Preprint Article Version 1 This version is not peer-reviewed

Experimental Analysis of Heavy Metal Uptake in Soil and Citrus Plants from Irrigation Water

Version 1 : Received: 4 April 2018 / Approved: 9 April 2018 / Online: 9 April 2018 (07:48:31 CEST)

A peer-reviewed article of this Preprint also exists.

Zhang, A.; Cortes, V.; Phelps, B.; van Ryswyk, H.; Srebotnjak, T. Experimental Analysis of Soil and Mandarin Orange Plants Treated with Heavy Metals Found in Oilfield-Produced Wastewater. Sustainability 2018, 10, 1493. Zhang, A.; Cortes, V.; Phelps, B.; van Ryswyk, H.; Srebotnjak, T. Experimental Analysis of Soil and Mandarin Orange Plants Treated with Heavy Metals Found in Oilfield-Produced Wastewater. Sustainability 2018, 10, 1493.

Journal reference: Sustainability 2018, 10, 1493
DOI: 10.3390/su10051493

Abstract

Oilfield produced water (OPW) is used to boost freshwater sources for crop irrigation in California's agriculturally important Central Valley. OPW is known to contain salts, metals, hydrocarbons, alkylphenols, naturally radioactive materials, biocides, and other compounds from drilling and production processes. Less is known about the potential uptake and accumulation of these compounds in crops and soil irrigated with OPW. In this study 23 potted mandarin orange plants were irrigated 2-3 times weekly (depending on season) with water containing three different concentrations of the known OPW heavy metals barium, chromium, lead, and silver. Seven sets of samples of soil and leaves and all fruits were collected and processed using microwave-assisted digestion (EPA Method 3051A). Processed samples were analyzed using ICP-OES. ANOVA, ANCOVA, and Tukey’s honest significant difference test were used to examine the effects of metal concentrations in the irrigation water, sample number, and number of watering days on the metal concentrations in the soil, leaf, and fruit samples. Accumulation of barium in soil and leaves was strongly positively associated with sample and number of watering days, increasing nearly 2,000-fold. Lead also showed an upward trend, increasing up to 560-fold over baseline level. Chromium showed an increase in the soil that tapered off, but less consistent results in the leaves and fruit. The silver results were more volatile, but also indicated at least some level of accumulation in the tested media. The smallest absolute accumulation was observed for chromium. Concentrations in the fruit were highest in the peel, followed by pith and juice. Accumulation of all heavy metals was generally highest in the soil and plants that received the highest irrigation water concentration. Considering the potential for adverse human health effects associated with ingesting soluble barium contained in food and drinking water, and to a lesser extent chromium and lead, the study signals that it is important to conduct further research into whether OPW contaminants can enter the food chain and pose risks to consumers.

Subject Areas

oilfield produced water; wastewater; heavy metals; irrigation; bioaccumulation; soil health; California

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