Detection of Ni, Cd, and Cu in green leafy vegetables collected from different cultivation areas in and around Colombo District, Sri Lanka

Applying Monte Carlo simulation to assess health risks of potentially toxic elements in fruits and nuts grown in the capital of Iran

This study investigated harmful elements (PHEs) in three fruits (figs, oranges, persimmons) and two nuts (walnuts, hazelnuts) grown in Tehran, Iran, using inductively coupled plasma mass spectrometry (ICP-MS) to evaluate health risks. The results showed that chromium (Cr) exceeded the 0.1 mg/kg standard in walnuts (mean = 6.15 mg/kg) and figs (mean = 5.23 mg/kg). Copper (Cu) surpassed 2 mg/kg in all produce except figs. Arsenic (As) exceeded the standard in walnuts, persimmons, and oranges, while cadmium (Cd) surpassed the limit only in persimmons. Iron (Fe) levels were significantly high, peaking in persimmons (mean = 71.79 mg/kg). Lead (Pb), manganese (Mn), and mercury (Hg) exceeded safety limits in all samples, while barium (Ba) was the most abundant metal, especially in hazelnuts and oranges. The correlation and clustering analysis indicated that the sources of PHEs may be influenced by a combination of agricultural practices, atmospheric transport, traffic emissions, historical pollution, and natural background levels. Monte Carlo simulation results show Pb poses the highest non-carcinogenic risk for children (TTHQ50th: 12.56) and adults (TTHQ50th: 5.62). Ni presents the highest carcinogenic risk (TCR50th: 1.58E-03 for children, 3.50E-03 for adults. Hence, urgent monitoring of PHEs in local produce is essential.

Soil cadmium pollution facilitated the invasion of alligator weed through enhanced herbivore resistance and competitive ability over a congeneric species

A number of invasive plant species, such as Alternanthera philoxeroides, have been documented to be able to accumulate trace metal elements in their tissues. Since metal accumulation in plants can serve as a defence against herbivores, we hypothesized that metal pollution will increase herbivore resistance of metal-accumulating invasive plant species and such a benefit will grant them a competitive advantage over local co-occurring plants. In this study, we compared the differences in plant growth and herbivore feeding preference between A. philoxeroides and its native congener Alternanthera sessilis in single and mixed cultures with and without soil cadmium (Cd) pollution. The results showed that A. philoxeroides plants were more tolerant to Cd stress and accumulated more Cd in the leaves than A. sessilis. Cd exposure increased the resistance of A. philoxeroides against a specialist and a generalist herbivore compared with A. sessilis. Competition experiments indicated that Cd stress largely increased the competitive advantage of A. philoxeroides over A. sessilis with or without herbivore pressures. The differences in herbivore resistance between the two plant species under soil Cd stress are most likely due to the deterring effect of Cd accumulation and Cd-enhanced mechanical defences rather than changes in leaf specialized metabolites.

Biomonitoring of heavy metals in the feathers of House crow (Corvus splendens) from some metropolitans of Asia and Africa

Urban-dwelling birds can be useful biomonitors to assess the impact of the urbanisation on both public and wildlife health. Widely distributed urban bird species, the House crow, was studied for heavy metal accumulation levels from nine cities of South Asia, Southeast Asia and Africa that border the Indian Ocean. Feathers were spectroscopically investigated for the deposition of ten heavy metals, i.e. As, Zn, Pb, Cd, Ni, iron Fe, Mn, Cr, Cu and Li. Fe and Zn were found to be the most prevalent metals in all sites. Measured concentrations of Pb (4.38-14.77 mg kg^-1) overall, and Fe (935.66 mg kg^-1) and Cu (67.17 mg kg^-1) at some studied sites were above the toxicity levels reported lethal in avian toxicological studies. Multivariate analysis and linear models supported geographical location as a significant predictor for the level of most of the metals. Zn and Cu, generally and Pb, Cd, Mn, Cr at some sites exhibited potential bioaccumulation from surrounding environments. Inter-species comparisons strengthen the inference that the House crow is a reliable bioindicator species for the qualitative assessment of local urban environmental pollution and could be a useful tool for inter-regional monitoring programs.

Long period exposure to serious cadmium pollution benefits an invasive plant (Alternanthera philoxeroides) competing with its native congener (Alternanthera sessilis)

Many aggressive plants possess high tolerance to heavy metals, but little is known about their invasiveness at heavy metal polluted sites. We performed a greenhouse experiment to examine the impacts of Cd (0, 10, 30, 60, and 100 mg kg^-1) and inter-specific competition on the reproductive capability of an invasive plant, Alternanthera philoxeroides, and its native congener, Alternanthera sessilis. We also examined the population dynamics of both native and invasive species in a simulated field experiment. Compared with A. philoxeroides, native A. sessilis was a stronger competitor as measured by vegetative growth, sexual reproduction, and dominance status in a mixed culture. However, A. philoxeroides showed great plasticity in root mass ratio that was positively affected by inter-specific competition and high Cd levels. Such high root allocation might allow for delayed growth of A. philoxeroides rhizomes as the relative cover of A. philoxeroides to A. sessilis in the field experiment gradually increased and > 1 after nine months culture, especially at high Cd treatment. Our results suggest that the invasiveness of A. philoxeroides is highly context- and time-dependent. In severely polluted environments, clonal propagation of A. sessilis is likely inhibited by the synergistic negative effects of inter-specific competition and heavy metal pollution, and a long time co-existence of these two competing species would facilitate the colonization of invasive plant.

