Chan Thnal reservoir, built during the Pol Pot period, is the major water source for the people in Krang Chek commune, Kampong Speu Province, Cambodia. Metal pollution caused by agricultural activities, improper wastewater treatment, and municipal waste disposal poses serious environmental health problems. In this study, the concentrations of four potential toxic metals (i.e., Cd, Cu, Pb, and Zn) from six locations across the reservoir were investigated both in the water and sediment. The results reflected progressive deterioration and indicated moderate to heavy pollution from the metals. The metal levels in the water were in the order of Zn > Cu > Pb > Cd. The statistical analysis revealed primary sources of heavy metals contamination in the water. Cd, Cu, Zn, and Pb in the water likely originate from anthropogenic activities including agricultural runoff (i.e., the use of fertilizers and pesticides) and urban runoff (i.e., improper wastewater discharge and waste disposal). Among the four metals, the Pb levels in the water significantly exceeded the guideline for drinking water in all locations. The health risk assessment revealed serious non-carcinogenic risks of Pb intake in the children at the age below 10 and infants. Appropriate control and protection strategies are urgently needed to cut off the main Pb exposure pathway in pregnant women, children, and infants.

Molecularly imprinted polymers@ethylenediamine-modified carbon dots grafted on cotton fabrics (MIPs@EDA-CDs/CF) and smartphone-based fluorescence image analysis were proposed and used for the first time for the detection of 17 α-methyltestosterone (MT). The EDA-CDs were synthesized and grafted on cotton fabric before coating with the MIPs. The MIPs were synthesized using the MT as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator. The MIPs@EDA-CDs/CF were characterized using FTIR, SEM-EDS, and RGB fluorescence imaging. The fluorescence images were also taken using a smartphone and the ImageJ program was used for RGB measurement. The Δ red intensity was linearly proportional to MT concentration in the range of 100 to 1000 μg/L (R² = 0.999) with a detection limit of 44.4 μg/L and quantification limit of 134 μg/L. The MIPs@EDA-CDs/CF could be stored at 4 °C for a few weeks and could be reused twice. The proposed method could apply for the specific determination of MT in water and sediment samples along with satisfactory recoveries of 96–104% and an acceptable relative standard deviation of 1–6% at the ppb level.

Metal contamination from farming, inadequate wastewater treatment, and poor disposal of municipal garbage are major threats to public health. This research aimed to (1) assess the extent of heavy metal contamination in sediment samples, (2) describe the distribution of heavy metals by locating likely pollution sources using a positive matrix factorization (PMF) model, and (3) quantify the potential ecological consequences associated with these metals at six different places around the Chan Thnal Reservoir. The findings indicated steady degradation and suggested moderate to high metal contamination. Fe > Zn > Cr > Cu > Pb > Co > As > Mn > Cd was the trend of metal concentrations in the sediment. Various soil pollution indices showed that most of the studied sediment samples were clean, moderately clean, or slightly contaminated. However, Co and Cd reached high-risk conditions posing a severe problem to the local population living in and around the Chan Thnal Reservoir. Principal component analysis (PCA) was used to estimate primary factors in PMF analysis. It was found that the contamination of As, Cu, Zn, Cd, and Pb originated from agricultural and traffic vehicle sources; however, Zn, Fe, Mn, Cr, and Cu were derived from natural sources (e.g., atmospheric deposition and compost amendment). Furthermore, Fe, Cd, Mn, Co, Pb, and Cr were generated from urban and industrial sources (metal coatings, plastic burning, wastewater irrigation, and sewage sludge). Accordingly, this research improves our knowledge of the prevalence of heavy metal pollution in agroecosystems, which may be used to foresee and mitigate the risks of heavy metal exposure to humans and other organisms.

The persistent presence of 2,4-dichlorophenoxyacetic acid (2,4-D) in aquatic ecosystems poses a significant risk to both the environment and human health. This study presents a novel fluorescence-based sensor designed to detect ultra-trace amounts of the pesticide 2,4-D. The sensor utilizes a dual-functional approach by combining nitrogen-doped carbon dots (N-CDs) and molecularly imprinted polymers (MIPs) integrated into a PVDF membrane. N-CDs were synthesized using a hydrothermal method with citric acid and ethylenediamine (EDA). The N-CDs were then modified with 3-aminopropyltriethoxysilane (APTES) to enhance their photoluminescence stability and their ability to recognize specific molecules. These functionalized nanomaterials were then covalently attached to a Piranha-activated polyvinylidene fluoride (PVDF) membrane. For the first time, this modified membrane was used as a substrate for 2,4-D molecular imprinting and exploited to reveal its physicochemical resilience, high porosity, and modifiable surface chemistry. A Schiff-base sol–gel imprinting approach enabled the fabrication of a robust molecularly imprinted polymer (MIP) layer with high affinity and selectivity toward 2,4-D. The dual-functional N-CDs simultaneously served as optical transducers and recognition elements. Fluorescence quenching, specifically in the context of binding 2,4-D, was detected using smartphone imaging and ImageJ analysis. The proposed sensor exhibited satisfactory linearity in the 2,4-D concentration range of 10–150 μg L⁻¹ with the limit of detection (LOD) being 1.97 μg L⁻¹ and the limit of quantification (LOQ) being 5.97 μg L⁻¹. This sensor also exhibited photostability for 23 days at 4 °C, recoveries ranging from 96% to 103% and RSD value of less than 6. This work presents a smartphone-compatible MIP/N-CDs membrane designed for the detection of 2,4-D in water samples.