Characterization of Natural Organic Matter in the Yeongsan River by Fluorescence Spectroscopy, XAD and FT-IR

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1 2012 2nd International Conference on Environmental and Agriculture Engineering IPCBEE vol.37 (2012) (2012) IACSIT Press, Singapore Characterization of Natural Organic Matter in the Yeongsan River by Fluorescence Spectroscopy, XAD and FT-IR Dongjin Lee + and Byungjin Lim The National Institute of Environmental Research, Gwangju, , Republic of Korea Abstract. This work has examined the characteristics of natural organic matter (NOM) from the Yeongsan River basin by the 3D fluorescence excitation-emission matrix (FEEM), XAD resin, and Fourier transform infrared (FT-IR). In FEEM investigation, fulvic and humic substances were found in most of the sites, and protein-like substances were found in winter in sites of the city of Gwangju which is biggest city in the Yeongsan River basin. These results showed an equivalent trend to the fluorescence index (F 450/500 ) in most of sites, and the higher F 450/500 in the sites of Gwangju city indicates more microbial-derived substances due to effluent organic matters (EfOM) from Gwangju sewage treatment plants. In XAD investigation, most of the samples were mainly hydrophilic substances. In March, hydrophobic substances were dominant in upper reaches of Gwangju (Gwangju 1 site), while hydrophilic substances were dominant in other sites. In FT-IR investigation, most of the broad and large peaks were assigned to aliphatic group, particularly OH group, C- H, C-H 2, C-H 3, and C-O alcohol group, which are related to hydrophilic substances. Other peaks were shown in the aromatic group, particularly C=O (ketone) group. As a result, this work showed characteristic of NOM in the Yeongsan River basin that composed of mainly hydrophilic substances and functional groups (OH, C- H etc.) of aliphatic compound. Keywords: Natural Organic Matter, Fluorescence Excitation-Emission Matrix, Xad Resins, Fourier Transform Infrared 1. Introduction Natural organic matter (NOM) shows different compositions and distributions by region, season and river basin, and consists of heterogeneous compounds, which makes it difficult to determine its characteristics [1]. A variety of analysis methodologies are used to understand the characteristics of NOM. 3D Fluorescence excitation-emission (FEEM) spectroscopy is widely used in NOM analyses of river and freshwater [2,3], marine water [4], sewage effluent from sewage treatment plants [5], and industrial sewage water [6], because of the relatively rapid analysis, no sample preparation prior to analysis, and a little amount of sample required [2]. NOM fractionation by XAD 8/4 resins has been used for classification of hydrophobic and hydrophilic substances. Fourier transform infrared (FT-IR) spectroscopy has been applied to the identification of functional groups in the structure of NOM. This study investigates the distribution characteristics of NOM from the main stream of the Yeongsan River basin, from Gwanjucheon (GJC) among the tributaries, and from Gwangju Sewage Treatment Plant (GJS), by season. In particular, this study aims to provide fundamental data for understanding water origin and water quality control based on the distribution characteristics of NOM in the basin using FEEM, XAD and FT-IR. 2. Experimental Results and Discussions 2.1. Sample Preparation and Methods + Corresponding author :Tel.: ; Fax: address: dongj7@korea.kr 20

2 The sampled were analyzed for water characteristics(ph, DO, electrical conductivity, BOD, COD, TN, TP, Chl-a, DOC, UV 254, SUVA) and for the characteristics of NOM using F-2500 fluorescence spectrophotometer(hitachi), XAD 4/8 resins(amberlite) and 460 plus FT-IR(Jasco). To investigate the NOM in the Yeongsan River basin, 6 sites at the main stream (Damyang (DY), Gwangju 1 (GJ1), Gwangju 2 (GJ2), Gwangsan (GS), Naju (NJ), Muyan (MY)), 1 site (GJC) at the tributary and the Gwangju sewage treatment plant (GJS) were selected, and samples were gathered 2 times per month in February, May, August, and October, Fig. 1: Sampling sites for analyzing natural organic matter in the Yeongsan River basin. DY : Damyang, GJ1 : Gwangju 1, GJC : Gwangjucheon, GJS : Gwangju sewage treatment plant, GJ2 : Gwangju 2, GS : Gwangsan, NJ : Naju, MY : Muyan Results of FEEM Investigation In FEEM investigation, NOM in the Yeongsan River were usually composed of humic and fulvic substances in winter. However, protein-like substances were also found, not only in NOM from the Gwangju (GJC, GJS) but also in those from the main stream of the Yeongsan River (GJ2, GS) which may be strongly influenced by the sewage effluent. Gwangjucheon flows through the central area of the city of Gwanju, so the sewage effluent generated by Gwangju resident flows in the tributary, and anthropogenic NOM were also identified. The NOM from GJS was classified as effluent organic matter (EfOM) [7]. In spring, no proteinlike substances were found in any of the sites. It is presumed that the protein-like substances found in the winter samples may have been decomposed and reduced in the process of active metabolism of microorganisms with the rising water temperature in spring. The NOM found in the summer samples also consisted of only humic and fulvic substances, as with the spring samples. However, the protein-like substances were found in GJC, which could be the result from the sewage water generated in Gwangju city where the installation rate of separate sewer systems was very low (approx. 38%). The NOM found in the fall samples was comprised of only humic and fulvic substances, similarly to those in the spring samples. The maximum fluorescence levels (F max ) and F 450/500 values became stronger from the upper to the middle reaches of the river, and then weaker from the middle and lower reaches after GJS. This trend is similar to those of BOD, COD, and DOC that were identified at sites of the Yeongsan River basin. F 450/500 was higher than 1.7 at all the investigated sites in Yeongsan River regardless of season, and it can be interpreted that the NOM was microbial-derived. In particular, F 450/500 was very high at GJS and GJC ( ), GJ2 and GS ( ), and the microbial-derived NOM was shown to be strong Results of XAD investigation In investigation by XAD resin, Yeongsan River was generally shown to be more hydrophilic and transphilic than hydrophobic in February. GJ1 near the upper reaches of Yeongsan River was shown to be more hydrophobic, and was believed to contain lots of allochthonous NOM or authochthonous NOM. In particular, the sewage effluent of GJS serves as the main source of the maintenance water to GJC in the dry season, so the characteristic of NOM in GJC has a high correlation with that of EfOM. In spring, all investigated sites were shown to be more hydrophilic than hydrophobic. Overall hydrophilic and transphilic 21

