Sorption of the herbicide terbuthylazine in two New Zealand forest soils amended with biosolids and biochars

Abstract

Background, aim, and scope Terbuthylazine is one of the most commonly used herbicides for vegetation management in forest plantations in New Zealand. Knowledge about the sorption of terbuthylazine on forest soils, especially the influence of coexisting organic amendments, remains obscure. In this study, we evaluated the effects of biosolids and biochars on the sorption of terbuthylazine to forest soils. Materials and methods Two pumice soils, including a forest landing site soil with low soil organic matter content and an organic carbon rich topsoil under standard forest management, were sampled from a 2-year-old replanted pine plantation. The soils were mixed with four organic amendments, including two thermally dried biosolids with one digested and the other undigested, a biochar produced from high temperature pyrolysis (700°C), and a biochar from pyrolysis with a lower temperature (approximately 350°C). A batch equilibration method was used to determine terbuthylazine adsorption-desorption in organic amendment-treated and untreated soils. Adsorption and desorption isotherms were described with the Freundlich equation.Results and discussion Adsorption and desorption isotherms in the soils with or without organic amendments were well described by the Freundlich model. The undigested or digested biosolids added to the topsoil had a negligible or limited effect on the adsorption to terbuthylazine. The addition of the other amendments to the two soils all enhanced the adsorption. The biochars displayed higher efficiency in improving soils' adsorption capacity to terbuthylazine than the biosolids. Among the organic amendments evaluated, the biochar obtained from high temperature pyrolysis demonstrated the most significant enhancement on adsorption with an enhancing factor of 63; whereas, the digested biosolids showed the weakest enhancement. Furthermore, terbuthylazine adsorbed by the digested biosolids appeared to be more easily desorbed than that by biochar treatments. Conclusions This work indicates that the addition of organic amendments to forest soils, particularly biochar to a soil with low native organic matter, may enhance soil sorption of terbuthylazine and thus reduce the possibility of the hydrophobic herbicide leaching to groundwater.

Biochar: Pyrogenic Carbon for Agricultural Use - A Critical Review

“…This feature should be considered carefully when choosing pyrolysis conditions of biochar, since undesirable interactions with certain products (e.g. systemic pesticides) are possible, reducing the effectiveness and requiring dose adjustments, while on the other hand, biochar can be extremely useful to reduce the environmental impact of contact pesticides and for environmental remediation (Spokas et al, 2009;Wang et al, 2009). Biochar resulting from slow pyrolysis however, can immobilize metals such as Cu 2+ and others heavy metals, due its higher carboxyl content (Uchimiya et al, 2010) and the resulting metal complexation capacity.…”

Contamination and remediation of phthalic acid esters in agricultural soils in China: a review

“…The adsorption of polycyclic aromatic hydrocarbons onto pure charcoal was about 10-1000 times stronger than the adsorption onto organic carbon in soils and sediments (Accardi-Dey and Gschwend 2002). Soils amended with biochar were also found to be particularly effective at enhancing soil adsorption of organic contaminants and thus reduce the bioavailability, leaching risk, and plant uptake of those contaminants (Kookana et al 2011;Sheng et al 2005;Wang et al 2010a;Zhang et al 2010;Zhang et al 2012;Sopeña et al 2012). Therefore, biochar and other types of organic matter are useful materials to consider when designing phthalic acid ester immobilization technologies for the reduction of phthalic acid ester bioavailability ).…”

The Influence of Biochar Production on Herbicide Sorption Characteristics

“…Biochar, added in filter strips and waterways, eroded landscapes, or other areas where increased sorption is desired, may aid in cleaning water running off fields by sorbing undesirable contaminants. Increased sorption may also slow or stop herbicides from leaching, so highly sorbent biochar types may be desired over shallow aquifers or in areas low in native organic matter (Wang et al, 2010). Herbicide bioavailability in some cases may be reduced, protecting sensitive plants.…”