted in the heavy metals transforming into fractions easily absorbed by plants. The results of the single potential ecological risk index showed that Cd in vegetable greenhouse soils had a strong ecological risk with the increase in planting years, whereas Cu, Pb, Zn, and Ni were in the mild risk category. The comprehensive potential ecological risk index showed that the heavy metals in the vegetable greenhouse soils of different planting years have reached a strong or very strong ecological risk.