3 characteristics in the river were stronger than its hydrophobic characteristics in August. In autumn the hydrophilic characteristic was overall shown to be higher, except for the samples from GJ1 that were similar to those in February. As a result, in the seasons when the water temperature fell, the degradation activities performed by microorganisms became slower, and hydrophobic substances were slightly more present than hydrophilic substances. Fig. 2: Spatial changes of natural organic matter in fluorescence index [F 450 /F 500 ] from upper to lower reaches in the Yeongsan River basin FT-IR Investigation In FT-IR investigation, the main functional group was shown to be an O-H stretch, which is usually broad and strong in the 3400~2500 cm -1 range. Aliphatic groups including C-H, C-H 2, and C-H 3 stretches were strong between 2950~2850 cm -1, and the C-O stretching occurred in the 1250 ~ 1000 cm -1 range that was shown to be hydrophilic neutral compounds. These results indicate that the NOM in Yeongsan River mainly consists of hydrophilic substances, and the fact that the O-H stretch is shown to be highest and widest may mean that it showed hydrophilic acid compounds. On the other hand, C=O stretches occurring at frequency range 1640~1585cm -1 were ketones and quinines that were aromatic or alicyclic and showed hydrophobic compounds. The C-H aldehyde stretches were weak at frequency range cm -1. The O- 22

4 H functional group attached to the carboxyl group appeared in the 880 ~ 750 cm -1 range, which indicated the existence of hydrophobic substances. The FT-IR spectra analysis of the samples of May was very similar to that of the samples taken in February. The C-H stretch of the aliphatic group was shown to be strong in 1470~1420 cm -1 range, from which it can be inferred that the higher water temperature in May than in February and degraded organ matter led to a stronger hydrophilic characteristic. The C-H aldehyde stretches almost disappeared. For this reason, it is possible to infer that Yeongsan River became more hydrophilic in May than in February, as was the case in the results using XAD8/4 resins. FTIR results of August and October were shown to be almost consistent with those of May. (a) (b) (c) (d) Fig. 3: Distribution of NOM fractionated from the Yeongsan River: (a) February (b) May (c) August (d) October. As a consequence, in the structural analysis of NOM using XAD and FTIR, since GJS and GJC were both affected by the sewage effluent generated by Gwangju residents, the hydrophilic characteristic was shown to be very strong and the result was very similar in the functional groups analysis. NOM of Yeongsan River slightly has a different characteristic by season, affecting the activity of microorganism metabolism and by organic sources such as EfOM released from Gwangju residents. 3. References [1] G.R. Aiken, Evaluation of Ultrafiltration for Determining Molecular Weight of Fulvic Acid. Environ. Sci. Technol. 1984, 18: [2] R.K. Henderson, A. Baker, K.R. Murphy, A. Hambly, R.M. Stuetz, S.J. Khan. Fluorescence as a Potential Monitoring Tool for Recycled Water System: A Review. Water Research. 2009, 43: [3] N. Hudson, A. Baker, D. Reynolds. Fluorescence Analysis of Dissolved Organic Matter in Natural, Waste and Polluted waters A Review. River Research and Applications. 2007, 23:

5 [4] P.G. Coble. Characterization of Marine and Terrestrial DOM in Seawater using Excitation-emission Matrix Spectrometry. Marine Chemistry. 1996, 51: [5] D.M. Reynolds, S.R. Ahmad. Rapid and Direct Determination of Wastewater BOD Values using a Fluorescence Technique. Water Research. 1997, 31: [6] T. Janhom, S. Wattanachira, P. Pavasant. Characterization of Brewery Wastewater with Spectrofluorometry Analysis. J. Environmental Management. 2009, 90: [7] R.T. Ahmad, T.V. Nguyen, A. Vigneswaran, D.P. Ho. Removal of Effluent Organic Matter by Purolite Fluidized Bed and Submerged Membrane Hybrid System. Desal. Water. Treat. 2011, 32: (a) (b) (c) (d) Fig. 4: FT-IR spectra of NOM in the Yeongsan River: (a) February (b) May (c) August (d) October. 24