Crops irrigated with reclaimed wastewater or grown in biosolids-amended soils may take up pharmaceuticals and personal care product ingredients (PPCPs) through their roots. The uptake pathways followed by PPCPs and the propensity for these compounds to bioaccumulate in food crops are still not well understood. In this critical review, we discuss processes expected to influence root uptake of PPCPs, evaluate current literature on uptake of PPCPs, assess models for predicting plant uptake of these compounds, and provide recommendations for future research, highlighting processes warranting study that hold promise for improving mechanistic understanding of plant uptake of PPCPs. We find that many processes that are expected to influence PPCP uptake and accumulation have received little study, particularly rhizosphere interactions, in planta transformations, and physicochemical properties beyond lipophilicity (as measured by Kow). Data gaps and discrepancies in methodology and reporting have so far hindered d...

Root Uptake of Pharmaceuticals and Personal Care Product Ingredients.

Arsenic (As) and cadmium (Cd) are two toxic elements that have a relatively high risk of transfer from paddy soil to rice grain. Rice is a major dietary source of these two elements for populations consuming rice as a staple food. Reducing their accumulation in rice grain is important for food safety and human health. We review recent progress in understanding the biogeochemical processes controlling As and Cd bioavailability in paddy soil, the mechanisms of their uptake, translocation and detoxification in rice plants, and strategies to reduce their accumulation in rice grain. Similarities and differences between the two elements are emphasized. Some knowledge gaps are also identified. The concentrations of As and Cd in rice grain vary by three orders of magnitude, depending on the bioavailability of the two elements in soil, rice genotype and growing conditions. The redox potential in paddy soil has a profound but opposite effect on As and Cd bioavailability, whereas soil pH affects Cd bioavailability more than As bioavailability. A number of key genes involved in As and Cd uptake, translocation, sequestration, and detoxification in rice have been characterized. Allelic variations of several genes underlying the variations in Cd accumulation have been identified, but more remains to be elucidated, especially for As. Two types of strategies can be used to reduce As and Cd accumulation, reducing their bioavailability in soil or their uptake and translocation in rice. Reducing the accumulation of both As and Cd in rice simultaneously remains a great challenge.

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Arsenic and cadmium accumulation in rice and mitigation strategies

Mechanistic understanding and holistic approach of phytoremediation: A review on application and future prospects

Organic contamination and remediation in the agricultural soils of China : a critical review

The ever-increasing requirement for determination of environmental pollutants and studies of comprehensive metabolite networks in complex real-life samples parallel advancements in solid-phase microextraction (SPME). The availability of state-of-the-art analytical instrumentation offering higher sensitivity and specificity has contributed to an increased range of applications covered by SPME.

This review summarizes the most basic aspects in SPME development, addresses some of the challenges encountered in the analysis of food and environmental samples, and particularly emphasizes complex sample analysis. We also outline the development of new extracting materials, novel sampling configurations and approaches compatible with complex sample and/or on-site determinations.

To serve as a guide to potential opportunities for continued innovation in SPME applications, we especially emphasize the evolution of on-site and in vivo SPME techniques and their feasibility for targeted determination of organic pollutants and biologically-active compounds, and global metabolite analysis.

Recent trends in SPME concerning sorbent materials, configurations and in vivo applications

Plants can interact with a variety of organic compounds, and thereby affect the fate and transport of many environmental contaminants. Volatile organic compounds may be volatilized from stems or leaves (direct phytovolatilization) or from soil due to plant root activities (indirect phytovolatilization). Fluxes of contaminants volatilizing from plants are important across scales ranging from local contaminant spills to global fluxes of methane emanating from ecosystems biochemically reducing organic carbon. In this article past studies are reviewed to clearly differentiate between direct- and indirect-phytovolatilization and we discuss the plant physiology driving phytovolatilization in different ecosystems. Current measurement techniques are also described, including common difficulties in experimental design. We also discuss reports of phytovolatilization in the literature, finding that compounds with low octanol-air partitioning coefficients are more likely to be phytovolatilized (log KOA < 5). Reports ...

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Phytovolatilization of Organic Contaminants

Nine-Month Evaluation of Runoff Quality and Quantity from an Experiential Green Roof in Missouri, USA

Silicon-rich amendments in rice paddies: Effects on arsenic uptake and biogeochemistry.

The root–soil boundary represents one of the largest global biotic–abiotic mass-transfer interfaces and is a primary pollutant entry point to the food chain. This interface is also critically important in phytoremediation efforts and herbicide design. Experimental data and single-parameter models have resulted in the current understanding that moderately hydrophobic organic compounds are most likely to be translocated by plants, although recent evidence indicates plants can also translocate some hydrophilic compounds. Molecular descriptors initially applied for drug discovery and for transmembrane migration in mammalian systems were applied here to determine the physicochemical domains and weighted desirability functions to identify compounds amenable to translocation by plants. Considering molecular descriptor cutoffs defined in this work, chemicals likely to be translocated by plants more closely resemble those that can cross the blood–brain barrier as compared to the intestine. Desirability functions w...

Plant Translocation of Organic Compounds: Molecular and Physicochemical Predictors

While root Si transporters play a role in the uptake of arsenite and organic As species dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) in rice ( Oryza sativa L.), the impact of Si addition on the accumulation of DMA and MMA in reproductive tissues has not been directly evaluated, particularly in isolation from inorganic As species. Furthermore, DMA and MMA are suspected causal agents of straighthead disorder. We performed a hydroponic study to disentangle the impact of Si on accumulation of DMA and MMA in rice grain. At 5 μM, MMA was toxic to rice, regardless of Si addition, although Si significantly decreased root MMA concentrations. Plants dosed with 5 μM DMA grew well vegetatively but exhibited straighthead disorder at the lowest Si dose, and this DMA-induced yield loss reversed with increasing solution Si. Increasing Si also significantly decreased DMA concentrations in roots, straw, husk, and grain, particularly in mature plants. Si restricted grain DMA through competition for root uptake and downregulation of root Si transporters particularly at later stages of growth when Si uptake was greatest. Our finding that DMA causes straighthead disorder under low Si availability but not under high Si availability suggests Si as a straighthead management strategy.

Matt A. Limmer

Papers

Phytovolatilization of Organic Contaminants

Nine-Month Evaluation of Runoff Quality and Quantity from an Experiential Green Roof in Missouri, USA

Silicon-rich amendments in rice paddies: Effects on arsenic uptake and biogeochemistry.

Plant Translocation of Organic Compounds: Molecular and Physicochemical Predictors

Silicon Decreases Dimethylarsinic Acid Concentration in Rice Grain and Mitigates Straighthead Disorder