Copper Toxicity and Prediction Models of Copper Content in Leafy Vegetables

Copper (Cu), a toxic metal pollution found in the soil and water of industrialized areas, causes continuous issues for agriculture product contamination and human health hazards. However, information on copper phytotoxicity and its accumulation in vegetables is largely unknown. To evaluate the related agricultural loss and health risks, it is necessary to assess copper phytotoxicity and develop prediction models for copper concentration in vegetables. Here, we assess the growth performance and copper concentration of four leafy vegetables: Water spinach, amaranth, pakchoi, and garland chrysanthemum in copper-contaminated soil. The plant’s height and fresh weight is dramatically reduced when the soil copper concentration is over ~250 mg·kg−1. This yield reduction and copper accumulation are associated with an increase of soil copper concentration, suggesting high copper phytotoxicity levels in plants and soil. The prediction models of plant copper concentration were developed using multiple regressions based on one-step extractions of the soil copper as independent variables. One prediction model derived for amaranth copper using hydrochloric acid (HCl)-extractable and ethylenediaminetetraacetic acid (EDTA)-extractable copper from soil is able to describe 78.89% of the variance in the measured copper. As a result, the phytotoxic copper level for four leafy vegetables is revealed. Although the prediction models may not be universal, the predicted and phytotoxic copper levels are useful tools for evaluating vegetable yield and daily copper intake.

Potentially Harmful Element Concentrations in the Vegetables Cultivated on Arable Soils, with Human Health-Risk Implications

Potentially harmful elements (PHEs) were investigated in eight groups of vegetables cultivated in southern Poland and the relevant health-risk implications were assessed. The PHE contents belonged to the following ranges (mg/kg wet weight) in edible parts: As < limit of detection (LOD)-0.056, Cd < LOD-0.375, Co < LOD-0.029, Cu < LOD-7.638, Hg < LOD-0.163, Ni < LOD-0.299, Pb < LOD-0.580, Sb < LOD-0.163, Tl < LOD-0.128, and Zn 1.23-34.9. The PHE concentrations decreased in the following order: Zn > Cu > Ni > Cd > Pb > Sb > Hg > Tl > As > Co. The concentrations of essential PHEs decreased as follows: root > leaf > seed > tuber > legume > inflorescence > shoot > fruit, while the unnecessary PHEs followed this sequence: leaf > root > tuber > legume > inflorescence > seed > shoot > fruit. Soil-to-plant transfer factors revealed capacities to adsorb Cd, Hg, and Tl in roots; Cd, Hg, Tl, and Zn in leaves; Cd, Hg, and Sb in tubers; and Cu, Sb, and Zn in legumes and seeds. The daily intake rates, as a percentage of permissible maximum tolerable daily intake, amounted to the following proportions: Cd 23%, Tl 13%, Hg 5.0%, Ni 3.1%, Pb 2.6%, and As 0.4%. Non-carcinogenic risk described as hazard quotient (HQ) was exceeded in root (HQ = 12.1), leafy (HQ = 2.1), and tuber (HQ = 1.4) vegetables. The carcinogenic risk of As (CR = 8.54 × 10-5) was found unacceptable. The margins of exposure for adults (MOE = 3.1) and children (MOE = 1.6), respectively, indicated a low health risk of Pb in consumed vegetables.

Potential of joyweed Alternanthera sessilis for rapid treatment of domestic sewage in SHEFROL® bioreactor

In a first-ever report on this subject, it is shown that a common amphibious plant joyweed (Alternanthera sessilis) can be used in rapid and efficient treatment of biodegradable wastewaters, typified by domestic sewage. The plant was effective when used indoors under artificial lighting, as well as outdoors. It enabled treatment of sewage, varying widely in strength (from 300 mg/L to 1800 mg/L in chemical oxygen demand), to the extent of 78.9-83.9%. It was also able to remove biological oxygen demand, suspended solids, phosphorous, nitrogen, and the heavy metal copper to the extent of 87%, 93%, 45%, and 43%, respectively. Over 99% of total coliforms, faecal coliforms, and faecal streptococci were also removed. The treatment was very swiftly achieved, at a hydraulic retention time of just 6 h, in the "sheet flow root level" (SHEFROL^®) bioreactor developed earlier by us and of which a patent claim has been registered. The findings indicate that A. sessilis has the potential to affect primary, secondary, and tertiary treatment of domestic sewage along with significant pathogen removal in a single process step when used in SHEFROL^® bioreactors.