Metal and semimetal loadings in sediments and water from mangrove ecosystems: A preliminary assessment of anthropogenic enrichment in São Tomé island (central Africa)

Chemosphe e 334 (2023) 138973 A ailable online 19 May 2023 0045-6535/© 2023 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). Me al and semime al loadings in sedimen s and wa e om mang o e ecosys ems: A p elimina y assessmen o an h opogenic en ichmen in S˜ ao Tom´ e island (cen al A ica) F. A onso a , * , C. Palma b , ** , A.C. B i o a , c , P. Chainho a , d , R. de Lima e , , g , h , J.A. Heumülle a , F. Ribei o a , P.M. F´ elix a a MARE – Ma ine and En i onmen al Sciences Cen e/ ARNET - Aqua ic Resea ch Ne wo k, Faculdade de Ciˆ encias, Uni e sidade de Lisboa, Campo G ande, 1749-016 Lisboa, Po ugal b Ins i u o Hid og ´ a ico, Rua das T inas 49, 1249-093 Lisboa, Po ugal c Depa amen o de Biologia Vege al, Faculdade de Ciˆ encias da Uni e sidade de Lisboa, Campo G ande 016, 1749-016 Lisboa, Po ugal d CINEA and ESTS, IPS – Ene gy and En i onmen Resea ch Cen e , Ins i u o Poli ´ ecnico de Se úbal, Es e anilha, 2910-761 Se úbal, Po ugal e Depa amen o de Biologia Animal, Faculdade de Ciˆ encias da Uni e sidade de Lisboa, Campo G ande 016, 1749-016 Lisboa, Po ugal cE3c - Cen e o Ecology, E olu ion and En i onmen al Changes, Faculdade de Ciˆ encias da Uni e sidade de Lisboa, Campo G ande 016, 1749-016 Lisboa, Po ugal g CHANGE - Global Change and Sus ainabili y Ins i u e, Faculdade de Ciˆ encias da Uni e sidade de Lisboa, Campo G ande 016, 1749-016 Lisboa, Po ugal h CBGG - Cen o de Biodi e sidade do Gol o da Guin´ e, S˜ ao Tom´ e, S˜ ao Tom´ e Island, Sao Tome and P incipe HIGHLIGHTS GRAPHICAL ABSTRACT •High concen a ions o Cu and Ni in S˜ ao Tom´ e mang o es ha e a li hogenic o igin. •Con amina ion by As and C sugges a s ong con ibu ion om human ac i i ies. •Smalles sys ems had highe me al con- en in wa e , bu no sedimen con amina ion. •Highe wa e con amina ion ep esen s he con inuous inpu om was e and chemicals. •Non-indus ialized landscapes may also show se e e con amina ion by human ac i i ies. ARTICLE INFO Handling Edi o : Giulia GUERRIERO Keywo ds: Geochemical index Heal h isk Me al con amina ion Pollu ion sou ce ABSTRACT Mang o es ac as bu e a eas o ma ine sys ems, p o iding a ba ie o con amina ion om con inen al sou ces by e aining me al pollu an s. This s udy e alua es me al and semime al con amina ion in he wa e column and sedimen s o ou mang o es loca ed on he olcanic island o S˜ ao Tom´ e. Se e al me als had a widesp ead dis ibu ion, wi h occasional high concen a ions, linked o po en ial sou ces o con amina ion. Howe e , he wo smalle mang o es, loca ed in he no he n pa o he island, ended o ha e high me al concen a ions. A senic and ch omium concen a ions we e no ably conce ning, pa icula ly i we conside his is an isola ed and non- * Co esponding au ho .MARE – Ma ine and En i onmen al Sciences Cen e, Faculdade de Ciˆ encias da Uni e sidade de Lisboa, Campo G ande, 1749-016 Lisboa, Po ugal. ** Co esponding au ho . E-mail add esses: [email p o ec ed] (F. A onso), [email p o ec ed] (C. Palma). Con en s lis s a ailable a ScienceDi ec Chemosphe e jou nal homepage: www.else ie .com/loca e/chemosphe e h ps://doi.o g/10.1016/j.chemosphe e.2023.138973 Recei ed 1 Ma ch 2023; Recei ed in e ised o m 11 May 2023; Accep ed 16 May 2023 Chemosphe e 334 (2023) 138973 2 T ansi ional aqua ic sys ems Volcanic en ichmen indus ialized island. This wo k highligh s he need o u he assessmen s and a be e unde s anding o p o- cesses and implica ions o me al con amina ion in mang o es. This assumes a pa icula ele ance in a eas ha ha e speci ic geochemical composi ions (i.e., olcanic o igin) and in de eloping coun ies, whe e people o en ely di ec ly and hea ily on esou ces ob ained om hese ecosys ems. 1. In oduc ion Mang o es a e ansi ional aqua ic sys ems ha connec e es ial, i e ine and ma ine sys ems. They a e mos ly ound in de eloping coun ies loca ed in opical a eas, and p o ide a conside able numbe o se ices, no only locally (A onso e al., 2021) bu also on wide scales (Bayen, 2012). One o he aluable se ices hey p o ide is p o ec ion om me al pollu ion and o he con aminan s due o hei bu e ing capaci y. As ecei e s o con inen al un-o , hey can in luence he occu ence and a ailabili y o me als, due o hei abili y o ap hese elemen s, hus, hal ing he con amina ion o adjacen ma ine ecosys- ems (Ha bison, 1986; Scha elke e al., 2005). Mang o e sedimen is ich in sulphide