Review of Measurement report: Size-resolved chemical characterisation of aerosols in low-income urban settlements in South Africa by

Constance K. Segakweng, Pieter G. Van Zyl, Cathy Liousse, Johan P. Beukes, Jan-Stefan  Swartz, Eric Gardrat, Maria Dias-Alves, Brigitte Language, Roelof P. Burger, Stuart J. Piketh

This paper is the first comprehensive report of aerosol composition based on samples collected on the South African Highveld in four low-income urban settlements each of which represents an important pollution source region from economic and elemental points of view. Thirty-five trace elements are analyzed as well as Organic and Elemental carbon (OC, EC). Comparisons are made with similar studies for other South African regions, west Africa and on Europe (e.g., Spain) and Asia (India, China). The methods are well-established and the assembly of data is clear.  Comparisons are made in Tables of summary data. Although characterizing exposure of the population is the goal of the project, few interpretations are made; hence the title “Measurement Report.”  With a few grammatical changes, marked on a separate copy, the paper is suitable for publication in ACP and will be very welcome by the aerosol community as well as policymakers within South Africa.

Overall, really well-written paper! The methods were especially clear and detailed, and a wonderfully thorough discussion of results. Also interesting how higher indoor concentrations seem to be characteristic of South African studies/industrial activity. I think it is an excellent reference for detailed analyses of various kinds of pollutants and health hazards.

Minor comments:

- Lines 317-318 were a bit confusing to me, I'm not sure which two size distributions (or indoor vs. outdoor?) "higher" is relating, and if "while" suggests that there should be different behavior between the summer and winter indoor data for the PM2.5-10 bracket

- additional discussion of the validity/limits of using an ion balance to calculate the acidity of the aerosol

- some grammatical issues, not sure if related to local writing conventions vs. those in the US