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RESEARCH ARTICLE

Distribution of organic carbon: possible causes and impacts in the Pangani River Basin ecosystem, Tanzania

Juma R. Selemani A E F , Jing Zhang A , Ying Wu A , Alfred N. N. Muzuka B , Karoli N. Njau B , Guosen Zhang A , Maureen K. Mzuza C , Arafa Maggid D , Miao Zhang A and Lijun Qi A
+ Author Affiliations
- Author Affiliations

A State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, People’s Republic of China.

B Nelson Mandela African Institution of Science and Technology, PO Box 477, Arusha, Tanzania.

C Faculty of Education, North West University, Potchstroom 2520, South Africa.

D Pangani River Basin Water Board, PO Box 7617, Moshi, Tanzania.

E Tanzania Meteorological Agency, Environmental Section, PO Box 3056, Dar es Salaam, Tanzania.

F Corresponding author. Email: rajjuma2004@yahoo.co.uk

Environmental Chemistry 15(3) 137-149 https://doi.org/10.1071/EN17185
Submitted: 22 October 2017  Accepted: 26 January 2018   Published: 8 June 2018

Environmental context. Understanding the sources of organic carbon and its spatial and seasonal variation is essential for implementing measures to control water pollution. There is, however, only limited information about organic carbon in east African rivers. This study reports the distribution of dissolved and particulate organic carbon in the Pangani River Basin, using isotopes to trace sources of carbon to the basin and its flux to the Indian Ocean.

Abstract. There is limited information on organic carbon in African rivers, especially from the eastern side. Here, we report distribution and impacts of total suspended matter (TSM), and dissolved and particulate organic carbon (DOC & POC) in the Pangani River Basin (PRB) ecosystem together with their fluxes to the Indian Ocean. δ13C was also used to trace sources of carbon in the basin. Results showed that the basin is supplied with carbon from allochthonous sources dominated by C3 plants, with higher levels of TSM and DOC in the wet season than in the dry season. Several factors, including altitude, temperature, rainfall, lithology and anthropogenic activities, have a significant influence on the seasonal and spatial distribution of organic carbon in the basin. High discharge in the wet season mobilised terrestrial organic carbon to elevate concentrations of DOC, POC and TSM. Mean concentrations of DOC, dissolved inorganic carbon (DIC), POC and TSM in PRB were in ranges comparable to that in other tropical rivers but their fluxes were lower than in most tropical rivers around the world. Diverting water from the river for irrigation and hydroelectric power production was one of the factors that reduced the flux of carbon. Observed hypoxic conditions in the reservoir indicates that the quality of water for human and aquatic ecosystem health is possibly threatened by a high level of organic carbon; furthermore, the trends of increasing population, deforestation, temperature and rainfall will likely increase the concentration of organic carbon in the future. Better management of waste, afforestation and reforestation are recommended to restore degraded natural forest, so as to reduce uptake of organic carbon from the terrestrial environment.

Additional keywords: water chemistry.


References

Aschermann G, Jeihanipour A, Shen J, Mkongo G, Dramas L, Croue J, Schafer A (2016). Seasonal variation of organic matter concentration and characteristics in the Maji ya Chai River (Tanzania): impact on treatability by ultrafiltration. Water Research 101, 370–381.
Seasonal variation of organic matter concentration and characteristics in the Maji ya Chai River (Tanzania): impact on treatability by ultrafiltrationCrossref | GoogleScholarGoogle Scholar |

Badr EA (2016). Spatio-temporal variability of dissolved organic nitrogen (DON), carbon (DOC), and nutrients in the Nile River, Egypt. Environmental Monitoring and Assessment 188, 580
Spatio-temporal variability of dissolved organic nitrogen (DON), carbon (DOC), and nutrients in the Nile River, EgyptCrossref | GoogleScholarGoogle Scholar |

Balakrishna K, Probst JL (2005). Organic carbon transport and C–N ratio variations in a large tropical river: Godavari as a case study, India. Biogeochemistry 73, 457–473.
Organic carbon transport and C–N ratio variations in a large tropical river: Godavari as a case study, IndiaCrossref | GoogleScholarGoogle Scholar |