and o ganic ma e (Sil a e al., 1990; Tam and Wong, 2000), which a ou s he e en ion o me als ha o m complexes wi h sulphides (Cla k e al., 1998). Despi e he abili y o plan oo s o egula e me al up ake, hese complexes end o acili a e me al mobili- za ion and bioa ailabili y o oo up ake, a ou ing accumula ion in he plan s (Cla k e al., 1998; MacFa lane and Bu che , 2002). While sed- imen s end o ap me als, he wa e column anspo s hem, bu emobiliza ion can con ey me als om he sedimen back o he wa e column in a dynamic cycle (Caccia e al., 2003; MacFa lane e al., 2007; Zhang e al., 2017). This means ha emobiliza ion can ans o m he sedimen in o a seconda y sou ce o me al con amina ion o he wa e column (Bodin e al., 2013). Ne e heless, he e is a gap in knowledge o opical eco oxicology, namely ega ding he esponse o mang o es o he in usion o me als (Dua e e al., 2019). Me al occu ence in ecosys ems can ha e na u al o an h opogenic sou ces, and his dis inc ion is impo an when assessing en i onmen al isk (Dias and Edwa ds, 2003). Apa om soil and ock wea he ing, olcanism is also an impo an na u al sou ce o me als (Gnandi e al., 2011). Me al pollu ion is conside ed o be one o he mos damaging ypes o an h opogenic con amina ion, due o hei oxici y, pe sis ence, ubiqui y, non-biodeg adabili y, and bioaccumula ion (Duman e al., 2007; MacFa lane e al., 2007). In mang o es, an h opogenic me al con amina ion has been linked o u baniza ion, ag icul u e un-o , in- dus ial e luen s, leaching om domes ic ga bage dumps, boa emis- sions, and an i- ouling chemicals om boa pain (Pe e s e al., 1997). Coun e in ui i ely, we land con amina ion is no necessa ily mo e se- e e in de eloped coun ies. The Nige Del a, Nige ia, showcases his p oposi ion, as i is conside ed he mos se e ely damaged ecosys em in he wo ld (Kada a, 2012). Some me als a e essen ial o human heal h, while o he s can be oxic e en a low concen a ions. When in oduced in ecosys ems on which people a e s ongly dependen , hese elemen s can ha e se ious e ec s on he physiological p ocesses o he human body, leading o se e e heal h consequences (Bosch e al., 2016; Rehman e al., 2018). Apa om inges ion, me als can also en e he human body by inhala ion o de mal con ac (F´ elix, 2012). In child en up o six yea s old, one speci ic ga eway o me al in ake is he hand- o-mou h beha iou ha leads hem o inges 39–271 mg day −1 o soil (Ljung e al., 2007; Wang e al., 2021). Conside ing he po en ial damage ha me als can ha e on human heal h and ecosys ems, i is essen ial o imp o e en i onmen al isk assessmen . The e a e se e al ools o assess me al con amina ion, and o dis inguish li hogenic and an h opogenic sou ces. Se e al empi ical me hodologies a e used o assess he s a us o me al pollu ion, and o es ima e he impac o human ac i i ies on ecosys em heal h (Alzah ani e al., 2018; Chabukdha a and Nema, 2012). O hese, he geochemical indices, such as he con amina ion ac o and he en ichmen ac o , compa e ield measu emen s o s anda d alues o de e mine a con amina ion deg ee (B ady e al., 2015; Na h e al., 2014). The en ichmen ac o compa es me al concen a ions o hose o a e e ence si ua ion, allowing he quan i ica ion o human-induced changes in he ecosys em (OSPAR Commision, 2009). The dominan ac o o de e mining he me al con en in soils is he pa en ock, and olcanic soils end o show high concen a ions o me al elemen s (B nický e al., 2020), namely ch omium, me cu y, and cad- mium (Ahn and Chon, 2010; McMu y e al., 1995). This s udy aims o de e mine me al and semime al concen a ions and po en ial an h o- pogenic en ichmen in he sedimen and in he wa e column o man- g o es loca ed on he olcanic island o S˜ ao Tom´ e, Gul o Guinea. Fou mang o es wi h con as ing ea u es a e used o compa e an h opogenic con amina ion. This in o ma ion is i al o s a iden i ying haza dous e ec s o po en ial high concen a ions o me als on people and eco- sys ems, and o de ine s a egies o maximize he capaci y o mang o es o sink me allic elemen s. 2. Ma e ials and me hods 2.1. S udy a ea The s udy was de eloped on he olcanic island o S˜ ao Tom´ e (S˜ ao Tom´ e and P íncipe, Gul o Guinea, cen al A ica), which is p edomi- nan ly composed o ecen basal ic la as (Caldei a and Munh´ a, 2002). Fou mang o es (Fig. 1), displaying con as ing en i onmen al con ex s and le els o an h opogenic p essu e, we e selec ed: Malanza, Ango- la es, P aia das Conchas, and Diogo Nunes (Table 1). Malanza (Fig. 1) and P aia das Conchas (Fig. 1) a e bo h in