Table 1. Summary of Polypropylene Microplastic Photochemical Degradation, Carbon Tracking, and Chemical Changes Initial, Final, and Percent Recovery of Plastic Mass, as well as Carbon Accounting of Plastic C as Plastic, DOC, or Purgeable Carbon^a.

	Plastic mass recovery			Carbon accounting
Irradiation time (days)	Starting PP mass (g)	Recovered PP mass (g)	% of initial PP mass recovered	PP % C by mass	% of initial plastic-C recovered	DOC accumulation (mg DOC g plastic-C–1)	% of initial plastic-C as DOC	% of initial plastic-C as purgeable-C
0	0.300 ± 0.001	0.296 ± 0.001	100.0 ± 0.5	90.4 ± 0.7	100.0 ± 1.0	0.114 ± 0.022	0.00 ± 0.00	0.00 ± 0.96
26	0.302 ± 0.001	0.292 ± 0.001	98.0 ± 0.5	88.4 ± 1.7	95.6 ± 1.8	0.89 ± 0.18	0.08 ± 0.02	3.98 ± 1.84
53	0.299 ± 0.001	N/A	N/A	N/A	N/A	8.36 ± 0.18	0.82 ± 0.02	N/A
181	0.299 ± 0.001	0.253 ± 0.001	85.9 ± 0.4	86.8 ± 0.5	82.6 ± 0.2	82.09 ± 0.32	8.20 ± 0.03	9.17 ± 0.7
279	0.299 ± 0.001	0.233 ± 0.001	79.3 ± 0.4	85.8 ± 1.4	75.3 ± 1.3	123.0 ± 6.7	12.3 ± 0.67	12.4 ± 1.5
364	0.302 ± 0.001	0.215 ± 0.001	72.5 ± 0.4	85.9 ± 0.8	69.0 ± 0.8	172.9 ± 2.2	17.3 ± 0.22	13.7 ± 0.8
Dark 364	0.301 ± 0.001	0.295 ± 0.001	99.3 ± 0.5	90.1 ± 0.2	99.1 ± 0.6	0.129 ± 0.022	0.00 ± 0.00	0.92 ± 0.57

^aPlastic carbon content and DOC accumulation values included for carbon tracking. Missing data for day 56 is due to sample loss during analysis.