Barker PA, Hurrell ER, Leng MJ, Plessen B, Wolff C, Conley DJ, Keppens E, Milne I, Cumming BF, Laird KR, Kendrick CP, Wynn PM, Verschuren D (2013). Carbon cycling within an East African lake revealed by the carbon isotope composition of diatom silica: a 25-ka record from Lake Challa, Mt. Kilimanjaro. Quaternary Science Reviews 66, 55–63.
Carbon cycling within an East African lake revealed by the carbon isotope composition of diatom silica: a 25-ka record from Lake Challa, Mt. KilimanjaroCrossref | GoogleScholarGoogle Scholar |

Bouillon S, Dehairs F, Schiettecatte L, Borges AV (2007). Biogeochemistry of the Tana estuary and delta (northern Kenya). Limnology and Oceanography 52, 46–59.
Biogeochemistry of the Tana estuary and delta (northern Kenya)Crossref | GoogleScholarGoogle Scholar |

Cory RM, Crump BC, Dobkowski JA, Kling GW (2013). Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the Arctic. Proceedings of the National Academy of Sciences, USA 110, 3429–3434.
Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the ArcticCrossref | GoogleScholarGoogle Scholar |

da Costa END, Souza JC, Pereira MA, Souza MFL, Souza WFL, Silva DML (2017). Influence of hydrological pathways on dissolved organic carbon fluxes in tropical streams. Ecology and Evolution 7, 228–239.
Influence of hydrological pathways on dissolved organic carbon fluxes in tropical streamsCrossref | GoogleScholarGoogle Scholar |

Cunha DGF, Sabogal-Paz LP, Dodds WK (2016). Land use influence on raw surface water quality and treatment costs for drinking supply in São Paulo State (Brazil). Ecological Engineering 94, 516–524.
Land use influence on raw surface water quality and treatment costs for drinking supply in São Paulo State (Brazil)Crossref | GoogleScholarGoogle Scholar |

Dai M, Yin Z, Meng F, Liu Q, Cai WJ (2012). Spatial distribution of riverine DOC inputs to the ocean: an updated global synthesis. Current Opinion in Environmental Sustainability 4, 170–178.
Spatial distribution of riverine DOC inputs to the ocean: an updated global synthesisCrossref | GoogleScholarGoogle Scholar |

Dai A, Rasmussen RM, Ikeda K, Liu C (2017). A new approach to construct representative future forcing data for dynamic downscaling. Climate Dynamics 382, 1–9.

Feng XJ, Simpson AJ, Wilson KP, Williams DD, Simpson MJ (2008). Increased cuticular carbon sequestration and lignin oxidation in response to soil warming. Nature Geoscience 1, 836–839.
Increased cuticular carbon sequestration and lignin oxidation in response to soil warmingCrossref | GoogleScholarGoogle Scholar |

Freeman C, Fenner N, Ostle NJ, Kang H, Dowrick DJ, Reynolds B, Lock MA, Sleep D, Hughes S, Hudson J (2004). Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels. Nature 430, 195–198.
Export of dissolved organic carbon from peatlands under elevated carbon dioxide levelsCrossref | GoogleScholarGoogle Scholar |

Gaillardet J, Dupre B, Louvat P, Alle’gre CJ (1999). Global silicate weathering and silicate weathering and CO2 consumption rates deduced from the chemistry of large rivers. Chemical Geology 159, 3–30.
Global silicate weathering and silicate weathering and CO2 consumption rates deduced from the chemistry of large riversCrossref | GoogleScholarGoogle Scholar |

Gao Q, Tao Z, Shen C, Sun Y, Yi W, Xing C (2002). Riverine organic carbon in the Xijiang River (South China): seasonal variation in content and flux budget. Environmental Geology 41, 826–832.
Riverine organic carbon in the Xijiang River (South China): seasonal variation in content and flux budgetCrossref | GoogleScholarGoogle Scholar |

Gao QZ, Tao Z, Yao GR, Ding J, Liu ZF, Liu KX (2007). Elemental and isotopic signatures of particulate organic carbon in the Zengjiang River, southern China. Hydrological Processes 21, 1318–1327.
Elemental and isotopic signatures of particulate organic carbon in the Zengjiang River, southern ChinaCrossref | GoogleScholarGoogle Scholar |

Gichuki JW, Triest L, Dehairs F (2005). The fate of organic matter in a papyrus (Cyperus papyrus L.) dominated tropical wetland ecosystem in Nyanza Gulf (Lake Victoria, Kenya) inferred from δ13C and δ15N analysis. Isotopes in Environmental and Health Studies 41, 379–390.
The fate of organic matter in a papyrus (Cyperus papyrus L.) dominated tropical wetland ecosystem in Nyanza Gulf (Lake Victoria, Kenya) inferred from δ13C and δ15N analysisCrossref | GoogleScholarGoogle Scholar |

