RESUMO
In this paper, study of the biosorption of Cd(2+) and Pb(2+) by nonliving Laminaria japonica in a batch adsorption system is described. The content of acidic sites and the dissociation constant of carboxylic acid functional groups (metal-binding site) of L. japonica were experimentally determined by conductometric and potentiometric titrations and theoretically predicated by using monodentate and bidentate binding models. The models are based on the monodentate or bidentate binding reactions of bivalent metal ions to acidic sites. The acidic site content and carboxylic acid dissociation constants determined are 1.25 and 0.18 mmol L(-1), respectively. The results showed that the bidentate adsorption model fits well the biosorption of bivalent metal ions onto L. japonica with the bidentate binding constants for Cd(2+) and Pb(2+) being 5.72 × 10(3) and 6.24 × 10(4) L mol(-1), respectively. The adsorption process of L. japonica followed the pseudo-second-order kinetics.
Assuntos
Cádmio/isolamento & purificação , Laminaria/química , Chumbo/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Condutometria , Cinética , PotenciometriaRESUMO
Since 2007, the world's largest macroalgal blooms have occurred along the coastal area of the Yellow Sea for 6 consecutive years. In 2012, shipboard surveying and satellite remote sensing were used to monitor the whole blooming process. The blooms originated in Rudong sea area of the South Yellow Sea where bloom patches were of dark green and filamentous thalli were the dominant morphology. The scale of the blooms reached its peak size in Rizhao sea area of the North Yellow Sea, and decreased promptly and became insignificant in Qingdao coast where the blooms turned yellow, mostly with air sac blades. Meanwhile, vegetative cells of the green tide algae changed into cytocysts gradually from which germ cells were released as the blooms drifted northward. Additionally, chlorophyll contents and fluorescence activity of free-floating thalli in the North Yellow Sea were both significantly lower than that in the South Yellow Sea. Those studies presented here contributed to increasing our understanding about how the green tide declined gradually in the North Yellow Sea.
Assuntos
Fotossíntese , Ulva/fisiologia , Clorofila/metabolismo , Monitoramento Ambiental/métodos , Eutrofização/fisiologia , Fluorescência , Oceanos e Mares , Tecnologia de Sensoriamento RemotoRESUMO
A series of consecutively adjustable submerged vegetation nets were constructed in a polluted shallow river with a length of about 200 m and nearby the water resource protection area of Taihu Lake in East China, forming an aquatic vegetation consisted of submerged plant species Cabomba caroliniana, Vallisneria natans, Elodea nuttallii, Hydrilla verticillata, and Potamogeton crispus. The water quality indices including total nitrogen (TN), ammonium nitrogen (NH4(+)-N), nitrite nitrogen (NO2(-)-N), nitrate nitrogen (NO3(-)-N), total phosphorus (TP), and phosphate (PO4(3-)-P) were monitored, and the bioremediation effect of the vegetation nets was evaluated. After setting up the vegetation nets, the Secchi depth (SD) of the river changed from 0.5 m to 1.7-1.8 m, and the TN and TP concentrations 15 and 20 days after the nets constructed decreased by 35.6% and 66.3%, and 29.4% and 63.2%, respectively. After five months, the concentrations of NH4(+)-N, NO2(-)-N, NO3(-)-N, TN, TP, and PO4(3-)-P decreased by 92.4%, 76.8%, 72.7%, 73.9%, 90.5%, and 92.0%, respectively. This study showed that consecutively adjustable submerged vegetation net could be a potential approach for treating polluted river waters, particularly for the bioremediation of polluted small landscape shallow water bodies.