Patuakhali Science and Technology University

Biochar has emerged as an effective and sustainable amendment for improving soil fertility and mitigating environmental pollution in soil–plant systems. This review synthesizes recent advances in biochar production, characteristics, and applications in soil restoration and contaminant remediation. Biochar is typically produced through slow pyrolysis of biomass feedstocks such as crop residues, wood waste, and animal manure at temperatures ranging from 350–700 °C, producing a stable carbon-rich material with high surface area and porous structure. Most effective applications involve fine to medium particle sizes (< 2 mm) and soil application rates of approximately 5–30 t ha–1, depending on soil properties and management goals. Evidence indicates that biochar is particularly beneficial in degraded, acidic, and sandy soils, where it significantly improves soil physical properties (aggregation, porosity, bulk density, and water-holding capacity), chemical properties (pH buffering, cation exchange capacity, and nutrient retention), and biological properties (microbial biomass, enzyme activity, and rhizosphere interactions). In polluted soils, biochar plays a critical role in mitigating contaminants through mechanisms including adsorption, ion exchange, surface complexation, precipitation, and redox reactions, which reduce the mobility and bioavailability of heavy metals and organic pollutants. Its highly porous structure and functional surface groups also facilitate microbial colonization and phytoremediation processes, enhancing pollutant degradation and improving plant tolerance under stress conditions. Overall, biochar-based strategies provide a multifunctional approach for soil fertility restoration, pollution mitigation, and climate-resilient agriculture, although further long-term field studies are required to optimize biochar properties, application rates, and soil-specific management practices for large-scale implementation.

Microplastics (MPs) are an emerging threat to freshwater ecosystems and aquatic life, yet data on MPs pollution in aquaculture systems especially in Bangladesh, remain scarce. This study investigated the tissue accumulation and polymer compositions of MPs influenced by the feeding habits of Oreochromis niloticus and Pangasius hypophthalmus from aquaculture ponds. MPs were predominantly detected in the gastrointestinal tract (GIT) and muscle tissues, with fibers (<0.5 mm) being the most common type and black the dominant color. Interestingly, feeding habits did not significantly affect the overall MP intake. Principal component analysis (PCA) revealed 70.3 % of the total variation in Tilapia and 53.7 % in Pangas, with 1 to 5, transparent, and filament (fiber) showing significant positive contributions as the main components. Fourier-transform infrared spectroscopy (FTIR) analysis detected polyethylene as the most abundant polymer, followed by polyester, polypropylene, cellulose, non-plastic, and unidentified particles. These findings highlight the prevalent presence of MPs in aquaculture systems, raising concerns about trophic transfer and eventual risks to human health. The study highlights the pressing need for operational management policies to alleviate MP pollution in aquaculture environments.

Plastic pollution, particularly microplastics (MPs) and nanoplastics (NPs), has emerged as a critical environmental challenge, with Asia serving as a global epicenter of plastic production and mismanaged waste. These particles act as carriers for hazardous chemical pollutants, including heavy metals, persistent organic pollutants, and emerging contaminants. This systematic review supports decision optimization by synthesizing current evidence on the role of plastics as vectors for chemical pollutants in marine environments across South Asia, Southeast Asia, and East Asia, while evaluating how region-specific environmental drivers, tropical temperatures (>25-30 degrees C), monsoonal salinity gradients (0 parts per thousand to 35 parts per thousand), and high UV radiation, modulate pollutant adsorption-desorption mechanisms. MP concentrations across Asia exhibit pronounced spatial variability, ranging from 0.05 to 7.32 particles g(-1) in biota, 9.97 to 21 items m(-3) in water, and 13.1 to 866.59 items kg(-1) in sediment. Asian marine systems function as high-flux reactors where monsoonal pulses accelerate plastic weathering, and MPs traversing salinity gradients may release approximately 10-30% of their adsorbed pollutant load upon entering marine waters. Critical knowledge gaps persist regarding nanoplastic-emerging pollutant interactions, deep-sea accumulation, transboundary transport dynamics, and the effectiveness of existing regulatory interventions. To enable optimized environmental decision-making, future priorities should include coordinated monitoring across major river-estuary systems and the development of integrated frameworks that combine data-driven risk assessment, policy optimization, and sustainability education tailored to Asian coastal communities, where seafood provides 50-80% of animal protein. This review establishes a scientific basis for decision optimization strategies aimed at mitigating chemical pollutant transport by plastics and strengthening evidence-based management of marine pollution in Asia.

Urbanization, industrial activity, and climate change are accelerating the accumulation of inorganic contaminants, such as heavy metals, metalloids, radionuclides, nitrates, and phosphates, in global water systems, posing persistent risks to human health and aquatic ecosystems. This review systematically synthesizes evidence from 244 peer-reviewed studies, integrating contaminant sources, exposure pathways, ecological and human-health impacts, monitoring technologies, and remediation strpeer-reviewedategies. In addition, it incorporates decision-optimization frameworks to support the prioritization of monitoring efforts, the selection of cost-effective treatment technologies, and improved resource allocation in settings with limited capacity.By combining analytical advancements (AAS, ICP-MS, biosensors, IoT and remote-sensing systems), emerging remediation approaches, and ecological informatics, the review provides an interdisciplinary assessment of inorganic contaminant dynamics and management options. Decision-optimization methods add value by enabling transparent trade-off evaluation, targeted mitigation, and scenario-based planning under uncertainty. Key takeaways demonstrate that: (i) current regulatory and monitoring capacities remain insufficient in many regions; (ii) scalable, context-appropriate remediation technologies are essential for reducing long-term exposure; and (iii) integration of real-time monitoring, ecological informatics, and optimization-based decision tools can substantially strengthen progress toward SDG-aligned water security.

Crab aquaculture is becoming increasingly important for global food security and economic growth, yet the complexities of crab reproduction present significant challenges. The reproductive physiology of crabs is a critical factor in the sustainability and productivity of crab aquaculture. This review comprehensively explores recent advances in the molecular and physiological mechanisms underlying crab reproduction, with a focus on both male and female reproductive systems. Specifically, the review examines the molecular mechanisms of spermatogenesis and oogenesis, with an emphasis on identifying key genes involved in these processes. Key topics include the genetic and molecular regulation of gonadal development, sex determination, reproductive pathways governed by hormonal and molecular factors, the regulatory role of microRNAs in reproduction, anti-bacterial mechanisms in reproduction, and the use of transcriptomics and proteomics to uncover reproductive mechanisms. Special attention is given to recent advances in reproductive biotechnology and their practical implications for aquaculture. Male reproductive physiology is discussed in depth, covering seminal plasma composition, sperm morphology, sperm transport, spermatophore formation, the molecular regulation of the acrosome reaction, and sperm quality. Additionally, the review examines the impacts of environmental stressors, such as pollutants and climate change, on reproductive success. By identifying critical research gaps and proposing future directions—including genome editing and germplasm banking—this review aims to bridge knowledge gaps and offer actionable insights for improving reproductive performance in crab aquaculture. These advancements might be applicable for molecular breeding, monosex crab production, sustainable seed production, broodstock management, and enhancing the resilience of crab farming systems globally.