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Contamination by heavy metals is a significant issue worldwide. In recent decades, soil heavy metals pollutants in China had adverse impacts on soil quality and threatened food security and human health. Anthropogenic inputs mainly generate heavy metal contamination in China. In this review, the approaches were used in these investigations, focusing on geochemical strategies and metal isotope methods, particularly useful for determining the pathway of mining and smelting derived pollution in the soil. Our findings indicate that heavy metal distribution substantially impacts topsoils around mining and smelting sites, which release massive amounts of heavy metals into the environment. Furthermore, heavy metal contamination and related hazards posed by Pb, Cd, As, and Hg are more severe to plants, soil organisms, and humans. It’s worth observing that kids are particularly vulnerable to Pb toxicity. And this review also provides novel approaches to control and reduce the impacts of heavy metal pollution. Hydrometallurgy offers a potential method for extracting metals and removing potentially harmful heavy metals from waste to reduce pollution. However, environmentally friendly remediation of contaminated sites is a significant challenge. This paper also evaluates current technological advancements in the remediation of polluted soil, such as stabilization/solidification, natural attenuation, electrokinetic remediation, soil washing, and phytoremediation. The ability of biological approaches, especially phytoremediation, is cost-effective and favorable to the environment.

Rocky desertification has become a major environmental issue in the karst region of southwestern China. Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils, despite the relatively higher soil organic matter (SOM) content in limestone soil. The underlying mechanism remains ambiguous. We speculated that the geochemical characteristics of limestone soils in the karst region plays an essential role, especially the high calcium content of limestone soil. To test this hypothesis, we collected limestone soil samples from a limestone soil profile in the southwestern China karst region and extracted humic acid (HA) from these limestone soil samples. We investigated the interaction of Ca2+ and three HA samples on a joint experimental platform, which consists of an automatic potentiometric titrator, a UV–visible spectrometer, and a Fluorescence spectrometer. HA solutions were titrated by Ca2+ and optical spectra of the HA solutions were monitored during the titration experiments. The results indicated that: (1) the interaction of Ca2+ and HA is a combined process of adsorption and complexation. Adsorption dominated the overall distribution behavior of Ca2+, which could be fit by Langmuir and Freundlich isotherm models. Complexation was distinguished only when the concentration of Ca2+ is low; (2) the changes of UV–visible spectroscopy and excitation–emission matrix fluorescence spectroscopy spectra of HA samples when they were binding with Ca2+ implied the apparent molecular size and structure of HA became larger and more complex; (3) the combination of Ca2+ and HA plays an important role in the SOM preservation of limestone soils but the stability of the Ca–HA association was relatively weak. The present study draws attention to maintaining the relatively higher Ca2+ concentration in limestone soils in ecologic restoration attempts in karst regions.

This study prioritized initiatives within the China–Pakistan Economic Corridor (CPEC), foreign funding, and the associated environmental and national issues. Additionally, it analyzed these factors’ effects on improving infrastructure, commerce, and economic cooperation between China and Pakistan. Besides that, it also studies the current climatic, economic, and political challenges, mainly focused on water and agriculture issues. Climate, economic, and political issues affect the environment. These concerns deserve global attention. Pakistan mainly relies on agriculture, and its water scarcity predisposes it to economic losses, urbanization, and many socioeconomic problems. Climate change and the current flood have devastated the agriculture sector. Water scarcity affects agriculture too and significantly impacts the economy and food resources. The nation has not previously experienced such a profoundly distressing epoch. Pakistan has faced several environmental, economic, and political challenges; specifically, the fields of agriculture and water present notable apprehensions. Unfavorable climatic conditions impede the attainment of sustainable agriculture in Pakistan. Considering the strong reliance of agriculture on water resources, it is crucial to acknowledge that industrialization has resulted in substantial water contamination due to the presence of microplastics and heavy metals. Moreover, the South Asian region experiences a significant scarcity of water resources. Besides that, CPEC is the solution for the financial issues, but it is a big challenge for environmental degradation in the current stage, especially since foreign funding is a key challenge for increasing corruption and bringing more burden on the economy. Unfortunately, foreign funding is not good for Pakistan. To ensure safety, security, and sustainability, CPEC projects should follow environmental regulations. This study provides a new list of CPEC initiative priority tasks that more openly disrupt the initiative, serve the whole project, and give appropriate recommendations for future research and policy-making.

