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This study examined how maturation time (3, 6 and 12 months) of sewage sludge compost added to soil contaminated with heavy metals (HMs), i.e., Cu and Zn affects: (1) the redistribution pattern of HMs; (2) metal mobility (as mobility factor, M F) and metal stability (as reduced partition index, I R); (3) rate constants of metal transformations in exchangeable and acid-soluble (F1) fraction and rate constants of metal redistribution in all fractions (F1–F4). Soil without amendments was used as a control. It was shown that compost maturation time did not affect metal redistribution. After 12 months of incubation in non-amended soil, Cu still showed medium mobility (M F = 16.5 %), while in amended soil it had low environmental risk (M F = 6.2 %). In contrast, Zn was highly mobile (M F = 43.4 %) in all treatments. Compost addition favored only Cu redistribution into more stable fractions. For both metals, the rate constants of redistribution were an order of magnitude lower than rate constants of metal transformations in the F1 fraction.

To address climate change, one of the toughest contemporary environmental issues, growing importance is attached to the role of the digital economy in combating environmental degradation. Using panel data from 237 Chinese cities during the period 2011–2018, this paper attempts to provide a more systematic view of the relationship between the digital economy and urban low-carbon sustainable development to make up for the existing empirical inconclusiveness. Based on the fixed-effect model, results show that boosting the digital economy can effectively promote urban low-carbon sustainable development, and the conclusion remains robust across a series of robustness checks. Furthermore, innovation factor mobility is the critical transmission channel through which the digital economy affects urban low-carbon sustainable development. Spatiotemporal heterogeneity analysis reveals that the promoting effect of the digital economy on urban low-carbon sustainable development decreases from the northeast to the southeast of China, whereas the impact of innovation factor mobility on urban low-carbon sustainable development decreases from the southeast to the northeast with the Pearl River Delta as the core. Panel threshold regression analysis shows that the impact of the digital economy on urban low-carbon sustainable development is getting stronger with the increase of economic development level charactered with nighttime lights.

In the context of the rapid development of the Internet, the digital economy has become an important growth engine, which has an important impact on the optimization of resource allocation. This paper takes the digital economy for resource allocation efficiency as the research framework and explores the impact mechanism of the digital economy from the perspective of factor flow. After relevant data research, the development capacity of the digital economy has an important positive impact on both capital and labor dimensions in terms of resource allocation, and the digital economy can balance the way of resource allocation in different regions under the perspective of factor mobility. The current analysis of regional heterogeneity shows that the impact of the digital economy in China’s inland regions is higher than that in China’s coastal regions. Based on the above conclusions, this study suggests that it is necessary to further develop digital technology, promote the deepening reform of government policies, regulations, and institutions, and promote the reform of the factor market, to enhance the efficiency enhancement of the digital economy in the allocation of resources.

The international movement of economic factors such as capital and skilled labor has complex effects on the economies involved, especially when multiple factors move at the same time. One important effect is the potential change in wage inequality between skilled and unskilled labor—particularly, in developing countries that have agreed to trade with developed countries. This study considers a small open economy with two goods and three factors to determine whether wage inequality increases or decreases due to increased movement of these factors. The key findings are that wage inequality can unambiguously increase and decrease, under certain circumstances regarding the capital intensity of the sector(s), the initial amount of foreign factors, and the shares of factors in national income.

Polymetallic ore processing plants are serious sources of heavy metal pollution. The present study examined the degree of pollution of surface soils with the metals zinc, cadmium, lead, and copper in the single-industry town of Kentau, Kazakhstan, where an enterprise for the processing of lead–zinc ore has been operating for a long time. This enterprise ceased operations in 1994, and this study may be of interest in terms of assessing the current ecological state of urban soils after a 27-year period of possible soil self-cleaning processes. The study showed that the surface soils of Kentau retain fairly high concentrations of metals. The maximum detected concentrations of zinc, cadmium, lead, and copper were 592 mg/kg, 1.651 mg/kg, 462 mg/kg, and 82.5 mg/kg, respectively. According to the classification of the geoaccumulation index, the soils of the town belong to pollution classes II, III, and IV with moderate and strong pollution. The calculated potential ecological risk factor indicates that cadmium poses a considerable potential ecological risk, while lead showed a moderate ecological risk. In general, according to the obtained values of potential ecological risk factors, metals can be arranged in the following order: Cd > Pb > Zn > Cu. In this study, a five-step sequential extraction procedure by the method of A. Tessier was used, and the mobility factors of metals were calculated. Based on the data obtained, it was found that cadmium and lead have the highest mobility and, consequently, availability for biota in modern conditions, which may pose a potential risk to public health in the town.

