An investigation was made into the effects of tannery sludge on soil chemical properties and microbial communities in a typical soil profile with long-term tannery sludge contamination, North China. The results showed that trivalent chromium (Cr(III)), ammonium, organic nitrogen, salinity and sulfide were the predominant contaminants in tannery sludge. Although the tannery sludge contained high chromium (Cr, 3,0970 mg/kg), the proportion of mobile Cr forms (exchangeable plus carbonate-bound fraction) only accounted for 1.32%. The X-ray diffraction and X-ray photoelectron spectroscopy results further demonstrated that the Cr existed in a stable state of oxides and iron oxides. The alkaline loam soil had a significant retardation effect on the migration of salinity, ammonium, Cr(III) and sulfide, and the accumulation of these contaminants occurred in soils (0–40 cm). A good correlation (R² = 0.959) was observed between total organic carbon (TOC) and Cr(III) in the soil profile, indicating that the dissolved organic matter from sludge leachate promoted the vertical mobility of Cr(III) via forming Cr(III)-organic complexes. The halotolerant bacteria (Halomonas and Tepidimicrobium) and organic degrading bacteria (Flavobacteriaceae, Tepidimicrobium and Balneola) became the dominant microflora in the soil profile. High contents of salinity, Cr and nitrogen were the main environmental factors affecting the abundance of indigenous microorganisms in soils.

To effectively control soil pollution, an action plan (called Soil Plan) was carried out by Chinese government in 2016, which may cost CNY 1.14 trillion during the 2016–2020 period. To evaluate the potential impacts of this action plan on the national economy and environmental control, this study employed a closed macro input-output model to quantitatively account for the economic and environmental impacts from the view of the whole domestic supply chain. Our results show that the implementation of the Soil Plan may stimulate economic development and bring more jobs. It will help generate a gross domestic product (GDP) of CNY 2.72 trillion, with CNY 358.11 billion (15%) made from direct contributions, and CNY 2.36 trillion (85%) from indirect contributions. Meanwhile, the scheme could also produce 2 million jobs within five years, of which 580,000 (29%) are a direct contribution, and 1.42 million (71%) are an indirect contribution. On the other hands, increased demands for products and services of various sectors (such as power/heat production and supply, and chemical products) would also cause more air and water pollutants along with domestic supply chains. The emissions of sulfur dioxide(SO₂), nitrogen oxide(NO_x), chemical oxygen demand (COD) and ammonia nitrogen(NH₃-N) would increase by a total of 5.20 × 10⁵ t, 5.27 × 10⁵ t, 1.62 × 10⁵ t and 9.36 × 10³ t, respectively. Our results may raise the concern about the indirect impacts of an environmental policy for the policy maker from both economic and environmental perspectives.

Identifying the driving factors of soil environmental quality is critical in raising countermeasures for managing the soil environment efficiently and precisely. In 2018, China issued risk control standards to divide soil environmental quality into three classes to meet the demands of environment management. However, there is a lack of knowledge of this new standard. An intensive field-sampling research (2598 top-soil samples were analyzed) was conducted in the agricultural land of Hubei province, central China, to find the driving factors of pollutants based on this new standard. According to the standard, the proportion of classes 1, 2, and 3 in the overall quality grade was 57.3%, 41.7%, and 1%, respectively. The standardized index showed that the pollution levels of cadmium, arsenic, lead, and chromium were higher than that of mercury. The first component of the principal component analysis explained 56.4% of the total variance, and the loading of cadmium, arsenic and lead were −53.5%, −52.1%, and −51.2%, respectively. The general linear modeling found that cadmium and arsenic showed positive and significant effects (p < 0.001) on the grading results of soil environmental quality. Based on the random forest algorithm, cadmium showed the greatest importance on soil environmental quality (increase in mean squared error = 32.5%). Overall, this study revealed that cadmium, arsenic, and lead were driving pollutants affecting soil environment quality grade. The large data size increased the reliability and robustness of the study’s conclusions, and it provided reference methods for future studies investigating China’s new standard for assessing soil environmental quality.