dis inc excla es o he Obˆ o Na u al Pa k, and bo h a e open sys ems ha ha e cons ic ions in hei connec ions o he sea (F´ elix e al., 2017). Diogo Nunes (Fig. 1), loca ed e y close o he ai po , is no in a p o ec ed a ea, i has he la ges hyd og aphic basin o all s udied mang o es and i is an in e idal mang o e ha is domina ed by sal wa e in usions du ing he high ide, and eshwa e on low ide. Angola es (Fig. 1) is also no in a p o ec ed a ea. I con eys wo sepa a e con iguous hyd og aphic basins and, hus, has wo ibu a ies d aining in o he mang o e, c ea ing wo a ms. The sou he n a m is pe manen ly open, while he no he n one is a lagoon ha is pe iodically closed by a sand ba ie due o he accumula ion o sedimen s by idal in luence. This ba ie b eaks pe iodically, mos ly du ing pe iods o s ong ains, due o i e ine in luence. Wa e accumula ion builds p essu e and, e en ually, b eaks he sand ba ie , which can emain open o a a iable pe iod o ime, depending on he balance be ween eshwa e and coas al dynamics, as in enclosed lagoons (F´ elix e al., 2013). The no he n a m o his sys em is closes o he S˜ ao Jo˜ ao dos Angola es ci y, easily accessible o locals o ishing, ba hing, and li e dumping (A onso e al., 2022). A S˜ ao Tom´ e, i e s a e o en commonly used as laund y a eas, whe e soaps and de e gen s a e used e e y day (A onso e al., 2022). Mos p oduc s om his ac i i y en e he mang o es ia un-o , bu a P aia das Conchas and Diogo Nunes laund y akes place di ec ly in he mang o es, whene e hese a e domina ed by eshwa e . Bo h hese sys ems a e also highly used o ash dump. The I´ ogoi´ ogo bay is a ma ine a ea adjacen o he Malanza mang o e, which is in ensi ely used by he nea by communi ies, no ably o suppo hei ishing ac i i ies, and has a s ong pollu ing po en ial, namely conside ing ha was e p oduc s om hese ac i i ies a e commonly dumped a he po a ea. Two main docks we e iden i ied in his bay: he F. A onso e al. Chemosphe e 334 (2023) 138973 3 ishing boa ha bou a Po o Aleg e , whe e boa and gea epai occu , bu also washing, pain ing and ga bage dumping; and he Pon a Baleia docking a ea, whe e mos passenge s and goods a e anspo ed o and om he Ilh´ eu das Rolas eso , 2.5 km sou h o he main island o S˜ ao Tom´ e (Fig. 1). 2.2. Sample collec ion and p epa a ion Wa e and sedimen sampling occu ed in Augus 2017, ep esen ing he sys ems’ en i onmen al a iabili y and especially he es ua ine longi udinal g adien . Sampling e o depended mos ly on mang o e size and a iabili y, wi h sampling s a ions selec ed a P aia das Con- chas, Diogo Nunes Angola es, Malanza, and a I´ ogoi´ ogo bay (Fig. 1). All eagen s used we e ul a-pu e (u.p.), and u.p. wa e (MilliQ, 18.2 MΩ.cm pu i ied by a Q-POD® Elemen Me ck Millipo e) was used in he p epa a ion o all solu ions. All sampling con aine s we e p e iously washed using 10% ni ic acid and hen insed wi h ul a-pu e MilliQ wa e . A o al o 32 wa e samples we e collec ed a all sampling s a ions: 3 samples om P aia das Conchas, 3 samples om Diogo Nunes, 6 samples om Angola es, 7 samples om Malanza and 13 samples om I´ ogoi´ ogo bay. The samples we e collec ed di ec ly o 1 L polye hylene con aine s, and hen acidi ied wi h concen a ed HNO 3 o a pH <2, and e ige a ed a 4 ◦C un il analysis. Be o e collec ion, con aine s we e insed h ee imes wi h wa e om he sampling loca ion, immedia ely be o e collec ion. Samples we e il e ed h ough p e-cleaned Wha man WCA 0.45 μ m il e s. A o al o 19 su ace sedimen samples we e collec ed: 3 samples om P aia das Conchas, 4 samples om Diogo Nunes, 5 samples om Angola es and 7 samples om Malanza. The op 3 cm o he sedimen we e collec ed di ec ly in o 2 di e en polye hylene con aine s, by p essing he con aine , upside-down, agains he sedimen , ca e ully scooping he ma e ial and co e ing he con aine s wi hou manipula- ion. All samples we e ozen be ween collec ion and analysis. To al o ganic ma e (TOM) in he sedimen was ob ained by loss on igni ion (EN15169, 2007). One o he con aine s was used o de e mine he g anulome y by he sepa a ion o d ied samples wi h calib a ed sie es and classi ied in o sil (<0.063 μ m), ine sand (0.063 μ m ≤x <0.250 μ m), medium sand (0.250 μ m ≤x <0.500 μ m) and coa se sand (0.500 μ m ≤x <2 mm), acco ding o (Blo and Pye, 2001). 