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In this study, we investigated the effect of sample pretreatments (ultrasonication and alkaline extraction) on total organic carbon (TOC) measurements for water samples containing suspended solids (SS) of four different origins (algae, soil, sewage sludge, and leaf litter) to more clearly assess the impact of particulate organic carbon (POC) in water. The effects each of ultrasonication (power, pulse, etc.) and alkaline extraction condition (concentration, time, etc.) on the TOC recovery and precision were investigated, and the results were compared with those of a new sample pretreatment method combining both methods. Alkaline treatment (0.01 mol/L NaOH) showed higher precision than ultrasonication (100/5 on/off pulse), and notably, the differences among the measured TOC values in samples of different origins were also further reduced in the alkaline treatment. This suggests that the ultrasonic pretreatment results can be mainly attributed to the increase in POC recovery through particle size reduction, whereas the alkaline treatment results are achieved through the enhancement of POC solubilization. It is also particularly noteworthy that a higher TOC recovery of 87.6% ± 7.4% with a higher precision of 8.4% could be obtained using the combined method, compared to each treatment (ultrasonic: TOC recovery 34.7%, relative standard deviation 63.1%; alkaline: 49.6% and 23.0%, respectively). Thus, simultaneous pretreatment with ultrasonication and alkaline extraction is expected to increase the oxidation rate of organic matter and the homogeneity of the samples, minimizing the loss of POC measurement values, and thereby improving the reliability of the TOC measurements of water samples containing SS.

Particulate organic matter (POM) in water systems can be converted into dissolved organic matter (DOM) through various pathways depending on its properties and transformation. Thus, information on the behavior of POM is crucial for fully understanding water systems and the carbon cycle. In this study, the effects of particle size and the source of POM, as well as photochemical and microbial changes in DOM characteristics subsequently released from POM were evaluated using various spectral indices, excitation-emission matrix combined with parallel factor analysis components, and principal component analysis. The amount of dissolved organic carbon (DOC) released from POM during suspension was significantly associated with the carbon content of POM (p0.05). The amount of DOC (mg-C/g-SS) decreased in mineral-bound POM as a result of microbial degradation but increased in biogenic POM as a result of microbial dissolution, owing to the structural differences in organic matter from different sources. Mineral-bound POM showed more DOC production by photochemical desorption than microbial degradation, whereas biogenic POM displayed the opposite trend. The DOM derived from fine POM had more humified terrestrial humic-like substances than those derived from coarse POM. Principal components 1 and 2 were associated with DOC production and degree of humification, respectively. The increase in the degree of aromaticity and humification of organic matter was higher in mineral-bound POM by photochemical desorption of highly humified organic matter and in the biogenic POM by microbial dissolution. In conclusion, this study was able to provide basic information on the transformation of POM, thus, it is expected to broaden the knowledge of the biogeochemical cycle of organic matter.

Particulate matter (PM) has long-term effects on water quality compared to dissolved matter (DM) during downstream transfer after inflows into an aquatic environment. In the present study, the characteristics, behavior, and effects of PM from an urban watershed under photo-irradiation were investigated through sequential resuspensions before being compared. Changes in the organic matter content, heavy metals (Mn, Fe, Zn, Pb), spectroscopic indices (SUVA254, slope ratio (SR), humidification index (HIX), fluorescence index (FI), and biological index (BIX)), excitation-emission matrix combined with parallel factor analysis components (EEM-PARAFAC), and disinfection by-product formation potential (DBPFP) were analyzed. According to our results, light enhanced the release of organic matter from PM but reduced dissolved heavy metals. The PMU affected by urban-derived pollutants (i.e., rainfall particles, road-deposited sediment, sewer-pipeline-deposited sediment) exhibited higher quantities of terrestrial humic-like organic matter than PMR, which contains base particles from riverines (i.e., soil, sediments). For the PMU, the humic-like fluorescent components (C1 and C2) enhanced under light conditions with every resuspension, whereas the components decreased in the PMR. Consistent with the PARAFAC results, the trihalomethane formation potential (THMFP) of the PMU was enhanced by approximately 2.8 times more than that of the PMR, and exhibited a high correlation with the fluorescent components (C1, r = 0.81, p

In this study, a combined media filtration process with micro-flocculation (CMF) was developed, to simultaneously treat particulate and dissolved contaminants in urban road runoff. Dual-size foam glass media with stone and sand layers were applied and the efficiency of road runoff treatment was investigated according to filtration and micro-flocculation under various experimental conditions (stone/sand layer ratio, linear velocity, and coagulant types). Moreover, the removal efficiencies of suspended solids (SS), phosphorus, organic carbon, and heavy metals (Zn, Cu, Pb, Cd) by CMF were evaluated. The removal rate of SS was maintained to be above 84.1% for 1 h filtration by the dual-size foam glass, regardless of increasing pressure. The removal of phosphorus by micro-flocculation was more suitable in alum than ferric due to a higher initial floc growth rate and an increased particle size. The performance of the CMF was significantly improved over media filtration only process (MF) in removing both particulate and dissolved contaminants. The removal efficiency of all particulate pollutants by CMF was found to be more than 90%, and notably, the dissolved phosphorus, which was mostly not removed by MF, was also removed by 97.4%. Meanwhile, the backwash efficiency of CMF was half that of MF. Physical removal mechanisms, such as internal diffusion, dominated MF, whereas chemical removal mechanisms, such as adsorption and surface precipitation, dominated CMF. These results show the potential of the CMF process for the treatment of urban road runoff and identify the removal mechanisms of the filtration process that use micro-flocculation with dual-size foam glass.

