Asian Journal of Environment & Ecology

Bioremediation of the Hindon River (Ghaziabad, India): A Review of Pollution Status, Remediation Techniques, Challenges, and Future Directions

Nisha Agrawal, Surya Prakash Singh — Mon, 08 Jun 2026 00:00:00 +0000

The Hindon River, flowing through Ghaziabad, India, faces severe pollution mainly due to untreated municipal sewage, industrial effluents, and solid waste dumping. This pollution results in increased levels of organic pollutants, heavy metals such as Cd, Pb, and Ni, and pathogenic contamination, making the river water unfit for domestic, agricultural, and other uses. Conventional physico-chemical remediation methods, such as chemical precipitation or dredging, are often expensive, generate secondary pollutants, and do not offer a sustainable, long-term solution. In this context, sustainable and eco-friendly remediation approaches are urgently needed to restore the river's ecological health. Bioremediation, which harnesses the metabolic activities of microorganisms and plants to degrade or remove contaminants, emerges as a promising method due to its cost-effectiveness, environmental compatibility, and potential for complete degradation of pollutants. This review comprehensively discusses the pollution status of the Hindon River, bioremediation techniques applicable to its restoration, government initiatives, challenges faced, and integrated strategies for sustainable river cleanup.

Value Chain and Market Potential of Natural Dyes: A Critical Review

Mon, 22 Jun 2026 00:00:00 +0000

Natural dyes, derived from botanical, animal, and microbial sources, are attracting renewed commercial and scientific attention, driven by mounting evidence of the ecological and toxicological consequences of synthetic dye production and discharge. This review critically examines the value chain architecture and market potential of natural dyes across their principal industrial applications, encompassing textiles, food and beverages, cosmetics, and emerging specialty sectors. The biological diversity of natural dye sources is surveyed with attention to chemically distinct classes of colouring compounds and their distribution across plant, insect, and microbial taxa. Established and advanced extraction technologies — including ultrasound-assisted, microwave-assisted, and supercritical fluid extraction — are evaluated in relation to their efficiency, scalability, and environmental profile. The structure of natural dye value chains is analysed from primary agricultural production through processing intermediaries to end-use markets, with particular attention to governance dynamics and the distribution of economic returns among chain participants. Global and regional market trends are assessed with reference to demand drivers in the food, textile, and cosmetics sectors, alongside the regulatory frameworks that increasingly govern natural colorant use in major markets. The environmental and social dimensions of natural dye production receive critical evaluation, including trade-offs between biodegradability benefits and agronomic costs, and the implications of value chain structure for rural livelihoods and gender equity. Biotechnological innovations — notably metabolic engineering for microbial dye production, microalgal cultivation, and biorefinery integration — are examined as pathways to improving cost competitiveness and scalability. Key barriers to market expansion, including colourfastness limitations, supply inconsistency, and regulatory fragmentation, are identified alongside practical recommendations for their resolution. The review concludes that natural dyes represent a strategically significant and commercially viable component of the emerging bio-based economy, though the full realisation of their market potential requires coordinated technological, institutional, and governance advances.

Nanotechnology in Site Remediation: A Review of Nanomaterials for Pollutant Removal from Soil and Water

Mon, 15 Jun 2026 00:00:00 +0000

Nanotechnology is the use of materials at the 1–100 nm scale with unique properties, applied in environmental science for efficient pollution detection, treatment, and remediation of air, water, and soil contaminants. This narrative review examines the application of nanotechnology in environmental site remediation, with particular emphasis on the mechanisms, effectiveness, and limitations of nanomaterials used in pollutant removal from soil and water systems. A structured literature search was conducted using major scientific databases, including PubMed, Scopus, Web of Science, and Google Scholar. Relevant peer-reviewed articles, review papers, and selected gray literature published in English were screened using keywords such as “nanotechnology,” “nanomaterials,” “site remediation,” “soil pollution,” and “water remediation.” Studies focusing on the use of nanomaterials for the removal or degradation of heavy metals, organic pollutants, and microbial contaminants were included in the review.

