Organic Matter Composition in Sediments of the Baiyangdian Lake in China

Available online at www.sciencedirect.com

Procedia Environmental Sciences 10 (2011) 1768 – 1773

2011 3rd International Conference on Environmental Science and Information Application Conference Title Technology (ESIAT 2011)

Organic Matter Composition in Sediments of the Baiyangdian Lake in China Xuan Zhao 1,a , Jiemin Chengγ2 1 College of Population Resources and Environment, Shandong Normal Universityˈ JinanˈShandongˈ250014, China 2 College of Population Resources and Environment, Shandong Normal Universityˈ JinanˈShandongˈ250014, China a [email protected]

Abstract The content and composition of organic matter (OM) in four areas(contrast area, aquaculture area, aquatic area and sewage area )of Baiyangdian lake are studied by using physical chemistry methods. The main objective of the study is to provide theoretical data for the management of Baiyangdian lake eutrophication. Compared with contrast area, aquaculture area and aquatic area sediment shows significantly higher concentrations of total organic matter in sewage area. These results suggest that more serious organic pollution in the sewage area sediment. Irrespective of the higher content of total organic matter, the light fraction organic matter (LFOM) is very low in four sample stations. Heavy fraction organic matter (HFOM) is the dominant class among organic matter composition in contrast areaǃaquaculture area ǃaquatic area and sewage area sediments contributing 85.80λǃ87.7λǃ78.71% and 85.00 λ respectively. These results indicate that HFOM account for most of organic matter while LFOM was completely decomposed. Correlation analysis of organic matter shows that labile organic matter (LOM), dissolved organic matter (DOM), LFOM and HFOM have remarkable positive correlation between them respectively.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [name organizer] ESIAT2011 Organization Committee. Keywords: Baiyangdian Lake; organic matter; Height and light fraction organic matter; Labile organic matter; Dissolved organic matter

Introduction Lake sediments are generally rich in organic matter, which consists of labile and refractory compounds, whose relative importance changes as a function of a complex array of processes, including degradation, heterotrophic utilization, transformation, accumulation and export [1]. Refractory organic compounds such as humic and fulvic acids, structural carbohydrates and “black” carbon account generally for most of the sedimentary organic matter [2, 3]. Conversely, the labile fraction of organic matter consists mainly of simple and/or combined molecules. It includes carbohydrates, lipids and proteins, which may be mineralized [4, 5]. Composition of organic matter is a diverse mixture, its distribution and forms are the key factor to control sorption/ desorption, migration and transformation of pollutants, some studies have been carried out [6,7,8,9].

1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee. doi:10.1016/j.proenv.2011.09.277

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It is well known that eutrophic shallow lakes are mainly located in the middle and lower region of Yangtze River. Eutrophic shallow lakes are characterized by gradually expanding of the scope of eutrophication, increasing of algae and the spread ing of algal blooms of lake algae [10]. So far, most studies dealing with sedimentary organic matter have been performed on selected sites, repeatedly investigated for source and biogeochemistry analysis and discussion of organic matter [11, 12, 13]. However, there is a conspicuous lack of information about concentration and distribution of organic matter in Baiyangdian lake sediments. The objective of the present study is to investigate the content and composition of OM in the sur¿cial sediments of the eutrophic lakes with macrophytic lake, thereby providing theoretical statistics in order to control eutrophic lakes. Materials and methods Study area. Baiyangdian lake is the only freshwater lake and wetland of Northern Plain in China by area (366km2, maximum depth 2~3m). The nine rivers flow into Baiyangdian Lake. The abundant rush vegetation of these regions, Baiyangdian lake is a typical macrophytic lake. Lake system has been shrinking due to pollution by human activities as well as water shortage [14]. Sampling and analytical methodology.Samples of water and sediments were taken from these locations in May 2010. Overlying water samples were taken using a clean plastic bucket. A cylindrical sampler is used for collecting surface sediments. Samples were transported into the lab on ice and stored in a deep freezer. All analyses were carried out on the top 10cm of sediment cores. The station locations and coordinates are reported in Table 1. pH in the overlying water was measured using a glass electrode [15]. Potassium persulfate - UV spectrophotometry and ammonium molybdate spectrophotometric were used for the estimation of total nitrogen and total phosphorus respectively [16]. CODCr was measured using potassium dichromate method [17]. Sediment samples were air dried and appropriately powdered using agate mortar for further analyses. Total carbon and nitrogen were determined to use a Vario EL III CHNS Analyzer. The amount of total organic matter (OM) was obtained by potassium dichromate - external heating method [18]. Gravity separation was used for the estimation of height and light fraction organic matter [19]. Perchloric acid digestion of a molybdenum antimony colorimetry resistance method was used for the total phosphorus [20]. Potassium permanganate oxidation method was used for the liable organic matter (LOM) [21]. Dissolve organic matter (DOM) was estimated by Baham method [17]. All analyses were carried out in triplicate and the average is reported. Table 1 The geographic location of the sampling site and its characteristics Items B-1 B-2 B-3 B-4