The effects of chlorination on 16 humic and fulvic acids (HAs and FAs, respectively) extracted from six different soil samples from Korea and two purchased soil samples (Canadian peat moss, Elliott Silt Loam Soil) were investigated to identify the changes in their structural characteristics and their effects on trihalomethane formation potential (THMFP) and haloacetic acid formation potential. The effect of chlorination was also investigated in fractionated samples (Aldrich HA, F1-F5) based on molecular weight (MW). Total organic carbon (TOC), specific UV absorbance (SUVA), fulvic-like fluorescence (%FLF), terrestrial humic-like fluorescence (%THLF), weight-average molecular weight (MWw), and carbon structures (13C NMR) were measured for each sample before and after chlorination, and factors relating to the chlorination mechanism were examined using principal component analysis (PCA). The results showed that the changes in the structural characteristics and the disinfection by-product formation of chlorinated HA and FA differed critically. For chlorinated HA, TOC and %FLF decreased due to oxidation, whereas %THLF was reduced via incorporation; MW also affected the structural changes and THMFP generation. In the PCA results, high SUVA, low MW, low N/C, and low O groups of aromatic C were associated with high THMFP production in HA, whereas low O groups of aliphatic C in FA were associated with both oxidation and incorporation in terms of THMFP. These results elucidate the mechanisms associated with the effects of chlorination in HA and FA and will support the prediction of THMFP generation in HA and FA based on their specific structural characteristics.

The importance of tributary management is increasing owing to the increase and diversity of pollutant sources in watersheds. In this study, the characteristics of dissolved and particulate contaminants in tributaries of the Anyang watershed, South Korea, were investigated using various analytical indicators (e.g., organic matter, nutrients, and spectroscopic analysis), heat maps, and multivariate analysis techniques, including cluster analysis and principal component analysis (PCA), to evaluate water quality characteristics of the tributaries and major pollutant sources. The influence of particulate matter from each tributary was also evaluated by investigating changes in sediment composition and re-suspended sediment oxygen demand (RSOD) at the mainstream of Anyang. The heat map patterns of the evaluated tributaries reflect sufficiently the characteristics of the pollutant sources, which enables the differentiation of the pollutant source according to the tributary locations and seasons. PCA results showed that water quality and spectral indicators reflected the different characteristics of the tributary; thus, it enabled a more diverse evaluation of tributary depending on pollutant source and season. The tributary watershed showed a high suspended solids (SS) discharge load depending on the watershed area (r = 0.94, p 80%). Our results demonstrate that comprehensive and visual evaluation—including spectral indicators and heat maps analysis—of the tributary characteristics of pollutant sources is an efficient approach of broadening the knowledge of the distribution and effects of particulate matter from tributaries.

In this study, we investigated the photochemical release of dissolved organic matter (DOM) from the particulate organic matter (POM) of soil and litter leaves (broad leaves; coniferous leaves) and compared the releasing characteristics of the DOM using UV-visible and fluorescence spectroscopy. The disinfection by-product formation potential (DBPFP) of the released DOM was also examined. Additional dissolved organic carbon (DOC) was released by UV irradiation for all POM sources (10.58 ± 2.7 mg-C L−1 g−1 for BL, 8.32 ± 2.6 mg-C L−1 g−1 for CL, and 0.20 ± 0.1 mg-C L−1 g−1 for soil). The excitation-emission matrix combined with parallel factor analysis results showed that the photo-released DOM from soil was mainly humic-like components (C1, C3) produced by photodesorption, resulting in high trihalomethane formation potential, while protein-like component (C2) was the major component of the photodissolved DOM from litter leaves, resulting in high haloaceticacid formation potential. Further, DBPFP from soil and litter leaves showed high correlation with humic-like components (C1+C3) and SUVA254, respectively. In conclusion, this study demonstrates that significant amounts of DOM could be released from POM under UV irradiation, although the characteristics and DBP formation of the photo-released DOM were highly dependent upon the POM source.

This study was conducted to develop and validate a more reliable total organic carbon (TOC) analytical procedure for water samples containing suspended solids (SS). The effects of the combined ultrasonic and alkaline pretreatment (CULA) on the TOC measurement were studied in water samples containing SS from three origins (algae, sewage particles, and soil) under different analytical conditions (SS concentration, oxidation methods, and sieve size). The applicability of turbidity as a homogeneity index was also evaluated. With CULA, TOC recovery remained high (&gt, 80%) for SS concentration ranges up to four times larger than ultrasonic pretreatment alone (UL) due to enhanced particulate organic carbon (POC) solubilization, and did not significantly differ depending on the oxidation methods, at low SS concentrations, or with varying sieve sizes. In particular, the turbidity change rate (i.e., NTU5/NTU0) of the pretreated water sample showed a high correlation with TOC precision (r2 = 0.73, p &lt, 0.01), which suggests that turbidity can be used as an indicator of sample homogeneity. A novel TOC analytical procedure is expected to be useful for more accurate assessments of the impact of particulate pollutants on water quality than current methods, and for the analysis of the carbon cycle, including POCs, in the environment.