2.3. Me al analysis To analyse me al concen a ion in he wa e (Cd, Cu, Fe, Mn, Ni, Pb and Zn), samples we e subjec ed o a p e-concen a ion by solid-phase ex ac ion (SPE) using selec i e ca idges ha e ain he me als while gene al ca ions o he saline samples a e elimina ed. To op imize he ex ac ion, samples we e p e iously adjus ed o a pH o 6.5, using Fig. 1. S˜ ao Tom´ e Island (main map on he le ), showing he loca ion o he mang o es a ge ed o his s udy (P aia das Conchas, Diogo Nunes, Angola es, and Malanza), de ailed on he igh -hand inse s. The inse on he op le shows he loca ion o S˜ ao Tom´ e in A ica. F. A onso e al. Chemosphe e 334 (2023) 138973 4 ammonia ace a e (0.5 M), ammonia (20–22%) and ni ic acid (2 M). The ca idges we e placed in he acuum ex ac ion sys em (Mani old), condi ioned wi h HNO 3 (2 M), u.p H 2 O and ammonia ace a e (0.5 M). Samples we e hen placed in he ca idges, which we e washed wi h H 2 O u.p.. The elu ion o me als wi h HNO 3 (2 M) was hen pe o med. This p ocedu e ollows ha o he DigiSep Blue Label ca idges om SCP Science ( e : CATALOG NUMBER MK-MKG003-SPEB-2.0-E). Quan i ica ion was done by A omic Abso p ion Spec oscopy (AAS) in a Solaa –The mo Elemen al equipmen . Cd, Pb and Ni we e analysed by g aphi e chambe , and Cu, Fe and Zn by lame. The calib a ion cu e was ob ained om ex e nal s anda ds, and he wo king solu ions o me als we e p epa ed using 1000 mg L −1 (Me ck) s anda d solu ions. The de ec ion limi was 0.01 mg L −1 o Ni, Cd and Pb, 0.1 mg L −1 o Cu, Mn and Zn, and 0.3 mg L −1 o Fe. The quali y con ol p ocedu e included analysis o duplica e samples (one o e e y ba ch o en samples), blanks be ween samples, eco e y es s and pa icipa ion in he in e calib a ion exe cise QUASIMEME (Quali y Assu ance o In o - ma ion in Ma ine En i onmen al Moni o ing) o ex e nal quali y con- ol. The esul s ob ained du ing he pe iod o his analysis showed a z- sco e <1, he a e age eco e ies o he s anda d solu ions we e be ween 80 and 110% o all he me als, which con i med he accu acy o he me hod. The p ecision o he me hod was con i med by he duplica e samples. To assess me al concen a ion in he sedimen (same elemen s ana- lysed in he wa e plus Al and C ), he <2 mm ac ion (using a cali- b a ed sie e) was eeze-d ied, homogenised, and educed o a ine powde using a mo a and pes le (acco ding o OSPAR Commission, 2015). Sedimen aliquo s o 0.45–0.55 g we e placed in Te lon essels (2 ml HF (40%) and 6 ml o aqua egia – HNO 3 (65%) and HCl (30%) (1:3), and hen acid-diges ed in a Miles one® ETHOS PLUS mic owa e o en . A e diges ion, each solu ion was neu alised wi h bo ic acid and dilu ed o 50 ml wi h ul apu e wa e . Me al concen a ions we e ana- lysed ia lame a omic abso p ion spec ome y in a The mo Scien i ic iCE™ 3500 (EPA 3051A s anda d, 2007; OSPAR Commission, 2015), excep o As, which was analysed in a hyd ide gene a o , wi h sodium bo ohyd ide added o con e As (III) o he ola ile hyd ide ha was hen pu ged om he solu ion by a s eam o a gon gas in a The mo Elemen al-VP90 Con inuous Flow apou Accesso y (ISO 17378-2:2014 E). The calib a ion cu e was ob ained by ex e nal s anda ds, and he wo king solu ions o me als we e p epa ed using 1000 mg L −1 (Me ck) s anda d solu ions. The de ec ion limi s we e 1.6 mg kg −1 o Cu, Fe, Mn and C , 0.6 mg kg −1 o Zn, 16 mg kg −1 o Al, 3 mg kg −1 o Pb, 2,5 mg kg −1 o Ni, 0,16 mg kg −1 o Cd and As, and 2.7 mg kg −1 o Hg. All eagen s we e o Me ck Sup apu e quali y and he u.p wa e used . The analy ical p ocedu e included one eagen blank in each ba ch o 20 samples, analysis o duplica e samples (one o e e y ba ch o en samples), eco e y o s anda d solu ions, ce i ied e e ence ma e ials (CRMs), and pa icipa ion in he QUASIMEME o ex e nal quali y con ol. CRMs (LGC 6187 and MESS-4) we e analysed ollowing he same p ocedu e. Ce i ied and measu ed alues ma ched, wi h eco e y be ween 80% and 120% o all CRMs and me als. Pa icipa ion in 50 QUASIMEME exe cises ( u he demons a ing da a quali y, wi h mo e han 90% accep able esul s (z-sco e <2)). This analysis con i med he p ecision and accu acy o he me hods o all he me als. All me al concen a ions we e calcula ed on a d y weigh basis, and wa e con en was measu ed by d ying known amoun s o sedimen a 105 ◦C. 2.4. Da a analysis A e age sedimen me al concen a ions ob ained in S˜ ao Tom´ e mang o es was compa ed o hose om o he mang o es and olcanic islands, compiled om he li e a u e. The po en ial o an h opogenic inpu o me als in o he en i onmen was assessed h ough se e al widely used me hods, only a ailable o sedimen concen a ions: The En ichmen Fac o (EF), he Geo- accumula ion Index (Igeo), and he Con amina ion Fac o (CF). The EF Table 1 Fea u es o he ou mang o es s udied in S˜ ao