Sampling stations contrast area aquaculture area aquatic area sewage area

Position N 38º50ƍ05.8Ǝ E 115º59ƍ52.0Ǝ N 38º50ƍ25.3Ǝ E 115º59ƍ18.1Ǝ N 38º49ƍ43.0Ǝ E 116º00ƍ56.6Ǝ N 38º50ƍ29.6Ǝ E 115º56ƍ28.3Ǝ

Note: B, Baiyangdian Lake Results Physical and chemical indicators of the overlying water.pH is slightly more alkaline. When the water total nitrogen (TN) >0.2mg/L or total phosphorus (TP) >0.02mg/L, it will lead to lake eutrophication [22]. The result indicated that overlying water of Baiyangdian lake had been into contaminated state (Table2). The N/P ratios in Baiyangdian lake is 14.29, recent studies have shown that the N/P ranged from 14~16

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[22], N/P ratios are most appropriate growth of bulrush. These data show that overproduction of bulrush has accelerated eutrophication in Baiyangdian lake. Table2. Characters of overlying water samples Lake Name Baiyangdian lake

pH

CODCr(mg/L)

TP(mg/L)

TN(mg/L)

7.85

31

0.04

1.09

Sediment characteristics.Total organic matter content(Table3) in contrast area station(B1) is 39.11±2.38 g/kg dry weight, whereas aquaculture zone (B2) is 33.02±2.47 g/kg dry weight, aquatic area (B3) is 26.14±2.0 g/kg dry weight and sewage area (B4) is 45.07±0.36. Total nitrogen content is 0.21±0.004 g/kg,0.38±0.07g/kg,0.26±0.003 and 0.33±0.011 g/kg dry weight respectively in B1, B2, B3 and B4 sediments. Content of total phosphorus B1 station is 0.17±0.01 g/kg, B2 is 0.32±0.005g/kg, B3 is 0.51±0.01 g/kg and B4 is 0.34±0.006 g/kg dry weight. Table3 Sedimentary parameters in the sediments of Baiyangdian lake parameters Total nitrogen ˄g/kg˅