Hellar-Kihampa H, Potgieter-Vermaak S, De Wael K, Lugwisha E, Van Espen P, Van Grieken R (2013). Concentration profiles of metal contaminants in fluvial sediments of a rural–urban drainage basin in Tanzania. International Journal of Environmental Analytical Chemistry 94, 1–22.
Concentration profiles of metal contaminants in fluvial sediments of a rural–urban drainage basin in TanzaniaCrossref | GoogleScholarGoogle Scholar |

Hong H, Yang L, Guo W, Wang F, Yu X (2012). Characterization of dissolved organic matter under contrasting hydrologic regimes in a subtropical watershed using PARAFAC model. Biogeochemistry 109, 163–174.
Characterization of dissolved organic matter under contrasting hydrologic regimes in a subtropical watershed using PARAFAC modelCrossref | GoogleScholarGoogle Scholar |

Hu Y, Lu YH, Edmonds JW, Liu C, Wang S, Das O, Liu J, Zheng C (2016). Hydrological and land use control of watershed exports of dissolved organic matter in a large arid river basin in northwestern China. Journal of Geophysical Research. Biogeosciences 121, 466–478.
Hydrological and land use control of watershed exports of dissolved organic matter in a large arid river basin in northwestern ChinaCrossref | GoogleScholarGoogle Scholar |

Huser BJ, Kohler SJ, Wilander A, Johansson K, Folster J (2011). Temporal and spatial trends for trace metals in streams and rivers across Sweden (1996–2009). Biogeosciences 8, 1813–1823.
Temporal and spatial trends for trace metals in streams and rivers across Sweden (1996–2009)Crossref | GoogleScholarGoogle Scholar |

Ireland EPA (2012). EPA drinking water guidance on disinfection by-products advice note no. 4. Version 2. Disinfection By-products in Drinking Water. Available at https://www.epa.ie/pubs/advice/drinkingwater/DrinkingWaterGuide4_v8.pdf [verified 24 September 2017].

Krishna MS, Prasad VR, Sarma VVSS, Reddy NPC, Hemalatha KPJ, Rao YV (2015). Fluxes of dissolved organic carbon and nitrogen to the northern Indian Ocean from the Indian monsoonal rivers. Journal of Geophysical Research. Biogeosciences 120, 2067–2080.
Fluxes of dissolved organic carbon and nitrogen to the northern Indian Ocean from the Indian monsoonal riversCrossref | GoogleScholarGoogle Scholar |

Kubo A, Kanda J (2017). Seasonal variations and sources of sedimentary organic carbon in Tokyo Bay. Marine Pollution Bulletin 114, 637–643.
Seasonal variations and sources of sedimentary organic carbon in Tokyo BayCrossref | GoogleScholarGoogle Scholar |

Lambert T, Darchambeau F, Bouillon S, Alhou B, Mbega J, Teodoru CR, Nyoni FC, Massicotte P, Borges AV (2015). Landscape control on the spatial and temporal variability of chromophoric dissolved organic matter and dissolved organic carbon in large African rivers. Ecosystems 18, 1224–1239.
Landscape control on the spatial and temporal variability of chromophoric dissolved organic matter and dissolved organic carbon in large African riversCrossref | GoogleScholarGoogle Scholar |

Ledesma JLJ, Köhler SJ, Futter MN (2012). Long-term dynamics of dissolved organic carbon: Implications for drinking water supply. The Science of the Total Environment 432, 1–11.
Long-term dynamics of dissolved organic carbon: Implications for drinking water supplyCrossref | GoogleScholarGoogle Scholar |

Lee HW, Choi JH (2009). Temporal analysis of trends in dissolved organic matter in Han River water. Environmental Engineering Research 14, 256–260.
Temporal analysis of trends in dissolved organic matter in Han River waterCrossref | GoogleScholarGoogle Scholar |

Lesack LR, Hecky RE, Melack JM (1984). Transport of carbon, nitrogen, phosphorous, and major solutes in the Gambia River, West Africa. Limnology and Oceanography 29, 816–830.
Transport of carbon, nitrogen, phosphorous, and major solutes in the Gambia River, West AfricaCrossref | GoogleScholarGoogle Scholar |

Li M, Peng C, Wang M, Xue W, Zhang K, Wang K, Shi G, Zhu Q (2017). The carbon flux of global rivers: a re-evaluation of amount and spatial patterns. Ecological Indicators 80, 40–51.
The carbon flux of global rivers: a re-evaluation of amount and spatial patternsCrossref | GoogleScholarGoogle Scholar |

Ludwig W, Amiotte-Suchet P, Probst JL (1996a). River discharge of carbon to the world’s oceans: determining local inputs of alkalinity and of dissolved and particulate organic carbon. Comptes Rendus de l’Académie des Sciences. Série 2. Sciences de la Terre et des Planètes 323, 1007–1014.