Soil contamination due to industrial activity in ceramics production is of concern because of the risk of heavy metal pollution. Successive extraction was used to measure and identify the concentrations of Cd, Mn, Ni, and Pb in farming soils near a ceramics company in Nigeria. Furthermore, soil pH and particle size analyses were determined. The concentration of Pb was the highest, followed by that of Ni, Mn, and Cd (lowest), and the mean level of Cd exceeded the regulatory allowed limit of 1.4 mg kg −1 . The order of the metals' mobility factors was as follows: Cd > Mn > Ni, Pb. While the Fe–Mn oxide phase had 37% (Mn) and 20 to 83% (Ni), the residual fraction had approximately 30% (Cd) and 19 to 50% (Pb). Soil pollution evaluation was performed using enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geoaccumulation index (I geo ). Values of EF indicated significant enrichment for all metals, as the EF mean values for Cd, Ni, and Pb in soil were > 1.5. Total EF is of the order Cd > Pb > Ni > Mn. CF results revealed moderate to very high contamination (CF < 1: 3 ≤ CF ≥ 6). Similarly, the PLI indicated moderately to severely polluted soil. The order is 100 m > 200 m > 300 m > 400 m. The I geo ranged from 1.46 to 2.76 (Cd), 0.07 to 1.62 (Ni), and 0.05 to 2.81 (Pb). The PCA, CA, and EF analyses suggest that the metals are a consequence of anthropogenic activities.

This research focused on chemical speciation of six heavy metals in the bottom sediments of River Rwizi in Mbarara City, Uganda. Heavy metals cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and iron (Fe) and physicochemical parameters, namely pH, oxidation–reduction potential (ORP), and organic matter (OM), were assessed during wet and dry seasons. Sequential extraction procedure was applied to fractionate metals into six fractions: water-soluble, exchangeable, carbonate bound, Fe–Mn oxides bound, bound to organics, and residual fraction. Quantitative determination of heavy metals was carried out using flame atomic absorption spectrophotometer. Speciation results revealed that the potential mobility of heavy metals decreased from wet to dry season, and it was in the increasing order of Zn > Cu > Cd > Pb > Ni > Fe, in both seasons. Higher concentrations of heavy metals were present in their immobile chemical forms than in their potentially mobile chemical forms. The total mean contents in mg kg−1 (except Fe in %) of the metals were Cd: 1.63 ± 0.21; Cu: 106.10 ± 23.22; Ni: 38.17 ± 6.07; Pb: 33.45 ± 3.33; Zn: 108.34 ± 30.51; Fe: 3.04 ± 0.75, and Cd: 1.64 ± 0.23; Cu: 111.10 ± 27.36; Ni: 39.81 ± 7.90; Pb: 33.98 ± 3.63; Zn: 115.72 ± 31.64; Fe: 3.08 ± 0.75 during wet and dry seasons, respectively. The geochemical accumulation indices of Cd, Cu, Pb, and Zn showed that the bottom sediments of River Rwizi ranged from unpolluted to severe polluted sediments, which implied anthropogenic input. Other parameters measured from wet to dry season were, pH: 6.8 ± 0.35 - 6.21 ± 0.08; ORP: 308.4 ± 44.7 mV - 342.1 ± 39.6 mV; OM: 2.0 ± 0.35% - 1.4 ± 0.31%. Conclusively, it was found that heavy metals (Zn, Cu, and Cd) were significantly present in their potential mobile fractions alarming that they may pose serious human and environmental problems.

