Copper, zinc and manganese in soils of two watersheds in Santa Catarina with intensive use of pig slurry

Jorge Luis Mattias,Eduardo Girotto,Eder Efrain Trentin,Carlos Alberto Ceretta,Cristiano Nunes Nesi,Renan Costa Beber Vieira,Cledimar Rogério Lourenzi

doi:10.1590/s0100-06832010000400040

Abstract

Systematic pig slurry application to crop soils may lead to the accumulation of heavy metals in regions with intensive pig raising. The aim of this study was to evaluate the accumulation of Cu, Zn and Mn in soils under systematic pig slurry application. For this purpose, soil samples were collected from two of the most representative watersheds of Santa Catarina where the predominant activity is pig raising. In each watershed, 12 properties were chosen to evaluate the different systems of pig husbandry (complete cycle (CC), farrowing (FaU) and finishing units (FiU)). Based on information of the producers, soil samples were collected in areas with and without systematic manure application. To determine the total Cu, Zn and Mn content in soils and manure, a methodology proposed by the Environmental Protection Agency of the United States (USEPA), method nº 3050B, was used. For the available heavy metal content, Cu and Zn was extracted with HCl 0.1 mol L-1 and Mn with KCl 1 mol L-1. Data were subjected to multivariate analysis, using the canonical discriminant analysis to identify the metals that best differentiate the soils studied within each swine housing system. Successive pig slurry applications cause an increase in Cu, Zn and Mn availability in the soil and this indicates the need for monitoring of the metal concentrations over time. The critical values of Cu in the soil can be reached and exceeded more rapidly than Zn. The results showed that the soil type may be one of the attribute underlying the determination of public policies in pig raising and waste management because soils such as Inceptisols were shown to be more prone to possible contamination since they may more rapidly reach total critical Cu levels.

Highlights

Due to industrialization, mainly in the last 50 years, a large quantity of elements has been dispersed in the environment, especially metals
The pH was determined in water in the proportion 1:1 according to the method proposed by Tedesco et al (1995) and in soil organic matter (SOM) through wet oxidation with potassium dichromate in a sulfuric acid medium (0.07 mol L-1) and determination by titration with ferrous ammonium sulfate 0.1 mol L-1 according to Embrapa (1997)
There are results where there was alteration in soil pH, and one example is the study of L’Herroux et al (1997), who observed an increase in the pH value, ranging from 5.9–7.0, after four years of pig slurry applications at a rate of approximately 1,000 m3 ha-1 year-1

Summary

Introduction

Mainly in the last 50 years, a large quantity of elements has been dispersed in the environment, especially metals. In the southern region of Brazil, in Rio Grande do Sul (RS) and Santa Catarina (SC) states, pig raising is an activity developed on small properties where the manure produced is used as fertilizer on areas of annual grain crops and pasture. Due to the high concentrations of Cu, Zn and Mn in the manure (L’Herroux et al, 1997; Jondreville et al, 2003; Mantovi et al, 2003; Gräber et al, 2005; Girotto, 2007), excessive accumulation of these elements in the soil can be expected over the years Other metals such as Pb, Ni, Cr, and Cd may be found in pig manure since they are present in minerals supplied in commercial feed. The speciation of heavy metals between the solid phase and the soil solution depends on the quantity added, the quantity and type of adsorbent (organic matter, silicate minerals, manganese and iron oxides and phosphate groups) and the geochemical conditions of the solution, especially the concentration of protons and ionic strength (McBride, 1994)

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