This study investigates the application of nanofluid (iNanoW)–polymer binary flooding system to enhance oil recovery efficiency in medium-to-high permeability reservoirs. Traditional polymer flooding technologies still have the potential for further improvement in these types of reservoirs. Therefore, this study combines iNanoW with the polymer flooding system to examine its effects on the rheological properties, injectability, interfacial performance, sweep volume, and recovery factor of the polymer solution. Experimental results show that iNanoW significantly improves the injectability of the polymer solution. The introduction of iNanoW reduces the size of polymer aggregates, as demonstrated by aggregate size and rheological performance experiments. Power-law model analysis reveals that the flow behavior of the polymer solution is further improved with the introduction of iNanoW, manifested by weakened shear-thinning behavior, reduced viscosity, and optimized flowability, which in turn helps to improve oil recovery efficiency. Moreover, iNanoW interacts with polymer molecules, lowering the surface tension and enhancing wettability, thereby improving oil–water separation efficiency. Core flooding experiments show that the introduction of iNanoW significantly increases sweep volume, particularly in medium- and small-pore spaces, where oil recovery efficiencies reached 57.97% and 61.54%, respectively. These results indicate that iNanoW not only optimizes the rheological properties of the polymer solution but also improves fluid distribution during the flooding process, significantly enhancing the overall oil recovery performance. This study provides a new approach to optimizing polymer flooding technology and highlights the potential of iNanoW in improving oil recovery efficiency.

In view of the problems of high permeability, high water cut and high recovery in offshore heterogeneous oil fields, the system including cross-linked polymer gel and flexible microgel gel was prepared indoors, which was used in the experiments of classified combination of waterflooding sweep control technology. The SMG microscopic oil displacement experiment shows that after the SMG system is injected into the model, the speed of the displacement fluid in the large pores decreases and the speed of the small pores increases, thereby effectively improving the oil recovery in the small pores. The long core experiment with multiple pressure points proves that the driving method of that cross-linked polymer gel and flexible microgel gel are alternately injected into core, which can block the dominant channel step by step and start. Then the low permeability area was displaced and the displacement fluid continuously diverted in the core, thus maximizing the purpose of oil recovery. The classification and grading water flooding control technology method provides effective technical support for the optimization of process parameters of offshore oilfield.

In this study, amphiphilic Janus nanoparticles with dumbbell-like structure have been synthesized by connecting two silica nanospheres with differential wettability. In this method, silica nanospheres were modified to be hydrophobic and hydrophilic respectively and then the nanospheres with different wettability were covalently connected together on a one-to-one basis simply by chemical bonds generating between surface groups. The dumbbell-like structure of particles can be observed clearly under scanning electron microscope and transmittance electron microscope. Results showed that 58% of the nanospheres were successfully coupled to build the dumbbell-like structure. Since these anisotropic nanoparticles were based entirely on inorganic materials and owned well-defined surface areas of different wettability, they may have a highly potential for many application fields such as optical and electrical engineering.

Conventional polymer flooding include polymer flooding, surfactant-polymer flooding (SP), alkaline-surfactant-polymer flooding (ASP), and crosslinked polymer gel flooding. However, these technologies in oilfield, especially in high temperature and high salinity, are limited due to the poor ability of temperature and salinity resistance of polymer. In this work, a novel polymer particle (soft microgel, SMG) is used as the research object under the reservoir condition of high salinity (20 × 104 mg/L) to evaluate the physical and chemical properties of submillimeter-scale SMG and the effect of profile control and oil displacement. The investigation of the physical and chemical properties of submillimeter-scale SMG shows that it has the characteristics of low viscosity, easy injection, good plugging property, swelling property, rheological property, and excellent thermal stability. After 6 months of high temperature and high salinity aging, there is no hydration and hydrolysis of submillimeter-scale SMG as the traditional polymers under high temperature and high salinity. The parallel two-core flooding experiments indicate that the submillimeter-scale SMG has a better effect of profile control and oil displacement, which increases the fraction flow rate(fw) of low-permeability core from 5.12% before SMG-flooding to 85.29% and the total increase of recovery as high as 14.07%. The comprehensive analysis demonstrates that the submillimeter-scale SMG has the potential to solve the problem that the polymer flooding cannot be applied to the high temperature and high salinity reservoir, and it is also expected to improve the uneven waterflooding in the reservoir.