Land-use change significantly impacts soil micro-nutrients distribution and transformations due to their inefficient scale- and location-specific management in different ecosystems. We studied the changes in micro-nutrients (viz. Zn, Cu, Fe and Mn) availability and their transformations in soils of hilly landscapes under five distinct land-use systems including mono cropping, double cropping, agroforestry, orchards and the vegetable crops to explore relationship between different fractions of variable solubility and their mobility in response to land-use change. Among the compared land-use systems, DTPA-Zn, Fe, Mn and Cu comprised ~ 3.0 to 8.2%, ~ 0.21 to 0.35%, ~ 1.2 to 6.3% and ~ 7.6 to 17.5% of their respective total content in soils. The agroforestry system had significantly (p < 0.05) higher DTPA-Zn and Mn, compared with mono-and double cropping system. However, the orchard soils had ~ 2.1, 2.0 and 3.4-times higher DTPA-Zn, Fe and Cu concentration than the agroforestry system. The agroforestry system was distinct with significantly highest proportion of total Cu retrieved as amorphous oxide bound (~ 20.5%), crystalline oxide bound (~ 33.6%), organic matter bound (~ 2.1%), while the lowest proportion was accumulated as residual form (~ 43.8%), compared with the other studied land-use systems. The mobility factor that explicit micro-nutrient transformations among soluble and stable pool revealed that monocropping had the significantly lowest (~ 3.3%), while the agroforestry system had the highest Zn mobility factor (~ 4.9%). On the other hand, agroforestry system had significantly lowest (~ 1.8%), while the soils under vegetable crops had the highest Mn mobility factor (~ 7.5%). The principle component analysis (PCA) elucidated residual micro-nutrient (Zn, Fe and Mn) fraction as significant contributors to discern land-use change in fragile hilly landscapes. These results highlight the importance of micro-nutrients management through robust interventions for long-term sustainability different land-use systems in a cold high altitude Himalayan mountainous region.

In previous analyses of regional underdevelopment, aspects such as technological progress, the implications of growth theory, depreciation (especially capital), capital input, and technology input have been completely ignored. Desmet and Ortίn analyze rational underdevelopment using a Ricardian model. This study investigates the underdevelopment of regions in the light of the Solow model. Two regions with two sectors are considered for the model. The regions are characterized by different technological equipment. The first region is industrial. The second region has an agricultural character. When a new technology is available, both regions can benefit under certain conditions. Financial transfers between regions equalize incomes. The security of transfer payments is positive; the increase in income levels without an increase in productivity is negative. The regions have different depreciation rates, factors, and technology endowments. Enlargement to a growth theoretical model framework (Solow model) should demonstrate the effects of an economy’s investments, constant depreciation rates, population growth, and technological progress. This will make it possible to see how the new influencing factors influence the utility of the two regions.

Open public data is a vital institutional arrangement for overcoming data constraints in corporate low-carbon technological innovation. Using a panel dataset of China’s Shanghai and Shenzhen A-share listed firms over the 2007–2023 period, this study employs a difference-in-differences (DID) approach to examine the impact of open public data on corporate low-carbon technological innovation. The results show that open public data has a significant positive effect on corporate low-carbon technological innovation, and the results remain robust across multiple validation tests. Mechanism tests point out that government transparency negatively moderates the promotional effect of public data openness on corporate low-carbon technological innovation, while barriers to factor mobility positively moderate this effect. The heterogeneity analysis indicates that the positive impact of open public data is more pronounced among firms characterized by higher R&D investment, lower financial constraints, and greater digitalization. Further analysis indicates that open public data also exhibits significant geographic and industry spillover effects, with the geographic spillover following an inverted U-shaped pattern of decay and the industry spillover driven by peer imitation. This study provides evidence on leveraging open public data to stimulate low-carbon innovation and facilitate green economic transformation, offering valuable insights for advancing data-driven sustainable development globally.