The effect of anthropogenic impoundments on dissolved organic matter

characteristics and copper binding affinity: insights from fluorescence

spectroscopy

Bin Hua, Peifang Wanga*, Chao Wanga, Jin Qiana, Jun Houa, Xiaoai Cuib, Nannan Zhangb

a Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on

Shallow Lakes, Hohai University, Chinab Jiangsu Academy of Environmental Industry and Technology Corporation, Nanjing 210036, China* Corresponding author, Present address: No.1 Xikang Road, Nanjing 210098, China, E-mail address:

pfwang2005@hhu.edu.cn

Supporting Information

Contents

Fig. S1. Daily precipitation in the Hongze Lake watershed. Green bars and gray bars represent the

rainy seasons. Black arrows indicate the date when the field sampling campaigns were conducted.

Fig. S2. Highly overlaid excitation and emission spectra were estimated using the split-half validation

procedure, with red lines representing six independent halves of the EEMs dataset and black lines

representing the entire dataset.

Fig. S3. Comparison among the integrated spectra of the sum of squared error in the excitation (upper

panel) and emission (lower panel) direction.

Fig. S4. Property-property plots of PCA factor loadings of DOM characteristics (a) and property-

property plots of PCA factors scores of samples collected from three sluices.

Fig. S5. Representative fluorescence quenching curves and the Ryan-Weber model for two

components (C1 and C4) of the Hongze Lake surface water DOM from April and November 2016.

Fig. S6. Changes in DOM characteristics (fluorescence component intensities, b: DOC concentrations,

SR, and SUVA) of surface water samples (site 22, November 2016) upon exposed to sunlight for 8

days.

Table S1 Description and likely origin of the five fluorescent components identified by PARAFAC

model in the present study, with secondary excitation maxima in parentheses and compared with

previous studies.

Table S2 Peason’s correlation matrix based on the characteristics of DOM.

Table S3 Physiochemical characteristics of four filtered water samples (site 1, 15, 17, and 21)

collected from April 2016 and November 2016 (mean value with standard deviation in parenthesis).

1

Fig. S1. Daily precipitation in the Hongze Lake watershed. Green bars and gray bars represent the

rainy seasons. Black arrows indicate the date when the field sampling campaigns were conducted.

Fig. S2. Highly overlaid excitation and emission spectra were estimated using the split-half validation

procedure, with red lines representing six independent halves of the EEMs dataset and black lines

representing the entire dataset.

2

Fig. S3. Comparison among the integrated spectra of the sum of squared error in the excitation (upper

panel) and emission (lower panel) direction.

Fig. S4. Property-property plots of PCA factor loadings of DOM characteristics (a) and property-

property plots of PCA factors scores of samples collected from three sluices.

3

Fig. S5. Representative fluorescence quenching curves and the Ryan-Weber model for two

components (C1 and C4) of the Hongze Lake surface water DOM from April and November 2016.

Fig. S6. Changes in DOM characteristics (fluorescence component intensities, b: DOC concentrations,

SR, and SUVA) of surface water samples (site 22, November 2016) upon exposed to sunlight for 8

days.

Compared with sediments, surface waters are expected to receive more solar irradiation, which

has a significant effect on the characteristics of DOM. Changes in DOM characteristics over the 8

days (17 November to 28 November, 2016) of sunlight irradiation of Hongze Lake water collected

4

(b)(a)

from site 22 at November 2016 are shown in Fig. S6. Fluorescence intensities of humic-like

components (C1, C2, and C3) decreased significantly with increasing irradiation days, while the

protein-like components showed no obvious differences after irradiation. These results suggested that

humic-like DOM could be easily photobleached or photodegraded, while protein-like DOM could not

be photobleached or photodegraded, which were consistent with results reported by Zhang et al.

(2013). Along with the decrease in fluorescence intensities, significant increase in S R and slight

decrease in SUVA were observed, indicating the decreases in aromatic DOM moieties and molecular

weight (Helms et al. 2013). However, no obvious decrease in DOM concentration was found in the 8

days of solar irradiation.

5

Table S1 Description and likely origin of the five fluorescent components identified by PARAFAC

model in the present study, with secondary excitation maxima in parentheses and compared with

previous studies.

