Bo-Ching Chen

Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha⁻¹) is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha⁻¹) have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate.

The accumulation of heavy metals, especially cadmium (Cd), in leafy vegetables was compared with other vegetables. Pak choi (Brassica campestris L. ssp. chinensis) is a leafy vegetable consumed in Taiwan and its safety for consumption after growing in contaminated soils is a public concern. A pot experiment (50 days) was conducted to understand the dynamic accumulation of Cd by pak choi grown in artificially contaminated soils. The edible parts of pak choi were sampled and analyzed every 2–3 days. The dry weight (DW) of pak choi was an exponential function of leaf length, leaf width, and chlorophyll content. The accumulation of Cd increased when the soil Cd concentration was raised, but was kept at a constant level during different growth stages. Pak choi had a high bioconcentration factor (BCF = ratio of the concentration in the edible parts to that in the soils), at values of 3.5–4.0. The consumption of pak choi grown in soils contaminated at levels used in this study would result in the ingestion of impermissible amounts of Cd and could possibly have harmful effects on health.

Purpose Although the ecotoxicological effects of copper (Cu) on grapevine are of global concern due to the intensive and long-term application of Cu-based fungicides in vineyards, comparatively little is known about the phytotoxicity, accumulation, and translocation of Cu in grapevines. Therefore, this study was to conduct a hydroponic experiment to determine the influence of solution Cu concentration not only on bioaccumulation and the translocation of Cu in grapevine roots, stems, and leaves, but also on the subsequent growth inhibition of the roots. Methods Grapevine cuttings were grown for 30 days and then exposed to various Cu concentrations (0.1–50 μM) for 15 days. The dose–response profile was described by a sigmoid Hill equation. Optical microscopy was used to examine the cytotoxicity of Cu on the roots. In addition, bioaccumulation factors (BAFs) and translocation factors (TFs) were calculated from the results of the hydroponic experiment. Results Copper was tolerated by grapevines at a concentration ≤1 μM. The median inhibition concentration (IC₅₀) obtained from the Hill model was 3.94 μM (95% confidence interval, 3.65–4.24). From the light micrographs of root tip cells, signs of toxicity including increased vacuolization and plasmolysis were observed at solution Cu concentrations ≥10 μM. In addition, a higher Cu concentration was found in the roots (25–12,000 mg kg⁻¹) than in the stems (5–540 mg kg⁻¹) and leaves (7–46 mg kg⁻¹), indicating a very limited translocation of Cu from the roots to the aboveground parts. Conclusions This study investigated not only the macroscopic root growth and Cu accumulation by grapevine, but also the microscopic changes in root tissue at the cell level after the exposure experiment. Based on the BAFs and TFs, the grapevine could be considered a Cu-exclusive plant. For toxic effects on the exposure of roots to Cu, this study also revealed that root growth, as well as the histological changes in rhizodermal cells, can be used as phytotoxic indicators of grapevine under Cu stress.

A major challenge in phytoextraction is to increase plants’ removal rates of metals from contaminated soils. In this study, we developed a phytoextraction model, by coupling a saturable Michaelis–Menten type accumulation model and an energy-based toxicity model, to predict copper (Cu) removal by switchgrass (Panicum virgatum L.) grown hydroponically under various exposure concentrations. Results of the present study indicated that the phytotoxicity of Cu to switchgrass is relatively low, whereas a certain accumulation capacity exists in the plant for Cu. In addition, the simulation results suggested that, under a lower dissolved concentration, Cu removal is increased more efficiently as the exposure duration increases. Although it is difficult to extrapolate the results from greenhouse-based hydroponic experiments to field conditions, we believe that the current methodology can offer a first approximation in predicting the phytoextraction duration needed for plant species to remove a specific metal from contaminated sites, which is crucial in evaluating the economic costs for remediation purposes.

Risk-based assessment is a way to evaluate the potential hazards of contaminated sites and is based on considering linkages between pollution sources, pathways, and receptors. These linkages can be broken by source reduction, pathway management, and modifying exposure of the receptors. In Taiwan, the Soil and Groundwater Pollution Remediation Act (SGWPR Act) uses one target regulation to evaluate the contamination status of soil and groundwater pollution. More than 600 sites contaminated with heavy metals (HMs) have been remediated and the costs of this process are always high. Besides using soil remediation techniques to remove contaminants from these sites, the selection of possible remediation methods to obtain rapid risk reduction is permissible and of increasing interest. This paper discusses previous soil remediation techniques applied to different sites in Taiwan and also clarified the differences of risk assessment before and after soil remediation obtained by applying different risk assessment models. This paper also includes many case studies on: (1) food safety risk assessment for brown rice growing in a HMs-contaminated site; (2) a tiered approach to health risk assessment for a contaminated site; (3) risk assessment for phytoremediation techniques applied in HMs-contaminated sites; and (4) soil remediation cost analysis for contaminated sites in Taiwan.