Assessment of effect of pH, temperature and organic matter on zinc mobility in a hydromorphic soil

Abstract

Before using Zn-rich sewage sludge in agricultural soil, it is very important to study the behavior of this pollutant and its mobility in semiarid climate to prevent the risk that may pose on the human health. Batch technique was used to study sorption and desorption experiments of zinc onto hydromorphic soil with a loamy texture. Results showed that the effect of pH ranged between 6 and 7.8 on zinc sorption amount was negligible. Whereas the coefficient of distribution K d at pH = 6 was 1-3 times greater than at pH = 7.8. The increase in temperature from 25 ± 2 to 40 ± 2°C increased zinc uptake by 4.37-63.2 % and 3.75-27.09 % at pH 7.8 and 6, respectively. The removal of organic matter slightly enhanced zinc sorption at alkaline pH; while it remarkably reduced it at acidic pH suggesting that organic matter effect depended significantly on pH. All sorption data of zinc fitted only the Freundlich equation. Also, the sorption energies (E) calculated from the Dubinin-Radushkevich equation were high implicating that the main process of zinc uptake was chemisorption. Zinc speciation after sorption experiments showed that the added zinc amount was mostly bonded to oxides fraction at alkaline pH and to organic matter at acidic pH. Zinc mobility in the two investigated soil pH values was similar, while its mobility was not very affected by the organic matter removal. The percentage of desorbed zinc (bioavailable) was higher into 0.05 M of ethylenediaminetetraacetic acid (about 20 %) than into distilled water (B4 %). From the principal component analysis, we deduced that pH was the main factor controlling zinc sorption and the coefficient of distribution K d was the best parameter that describes the mechanism of zinc retention onto hydromorphic soil.

Influence of Zn, Cd, and Cu fractions on enzymatic activity of arable soils

“…Nine soil samples ( Albic Luvisols ) from the agricultural fields covering 150-ha area were collected three times (April, July, and October) during the growing season in 2015, from a depth of 0–25 cm. Each sample (Ahumada et al 2009 ; Ahumada et al 2014 ; Azouzi et al 2015 ; Badura and Piotrowska-Seget 2000 ; Baran 2013 ; Binet et al 2003 ; Brokbartold et al 2012 ; Chaperon and Sauve 2007 ; Cheng et al 2011 ) consisted of six subsamples. Non-ploughing techniques of cultivation are used in this area (the fields have not been ploughed for 5 years).…”

Total nitrogen and pH-controlled chemical speciation, bioavailability and ecological risk from Cd, Cr, Cu, Pb and Zn in the water level-fluctuating zone sediments of the Three Gorges Reservoir

“…The pH is believed to be the key factor affecting the speciation of heavy metals [31]. Laboratory simulation has shown that exotic heavy metals are mostly bonded to oxides under alkaline conditions and onto organic matter in acidic conditions in soil [32]. The pH is positively correlated with the reducible fraction (F 2 ) of heavy metals [32].…”

“…Laboratory simulation has shown that exotic heavy metals are mostly bonded to oxides under alkaline conditions and onto organic matter in acidic conditions in soil [32]. The pH is positively correlated with the reducible fraction (F 2 ) of heavy metals [32]. Wang et al found that, with increasing pH, the speciation of heavy metals in sludge was transformed to oxidisable and residual fractions [33].…”

Fractionation and release of Cd, Cu, Pb, Mn, and Zn from historically contaminated river sediment in Southern China: Effect of time and pH

“…The effective time scales for slow desorption processes may be on the order of months to years. However, most desorption experiments have been measured for only short time periods, for example, over durations of 1 to 7 d (Rubinos et al ; Ren et al ), and/or even within 48 h (Oh and Shin ; Kasmaei and Fekri ; Zhao et al ; Mayel et al ; Azouzi et al ); only a few studies exist with a longer timespan (2 wk to 1 mo; Khaokaew et al ; Liao et al ).…”