The reviewed literature indicates that carbon-based nanomaterials, metal and metal oxide nanoparticles, and polymer-based nanocomposites demonstrate considerable potential in enhancing remediation efficiency through mechanisms such as adsorption, catalytic degradation, advanced oxidation, and nano-enhanced bioremediation. Nanoscale zero-valent iron, titanium dioxide nanoparticles, graphene, and carbon nanotubes were among the most frequently investigated materials, showing improved contaminant removal compared to conventional remediation approaches. Evidence from the reviewed studies also highlights successful applications in both in-situ and ex-situ soil and water treatment systems.

Despite these promising outcomes, the literature identifies important challenges related to environmental toxicity, long-term ecological effects, scalability, cost-effectiveness, and regulatory oversight. The review further discusses emerging trends, including the development of sustainable and eco-friendly nanomaterials and the integration of nanotechnology with biological and chemical remediation strategies. Overall, nanotechnology presents significant opportunities for sustainable environmental remediation; however, comprehensive risk assessment and stronger regulatory frameworks remain necessary for safe and effective implementation.

Assessing the Role of Anthropogenic Greenhouse Gas Emissions in Urban Climate Change: A Review of Evidence from Bengaluru, India

Yogesh Kumar Upadhyay, T. S. Harsha — Tue, 23 Jun 2026 00:00:00 +0000

Bengaluru, India's foremost technology hub and the capital of Karnataka state, has experienced one of the most rapid urban expansions in South Asian history, transforming its physical landscape, energy demand, and atmospheric composition over barely four decades. This critical narrative review synthesises peer-reviewed evidence on the role of anthropogenic greenhouse gas (GHG) emissions in driving urban climate change in Bengaluru, drawing on published research spanning land use and land cover change, sectoral emission analysis, surface temperature and precipitation trends, urban heat island dynamics, and climate policy evaluation. The review documents a dramatic expansion of Bengaluru's built-up footprint — from approximately 69 square kilometres in the early 1970s to approximately 455 square kilometres by 2010, with continued growth thereafter — accompanied by a precipitous decline in vegetated cover and the loss of many of the city's historically extensive water bodies. A narrative synthesis methodology was adopted for this review. Relevant literature was identified through systematic searches of major scientific databases using predefined search strings combined with Boolean operators. These landscape transformations, combined with emissions from transport, energy consumption, and industry, have contributed to measurable warming of the urban surface, elevated pollutant concentrations, increased precipitation variability, and heightened risks of flooding and heat stress. Whilst precise emission attribution remains constrained by the absence of comprehensive city-level GHG inventories and high-resolution climatic observation networks, convergent evidence from remote sensing, atmospheric science, and surface observations points to a significant anthropogenic contribution to Bengaluru's changing climate. The review critically evaluates national and subnational policy frameworks, identifies key methodological and data gaps, and recommends priorities for strengthening the evidence base in support of equitable and effective urban climate governance.

Indian Wetlands as Critical Habitats for Avian Diversity: Climate Change Impacts and Conservation Perspectives

Daisy Seva, Madhumita Pandey, Mandira Sen — Tue, 23 Jun 2026 00:00:00 +0000

Background: Wetlands are among the most productive ecosystems on Earth and provide essential habitats for resident and migratory birds. In India, wetlands support considerable avian diversity and contribute to ecological stability, biodiversity conservation, and ecosystem services. However, anthropogenic pressure and climate change are accelerating wetland degradation, creating serious risks for bird populations and wetland health.
Aim: This review examines the importance of Indian wetlands for avian diversity and evaluates climate change impacts and conservation strategies affecting wetland-dependent bird communities.
Methodology: Published scientific literature, government reports, and policy documents were reviewed to synthesise information on avian diversity, ecological drivers, climate-related threats, and conservation measures associated with Indian wetlands.

