Accumulation of Metals in Soils, Groundwater and Edible Parts of Crops Grown Under Long-Term Irrigation with Sewage Mixed Industrial Effluents

Wastewater irrigation in India: Current status, impacts and response options

Wastewater generated from urban agglomerations in India is estimated to be 26.4 km³ annually and 28% of it is treated. This has a potential to irrigate about 2.1 million-ha agricultural land, contribute 4 million Mg of plant nutrients, generate 2.8 million person-days of employment and reduce green house gas (GHG) emission by 73.7 million Mg CO₂-e. Farmers in peri-urban areas depend largely on raw and partially treated wastewater for livelihood via raising high value crops such as vegetable, fodders and fruits. Both controlled and uncontrolled disposal of waste waters leads to progressive and irreversible contamination of soils, surface and ground waters with pathogens, heavy metals and organic micro-contaminants and consequently their bio-transfer through the chain: sewage-soil-vegetation-animal-humans. This has led to the development of a considerable assortment of regulatory measures and guidelines aimed at reducing or eliminating wastewater related health risks. Because conventional treatment technologies are cost prohibitive, alternate methods based on biological and land treatment systems are being advocated. Since soils are the most logical sinks for wastewater, efforts are to optimise rates and methods of water application, quantify the sink capacity of soils to immobilise contaminants and protect the quality of produce. Reuse of diluted or undiluted wastewaters improves crop productivity by 10-36% though production sustainability depends on soil type, climatic conditions, crop grown, irrigation techniques and socio-political factors. Disposal of wastewater in tree plantations and constructed wetlands with consequent removal of toxic metals/compounds using hyper-accumulators/accumulators plants provide for a possible alternative. Ignoring the associated risks, using pisciculture for sewage disposal is quite popular in high rainfall areas. With growing water scarcities, it is utmost important to recognise wastewaters as a valuable resource and formulate appropriate policy initiatives considering the health and livelihood issues of the per-urban farmers and consumers of food as well as risks to environment.

Effect of Marginal-Quality Irrigation on Accumulation of some Heavy Metals (Mn, Pb, and Zn) in TypicTorripsamment Soils and Food Crops

Lack of active sorption sites in sandy soils renders metals added by irrigation water more labile and increases their soil-to-plant transfer. Thus, this study investigated the long-term impacts of irrigation using sewage effluents and contaminated groundwater on metal accumulations in TypicTorripsamment soils, and edible parts of food crops. Nine sites in El-Gabal El-Asfar farm, south-eastern to the Nile Delta of Egypt, were selected. At each site, irrigation water, soil (0–30 cm), and the crop’s edible part were sampled in triplicates and analyzed for Mn, Pb, and Zn. Results revealed significant (p < 0.05) differences in metal concentrations among water sources. Thus, constant irrigation caused significant spatial variations in total and available metal contents in soils. Total contents of Pb (in four sites) and Zn (in all sites) exceed the lithosphere range, while the available contents of the three metals exceeded the safe limits in all soils. The index of geo-accumulation indicated no Mn pollution but showed elevated pollution risks for Pb and Zn. The three metals showed high availability ratios, proving the effect of light soil texture. The multivariate statistical analysis indicated that Mn and Zn had similar geochemical behaviors in soils. Metal contents in all crop’s edible parts surpassed the safe limits. The bioaccumulation factor (BAF) was less than 1.0 for Mn and Zn but higher than 1.0 for Pb. The highest BAFs occurred in cabbage leaves, indicating the phytoextraction potential of this species. Sufficient water treatment and proper remediation techniques are recommended to alleviate metal accumulation in food crops and their transfer via the food chain.

An Insight into the Abiotic Stress Responses of Cultivated Beets (Beta vulgaris L.)

Cultivated beets (sugar beets, fodder beets, leaf beets, and garden beets) belonging to the species Beta vulgaris L. are important sources for many products such as sugar, bioethanol, animal feed, human nutrition, pulp residue, pectin extract, and molasses. Beta maritima L. (sea beet or wild beet) is a halophytic wild ancestor of all cultivated beets. With a requirement of less water and having shorter growth period than sugarcane, cultivated beets are preferentially spreading from temperate regions to subtropical countries. The beet cultivars display tolerance to several abiotic stresses such as salt, drought, cold, heat, and heavy metals. However, many environmental factors adversely influence growth, yield, and quality of beets. Hence, selection of stress-tolerant beet varieties and knowledge on the response mechanisms of beet cultivars to different abiotic stress factors are most required. The present review discusses morpho-physiological, biochemical, and molecular responses of cultivated beets (B. vulgaris L.) to different abiotic stresses including alkaline, cold, heat, heavy metals, and UV radiation. Additionally, we describe the beet genes reported for their involvement in response to these stress conditions.

