Formentini Thiago Augusto, Legros Samuel, Fernandes Cristovão Vicente Scapulatempo, Pinheiro Adilson, Le Bars Maureen, Levard Clément, Mallmann Fábio Joel Kochem, da Veiga Milton, Doelsch Emmanuel
Department of Sanitary and Environmental Engineering, Federal University of Santa Maria (UFSM), 97105-900 Santa Maria, RS, Brazil; Department of Hydraulics and Sanitation, Federal University of Parana (UFPR), 81531-980 Curitiba, PR, Brazil.
CIRAD, UPR Recyclage et risque, 18524 Dakar, Senegal; CIRAD, UPR Recyclage et risque, F-34398, Montpellier, France.
Environ Pollut. 2017 Mar;222:495-503. doi: 10.1016/j.envpol.2016.11.056. Epub 2017 Jan 4.
Spreading livestock manure as fertilizer on farmlands is a widespread practice. It represents the major source of heavy metal(loid)s (HM) input in agricultural soils. Since zinc (Zn) is present at high concentrations in manure, it poses special environmental concerns related to phytotoxicity, groundwater contamination, and introduction in the food chain. Therefore, investigations on the fate and behavior of manure-borne Zn, when it enters the soil environment, are necessary to predict the environmental effects. Nevertheless, long-term field studies assessing Zn speciation in the organic waste matrix, as well as within the soil after manure application, are lacking. This study was designed to fill this gap. Using SEM-EDS and XAS analysis, we reported the following new results: (i) ZnS made up 100% of the Zn speciation in the pig slurry (the highest proportion of ZnS ever observed in organic waste); and (ii) ZnS aggregates were about 1-μm diameter (the smallest particle size ever reported in pig slurry). Moreover, the pig slurry containing ZnS was spread on the soil over an 11-year period, totaling 22 applications, and the resulting Zn speciation within the amended soil was analyzed. Surprisingly, ZnS, i.e. the only species responsible for a nearly 2-fold increase in the Zn concentration within the amended soil, was not detected in this soil. Based on SEM-EDS and XAS observations, we put forward the hypothesis that Zn in the pig slurry consisted of nano-sized ZnS crystallites that further aggregated. The low stability of ZnS nanoparticles within oxic and complex environments such as the studied soil was the key explanation for the radical change in pig slurry-borne Zn speciation after long-term amendments.
在农田中施用家畜粪便作为肥料是一种普遍的做法。它是农业土壤中重金属（类金属）输入的主要来源。由于锌（Zn）在家畜粪便中含量很高，它引发了与植物毒性、地下水污染以及进入食物链相关的特殊环境问题。因此，有必要研究粪便携带的锌进入土壤环境后的归宿和行为，以预测其环境影响。然而，目前缺乏评估有机废物基质中以及施用粪便后土壤中锌形态的长期田间研究。本研究旨在填补这一空白。通过扫描电子显微镜-能谱仪（SEM-EDS）和X射线吸收光谱（XAS）分析，我们报告了以下新结果：（i）硫化锌（ZnS）占猪粪中锌形态的100%（这是在有机废物中观察到的ZnS的最高比例）；（ii）ZnS聚集体直径约为1μm（这是猪粪中报道过的最小粒径）。此外，含ZnS的猪粪在11年期间施用于土壤，共施用22次，并分析了改良土壤中产生的锌形态。令人惊讶的是，在该土壤中未检测到ZnS，而ZnS是导致改良土壤中锌浓度几乎增加两倍的唯一物质。基于SEM-EDS和XAS观察结果，我们提出了一个假设，即猪粪中的锌由纳米级ZnS微晶组成，这些微晶进一步聚集。在诸如所研究土壤这样的有氧和复杂环境中，ZnS纳米颗粒的低稳定性是长期改良后猪粪携带的锌形态发生根本变化的关键解释。
