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Influence of moisture source dynamics and weather patterns on stable isotopes ratios of precipitation in Central-Eastern Africa
•We report the first δ2H and δ18O of precipitation of the Virunga, Central-Eastern Africa.•δ2H and δ18O of precipitation show clear seasonality controlled by the season variation.•Moisture from soil-plants predominates in wet seasons and that from lakes in the dry season.•δ2H and δ18O of precipitati...
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| Published in: | The Science of the total environment 2018-07, Vol.628-629, p.1058-1078 |
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| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | •We report the first δ2H and δ18O of precipitation of the Virunga, Central-Eastern Africa.•δ2H and δ18O of precipitation show clear seasonality controlled by the season variation.•Moisture from soil-plants predominates in wet seasons and that from lakes in the dry season.•δ2H and δ18O of precipitation are typical of high altitude recycled continental moisture.•δ2H and δ18O of precipitation are intermediate between that from Central and East Africa.
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We report the first δ18O and δ2H data of Virunga rainfall in the Eastern Democratic Republic of the Congo, situated on the limit between Central and Eastern Africa. The dataset is from 13 rain gauges deployed at Mount Nyiragongo and its surroundings sampled monthly between December 2013 and October 2015. The δ18O and δ2H vary from −6.44 to 6.16‰, and −32.53 to 58.89‰ respectively, and allowed us to define a LMWL of δ2H = 7.60δ18O + 16.18. Three main wind directions, i.e. NE, E and SE, were identified in the upper atmosphere corresponding to three major moisture source regions. On the contrary, lower atmospheric winds are weaker in nature and originate mainly from the S and SW, creating a topographically-driven, more local moisture regime. The latter is due to the accumulation in the floor of the rift of water vapor from Lake Kivu forming a layer of isotopically enriched vapor that mediates the isotope enrichment of the falling raindrops. A strong seasonality is observed in both δ18O and δ2H data, and is primarily driven by combined seasonal and spatial variation in the moisture sources. The δ18O and δ2H seasonality is thus correlated to weather patterns, as the latter control the wet to dry season shifting, and vice versa. The key characteristic of seasonality is the variation of monthly precipitation amounts, since the mean monthly air temperature is nearly constant on an annual scale. Two regionally relevant hydrological processes contribute to the isotopic signature: namely moisture uptake from the isotopically enriched surface waters of East African lakes and from the depleted soil-water and plants. Consequently, the proportion of water vapor from each of these reservoirs in the atmosphere drives the enrichment or depletion of δ2H and δ18O in the precipitation. Thus, during wet periods the vapor from soil-plants evapotranspiration dominates yielding isotopically depleted precipitation, contrary to dry periods when vapor from lakes surface evaporation dominates, yielding isotopically enriche |
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| ISSN: | 0048-9697 1879-1026 |
| DOI: | 10.1016/j.scitotenv.2018.01.284 |