@article{fdi:010094513,
  title = {{N}ew particle formation dynamics in the central {A}ndes : contrasting urban and mountaintop environments},
  author = {{A}liaga, {D}. and {S}inclair, {V}.{A}. and {K}rejci, {R}. and {A}ndrade, {M}. and {A}rtaxo, {P}. and {B}lacutt, {L}. and {C}ai, {R}. and {C}arbone, {S}. and {G}ramlich, {Y}. and {H}eikkinen, {L}. and {H}eslin-{R}ees, {D}. and {H}uang, {W}. and {K}erminen, {V}.{M}. and {K}oenig, {A}.{M}. and {K}ulmala, {M}. and {L}aj, {P}. and {M}ardoñez-{B}alderrama, {V}. and {M}ohr, {C}. and {M}oreno, {I}. and {P}aasonen, {P}. and {S}cholz, {W}. and {S}ellegri, {K}. and {T}icona, {L}. and {U}zu, {G}a{\¨e}lle and {V}elarde, {F}. and {W}iedensohler, {A}. and {W}orsnop, {D}. and {W}u, {C}. and {X}uemeng, {C}. and {Z}ha, {Q}. and {B}ianchi, {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n this study, we investigate atmospheric new particle formation ({NPF}) across 65 d in the {B}olivian central {A}ndes at two locations: the mountaintop {C}hacaltaya station ({CHC}, 5.2 km above sea level) and an urban site in {E}l {A}lto-{L}a {P}az ({EAC}), 19 km apart and at 1.1 km lower altitude. {W}e classified the days into four categories based on the intensity of {NPF}, determined by the daily maximum concentration of 4-7 nm particles: (1) high at both sites, (2) medium at both, (3) high at {EAC} but low at {CHC}, and (4) low at both. {T}hese categories were then named after their emergent and most prominent characteristics: (1) {I}ntense-{NPF}, (2) {P}olluted, (3) {V}olcanic, and (4) {C}loudy. {T}his classification was premised on the assumption that similar {NPF} intensities imply similar atmospheric processes. {O}ur findings show significant differences across the categories in terms of particle size and volume, sulfuric acid concentration, aerosol compositions, pollution levels, meteorological conditions, and air mass origins. {S}pecifically, intense {NPF} events (1) increased {A}itken mode particle concentrations (14-100 nm) significantly on 28 % of the days when air masses passed over the {A}ltiplano. {A}t {CHC}, larger {A}itken mode particle concentrations (40-100 nm) increased from 1.1 × 103 cm-3 (background) to 6.2 × 103 cm-3, and this is very likely linked to the ongoing {NPF} process. {H}igh pollution levels from urban emissions on 24 % of the days (2) were found to interrupt particle growth at {CHC} and diminish nucleation at {EAC}. {M}eanwhile, on 14 % of the days, high concentrations of sulfate and large particle volumes (3) were observed, correlating with significant influences from air masses originating from the actively degassing {S}abancaya volcano and a depletion of positive 2-4 nm ions at {CHC} but not at {EAC}. {D}uring these days, reduced {NPF} intensity was observed at {CHC} but not at {EAC}. {L}astly, on 34 % of the days, overcast conditions (4) were associated with low formation rates and air masses originating from the lowlands east of the stations. {I}n all cases, event initiation (average 09:00 {LT}) generally occurred about half an hour earlier at {CHC} than at {EAC} and was likely modulated by the daily solar cycle. {CHC} at dawn is in an air mass representative of the regional residual layer with minimal local surface influence due to the barren landscape. {A}s the day progresses, upslope winds bring in air masses affected by surface emissions from lower altitudes, which may include anthropogenic or biogenic sources. {T}his influence likely develops gradually, eventually creating the right conditions for an {NPF} event to start. {A}t {EAC}, the start of {NPF} was linked to the rapid growth of the boundary layer, which favored the entrainment of air masses from above. {T}he study highlights the role of {NPF} in modifying atmospheric particles and underscores the varying impacts of urban versus mountain top environments on particle formation processes in the {A}ndean region.},
  keywords = {{ANDES}},
  booktitle = {},
  journal = {{A}erosol {R}esearch},
  volume = {3},
  numero = {1},
  pages = {15--44},
  ISSN = {2940-3391},
  year = {2025},
  DOI = {10.5194/ar-3-15-2025},
  URL = {https://www.documentation.ird.fr/hor/fdi:010094513},
}