Chemical fractionation of boron and heavy metals in soils
irrigated with wastewater in central Mexico
Carlos A. Lucho-Constantino
a
, Francisco Prieto-Garcı
´
a
b
, Luz Marı
´
a Del Razo
c
,
Refugio Rodrı
´
guez-Va
´
zquez
a
,He
´
ctor M. Poggi-Varaldo
a,
*
a
CINVESTAV-IPN, Depto de Biotecnologı
´
a y Bioingenierı
´
a, Apdo. Postal 14-/40, Me
´
xico 07000, D.F., Mexico
b
UAEH-Centro de Investigaciones Quı
´
micas. Carr. Pachuca-Tulancingo km. 4.5, Cd. Universitaria,
CP, 42067 Pachuca, Edo. de Hgo., Mexico
c
CINVESTAV-IPN, Seccio
´
n Externa de Toxicologı
´
a, Me
´
xico, D.F., Mexico
Received 18 May 2004; received in revised form 10 December 2004; accepted 15 December 2004
Abstract
The aim of the present work was to evaluate the accumulation of selected trace elements (boron, cadmium, chromium,
mercury, lead and arsenic) in agricultural soils of the Zone 1 of the Irrigation District 03 (DR03) in the State of Hidalgo, Mexico.
The soils of Zone 1 have, on average, been irrigated with raw wastewater for about 20 years (range 6–41 years). A clear positive
correlation between the organic carbon contents in soils and the irrigation time was found. The total concentrations of the
elements analysed were 0.51–1.89 mg Cd kg
À1
, 11.59–27.42 mg Cr kg
À1
, 3.99–47.08 mg Pb kg
À1
and 9.2–123.8 mg B kg
À1
.
Samples of topsoils (0–30 cm) were extracted using a modified Tessier method according to a six fraction scheme: easily soluble
(F0), exchangeable (F1), bound to carbonates (F2), associated with oxides of iron and manganese (F3), bound to organic matter
and sulphides (F4), and the residual fraction (F5). In general, the elements were distributed in the fractions F0, F4, and F5. The
concentrations of total arsenic and mercury were below the detection limits (0.03 and 0.01 mg kg
À1
, respectively) except for
0.77 mg Hg kg
À1
in one soil. The concentrations of total Cr and Pb did not exceed the maximum permissible levels set by the
regulations of the European Union whereas total Cd was on the verge. A linear increase between the total metal concentrations
and the irrigation time was found. In this study several crops harvested from soils showed Cd and Pb contents higher than those
recommended by the Dutch and German guidelines. It can be concluded that the soils may pose a potential risk to the trophic
chain and effective restrictions for the cultivation of crops that are sensitive to or known to accumulate heavy metals (i.e. nopal,
onions, garlic, lettuce, potatoes, beets, and turnips) should be considered.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Agriculture; Fractionation; Irrigation; Plants; Soil; Trace elements; Wastewater
1. Introduction
Water demand for agricultural, industrial, com-
mercial, and domestic uses is steadily increasing. The
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Agriculture, Ecosystems and Environment 108 (2005) 57–71
* Corresponding author. Tel.: +52 55 5747 3800x4324;
fax: +52 55 5747 7002.
E-mail address: hectorpoggi2001@yahoo.com
(H.M. Poggi-Varaldo).
0167-8809/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.agee.2004.12.013