Association between greenhouse gases and dissolved organic matter composition in the main rivers around Taihu Lake

Figures & data

Figure 1. Distribution of sampling sites in the main rivers around Taihu Lake.

Table 1. Analytical performance parameters for the determination of GHGs.

Compounds	Retention time (min)	Detection limits
CH4	2.786	0.20148
CO2	5.339	0.36339
N2O	7.081	0.02276

Table 2. Physical and chemical parameters of sampling sites.

Point	Temperature °C	DO mg/L	EC μs/cm	TDS	pH	ORP mV
1	8.53 ± 0.21	12.81 ± 0.48	258.47 ± 3.41	245.27 ± 2.63	7.86 ± 0.29	260.45 ± 21.71
2	5.43 ± 0.84	10.13 ± 0.48	262.00 ± 5.56	271.70 ± 3.38	8.32 ± 0.15	233.10 ± 9.76
3	4.90 ± 0.46	15.63 ± 1.16	335.73 ± 4.96	352.52 ± 3.70	7.97 ± 0.12	256.70 ± 12.01
4	5.97 ± 0.81	11.36 ± 0.78	407.90 ± 56.00	456.95 ± 59.29	8.03 ± 0.08	239.37 ± 13.90
5	4.80 ± 0.62	15.16 ± 1.33	325.10 ± 30.80	343.63 ± 26.91	7.96 ± 0.09	254.27 ± 3.27
6	5.80 ± 0.69	13.37 ± 0.50	344.43 ± 29.89	353.82 ± 33.66	7.67 ± 0.08	190.10 ± 30.41
7	4.30 ± 0.07	15.62 ± 0.31	88.30 ± 6.77	92.73 ± 5.53	8.21 ± 0.33	245.80 ± 23.31

Figure 2. Concentrations of TN (a), TP (b), NO₃⁻-N (c) and NH₄⁺-N (d) in the overlying water.

Figure 3. Concentrations of DTC (a), DIC (b) and DOC (c) in the overlying water.

Figure 4. Concentrations of the greenhouse gases N₂O (a), CH₄ (b) and CO₂ (c) in the overlying water.

Table 3. Pearson’s correlation between the water quality indices and gas production.

Index	TN	TP	NH4^+-N	NO3^−-N	DTC	DIC	DOC	N2O	CH4	CO2	T	DO	EC	TDS	pH	ORP
TN	1
TP	0.002	1
NH4^+-N	−0.288	0.110	1
NO3^−-N	−0.039	0.280	−0.073	1
DTC	−0.089	0.212	0.685**	−0.285	1
DIC	−0.087	0.157	0.644**	−0.311*	0.976**	1
DOC	−0.063	0.317	0.533**	−0.083	0.672**	0.494**	1
N2O	0.102	0.039	0.609**	0.286	0.174	0.091	0.387*	1
CH4	0.325	−0.395*	0.124	−0.245	−0.092	−0.053	−0.188	−0.064	1
CO2	−0.022	−0.079	0.424*	0.125	0.217	0.146	0.364*	0.367**	0.384**	1
T	−0.322	0.363	−0.331	0.455*	−0.434*	−0.395	−0.327	−0.402	−0.282	−0.174	1
DO	0.326	0.127	0.139	−0.072	0.068	0.027	0.146	0.263	−0.011	−0.416	−0.467*	1
EC	−0.852**	−0.441	−0.232	−0.470*	−0.145	−0.174	0.006	−0.523*	0.321	0.105	0.079	−0.199	1
TDS	−0.831**	−0.486*	−0.191	−0.511*	−0.105	−0.135	0.026	−0.487*	0.351	0.119	−0.014	0.156	0.995**	1
pH	0.290	0.212	−0.181	0.282	−0.215	−0.257	0.006	0.204	−0.245	−0.175	−0.324	0.150	−0.308	−0.287	1
ORP	−0.019	−0.025	0.119	0.089	−0.111	−0.120	−0.034	0.067	0.001	−0.550*	0.294	0.297	−0.101	−0.123	−0.448*	1

Figure 5. Typical EEMs of DOM in the samples.

Table 4. Major fluorescence peaks and their spectral positions of dissolved organic matter in previous studies (Coble et al. 1998; Coble et al. 2014; Xi et al. 2018).

Component	Exmax/Emmax (nm)	Fluorescence peak	Description
C1	295/344	T2	Tryptophan, Protein-like
C2	285/318	B	Tyrosine, Protein-like
C3	315/397	M	Microbial humic-like
C4	365(305)/456	C	Visible fulvic-like fluorescence

Figure 6. Comparison of UV and fluorescence characteristics of DOM.

Table 5. Relationships between gas production and DOM composition.

Index	C1	C2	C3	C4	N2O	CH4	CO2
C1	1
C2	0.972**	1
C3	0.306	0.332	1
C4	0.246	0.239	0.975**	1
N2O	−0.394	−0.503*	−0.216	−0.059	1
CH4	0.303	0.236	0.470	0.573*	−0.064	1
CO2	0.142	0.120	0.218	0.265	0.367**	0.384**	1

Coble PG, Castillo C, Avril B. 1998. Distribution and optical properties of CDOM in the Arabian Sea during the 1995 Southwest Monsoon. Deep-Sea Res Pt II. 45(10-11):2195–2223.

 Web of Science ®Google Scholar

Coble PG, Lead J, Baker A, Reynolds DM, Spencer GGM. 2014. Aquatic Organic Matter Fluorescence: Environmental Effects. Cambridge University Press. ISBN 978-0-521-76461-2.

 Google Scholar

Xi Y, Wang T, Ni JR, Han P, Yi ML, Zhen T, Jiang Y, Ma RQ, Cui F. 2018. Characterization of dissolved organic matter fractions in the Ning-Meng Section of the Yellow River and relationship with metal ions. Environ Sci. 39(09):4114–4121.

 Google Scholar