Category: Speciation analyses

Diffusive Gradients in Thin Films (DGT) is a passive sampling technique used to measure the concentrations and dynamics of trace metals, nutrients, and other substances in aquatic environments. A DGT device typically consists of a diffusive gel layer and a binding gel layer, both protected by a membrane filter. Target ions or molecules diffuse through the gel and are captured by the binding layer, allowing for time-integrated sampling. This method selectively measures the labile, or bioavailable, fraction of contaminants rather than the total concentration. DGT provides a more accurate reflection of chemical mobility and biological availability in situ compared to traditional grab sampling methods. It is widely used in environmental monitoring, pollution assessment, and geochemical studies due to its simplicity, sensitivity, and ability to operate without the need for active pumping systems or electricity. Following the 2011 Fukushima Daiichi nuclear accident, radioactive cesium (¹³⁷Cs) accumulated in forests has been transported to the ocean via rivers. Until now, ¹³⁷Cs in rivers has been primarily adsorbed onto clay mineral particles and exists in a suspended state, and the potential for its transfer from the suspended state to the more biologically available dissolved state has not been sufficiently evaluated. In this study, we aim to evaluate the dynamics of ¹³⁷Cs in river water (particularly the transition from the suspended state to the dissolved […]

Time resolved laser fluorescence spectroscopy (TRLFS) is the analytical technique which observes de-excitation processes of excited fluorophore created by short-pulsed laser. TRLFS data of a fluorescent metal ion includes shape of emission spectrum its temporal decay These information reflects the number of allowed transitions and their probabilities competitive non-fluorescent de-excitation pathways Thus, the spectral shape will change when a fluorescence metal coordinates with a ligand and changes its energy levels and/or associated transition probabilities due to variation of the symmetry around it. Similarly, fluorescence decay lifetime will vary when a ligand around the central metal ion is displaced by another ligand, as de-excitation pathways change. We can use these changes in TRLFS data to probe reactions with a fluorescent metal ion and estimate its structural information. As good approximation, For instance, Eu3+, a chemical homologue of trivalent actinides such as Am3+ and Cm3+, has the energy diagram as in Figure 1 and the emission spectrum as in Figure 2. Its decay lifetime is around 110 μsec. Three major peaks in Figure 2 corresponds to the transitions from the 5D0 states to the 7F1，7F2，and 7F4 states. Upon complexation with acetate ligand, the spectrum changes in Figure 3. Particularly, the peak around 620 nm due to so-called hyper-sensitive transition, 5D0 → 7F2, is significantly enhanced. An overtone of OH vibration of water molecule provides an efficient pathway for excited Eu3+; the […]