Ludwig W, Probst J, Kempe S (1996b). Predicting the oceanic input of organic carbon by continental erosion. Global Biogeochemical Cycles 10, 23–41.
Predicting the oceanic input of organic carbon by continental erosionCrossref | GoogleScholarGoogle Scholar |

Martins O, Probst JL (1991). Biogeochemistry of major African rivers: carbon and mineral transport. In ‘Biogeochemistry of Major World Rivers’. (Eds ET Degens, S Kempe, JE Richey) pp. 127–155. (John Wiley and Sons: New York, NY)

Meybeck M (1982). Carbon, nitrogen and phosphorus transport by world rivers. American Journal of Science 282, 401–450.
Carbon, nitrogen and phosphorus transport by world riversCrossref | GoogleScholarGoogle Scholar |

Moyer RP, Powell CE, Gordon DJ, Long JS, Bliss CM (2015). Abundance, distribution, and fluxes of dissolved organic carbon (DOC) in four small sub-tropical rivers of the Tampa Bay Estuary (Florida, USA). Applied Geochemistry 63, 550–562.
Abundance, distribution, and fluxes of dissolved organic carbon (DOC) in four small sub-tropical rivers of the Tampa Bay Estuary (Florida, USA)Crossref | GoogleScholarGoogle Scholar |

Muhammad N, Banoori N, Akbar A, Azizullah A, Khan M, Qasim M, Rahman H (2017). Microbial and toxic metal contamination in well drinking water: potential health risk in selected areas of Kohat, Pakistan. Urban Water Journal 14, 394–400.
Microbial and toxic metal contamination in well drinking water: potential health risk in selected areas of Kohat, PakistanCrossref | GoogleScholarGoogle Scholar |

Muzuka ANN (1999). Isotopic composition of tropical east African flora and their potential as source indicators of organic matter in coastal marine sediments. Journal of African Earth Sciences 28, 757–766.
Isotopic composition of tropical east African flora and their potential as source indicators of organic matter in coastal marine sedimentsCrossref | GoogleScholarGoogle Scholar |

National Bureau of Statistics (2013). Population distribution by age and sex. Available at http://ihi.eprints.org/2169/1/Age_Sex_Distribution.pdf [verified 25 September 2017].

Njau KN, Mlay H (2004). Wastewater treatment and other research initiatives with vetiver grass. Available at https://www.researchgate.net/publication/228487292 [verified 22 July 2017].

Noacco V, Wagener T, Worrall F, Burt TP, Howden NJK (2017). Human impact on long-term organic carbon export to rivers. Journal of Geophysical Research. Biogeosciences 122, 947–965.
Human impact on long-term organic carbon export to riversCrossref | GoogleScholarGoogle Scholar |

Pamba S, Shaghude YW, Muzuka ANN (2016). ‘Hydrodynamic Modelling on Transport, Dispersion and Deposition of Suspended Particulate Matter in Pangani Estuary, Tanzania, in Estuaries: a Lifeline of Ecosystem Services in the Western Indian Ocean, Estuaries of the World.’ (Eds S Diop, P Scheren, J Machiwa) pp. 141–160. (Springer International Publishing: Switzerland)

PBWB/IUCN (2008). Basin Delineation Report. Pangani Basin Water Board, Moshi and IUCN Eastern and Southern Africa Regional Programme, Nairobi. Available at https://cmsdata.iucn.org/downloads/basin_delineation_report.pdf [verified 10 June 2017].

PWBO/IUCN (2010). Climate change modelling for the Pangani Basin to support the IWRM planning process. Pangani River Basin Flow Assessment. Pangani Basin Water Board, Moshi and IUCN Eastern and Southern Africa Regional Programme. V+36 pp. Available at http://cmsdata.iucn.org/downloads/climate_change_modelling_by_uct.pdf [verified 10 June 2017].