Tom´ e Island (adap ed om A onso e al., 2021; Caldei a e al., 2003). Dash indica es ha his alue was no a ailable. Mang o e Malanza Angola es Diogo Nunes P aia das Conchas Mang o e a ea (km 2 ) 2.83 0.68 0.12 0.0012 A ea o he hyd og aphic basin (km 2 ) 7.41 7.82 23.35 13.31 Geologic composi ion o he hyd og aphic basin(s) Basal - achyphonoli e la as; allu ial deposi s; py oclas ic and la a cones Basal - achyphonoli e la as Basal ic la as; py oclas ic and la a cones Basal ic la as; allu ial deposi s Size o he closes human se lemen (habi an s) 1345 2037 392 180 Land use dominance in he su oundings Mang o e (53.6%) Ag o o es y (59.4%) Ag icul u e (47.5%) – F. A onso e al. Chemosphe e 334 (2023) 138973 5 di e en ia es an h opogenic and na u al sou ces o sedimen en ich- men o each elemen (Sze e e al., 1999). I was calcula ed using a o mula ha uses Al as he no malize o me al concen a ions: EF =(C/CAl)sample (C/CAl) e e ence whe e (C/C Al ) is he a io o concen a ion o he elemen o conce n (C) o ha o Al (C Al ), in bo h he sedimen sample (sample) and in an un- pollu ed e e ence sample ( e e ence). In he p esen s udy, he e e ence sample alues we e aken om he bibliog aphic e e ence o shallow wa e sedimen ha was closes o he condi ions ound in he s udy a ea (Salomons and Fo s ne , 1984). Fi e con amina ion ca ego ies a e acknowledged on he basis o he en ichmen ac o : 2 <EF <5 - de i- ciency o mode a e en ichmen ; 5 <EF <10 - mode a ely se e e en ichmen , 10 <EF <25 - se e e en ichmen ; 25 <EF <50 - e y se e e en ichmen ; and EF >50 - ex emely high en ichmen (Bi ch and Olmos, 2008). The Igeo quan i ies he deg ee o me al pollu ion (Mülle , 1979), and has been used in s udies o ace me al s udies in sedimen s and soils (e. g., Amin e al., 2009a). I was calcula ed as: Igeo =log2(Cn 1.5Bn) whe e C n is he concen a ion o a me al in he sedimen , and B n is he geochemical backg ound alue o ha same me al in shallow wa e sedimen (Mülle , 1979). The Igeo is hen classi ied in o se en classes: 0 (p ac ically uncon amina ed) - Igeo<0; 1 (uncon amina ed o mode a ely con amina ed) - 0 <Igeo<1; 2 (mode a ely con amina ed) - 1 <Igeo<2; 3 (mode a ely o hea ily con amina ed) - 2 <Igeo<3; 4 Fig. 2. Me al concen a ions ( μ g/L) in he wa e o S˜ ao Tom´ e s udied mang o e sys ems. Si es wi h unusually high concen a ion a e agged. F. A onso e al. Chemosphe e 334 (2023) 138973 6 (hea ily con amina ed) - 3 <Igeo<4; 5 (hea ily o ex emely con ami- na ed) - 4 <Igeo<5; 6 (ex emely con amina ed) - 5 <Igeo. The CF exp esses he le el o me al con amina ion o sedimen , being calcula ed as: CF =Cn Bn whe e C n is he concen a ion o a gi en me al in he sample, and B n is he geochemical backg ound alue o ha same me al in shallow wa e sedimen (Mülle , 1979). CF alues we e in e p e ed as: low con ami- na ion o CF <1; mode a e con amina ion o 1 <CF <3; conside able con amina ion o 3 <CF <6; and e y high con amina ion o CF >6 (Hakanson, 1980). 3. Resul s 3.1. Me al concen a ion in he wa e Me al concen a ions in he wa e column we e highly a iable be- ween si es and elemen s, wi h se e al si es highligh ed by high con- cen a ions o some elemen s (Table S1 – Fig. 2). The highes concen a ions in he wa e we e he ollowing: ups eam in Malanza o cadmium (M6 – 0.73 μ g/L); downs eam in Diogo Nunes (D1 – 3.46 μ g/ L) and in P aia das Conchas (PC1 – 2.99 μ g/L), and nea he ishing ha bou in I´ ogoi´ ogo Bay o coppe (B0 – 3.47 μ g/L); ups eam in Malanza o i on (M7 – 4345.68 μ g/L) downs eam in Diogo Nunes (DN1 – 134.44 μ g/L) and P aia das Conchas (PC1 – 139.08 μ g/L), and up- s eam in Malanza o manganese (M6 – 142.03 μ g/L, M7 – 121.60 μ g/ L); downs eam in Diogo Nunes (D1 – 46.79 μ g/L) and in a small shallow pound in Malanza o nickel (M1 – 13.57 μ g/L). The highes lead con- cen a ions we e ound in one o he a ms o Diogo Nunes, and nea he passenge docking a ea and no h sec ion o Malanza bay (DN3 – 2.45 μ g/L, B0 2.64 μ g/L, B5 3.58 μ g/L, Tables S1 – Fig. 2). Zinc concen a- ions we e highe in wa e samples om Angola es no h a m, ups eam a ea (A4 – 19.33 μ g/L, Table S1 – Fig. 2), in he small shallow pond o Malanza (M1 – 15.51 μ g/L, Table S1 – Fig. 2), and nea he ishing ha bou in Malanza bay (B0 – 13.83 μ g/L, Table S1 – Fig. 2). The compa ison o backg ound alues o me al con en (nickel, cadmium, lead, coppe , and zinc) showed ha S˜ ao Tom´ e mang o e wa e had highe concen a ions o coppe (Table S1). P aia das Conchas and Diogo Nunes p esen ed concen a ions o nickel, cadmium and zinc ha we e pa icula ly highe han he e e ence alues (Table S1). 