Results and Discussion: Indian wetlands provide breeding, feeding, nesting, roosting, and wintering habitats for many resident and migratory bird species. Avian diversity is shaped by climatic conditions, hydrological regimes, habitat structure, food availability, and anthropogenic activities. Climate change, habitat loss, pollution, urbanisation, agricultural expansion, and hydrological alterations have affected wetland ecosystems and bird populations by modifying habitat quality, migration patterns, and reproductive success. Birds also serve as important bioindicators of wetland health and ecological integrity. Conservation initiatives, including the Wetlands (Conservation and Management) Rules, 2017, and international frameworks such as the Ramsar Convention, contribute to wetland protection, although implementation remains challenging.

Conclusion: Indian wetlands are essential for maintaining avian biodiversity and ecosystem functioning. Habitat conservation, wetland restoration, climate-resilient management, and long-term ecological monitoring should be strengthened to safeguard wetland ecosystems and their avifaunal communities.

The Physico-Chemical Characteristics, Total Trace and Major Elements in Water and Surficial Sediments during Drought Conditions in the Highly Turbid Perennial Rivers, Hotspring and Lake Baringo, Kenya

Job Mwamburi — Mon, 08 Jun 2026 00:00:00 +0000

Environmental degradation, climate change impacts and increasing water pollution exacerbates the challenges and threats facing lotic and lentic ecosystems, resulting in the continued loss of aquatic habitats and biodiversity, contamination of drinking water sources and reduced fisheries production. We collected surface water and sediment grab samples during the dry conditions (March 2008 and February – March 2009) and characterized the trace element contents, sources and distribution in major perennial rivers, hot-spring and Lake Baringo, for better resource use planning and management. Dried sieved sediments and water sampled were acid digested with Aqua-Regia and concentrated Nitric acid respectively, before metal analysis using Atomic Absorption Spectrophotometer equipment. Cold vapour technique was used for mercury analysis. Standard method were used for chloride and fluoride determination. Sediments accumulated higher trace elements than those in aqueous phase. Mean F levels in lake (92% of samples) and warm spring (83%) water were above the maximum allowable concentration for drinking water. Lake Baringo surficial sediments exhibited depletion to minimal enrichment for Cr, Mn, Zn, Co, Pb, Ni, Hg and the geo-accumulation index indicated moderate sediment pollution with respect to Ni, Hg, Co, Cu and Zn. River sediments were enriched with Mn, Zn and Cd, Ni, The findings indicate that anthropogenic sources contribute to sediment Cd, Zn and Mn contents in river and lake sediments, besides lithogenic sources. The Ramsar wetland area is sensitive to climatic changes and the previous dry conditions greatly contributed to the changes in the hydrochemistry due to increased processes of evaporative concentration.

Exploring the Correlation between Primordial Radionuclides and Heavy Metal Concentrations in Surface Environmental Media of the Dhaka Region, Bangladesh

Mon, 08 Jun 2026 00:00:00 +0000

Rapid urbanization and industrial expansion in the Dhaka District of Bangladesh have led to significant soil contamination from heavy metals and naturally occurring radionuclides, posing increasing risks to environmental quality and human health. This study synthesizes published research on the correlation between primordial radionuclides (²²⁶Ra, ²³²Th, ⁴⁰K) and heavy metals (Pb, As, Zn, Mn, Cd, Fe, Cu, Cr) in soils, dust, and plants from industrial and rural areas in Dhaka District, Bangladesh. Data sources of Savar, Ashulia, and DEPZ were integrated to calculate radiological indices (Ra_eq, D, AEDE, AGDE, I_γ, H_ex, and H_in) and contamination indices (CF, EF, I_geo, and PLI) for assessing environmental and health risks. Mean activities of ²²⁶Ra, ²³²Th, and ⁴⁰K exceed the global reference values, especially in industrial zones, but their Ra_eqand related hazard indices remain within international limits. However, the rate of absorbed dose (D), AEDE, and, more importantly, AGDE, approximately two times higher than the world average in industrial (601.93 ± 100.72 µSv/yr) and rural (503.43 µSv/yr) locations, provides a warning of radiological concern. Anthropogenic contamination of industrial soils is characterized by enrichment of Pb, Zn, Cd, Cu, and Cr (PLI > 1). Correlation analysis reveals mostly weak or negative relationships between most radionuclides, meaning that the levels of each radionuclide are regulated by the geological background and certain anthropogenic additions instead of direct correlations with heavy metals.

