This is a pioneering work. The authors have addressed the Reviewers' comments satisfactorily. Some small technical corrections should be made:
1. Practical salinity is a dimensionless quantity, so the “unit” PSU should be deleted throughout the manuscript
2. The unit “ton” (imperial ton = 2240 lb) is used through most of the manuscript. I am aware that old habits die hard in the shipping industry and that the use of this unit may well persist. A note at the start of the paper would help to clarify that this old unit is used rather than “tonne” (= 1000 kg).
3. On a point of consistency, the adjective “riparian” is sometime capitalised, sometimes not. Consistent use is important: the uncapitalised version is to be preferred.
4. Lines 115 and 122: better to avoid the use of “species”, which also has biological connotations. “contaminant”, also used later in the text, is a good alternative
5. Line 128: using the term “days spent at sea” does not fully address the Reviewer’s concern since the implication for many readers is the number of days the boat is being actively used. “days spent in the water” would be much clearer
6. Lines 190-191: the load factor (70%) is the same as quoted on line 183, i.e. not higher
7. Line 335: should the second date be 3rd June?
8. Table 6: I assume that the final column is millions of km, “10^6 km” would be clearer