Ramesh R, Purvaja GR, Subramanian V (1995). Carbon and phosphorus transport by the major Indian rivers. Journal of Biogeography 22, 409–415.
Carbon and phosphorus transport by the major Indian riversCrossref | GoogleScholarGoogle Scholar |

Sarin MM, Sudheer AK, Balakrishna K (2002). Significance of riverine carbon transport: a case study of a large tropical river, Godavari (India). Science in China (series C) 45, 97–108.

Selemani JR, Zhang J, Muzuka ANN, Njau KN, Zhang G, Mzuza MK, Maggid A (2017a). Nutrients’ distribution and their impact on Pangani River Basin’s ecosystem – Tanzania. Environmental Technology 5, 1–15.
Nutrients’ distribution and their impact on Pangani River Basin’s ecosystem – TanzaniaCrossref | GoogleScholarGoogle Scholar |

Selemani JR, Zhang J, Muzuka ANN, Njau KN, Zhang G, Maggid A, Mzuza MK, Jin J, Pradhan S (2017b). Seasonal water chemistry variability in the Pangani River basin, Tanzania. Environmental Science and Pollution Research International 24, 26092–26110.
Seasonal water chemistry variability in the Pangani River basin, TanzaniaCrossref | GoogleScholarGoogle Scholar |

Spencer RGM, Hernes PJ, Aufdenkampe AK, Baker A, Gulliver P, Stubbins A, Aiken GR, Dyda RY, Butler KD, Mwamba VL, Mangangu AM, Wabakanghanzi JN, Six J (2012). An initial investigation into the organic matter biogeochemistry of the Congo River. Geochimica et Cosmochimica Acta 84, 614–627.
An initial investigation into the organic matter biogeochemistry of the Congo RiverCrossref | GoogleScholarGoogle Scholar |

Spencer RGM, Hernes PJ, Dinga B, Wabakanghanzi JN, Drake TW, Six J (2016). Origins, seasonality, and fluxes of organic matter in the Congo River. Global Biogeochemical Cycles 30, 1105–1121.
Origins, seasonality, and fluxes of organic matter in the Congo RiverCrossref | GoogleScholarGoogle Scholar |

Sun H, Han J, Li D, Lu X, Zhang H, Zhao W (2017). Organic carbon transport in the Songhua River, NE China: influence of land use. Hydrological Processes 31, 2062–2075.
Organic carbon transport in the Songhua River, NE China: influence of land useCrossref | GoogleScholarGoogle Scholar |

Tamooh F, Van den Meersche K, Meysman F, Marwick TR, Borges AV, Merckx R, Dehairs F, Schmidt S, Nyunja J, Bouillon S (2012). Distribution and origin of suspended matter and organic carbon pools in the Tana River Basin, Kenya. Biogeosciences 9, 2905–2920.
Distribution and origin of suspended matter and organic carbon pools in the Tana River Basin, KenyaCrossref | GoogleScholarGoogle Scholar |

Tamooh F, Meysman FJR, Borges AV, Marwick TR, Van Den Meersche K, Dehairs F, Merckx R, Bouillon S (2014). Sediment and carbon fluxes along a longitudinal gradient in the lower Tana River (Kenya). Journal of Geophysical Research. Biogeosciences 119, 1340–1353.
Sediment and carbon fluxes along a longitudinal gradient in the lower Tana River (Kenya)Crossref | GoogleScholarGoogle Scholar |

Tank SE, Striegl RG, McClelland JW, Kokelj SV (2016). Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean. Environmental Research Letters 11, 054015
Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic OceanCrossref | GoogleScholarGoogle Scholar |

Teodoru CR, Nyoni FC, Borges AV, Darchambeau F, Nyambe I, Bouillon S (2015). Dynamics of greenhouse gases (CO2, CH4, N2O) along the Zambezi River and major tributaries, and their importance in the riverine carbon budget. Biogeosciences 12, 2431–2453.
Dynamics of greenhouse gases (CO2, CH4, N2O) along the Zambezi River and major tributaries, and their importance in the riverine carbon budgetCrossref | GoogleScholarGoogle Scholar |

Tian YQ, Yu Q, Feig AD, Ye C, Blunden A (2013). Effects of climate and land-surface processes on terrestrial dissolved organic carbon export to major US coastal rivers. Ecological Engineering 54, 192–201.
Effects of climate and land-surface processes on terrestrial dissolved organic carbon export to major US coastal riversCrossref | GoogleScholarGoogle Scholar |

