title: Toxicity assessment of arsenic and cobalt in the presence of aquatic humic substances of different molecular sizes.
abstract: The release of contaminants in aquatic ecosystems can be influenced by humic acids. In this study, toxicity tests using environmentally relevant concentrations of arsenic and cobalt were conducted both in the presence and absence of aquatic humic substances (AHS) and the fractions of different molecular sizes in the range of (<5, 5-10;10-30; 30-100 and >100kDa) using the microcrustacean Ceriodaphnia dubia. AHS together with arsenic reduced the toxicity, and the toxicity decreased in fractions of larger molecular size AHS. Despite the presence of cobalt, the reduction in toxicity was not observed and that depended on the molecular size of AHS. There was a trend of enhanced toxicity for Co in fractions of larger molecular sizes, opposed to that found for arsenic. Thus, the humic substances alter toxicity of trace elements, and this effect varies depending on the size of the humic substances.
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Cláudia Hitomi
authors.initials: CH
authors.lastname: Watanabe
authors.affiliation: Institute of Chemistry, Sao Paulo State University (UNESP) - Campus Araraquara, Av. Professor Francisco Degni, 55 - Jardim Quitandinha, CEP: 14800-060 Araraquara, SP, Brazil.
authors.forename: Adnivia Santos Costa
authors.initials: AS
authors.lastname: Monteiro
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Erik Sartori Jeunon
authors.initials: ES
authors.lastname: Gontijo
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Vivian Silva
authors.initials: VS
authors.lastname: Lira
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Carolina de Castro
authors.initials: CC
authors.lastname: Bueno
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Nirmal Tej
authors.initials: NT
authors.lastname: Kumar
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Fracácio
authors.affiliation: Institute of Science and Technology, Sao Paulo State University (UNESP) - Campus Sorocaba, Av. Três de Março, 511 - Alto da Boa Vista, CEP: 18087-180 Sorocaba, SP, Brazil. Electronic address: ahrosa@sorocaba.unesp.br.
authors.forename: André Henrique
authors.initials: AH
authors.lastname: Rosa
mesh_terms: D000818:Animals; D001151:Arsenic / Q000633:toxicity*; D033361:Cladocera / Q000187:drug effects*; D003035:Cobalt / Q000633:toxicity*; D017753:Ecosystem; D004781:Environmental Exposure; D006812:Humic Substances; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical; D003035:Cobalt; D001151:Arsenic
keywords: Arsenic; C. dubia; Cobalt; Humic substances; Molecular size; Toxicity