Cd, Cr and Ni in drainage water from agricultural soils. Case study of South Alicante.

Mediterranean coastal areas have been cultivated for long time. Wetlands areas situated near to the coast have been drainaged by using drainage channels. Heavy metals can be transferred from soils to the channels under agricultural management practices, especially under flood and furrow irrigation (the most important in the area studied). Anthropogenic inputs, including excessive use of agrochemicals and manure, in agricultural soils contribute to an increase of the content of some toxic heavy metals [1].

The agricultural area situated in the South of the province of Alicante has an important drainage system (avoiding to be a coastal wetland), which more than a thousand kilometers that allow the cultivation on calcareous soils (mainly Fluvisols). However, land uses have been changing and an important transformation of rural areas to residential areas have been occurred in the recent decades.

Under this situation, the presence of Cd, Cr and Ni in drainaged waters derived from infiltration from agricultural soils, and runoff from some urban areas, have been checked in the main drainage system (13 drainage channels) in order to detect possible influences of soil management in metal pollution. Water samples were taking along the channels in three to ten points of each channel, depending on the length, and metals were analyzed following standard methods [2]. At the same time, the land cover has been analyzed by using the last data from National Aerial Orthophotography Plan (available from the National Center of Geographical Information, Spain).

The most important result obtained was that the presence of Cd in the waters was under the limit of detection of 0.1 μg/L. This result reflected the absence of pollution sources of this metal from soils to these drainage channels.

Moreover, in the case of Cr, the values obtained were even below the reference values ​​for drinking water [3]. However, the major concentrations of this metal were between 6 to μg/L in only 4 channels. Ni, whose concentrations were lower than those for Cr, has values under 7 μg/L. Heavy metal pollution, at least in the elements analyzed, does not seem to be a serious problem in terms of the quality of these waters.

Although many land cover changes have occurred, most of the soils are dedicated to agriculture. On the other hand, no clear effects related to the proximity of urban areas to the drainage channels have been observed.

 

Keywords

Heavy metals; irrigation; land cover changes, pollution, wetlands.

 

References

[1] Navarro-Pedreño, J.; Almendro-Candel, M.B.; Gómez, I.; Jordan, MM; Bech, J.; Zorpas, A.A. (2018). Trace metal content and availability of essential metals in agricultural soils of Alicante (Spain). Sustainability 10, 4534.

 [2] APHA, AWWA, WEF (2012). Standard Methods for the examination of water and wastewater. Ed. American Public Health Association, Washington.

[3] Real Decreto 314/2016, de 29 de julio, por el que se modifican el Real Decreto 140/2003, de 7 de febrero, por el que se establecen los criterios sanitarios de la calidad del agua de consumo humano.