Hazard-mapping and health risk analysis of iron and arsenic contamination in the groundwater of Sylhet district.

This study investigates groundwater contamination by arsenic and iron and its health implications within the Sylhet district in Bangladesh. Utilizing geographic information system (GIS) and inverse distance weighting (IDW) methods, hazard maps have been developed to evaluate contamination risk across various upazilas. The findings show significant arsenic and iron pollution, particularly in the northwestern part of the district. In about 50% of the area, especially in Jaintiapur, Zakiganj, Companiganj, and Kanaighat where arsenic levels surpass 0.05 mg/L which is the standard limit of Bangladesh. Iron levels peak at 13.83 mg/L, severely impacting 45% of the region, especially in Gowainghat, northeastern Jaintiapur, Zakigonj, and Golabganj. The study employs USEPA health risk assessment methods to calculate the hazard quotient (HQ) and hazard index (HI) for both elements via oral and dermal exposure. Results indicate that children face greater noncarcinogenic and carcinogenic risks than adults, with oral HI showing significant risk in Balagonj and Bishwanath. Dermal adsorption pathways exhibit comparatively lower risks. Cancer risk assessments demonstrate high carcinogenic risks from oral arsenic intake in all areas. This comprehensive analysis highlights the urgent need for effective groundwater management and policy interventions in the Sylhet district to mitigate these health risks and ensure safe drinking water.

An experimental investigation on utilization of ladle refined furnace (LRF) slag in stabilizing clayey soil.

The contemporaneous world of development and urbanization generates extreme stresses on building infrastructures, and the use of soil as a load-bearing material is a prerequisite for such activity. However, if the foundation soil lacks enough bearing capacity and shear strength and shows excessive settlements, unescapable failures will occur in constructed infrastructures. As such, improvement or stabilization of soft clay soil is crucial before initiating any construction project to limit the potentiality of post-construction faults and damages. In this research, the efficiency of ladle refined furnace (LRF) slag has been investigated to stabilize the geotechnical properties of poor conditioned-soft clayey soil, which will also lessen the environmental degradation due to the unplanned dumping of LRF slag. Various experimental programs such as the Atterberg limit, consolidation, compaction, unconfined compressive strength, and California Bearing Ratio tests were carried out in this study. Experimental results revealed that adding LRF slag in different percentages augmented the strength and dry density of the original soil to a considerable extent, and the optimum percentage of LRF slag was 20%. 20% LRF content in the soil increased the UCS value of the soil by 219%, CBR value by 47%, and reduced consolidation settlement by 30%. Additionally, the test results were further evaluated by the SEM-EDS test.

Improvement of consolidation properties of clay soil using fine-grained construction and demolition waste.

As urbanization spreads rapidly, more structures are being built, and more construction and demolition waste (CDW) is produced, occupying about 36-40% of the total solid waste generation in the world; hence, CDW has become a burden nowadays. Moreover, the construction of low-rise buildings on weak soil is always challenging and costly due to the soil's high compressibility and low bearing capacity. Sand or other granular materials are commonly used to improve the compressibility behavior and associated settlement, drainage, and shear strength of weak soil. The massive use of natural sand for construction purposes of different civil engineering structures have lessened their reserves in recent times, increasing their price and destroying the balance in the environment. Among the several methods of improving soil, this research uses fine-grained CDW to improve the geotechnical behavior of weak soil under study. The main objective of this research is to observe the changes in soil properties after mixing with CDW. Recycled waste mortar powder has been selected as CDW mixed in different percentages in the soil. In addition, CDW powder was inserted into soil mass as a circular powder column in triangular and square grid patterns as an alternative to the sand column. CDW in the soil samples improved consolidation settlement, and reduced settlement time and compression index. Increments in the pre-consolidation pressure, consolidation rate, and permeability of the clay-CDW mixtures were also remarkable. Soil improvement through reusing CDW is a sustainable way to solve problems in solid waste management and the soft soil settlement issue under a shallow foundation, ultimately reducing the environmental footprints, saving natural resources, and supporting the circular economy concept.

Sustainability assessment of arsenic-iron bearing groundwater treatment soil mixed mortar in developing countries, Bangladesh.

The open disposal of groundwater treated soil containing arsenic (As) and iron (Fe) is a critical environmental issue in developing countries like Bangladesh. The current study attempts to use the arsenic-iron soil (AIS) as partial replacement of aggregate for preparing the sustainable solid mortar composite. Four dosages (2.5-10%) of AIS were applied as the substitution of fine aggregate for finding the optimum quantity of AIS, justifying by strength and nominal leaching content of As and Fe in pH solution 4.0 and 7.0 and curing temperatures of 25, 30, and 35 °C. Also, the external surfaces of solidified matrices were modified with cement grouting solution and cement plaster to resist the migration of concerned contaminants to curing media. The analytical compressive and flexural strength results showed that the solid mortars blended with 2.5 and 5% AIS obtained over 80% of the control specimens throughout the testing ages. Moreover, the study found that 5% AIS bearing hardened composition with exterior cement plaster exhibited the releasing contents of As and Fe below the drinking water standard in both pH solutions and adopted three curing temperatures, which is safe as well as economical to use as a construction material. The scanning electron microscopy (SEM) observations and energy dispersive spectroscopy (EDS) analysis also demonstrated the encapsulation patterns of target contaminants by forming hard microstructures of calcium silicate hydrate, ettringite and calcium-arsenic compounds. The outcomes of the study showed the potentiality of recycling the contaminated groundwater treatment soil as building materials in an eco-friendly way.

Immobilization possibility of tannery wastewater contaminants in the tiles fixing mortars for eco-friendly land disposal.

The Hazaribagh tannery area of Bangladesh is currently facing an enormous problem regarding the harmful impacts of wastewater produced from leather industries on the surrounding environment due to the presence of contaminants at a toxic level. As such, the current study aims to analyze the entrapment of tannery wastewater's pollutants inside the mortar specimens for sustainability. Two types of binding agents such as Portland Composite Cement (PCC) and Ready Mixed Dry Mortar (RMDM) were employed to prepare separate mortar pastes in which the collected tannery wastewater was used as mixing liquid. Also, five types of samples including brick walls made with only the PCC, where tiles walls and blocks constructed with both types of binding agents were built. Analytical results show that the surrogate contaminated water mixed mortar blocks possessed about 6-14% lower compressive strength than that of the blocks prepared with drinking water. Moreover, the examined heavy metals were observed below the limit of detection in the curing liquid of studied tiles walls during the whole test protocol of 360 days period. The explicit outcomes of this study might be a promising solution to minimize the effects of tannery wastewater contaminants on the environment by utilizing this wastewater as a mixing component in the tiles fixing mortar of walls and floors.