@article{fdi:010064890,
  title = {{P}recipitation chemistry and wet deposition in a remote wet savanna site in {W}est {A}frica : {D}jougou ({B}enin)},
  author = {{A}kpo, {A}. {B}. and {G}aly-{L}acaux, {C}. and {L}aouali, {D}. and {D}elon, {C}. and {L}iousse, {C}. and {A}don, {M}. and {G}ardrat, {E}. and {M}ariscal, {A}rmand and {D}arakpa, {C}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n the framework of the {IDAF} ({IGAC}/{DEBITS}/{AF}rica) international program, this study aims to study the chemical composition of precipitation and associated wet deposition at the rural site of {D}jougou in {B}enin, representative of a {W}est and {C}entral {A}frican wet savanna. {F}ive hundred and thirty rainfall samples were collected at {D}jougou, {B}enin, from {J}uly 2005 to {D}ecember 2009 to provide a unique database. {T}he chemical composition of precipitation was analyzed for inorganic ({C}a2+, {M}g2+, {N}a+, {NH}4+, {K}+, {NO}3-, {C}l-, {SO}) and organic ({HCOO}-, {CH}3{COO}-, {C}2{H}5{COO}-, {C}2{O}42-) ions, using ion chromatography. {T}he 530 collected rain events represent a total of 5706.1 mm of rainfall compared to the measured pluviometry 6138.9 mm, indicating that the collection efficiency is about 93%. {T}he order of total annual loading rates for soluble cations is {NH}4+ > {C}a2+ > {M}g2+ > {K}+. {F}or soluble anions the order of loading is carbonates > {HCOO}- > {NO}3- > {CH}3{COO}- > {SO}42- > {C}l- > {C}2{O}42- > {C}2{H}5{COO}-. {I}n the wet savanna of {D}jougou, 86% of the measured p{H} values range between 4.7 and 5.7 with a median p{H} of 5.19, corresponding to a {VWM} ({V}olume {W}eighed {M}ean) {H}+ concentration of 6.46 mu eq . {L}-1. {T}his acidity results from a mixture of mineral and organic acids. {T}he annual sea salt contribution was computed for {K}+, {M}g2+, {C}a2+ and {SO}42- and represents 4.2% of {K}+, 41% of {M}g2+, 1.3% of {C}a2+, and 7.4% of {SO}42-. {T}hese results show that {K}+, {C}a2+, {SO}42-, and {M}g2+ were mainly of non-marine origin. {T}he marine contribution is estimated at 9%. {T}he results of the chemical composition of rainwater of {D}jougou indicates that, except for the carbonates, ammonium has the highest {VWM} concentration (143 mu eq.{L}-1) and nitrate concentration is 8.2 mu eq.{L}-1. {T}he distribution of monthly {VWM} concentration for all ions is computed and shows the highest values during the dry season, comparing to the wet season. {I}dentified nitrogenous compound sources ({NO}x and {NH}3) are domestic animals, natural emissions from savanna soils, biomass burning and biofuel combustions. {T}he second highest contribution is the calcium ion (133 mu eq.{L}-1), characteristic of dust aerosols from terrigenous sources, {C}alcium contributes up to 46% of the precipitation chemistry in {D}jougou. {F}inally, these results are compared to those obtained for other selected {A}frican sites representative of other main natural ecosystems: dry savanna and forest. {T}he study of the {A}frican ecosystem transect indicates a p{H} gradient with more acidic p{H} in the forested ecosystem. {N}itrogenous contribution to the chemical composition of rain in {L}amto, wet savanna, (24%) is equivalent to the one estimated in {D}jougou (24%). {T}he last contribution concerns organic acidity, which represents 7% of total ionic content of precipitation at {D}jougou. {T}he relative particulate contribution {PC} and the relative gaseous contribution {GC} are calculated using the mean chemical composition measured in {D}jougou for the studied period. {T}he comparison with other {A}frican sites gives 40% and 43% {PC} in wet savannas of {L}amto ({C}ote d'{I}voire) and {D}jougou ({B}enin) respectively, 20% {PC} in the equatorial forest of {Z}oetele ({C}ameroon) and 80% {PC} in dry savanna of {B}anizoumbou ({N}iger). {T}he results shown here indicate the existence of a {N}orth-{S}outh gradients of organic, marine, terrigenous and nitrogenous contributions along the transect in {W}est and {C}entral {A}frica.},
  keywords = {{P}recipitation chemistry ; {W}et deposition ; {N}eutralization factor ; {C}hemical composition ; {BENIN}},
  booktitle = {},
  journal = {{A}tmospheric {E}nvironment},
  volume = {115},
  numero = {},
  pages = {110--123},
  ISSN = {1352-2310},
  year = {2015},
  DOI = {10.1016/j.atmosenv.2015.04.064},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064890},
}