B1 0.21±0.004

B2 0.38±0.07

Total phosphorus˄g/kg˅

0.17±0.01

0.32±0.005

Total organic matter˄g/kg˅

39.11±2.38

33.02±2.47

Labile organic matter˄g/kg˅

6.79±1.8

5.08±0.13

Dissolve organic matter˄g/kg˅

1.14±0.02

0.89±0.05

Light fraction organic matter ˄g/kg˅ Height fraction organic matter ˄g/kg˅

3.17±0.11

2.97±0.06

33.56±2.57

28.73±3.01

B3 0.26±0.0 03 0.51±0.0 1 26.14±2. 0 4.31±0.0 5 0.75±0.0 9 3.98±0.0 3 20.57±1. 21

B4 0.33±0.01 1 0.34±0.00 6 45.07±0.3 6 7.05±0.18 1.32±0.2 3.38±0.05 38.31±2.4 9

Composition of sedimentary organic matter.Labile organic matter (LOM) content in contrast area station (B1) is 6.79±1.8 g/kg, whereas aquaculture area (B2) is 5.08±0.13 g/kg, aquatic area (B3) is 4.31±0.05 g/kg and sewage area (B4) is 7.05±0.18 g/kg respectively. The dissolve organic matter (DOM) content for B1, B2, B3and B4 is 1.14±0.02 g/kg , 0.89±0.05g/kg , 0.75±0.09 g/kg and 1.32±0.2g/kg respectively. The content of light fraction organic matte (LFOM) at these stations are 3.17±0.11g/kg, 2.97±0.06 g/kg, 3.98±0.03 g/kg and 3.38±0.05 g/kg respectively. Heavy fraction organic matter (HFOM) is 33.56±2.57 g/kg in contrast area, 28.73±3.01g/kg in aquaculture area, 20.57±1.21 g/kg in aquatic area and 38.31±2.49g/kg in sewage area (Table3). Discussion Light fraction organic matter˄LFOM density<2.0 g·cm-3 ˅ is considered to be more varied and not closely linked with the mineral, including animal and plant debris, small animals and micro-organisms [23], LFOM to total organic matter (TOM) ratio reflects the degree of decomposition of organic matter

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accumulation[24]. Heavy fraction organic matter˄HFOM˅is decomposed by the light fraction organic matter that remains after completion or re-synthesis, and a better ability to resist microbial degradation [25-26]. Light and heavy fraction organic matters are the total organic matter content with the changes (Table3). Irrespective of the higher content of total organic matter (OM), the light fraction organic matter was very low in Baiyangdian lake sediments. Hence a large fraction of total organic matter is represented by heavy fraction organic matter. In other words, the refractory fraction content is comparatively higher. 1. Total nitrogen and phosphorus concentrations of aquaculture area and aquatic area sediments are higher than that of contrast area and sewage area sediments (Table3). It is likely that high density of breeding and feeding makes a lot of bait in the waters and waste accumulation, this bait and waste are broken down and released nitrogen. Content of phosphorus in aquatic area is higher duo to different forms of phosphorus mineralization under the effect of root exudates. Stoichiometric ratios of nutrients are utilised to determine the origin and transformation of organic matter. The C/ N ratio is an indicator of protein content, source of organic matter by C/ N. Some studies have shown that the C/ N>12 is terrestrial as well as human-induced origins, C/ N<8 is degradation processes of organisms that have lived in the lake [27]. However the selective degradation of the different minerals in sediments can affect the C/N ratios of organic matter. The C/ N ratio in sewage area and contrast area ranged from13 -18 and in aquaculture area and in aquatic area it varied 8-10, these results show that sediment organic matter can be derived from allochthonous organic matter. Table4 Correlation between sedimentary parameters in Baiyangdian lake TN TP OM LOM DOM LFOM HFOM TN 1 TP 0.217 1 OM 0.019 -0.034 1 1 LOM -0.166 -0.735 0.967* * 0.977* 1 DOM -0.023 -0.599 0.992 LFOM -0.386 0.811 -0.503 -0.464 -0.402 1 0.958* 0.974* 0.593 1 HFOM 0.123 -0.689 0.994** * ** Note: .p<0.05; .p<0.01. Correlation analysis of Baiyangdian lake sediments (Table 4) shows that OM had highly signi¿cant positive relations with LOM, DOM and HFOM. LOM, DOM, and HFOM have remarkable positive correlation among them respectively. These correlation analysis shows that various components of organic matter are not completely separated, but contain each other in Baiyangdian lake sediments. Conclusion The content of sedimentary organic matter is higher in sewage area, suggesting more serious organic pollution in sewage area. This study also shows the percentage ratio of the light fraction organic matter to total organic matter, indicating that most of the deposited organic matter is refractory organic in Baiyangdian lake ecosystem. Correlation analysis reveals that LOM, DOM, and HFOM of organic matter have remarkable positive correlation among them respectively.

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