Xianjin An

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.

Microplastics are widely present worldwide and are of great concern to scientists and governments due to their toxicity and ability to serve as carriers of other environmental pollutants. The abundance of microplastics in different water bodies varied significantly, mainly attributed to the initial emission concentration of pollutants and the migration ability of pollutants. The migration process of microplastics determines the abundance, fate, and bioavailability of microplastics in water. Previous studies have proved that the physicochemical properties of water bodies and the properties of microplastics themselves are important factors affecting their migration, but the change in external environmental conditions is also one of the main factors controlling the migration of microplastics. In this paper, we focus on the effects of meteorological factors (rainfall, light, and wind) on the distribution and migration of microplastics and conclude that the influence of meteorological factors on microplastics mainly affects the inflow abundance of microplastics, the physical and chemical properties of water, and the dynamics of water. At the same time, we briefly summarized the effects of aquatic organisms, water substrates, and water topography on microplastics. It is believed that aquatic organisms can affect the physical and chemical properties of microplastics through the physical adsorption and in vivo transmission of aquatic plants, through the feeding behavior, swimming, and metabolism of animals, and through the extracellular polymers formed by microorganisms, and can change their original environmental processes in water bodies. A full understanding of the influence and mechanism of external environmental factors on the migration of microplastics is of great theoretical significance for understanding the migration law of microplastics in water and comprehensively assessing the pollution load and safety risk of microplastics in water.

Karst groundwater is one of the important drinking water sources in karst areas, and it has an important role in maintaining the regional ecosystem and human health. The study of microplastics (MPs) in karst groundwater has rarely been reported, and the occurrence and migration behavior of MPs under the unique environmental conditions of karst is unclear. This study selected cave groundwater and common MPs in karst areas to explore the occurrence characteristics of MPs in groundwater to clarify the factors affecting the distribution and migration of MPs. The results showed that the abundance of MPs in karst groundwater was between 2.33 and 9.50 items·L⁻¹, with an average abundance of 4.50 items·L⁻¹. The microplastic size, type, color, and chemical composition were primarily 1~5 mm, film and fiber, color and transparent, and PS and PE, respectively. The risk characterization ratio (RCR) index results indicated that 80% of the samples were at a low ecological risk level, whereas 60% of the sampling points after concentrated rainfall in June were a medium ecological risk. The study showed that rainfall events significantly changed the abundance and migration of MPs in karst groundwater. The Pearson analysis showed a positive correlation between microplastic distribution and suspended particles (SP), total organic carbon (TOC), and water velocity (WV) in water. The study indicated that strong soil erosion in karst areas may also be one of the main sources of MPs in karst groundwater, and that karst groundwater microplastic pollution is an environmental problem that should not be ignored.

Based on the core collection database of the Web of Science (WoS), the related papers research on pesticides in global soil system were analyzed. The development history, present situation and dynamic development trend of pesticides in soil system all over the world were analyzed by using the CiteSpace knowledge map analysis tool. The results showed that it was an active period of rapid development after 21 century in this field with number of annual papers was 143.95. The institution with the greatest number of papers, the highest total global citation frequency and the highest H index was the Chinese Academy of Sciences; the researchers with the greatest number of papers and the highest total global citation frequency were Qi S.H. from the College of the Environment, China University of Geosciences (Wuhan) and Kookana R.S. from the Commonwealth Scientific and Industrial Research Organization, respectively; and the highest citation per paper was Jones K.C. from Lancaster University. The hotspots in this field mainly were pesticide degradation, the content of pesticide in the water, pesticide residues, organochlorine pesticides, pesticide sorption and so on. The research shows that the effect of pesticides on soil ecosystem and the evaluation of ecological toxicity, the remediation methods of pesticides in soil, the management and control strategy of pesticide application in soil will be paid more attention to in the future.

Karst desertification areas are extremely fragile ecological environments. The migration and transformation of Polycyclic aromatic hydrocarbons (PAHs) in desertification soils are still rarely studied, and the relevant impact mechanisms remain unclear. The study selected lime soil with different rocky desertification grades in southwestern karst area and phenanthrene and pyrene in the environment as the research objects, and investigated the desorption behavior of PAHs in different rocky desertification soils and the impact mechanism of earthworm bioavailability. The results showed that in severe rocky desertification soil (SRDS), moderate rocky desertification soil (MRDS) and light rocky desertification soil (LRDS), fraction of rapid desorption (Frap) of phenanthrene increased by 18.51%, 14.03% and 9.65%, respectively compared with non-rocky desertification soil (NRDS); Frap of pyrene increases by 15.79%, 5.53% and 4.32%, respectively. The bioavailability fraction (Fbio) of PAHs in karst desertification areas was about twice that of Tenax1-6h extraction concentration. The desorption intensity and bioavailability components of PAHs in soils increase with the increase of rocky desertification. Pearson and redundancy analysis（RDA）showed base saturation, porosity and SOC were the main physical and chemical properties that affect the desorption capacity and bioavailability accumulation factors of PAHs in karst soils. Calcium ions in the soil of karst desertification areas may promote the desorption of PAHs.

Supergene geochemical processes (SGPs) occur ubiquitously in the Earth´s surface, but their effects on the fate and bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil remain unclear. Study selected phenanthrene and pyrene as representative PAHs and yellow soil (YS) and limestone soil (LS) of karst area in southwest China, to investigate the effects of SGPs on the desorption and bioavailability of PAHs. Two soils were subjected to repeated freeze-thawing and long-term storage for SGPs. The hysteresis index values of pollutants increased with increase cycles of freeze-thawing and storage time. Under the SGPs, the phenanthrene fast desorption fraction of YS and LS decreased by 22.01% and 24.79%, respectively, and that of pyrene were by 23.81% and 28.12%, respectively. The desorption fraction of 24 hours was a better proxy of the fraction of bioavailability than that of 6 hours. The desorption rate of PAHs was negatively correlated with the hydrophobicity of PAHs.