Components: Ex/Em Description Likely origin Previous studies

C1: 230(340)/415-

435

Humic-like Terrestrial C2: <250(340)/430 [1]

C1: <250(335)/428 [2]

C2: 245(305)/405 Humic-like Terrestrial and

marine

P1: <260(310)/414 [3]

C2: 250(320)/406 [4]

C3: 260(380)/460-500 Humic-like Terrestrial C3: 260(370)/490 [3]

C3: 250(375)/500 [4]

C4: 230(290)/350 Protein-like, tryptophan Autochthonous P7: 280/342 [3]

C4:<250(260)/345 [1]

C5: 275 (230)/320 Protein-like, tyrosine Autochthonous C5: <250(275)/315 [5]

C1: <250(279)/315 [6]

References

[1] Cuss C.W., Gueguen C., 2012. Determination of relative molecular weights of fluorescent components in dissolved organic matter using asymmetrical flow field-flow fractionation and parallel factor analysis. Anal. Chim. Acta. 733, 98-102.[2] Guo W., Yang L., Hong H., Stedmon C.A., Wang F., Xu J., Xie Y., 2011. Assessing the dynamics of chromophoric dissolved organic matter in a subtropical estuary using parallel factor analysis. Mar. Chem. 124, 125-133.[3] Murphy K.R., Stedmon C.A., Waite T.D., Ruiz G.M., 2008. Distinguishing between terrestrial and autochthonous organic matter sources in marine environments using fluorescence spectroscopy. Mar. Chem. 108, 40-58.[4] Hong H., Yang L., Guo W., Wang F., Yu X., 2011. Characterization of dissolved organic matter under contrasting hydrologic regimes in a subtropical watershed using PARAFAC model. Biogeochemistry. 109, 163-174.[5] Cuss C.W., Gueguen C., 2015. Relationships between molecular weight and fluorescence properties for size-fractionated dissolved organic matter from fresh and aged sources. Water Res. 68, 487-497.[6] Stedmon C.A., Markager S., Tranvik L., Kronberg L., Slätis T., Martinsen W., 2007. Photochemical production of ammonium and transformation of dissolved organic matter in the Baltic Sea. Mar. Chem. 104, 227-240.

6

Table S2 Peason’s correlation matrix based on the characteristics of DOM.

Variable

sDOC SUVA SR HIX BIX FC1 FC2 FC3 FC4 FC5 %FC1 %FC2 %FC3 %FC4

SUVA -0.52**

SR -0.24 -0.02

HIX 0.16 0.30* -0.56**

BIX 0.04 -0.54** 0.48** -0.83**

FC1 0.62** 0.22 -0.43** 0.67** -0.62**

FC2 0.61** 0.20 -0.54** 0.65** -0.61** 0.95**

FC3 0.46** 0.38** -0.5** 0.74** -0.70** 0.93** 0.93**

FC4 0.29* -0.30* 0.43** -0.80** 0.76** -0.19 -0.20 -0.33**

FC5 0.20 -0.10 0.27** -0.66** 0.52** -0.11 -0.06 -0.15 0.83**

%FC1 0.21 0.22 -0.45** 0.91** -0.83** 0.71* 0.61** 0.66** -0.76** -0.72**

%FC2 0.21 0.19 -0.65** 0.85** -0.78** 0.62* 0.73** 0.69** -0.73** -0.59** 0.79**

%FC3 0.07 0.45** -0.53** 0.90** -0.84** 0.63* 0.65** 0.81** -0.78** -0.59** 0.81** 0.81**

%FC4 -0.21 -0.32** 0.57** -0.94** 0.90** -0.75* -0.74** -0.80** 0.78** 0.58** -0.94** -0.90** -0.92**

%FC5 -0.12 -0.15 0.41** -0.84** 0.70** -0.53* -0.46** -0.52** 0.77** 0.89** -0.92** -0.78** -0.76** 0.82**

* p<0.05.**p<0.01.

7

Table S3 Physiochemical characteristics of four filtered water samples (site 1, 15, 17, and 21)

collected from April 2016 and November 2016 (mean value with standard deviation in parenthesis).

Sampling date pH K+ Na+ Ca2+ Mg2+ SO42- Cl- HCO3

- CO32-

mg L-1

April 2016

(early impoundment)

8.31

(0.26)

6.06

(0.59)

48.4

(1.68)

30.0

(1.88)

19.7

(1.46)

31.1

(3.66)

37.5

(5.14)

107

(9.45)

5.07

(1.07)

November 2016

(late impoundment)

8.19

(0.34)

7.64

(0.42)

42.2

(2.37)

21.0

(3.47)

16.4

(1.28)

37.5

(2.89)

41.8

(5.78)

93

(8.79)

3.69

(0.79)

8