Effects of Conservation Tillage Practices on Soil Microbial Diversity and Enzymatic Activity

Mon, 08 Jun 2026 00:00:00 +0000

Due to intensive agriculture, increasingly large areas are becoming degraded and unsuitable for agricultural purposes. Therefore, soil restoration is a critical task. Various soil-saving tillage technologies, which minimize damage and promote the accumulation of organic matter in the soil, are attracting increasing attention.

This paper presents the results of a comparative study of the preservation and improvement of soil microbiomes under various tillage methods, using soils from fields in a farming cluster in the Kibray district of Tashkent region as an example. It was shown that no-tillage increases both the total number of microorganisms and those involved in the nitrogen cycle, which is important for plant growth and development. Increases in humus content (1.7%) and the activity of phosphatase and urease enzymes, as well as the ratio of polyphenol oxidase to peroxidase, were also observed.

It is known that there is a direct relationship between the physicochemical and ecological state of the fertile soil layer and its microbiota, which in turn determines the enzymatic activity of soils due to the vital activity of microorganisms. It has been shown that creating favorable conditions for the normal functioning of the microbial community contributes to increased soil enzymatic activity, activating the microbial community and, consequently, improving agricultural efficiency, fertility, and crop yields. A comparative assessment of the qualitative and quantitative composition of the microbiome in agricultural soils will enable the development of recommendations for the rational application of environmental technologies in the agro-industrial complex.

Spatial Environmental Sensitivity and Land Degradation Risk in Organized Industrial Zone Site Selection: A Multi-Criteria Assessment of Sakarya, Türkiye

Mahnaz Gümrükçüoğlu Yiğit, Zeynep Özdamar, Ekrem Biçer — Mon, 22 Jun 2026 00:00:00 +0000

Unplanned industrialisation can contribute to environmental degradation when industrial zones are located without sufficient consideration of land capability, water resources and ecological sensitivity. Organized Industrial Zones (OIZs) provide planned infrastructure and centralised services, yet inappropriate site selection may increase land-use conflicts and potential degradation, particularly in regions where productive agricultural land and sensitive ecosystems coexist. This study evaluates the relationship between spatial environmental sensitivity and potential land degradation risk in OIZ site selection in Sakarya Province, Türkiye. Seven active OIZs were assessed using a multi-criteria decision-making framework supported by Geographic Information Systems and a 1-5 scoring scale. The assessment included 26 criteria covering spatial characteristics, infrastructure adequacy, environmental impacts and socio-economic factors. Expert-based weighting assigned the highest importance to environmental impacts, followed by spatial characteristics, infrastructure adequacy and socio-economic factors. The analysis showed notable variation among the OIZs. Karasu OIZ obtained the highest total score (82), followed by Sakarya Second OIZ (76), Ferizli OIZ (74), Sakarya Third OIZ (73), Kaynarca Furniture Specialized OIZ (68), Sakarya First OIZ (67) and the Eastern Marmara Machinery Manufacturers Specialized OIZ (66). The findings indicate that environmental criteria are as important as economic and infrastructural considerations in determining suitable industrial locations. OIZs established on fertile agricultural land or near sensitive water resources require stronger monitoring and management. The results also show that sensitivity-based scoring can identify improvement priorities without excluding operational and socio-economic considerations. The proposed framework offers a flexible and transferable approach for evaluating environmental performance, supporting more context-sensitive OIZ planning and land-use decision-making.