Latest update: 2017-9-20

R/V: Blue Heron.

Sample date: June 14 ~ 21, 2017.

Data measurements: UV-Visable spectrom, EEMs, DOC, DN, FlFFF.

Sampling sites:

Lake water samples were collected on board the R/V Blue Heron between June 14th and 21st. Surface water samples were collected using the pump. Deep water samples (S30-278m, S13-125m) were collceted via Niskin bottles amounted on a CTD rossete.

DOC concentration, a254, and SUVA254

We found robust linear relationship between CDOM a254 and DOC in Lake Michigan, but not in Lake Superior due to the consistency of Lake Superior. However, in the colloidal fractionation and < 1kDa fractionation the relationships were not observed in Lake Michigan. But the a254-DOC relationship were significant in Lake Superior. DOC concentration and CDOM a254 values, which are comparatively lower in Lake Superior than Lake Michigan agree with measures in Zhou et al. (2013).

EEMs analysis

Four FDOM components decomposed by parallel factor analysis are shown below.

Component1 is a typical Humic-like component. It contains peaks A (Ex:260 nm, Em:380~460 nm) and peaks C (Ex:330 nm, Em:420~480 nm). It was the most intense peak in all fluorescence EEMs.

Component 2 is corresponding to peaks B (Ex:275 nm, Em:310 nm) and/or peaks T (Ex:275 nm, Em:350 nm). It seems like a combination of peaks T and peaks B. Whatever it would be a Protein-like fluorophore.

The second highest peak from Component 3 is corresponding to peaks M (Ex: 312 nm, Em:380~420 nm). It is probably a humic-like component.

Component 4 is probably a noise-derived component.

Distribution of C1~C4

High correlation relationship is observed between Component 1 and Component 3, which indicates similar source of these two components. Distribution of Component 2 demonstrated more autochthonous fluorescence matter in Lake Michigan than Lake Superior.

Correlation between parameters

Size distribution of colloids in the Great Lakes

Concentration Normalization completed.

Hydrodynamic diameters of the dissolved organic colloids (UV254)

Hydrodynamic diameters of the Protein-like colloids

The small peak disappeared in Sample S23-0m and Sample S22B-0m.

Hydrodynamic diameters of the Humic-like colloids

Molecular weights of peak in size chromotography

\[M_n = \frac{\sum M_i \cdot n_i}{\sum n_i}\] \[M_w = \frac{\sum M_i \cdot w_i}{\sum w_i} = \frac{\sum M_i^2 \cdot n_i}{\sum M_i \cdot n_i}\] \[DPI = \frac{M_w}{M_n}\]

Integration - UV1

Integration FLD1 Huimic-like

1 One peak;

2 Normalized distribution;

Integration -FLD2 Protein-like

Pie charts

UV1

Huimic-like (FLD1)

Protein-like (FLD2)

HMW fractionation (>100 kDa) in protein-like FDOM occupied averagely more than half of the integration (57.32%) in Lake Michigan. Meanwhile, the largest protein-like fractionation (>100 kDa) has greatest proportion of FDOM integration chromotography.

Lake Michigan   Lake Superior  
UV1      
1-5kDa      
S3-0m 44.04 S23-0m 46.64
KS103-0m 44.02 S22B-0m 51.09
S13.5-0m 38.21 S30-0m 48.25
S13-125m 38.13 S30-278m 48.79
Average 41.1 Average 48.69
> 100 kDa      
S3-0m 19.42 S23-0m 12.21
KS103-0m 19.15 S22B-0m 7
S13.5-0m 30.03 S30-0m 6.75
S13-125m 26.81 S30-278m 5
Average 23.85 Average 7.74
Humic-like fluorescence      
1-5kDa      
S3-0m 51.6 S23-0m 55.24
KS103-0m 52.93 S22B-0m 58.71
S13.5-0m 50.66 S30-0m 55.11
S13-125m 52.06 S30-278m 55.66
Average 51.81 Average 56.18
> 100 kDa      
S3-0m 5.36 S23-0m 4.45
KS103-0m 6 S22B-0m 4.24
S13.5-0m 7.31 S30-0m 3.93
S13-125m 6.45 S30-278m 2.19
Average 6.28 Average 3.70
Protein-like fluorescence      
1-5kDa      
S3-0m 28.06 S23-0m 27.46
KS103-0m 13.07 S22B-0m 36.24
S13.5-0m 24.5 S30-0m 34.14
S13-125m 27.36 S30-278m 27.31
Average 23.25 Average 31.29
> 100 kDa      
S3-0m 50.49 S23-0m 45.7
KS103-0m 72.21 S22B-0m 30.16
S13.5-0m 59.49 S30-0m 30.65
S13-125m 47.07 S30-278m 45
Average 57.32 Average 37.88

Pie charts

UV1

Huimic-like (FLD1)

Protein-like (FLD2)

PCA Analysis

Summary