Polymer flooding is a key technology for improving reservoir heterogeneity around the world, and it has made great progress. However, the traditional polymer has many shortcomings in the theory and application, which causes the efficiency of polymer flooding to gradually decrease and secondary reservoir damage after a long period of polymer flooding. In this work, a novel polymer particle (soft dispersed microgel, SMG) is used as the research object to further investigate the displacement mechanism and reservoir compatibility of SMG. The visualization experiments of the micro-model prove that SMG has excellent flexibility and can be highly deformable to realize deep migration through the pore throat smaller than SMG itself. The visualization displacement experiments of the plane model further show that SMG has a plugging effect, which makes the displacing fluid flow into the middle and low permeability layers, improving the recovery of these layers. The compatibility tests show that the optimal permeability of the reservoir for SMG-μm is 250–2000 mD, and the corresponding matching coefficient range is 0.65–1.40. For SMG-mm−, its corresponding optimal permeabilities of reservoir and matching coefficient are 500–2500 mD and 1.17–2.07, respectively. The comprehensive analysis demonstrates that the SMG has excellent ability of the water-flooding swept control and compatibility with reservoirs, having the potential to solve the problem of traditional polymer flooding.

Heavy metal contamination, waste, and COVID-19 are hazardous to all living things in the environment. This review examined the effects of heavy metals, waste, and COVID-19 on the ecosystem. Scientists and researchers are currently working on ways to extract valuable metals from waste and wastewater. We prefer Tessier sequential extraction for future use for heavy metal pollution in soil. Results indicated that population growth is another source of pollution in the environment. Heavy metal pollution wreaks havoc on soil and groundwater, especially in China. COVID-19 has pros and cons. The COVID-19 epidemic has reduced air pollution in China and caused a significant reduction in CO2 releases globally due to the lockdown but has a harmful effect on human health and the economy. Moreover, COVID-19 brings a huge amount of biomedical waste. COVID-19’s biomedical waste appears to be causing different health issues. On the other hand, it was discovered that recycling has become a new source of pollution in south China. Furthermore, heavy metal contamination is the most severe ecological effect. Likewise, every problem has a remedy to create new waste management and pollution monitoring policy. The construction of a modern recycling refinery is an important aspect of national waste disposal.

Sol-gel and dip-coating are common methods for preparing TiO 2 thin films. However, due to the incomplete hydrolysis of the precursor, the surface of TiO 2 nanoparticles still contains a lot of alkoxy groups, which has an adverse effect on the wettability of TiO 2 films. In this work, superhydrophilic TiO 2 films with enhanced photocatalytic performance were prepared by chemical modification of TiO 2 sol. FTIR spectroscopy and TGA verified that the carboxyl group was successfully grafted onto the surface of TiO 2 nanoparticles after two steps of modification. With the increase of the amount of modified reagents, the hydrophilic and photocatalytic properties of the film were gradually enhanced. When the mass of 3-triethoxysilylpropylamine (KH550) used reached 50% of the dry weight of TiO 2 (T-50), the film showed superhydrophilic and excellent photocatalytic properties. The enhanced wettability and photocatalytic performance make the modified TiO 2 films have greater advantages in the field of self-cleaning. Graphical Abstract TiO 2 films with enhanced hydrophilic and photocatalytic properties were obtained by two-step chemical modification of sol and dip coating. Highlights Both reactions are carried out under mild conditions; The hydrophilic and photocatalytic properties of the films are greatly improved; The superhydrophilicity films with enhanced photocatalytic properties were capable of being optical materials.