3.2. Me al loadings in su ace sedimen s 3.2.1. Sedimen cha ac e iza ion: g anulome y and o ganic ma e con en G anulome y o su ace sedimen was highly a iable be ween and some imes wi hin mang o es, e en hough i was mos ly composed by sands and sil s (Fig. 3). All samples om Diogo Nunes we e classi ied as sand wi h small amoun s o o ganic ma e . The downs eam a eas o Angola es om bo h a ms we e p edominan ly sandy (99% a A1, and 98.8% a A2), while he no he n a m had muddy sand in he middle (A3, A4 – 54% and 67% sand espec i ely) and sandy g a el ups eam (A5 – 20% sand). In Malanza, he sedimen was e y homogenous in ups eam a ea, being mos ly muddy sand (61% sand a M5, 56% a M6, and 65% a M7) wi h high amoun s o o ganic ma e (42%, 61% and 63% espec i ely), while downs eam loca ions (99% sand a M2, 85% and M3, and 85% a M4) we e mos ly sandy wi h a small p opo ion o o ganic ma e (7%, 11% and 13%, espec i ely). P aia das Conchas had muddy sand ups eam (80% sand a P3), sandy g a el in he middle (51% g a el and 48% sand a P2), and sand downs eam (98% sand a P1). Fig. 3. G anulome y e na y diag am. Each colou ep esen s a sampling loca ion, and he size o he ci cles indica es o ganic ma e con en (i.e., la ge ci cles indica e highe amoun s o o ganic ma e ). (Fo in e p e a ion o he e e ences o colou in his igu e legend, he eade is e e ed o he Web e sion o his a icle.) F. A onso e al. Chemosphe e 334 (2023) 138973 7 3.2.2. Compa ing sedimen me al concen a ion in S˜ ao Tom´ e mang o es wi h simila sys ems We s a ed by compa ing a e age elemen al concen a ions ob ained in S˜ ao Tom´ e mang o es wi h hose om o he mang o e and olcanic islands, compiled om he li e a u e. Since alues wi h aluminium no maliza ion a e mos ly applied in sedimen s wi h ma ine o igin (He u and Sandle , 2006), he compa ison was based only on absolu e concen a ions. S˜ ao Tom´ e mang o e sedimen s ended o p esen highe mean me al concen a ions when compa ed o o he mang o es and olcanic islands, excep o lead in o he mang o e sys ems and coppe and nickel in o he olcanic islands (Table 2). 3.2.3. En ichmen and con amina ion En ichmen (EF) and con amina ion (Igeo and CF) based on me al concen a ions in he su ace sedimen (Table S2), we e highly a iable be ween si es and elemen s, also showing ele an di e ences be ween indices (Table 3). Cadmium concen a ions in he sedimen we e e y close o he quan i ica ion le el, he e o e he indices we e no calcu- la ed. S˜ ao Tom´ e mang o es had consis en ly low en ichmen and con amina ion by coppe , li hium and lead, while i on, me cu y and zinc had only occasional high alues o en ichmen , ups eam in Malanza (M6). Manganese en ichemen was ound a all sampling poin s o Diogo Nunes, ups eam a Malanza (again, M6) and downs eam a P aia das Conchas (P1), while nickel en ichemen was ound ups eam a Diogo Nunes (D3 and D4) and ac oss mos sampling poin s o Malanza (excep M6 and M7) and showed occasional con amina ion a he small con iguous pond in Malanza (M1) and ups eam a P aia das Conchas (P3). Only a senic and ch omium p esen ed a widesp ead en ichmen and con amina ion, and e y se e e en ichmen and hea y con amina- ion a a ew loca ions. A senic en ichmen and con amina ion we e pa icula ly no iceable a Diogo Nunes and Malanza. 4. Discussion The assessmen o he me al loadings in ou mang o es in S˜ ao Tom´ e Island depic ed, gene ally, he same pa e ns as in hose ound in Wes A ican egions, which a e gene ally iche in cadmium, ch omium, nickel, and zinc, especially in coas al a eas (Gnandi e al., 2011). P aia das Conchas and Diogo Nunes e en being he smalles s udy a eas we e cha ac e is ically he sys ems ha p esen ed highe me al con en . On he o he hand, Angola es p esen ed he lowes en ichmen and con amina ion le els. Table 2 Mean sedimen me al concen a ions (absolu e alues, mg kg −1 ) o S˜ ao Tom´ e mang o es (cu en s udy), and in o he mang o e sys ems and olcanic islands ( aken om he li e a u e). Values highligh ed in g ey show mean concen a ions ha we e lowe han hose ound in S˜ ao Tom´ e mang o es. Dashes indica e ha hose alues we e no a ailable. [1] (K ui wagen e al., 2008); [2] (Gnandi e al., 2011); [3] (Cuong e al., 2005); [4] (Essien e al., 2009); [5] (Amin e al., 2009b); [6] (Vane e al., 2009); [7] (Ma chand e al., 2006); [8] (P eda and Cox, 2002); [9] (Coelho e al., 2016); [10] (Dœlsch e al., 2006); [11] (Ahn and Chon, 2010); [12] (B nický e al., 2020); [13] (Cab al