## 4 Bioavailability Assessment of Organic Pollutants Using DGT
### Determination of Hydrophobic Organic Matter Using DGT
The diffusion coefficient of MeHg\({}^{+}\) in the agarose diffusion layer is higher than that of polyacrylamide, but the absorption capacity of P-DGT is slightly higher, which is a better choice for monitoring extremely low concentrations of MeHg\({}^{+}\) in eutrophic waters. The ocean is an important sink of major pollutants, and a variety of antibiotics have also been detected in China's coastal waters [88]. [PERSON] et al. used o-DGT with XDA-1 resin as the binding phase to determine the antibiotics in seawater. The results showed it has a high adsorption capacity for antibiotics and can adapt to fluctuating seawater conditions (pH 7.9-8.2, IS 0.7 M) [89]. The hydrophilic-lipophilic-balanced (HLB) resin is another of the most commonly used binding phase materials. In 2017, [PERSON] et al. [90] systematically evaluated the frozen storage stability of o-DGT prepared by HLB resin for 30 pesticides and insecticides, indicating that the stability of analytes on o-DGT is feasible for at least 1 year. If it cannot be frozen immediately, it is a better choice to temporarily refrigerate the sampler or the binding phase gel in a suitable storage solvent at 4 \({}^{\circ}\)C, and it should be determined as soon as possible, if possible. If it cannot be frozen immediately, it is a better choice to temporarily refrigerate the sampler or the binding phase gel in a suitable storage solvent at 4 \({}^{\circ}\)C, and it should be determined as soon as possible, if possible [91]. The o-DGT technique has been increasingly used to provide time-weighted average concentrations of biologically relevant fractions of organic pollutants in water, with a view to obtaining high spatial and temporal resolution. Targeted methods have been developed for a wide range of compounds, including pharmaceuticals, chemicals in the household and personal care products (HPCPs), pesticides, hormones, endocrine disrupting chemicals (EDCs), organophosphorus flame retardants, bisphenol,nitrophenol, perfluoroalkyl substances, and illicit drugs [92; 93; 94; 95; 96; 97; 98]. Except for the above binding phase materials, nano-sized zero-valent iron-assisted biochar (nZVI@bichorbar) binding gel exhibits high capacity and fast absorption of phenol [99]; hypercross-linked \(\beta\)-cyclodextrintrim polymers can stably and effectively monitor phthalate esters (PAEs) concentration [100]; and even activated carbon [101], TiO\({}_{2}\)[102], and commercial solid-phase extraction (SPE) packings [103] can be used as adsorbents in bound-phase gels. In addition, although biofouling adhered to the surface of the DGT sampler, the filter membrane played a strong protective role in the diffusion and binding membranes, which was also confirmed in the wastewater matrix [91]. Soil is an important sink for organic chemicals. After organic pollutants enter the soil, they will interact with soil components. Due to the complex and highly heterogeneous composition of soil components, the occurrence state of pollutants changes and differentiates greatly. As a result, the mobility, bioavailability, and even chemical reactivity of pollutants are reduced to varying degrees, which has a significant impact on their environmental ecological risks and restoration efficiency. The application of o-DGT in soil started a little later than in water, but developed equally rapidly [97]. O-DGT has been performed for various types of organic compounds (e.g., pesticides, pharmaceuticals, hormones, EDCs, HPCP). The DGT-DIFS method provides kinetic information, such as distribution coefficients, response times, and desorption/adsorption rates of organic pollutants in soil. The effectiveness of atrazine in the non-rhizosphere and rhizosphere was evaluated by DGT, and the relationship between atrazine morphology and rhizosphere soil properties was further analyzed. The influence mechanism of soil pH value and organic matter on the bioavailability of atrazine was clarified [104]. [PERSON] et al.