Abstract
By investigating the uptake of 16 priority polycyclic aromatic hydrocarbons (PAHs) and five heavy metals from soils to maize at the farmlands with industrial wastewater irrigation, this study revealed the effects of heavy metals on PAHs uptake in terms of co-contamination. The results of 15 investigated soils showed medium contamination level and the vertical PAHs distribution in soils indicated that 2–3 rings PAHs with low octanol-water partition coefficient (log Kow < 4.5) were easier to transport in soils, causing a great potential risk immigrating to the groundwater. The 3-ring PAHs were most likely to be taken up by maize roots whereas 2- and 4–6 ring PAHs had the lower likelihood. The translocation of PAHs in maize tissues has positive relationship with log Kow less than 4.5, while negatively correlated otherwise. Redundancy analysis indicated the unexpected results that, except for soil PAHs concentration, the PAHs translocation by maize was reduced by Pb uptake, but not significantly affected by soil organic matters, pH or the other four heavy metals (Cr, Cu, Ni and Zn). This study for the first time provides the restricted factors of PAHs and heavy metal acropetal translocation by maize when they co-exist at wastewater irrigation sites.
Highlights
Given the fact of freshwater shortages and economic demands, untreated or partially treated wastewater reuse is widely practiced for agricultural land irrigation, in arid areas at a global scale[1,2]
The present study evaluates the co-occurrence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in soils irrigated with wastewater in Inner Mongolia and studied their uptake and translocation by maize
We find that PAHs and heavy metals in surface soils showed moderately contamination, and their accumulation in maize grain posed health risks
Summary
Given the fact of freshwater shortages and economic demands, untreated or partially treated wastewater reuse is widely practiced for agricultural land irrigation, in arid areas at a global scale[1,2]. Many previous studies have addressed the sources, accumulation and transfer of PAHs or heavy metals in wastewater-irrigated soils[3,5,6,7], but not characterizing the bioaccumulation in case of their co-existence and whether it can affect their distribution in food chain. As food chain is the most important pathways for pollutants entry and counts for 90% ingestion of contaminants into human body[12], the uptake of carcinogenic PAHs and heavy metals through soil-to-root system and their translocation/accumulation in plant tissues has attracted many attentions, for food crops cultivated on the wastewater-irrigated soils. It is of great importance to investigate the impacts of PAHs-metal co-existence on their uptake and acropetal translocation
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