Pin o e al., 2015); [14] (Ama al e al., 2006); [15] (Mo a e al., 2012); [16] (Mendoza-G im´ on e al., 2014); [17] (Su he land and Tack, 2000); [18] (Kazakou e al., 2010). F. A onso e al. Chemosphe e 334 (2023) 138973 8 4.1. Me al loadings in wa e and sedimen In P aia das Conchas and Diogo Nunes despi e being sys ems wi h high me al con en , he e was no con amina ion o mos o he assessed me als and a e, simul aneously, ep esen ed by a eas wi h small amoun s o sedimen o ganic ma e . Due o he s ong a ini y be ween o ganic ma e and me als, he e is less abili y o he sedimen o ap and s o e he me als a ailable in he sys em. Al hough hese sys ems had a high me al con en in wa e and sedimen samples, he indices did no show con amina ion o mos o he me als assessed. Con a ily, Malanza was he sys em wi h he highes p opo ions o sil and o ganic ma e in he sedimen , which inc eases he numbe o co alen bonds wi h me als, a ou ing hei accumula ion in he sedimen . Hence, hese si es could ha e an impac on he elemen e en ion in he sedimen , e en hough his phenomenon alone canno explain he con amina ion and en ichmen in he sys em. Table 3 Indices es ima ed o each me al in samples om all s udy a eas (EF- En ichmen Fac o ; Igeo – Geoacumula ion index; CF – Con am- ina ion Fac o ). F. A onso e al. Chemosphe e 334 (2023) 138973 9 4.2. Na u al and an h opogenic sou ces o me al en ichmen and con amina ion To be e unde s and he na u al endency o me al concen a ion, he collec ed da a was compa ed wi h he esul s om sedimen samples om o he mang o es in he opical egion and wi h olcanic islands. Compa ison be ween sedimen s om he s udy a ea wi h o he mang o e sys ems has shown San omean mang o es o ha e highe me al con en s. Howe e , land sys ems om o he olcanic islands p esen ed highe coppe , lead and nickel concen a ions, al hough he backg ound alues (OSPAR Commision, 2009) o coppe and nickel a e lowe han he alues de ec ed in S˜ ao Tom´ e. This sugges s ha he highe con en in coppe and nickel migh ha e a li hogenic o igin. Ne e heless, he backg ound alues conside ed a e es ic i ely ep e- sen a i e o he No h-Eas A lan ic Region which means ha conclu- sions based on hese alues mus be aken wi h cau ion due o di e en geological o ma ions. A common obse a ion in all sys ems was he high en ichmen and con amina ion wi h a senic and ch omium. In non- olcanic islands, he con amina ion wi h a senic has been p o en o be de i ed om ag i- cul u e uno and he use o disin ec ion and pes elimina ion de e gen s in aquacul u e p ac ices, while he ch omium con amina ion was conside ed o be mainly a esul o ag icul u e uno (Li e al., 2022). In olcanic islands, he a senic con amina ion in mang o e sys ems esul- ed om na u al p ocesses, such as he leaching o olcanic ocks, bu also om an h opogenic o igin, linked o ha bou s and was ewa e discha ge. The same ype o con amina ion wi h a senic was ound in mang o es om he mainland possibly caused by an h opogenic ac i - i ies, o ins ance, pe ochemical was es and desalina ion plan s (Al-Kah any e al., 2018). Howe e , ch omium con amina ion is mos commonly he esul o eshwa e inpu and e osion o olcanic ocks (Ca y, 1982). In P aia das Conchas and Diogo Nunes, he sou ces o en ichmen in i on and zinc a e mos p obably local and sho - e m, due o he an h opogenic ac i i ies ha a e common in he sys em (i.e., laund y washing and ash deposi ion). Diogo Nunes, howe e , showed a con amina ion wi h ch omium and manganese, which can esul om a long- e m elease o hese me als, possibly om ag icul u e un-o , he main land use in he a ea. Angola es p esen ed he lowes concen a ion o mos o he me als and ewe signs o sedimen con amina ion ou o all s udied mang o es. Con a y o wha was expec ed, conside ing he p oximi y o he land ill om he sou h a m, i was he no he n a m ha p esen ed highe me al con amina ion. This may be explained by ei he he p oximi y o he ci y o S˜ ao Jo˜ ao dos Angola es, o by a highe me al con ibu ion o ha pa icula hyd og aphic basin. In Malanza, besides he possible sou ces o pollu ion om he i e ibu a ies, his sys em may also ha e on o he possible ex e nal sou ce o con amina ion, he I´ ogoi´ ogo bay, due o in ense ishing and o he an h opogenic ac i i ies and he egula boa a ic. Fo ins ance, nea he ha bou , he concen a ion o coppe , lead, and zinc was clea ly highe , and hese a e me als usually p esen in boa emissions and an i ouling chemicals used in boa pain s (Bad e al., 2009; Nase , 2013; Usman e al., 2013; Zhang e al., 2012). This