Traving SJ, Rowe O, Jakobsen NM, Sørensen H, Dinasquet J, Stedmon CA, Andersson A, Riemann L (2017). The effect of increased loads of dissolved organic matter on estuarine microbial community composition and function. Frontiers in Microbiology 8, 1–15.
The effect of increased loads of dissolved organic matter on estuarine microbial community composition and functionCrossref | GoogleScholarGoogle Scholar |

Wang X, Ma H, Li R, Song Z, Wu J (2012). Seasonal fluxes and source variation of organic carbon transported by two major Chinese Rivers: the Yellow River and Changjiang (Yangtze) River. Global Biogeochemical Cycles 26,
Seasonal fluxes and source variation of organic carbon transported by two major Chinese Rivers: the Yellow River and Changjiang (Yangtze) RiverCrossref | GoogleScholarGoogle Scholar |

Worrall F, Burt TP (2010). Has the composition of fluvial DOC changed? Spatiotemporal patterns in the DOC-color relationship. Global Biogeochemical Cycles 24, 1–12.
Has the composition of fluvial DOC changed? Spatiotemporal patterns in the DOC-color relationshipCrossref | GoogleScholarGoogle Scholar |

Wu Y, Zhang J, Liu SM, Zhang ZF, Yao QZ, Hong GH, Cooper L (2007). Sources and distribution of carbon within the Yangtze River system. Estuarine, Coastal and Shelf Science 71, 13–25.
Sources and distribution of carbon within the Yangtze River systemCrossref | GoogleScholarGoogle Scholar |

Wu Y, Bao H, Unger D, Herbeck L, Zhu Z, Zhang J, Jennerjahn T (2013). Biogeochemical behaviour of organic carbon in a small tropical river and estuary, Hainan, China. Continental Shelf Research 57, 32–43.
Biogeochemical behaviour of organic carbon in a small tropical river and estuary, Hainan, ChinaCrossref | GoogleScholarGoogle Scholar |

Yanda PZ, Shishira EK (2001). Forestry conservation and resource utilisation on the southern slopes of Mount Kilimanjaro: trends, conflicts and resolutions. In ‘Water resources management in the Pangani River Basin: challenges and opportunities’. (Ed. JO Ngana) pp. 104–117. (Dar es Salaam University Press: Dar es Salaam)

Zhang J, Wu Y, Jennerjahn TC, Ittekkot V, He Q (2007). Distribution of organic matter in the Changjiang (Yangtze River) Estuary and their stable carbon and nitrogen isotopic ratios: implications for source discrimination and sedimentary dynamics. Marine Chemistry 106, 111–126.
Distribution of organic matter in the Changjiang (Yangtze River) Estuary and their stable carbon and nitrogen isotopic ratios: implications for source discrimination and sedimentary dynamicsCrossref | GoogleScholarGoogle Scholar |

Zhang S, Lu XX, Sun H, Han J, Higgitt DL (2009). Geochemical characteristics and fluxes of organic carbon in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), China. The Science of the Total Environment 407, 815–825.
Geochemical characteristics and fluxes of organic carbon in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), ChinaCrossref | GoogleScholarGoogle Scholar |

Zhang LJ, Wang L, Cai WJ, Liu DM, Yu ZG (2013). Impact of human activities on organic carbon transport in the Yellow River. Biogeosciences 10, 2513–2524.
Impact of human activities on organic carbon transport in the Yellow RiverCrossref | GoogleScholarGoogle Scholar |

Zhang C, Zhang W, Huang Y, Gao X (2017). Analysing the correlations of long-term seasonal water quality parameters, suspended solids and total dissolved solids in a shallow reservoir with meteorological factors. Environmental Science and Pollution Research International 24, 6746–6756.
Analysing the correlations of long-term seasonal water quality parameters, suspended solids and total dissolved solids in a shallow reservoir with meteorological factorsCrossref | GoogleScholarGoogle Scholar |

Zigah PK, Minor EC, McNichol AP, Xu L, Werne JP (2017). Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses. Geochimica et Cosmochimica Acta 208, 102–118.
Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analysesCrossref | GoogleScholarGoogle Scholar |

Zuijdgeest AL, Zurbrügg R, Blank N, Fulcri R, Senn DB, Wehrli B (2015). Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin. Biogeosciences 12, 7535–7547.
Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basinCrossref | GoogleScholarGoogle Scholar |