may also jus i y he di e en me als p esen in he wa e column o he Malanza mang o e om he ups eam and downs eam a eas, as a esul o seawa e in usion om he nea by bay, as he ha bou is close o he mang o e. Sedimen s can be used o assess he en i onmen al condi ion o a speci ic ecosys em, based on en ichmen and con amina ion indexes ha e alua e he sample and me al load. Howe e , he use o se e al indices can esul in i egula ou pu s and inconsis encies be ween hem. Fo ins ance, he Igeo scale can ange om nega i e o posi i e alues, while all he o he indices ha e di e en scales ha only ange in posi i e alues, being ambiguous how hey complemen each o he and which classes a e equi alen (Bi ch, 2023). Thus, e en hough classi ica ion schemes o sedimen s can be an ad an age o any s udy ela ed o he e alua ion o sedimen quali y and me al pollu ion, he ou pu s mus be conside ed wi h cau ion. 4.3. Heal h implica ions In de eloping coun ies, u baniza ion had a apid ad ance in he las yea s, howe e , he lack o managemen plans associa ed wi h he excessi e use o e ilize s and disposal o domes ic was e in inapp o- p ia e a eas ha e caused de imen al e ec s on he quali y o wa e , sedimen , and aqua ic auna (Ali e al., 2016; Isa e al., 2014; Ledin e al., 1989). Addi ionally, he coun ies’ legisla ion abou ecosys em con amina ion is weak and he lack o mone a y suppo comp omises he ac ual law en o cemen (Kumie and Kloos, 2006). As a consequence o some o hose limi a ions, i was c ea ed he One Heal h app oach (www.oneheal hcommision.o g) ocused on p o ec ing people’s heal h, animals, and he en i onmen . This app oach add esses he oo causes and sea ches o sus ainable solu ions applicable o ood and wa e sa e y, as well as pollu ion managemen . In his scope, and conside ing he speci ic case o S˜ ao Tom´ e mang o es, some o he possible esponses o p e en mo e heal h damages by me al con amina ion would be he implemen a ion o policies o ecosys em moni o ing (i.e., moni o ing me al concen a ion in shell ish and ish om local ma ke s), as well as he implemen a ion o an i- o low-pollu ion policies. The de elopmen and in es men in educa ion p og ams a e also impo an ools o aise awa eness on he bes p ac ices o sys em p o ec ion, pollu ion sou ces and impac s on he ecosys ems and human heal h (Beyene e al., 2009). Fu he mo e, engaging wi h he communi ies can help educe heal h isk inc easing p ac ices, as well as o de ec ea ly symp oms o me al con amina ion. 5. Conclusions To he bes o ou knowledge, his was he i s assessmen o he me al concen a ion in he mang o es om S˜ ao Tom´ e. I showed ha hese sys ems p esen highe me al concen a ions han mos mang o es and olcanic islands, p obably due o he combina ion o a olcanic o igin, which ends o inc ease he na u al me al concen a ions han si es wi h o he li hogenic o igins, and sedimen composi ion ha a- ou s he e en ion o hose me als. Howe e , occasional high concen- a ions and high con amina ion alues sugges ha , a leas in some cases, he high concen a ion o some me als ha e an an h opogenic o igin. A senic and ch omium showed se e e en ichmen and con am- ina ion a di e en si es, which aises heal h conce ns. These esul s ein o ce he need o gain a be e unde s anding o ac ual sou ces o me al con amina ion in S˜ ao Tom´ e, which can hen enable he p epa a- ion and applica ion o mi iga ion measu es. Fu u e s udies and moni- o ing o me al concen a ions, en ichmen and con amina ion in S˜ ao Tom´ e should go beyond mang o e a eas, ex ending o o he aqua ic and e es ial ecosys ems, and including he s udy o bioaccumula ion. O e all, his s udy shows how me al pollu ion migh be ele an e en in a emo e and non-indus ialized island, highligh ing he need o a be e unde s anding o how me als a e dis ibu ed in he en i onmen , and pa icula ly in de eloping coun ies, whe e people a e o en mo e di ec ly elian on na u al esou ces and mo e likely o unknowingly be exposed o high me al concen a ions and i s dele e ious heal h consequences. C edi au ho s a emen Filipa A onso: In es iga ion, W i ing – o iginal d a , Visualiza ion; Ca la Palma: Valida ion, Fo mal analysis, Resou ces, W i ing – e iew & edi ing, Visualiza ion; Ana C. B i o: W i ing – e iew & edi ing; Paula Chainho: In es iga ion, W i ing – e iew & edi ing; Rica do de Lima: In es iga ion, W i ing – e iew & edi ing, Visualiza ion; Joshua A. Heumülle : In es iga ion, W i ing – e iew & edi ing; Filipe Ribei o: In es iga ion, W i ing – e iew & edi ing; Ped o M. F´ elix: F. A onso e al.