Challenges in diagnosing lead poisoning: A review of occupationally and nonoccupationally exposed cases reported in India

Lead is a nonessential metal which enters the body through various means and is considered as one of the most common health toxins. Several cases of lead poisoning are reported as a result of inhalation or ingestion of lead in employees working as painters, smelters, electric accumulator manufacturers, compositors, auto mechanics, and miners. In addition to occupational lead exposure, several cases of lead poisoning are reported in the general population through various sources and pathways. Innumerable signs and symptoms of lead poisoning observed are subtle and depend on the extent and duration of exposure. The objective of this review article is to discuss occupationally and nonoccupationally exposed lead poisoning cases reported in India and the associated symptoms, mode of therapy, and environmental intervention used in managing these cases. Lead poisoning cases cannot be identified at an early stage as the symptoms are very general and mimic that of other disorders, and patients might receive only symptomatic treatment. Knowledge about the various symptoms and potential sources is of utmost importance. Medical practitioners when confronted with patients experiencing signs and symptoms as discussed in this article can speculate the possibility of lead poisoning, which could lead to early diagnosis and its management.

XRF techniques to quantify heavy metals in vegetables at low detection limits

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Calibration routines for quantification of Pb in vegetables with XRF are optimized.

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These XRF methods achieved detection limits of 0.3 μg g⁻¹ for Pb in dry vegetables.

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Pb in raw vegetables is quantified at levels as low as 1 μg g⁻¹ with ED-XRF.

Sample preparation techniques, measurement routines and custom calibrations were developed and optimized for the quantification of Pb and additional heavy metals in dried and wet consumable vegetable tissues via WD-XRF and/or portable ED-XRF spectroscopy. After mitigating matrix influences fundamental to XRF quantification of heavy metals in a carbon matrix, the custom measurement and calibration routines were capable of detecting and quantifying Pb in dried prepared vegetable samples at concentrations relevant to the World Health Organization. The viability of each calibration was evaluated with measurements of vegetables grown in metals-rich garden soil collected from residential properties. Although robust calibrations for dried vegetables were obtained with WD-XRF, the slight compromise in the precision and accuracy of measurements with portable ED-XRF is offset by the portability of this technology. Heavy metal concentrations in wet coarsely-homogenized raw consumable vegetable tissues were quantified; however, further work is needed to test the viability of ED-XRF calibrations.

Trace Metal(oid) Accumulation in Edible Crops and Poplar Cuttings Grown on Dredged Sediment Enriched Soil

The development of a biomonitor in the context of multiple-element contamination in urban environments was tested by comparing element transfer in edible crops and poplar ( Torr. × A. Henry cutlivar 'Skado'). A multielemental analysis was performed with various common edible crops (cucumber [ L.], pepper [ L.], cabbage [ L.], and lettuce [ L.]) and the Skado poplar cultivar grown on soils that received sediments dredged from water canals in the 1960s. Sediments were distributed unevenly on the soil, allowing us to sample two types of areas that were either weakly (Area 1) or highly (Area 2) contaminated, mainly by Cd, Pb, and Zn. We registered an accumulation of Cd and Zn in the edible parts of crops, with higher values recorded for leafy vegetables than for fruit vegetables. We did not detect any accumulation of Pb in the plant species studied. We calculated the fresh mass that must be consumed daily to reach tolerable daily intake (TDI) recommendations for each element and found evidence that Cd could be ingested in sufficient amounts to reach the TDI in this context. Poplar and pepper leaves accumulated more Cd and Zn than the edible parts of the study crops grown on both substrates, which suggests that poplar and pepper may be suitable species for biomonitoring element transfer to vegetation in this context.

Effect of Sewage Irrigation on the CT-Measured Soil Pore Characteristics of a Clay Farmland in Northern China

Sewage irrigation has a strong influence on the physical, chemical, and biological properties of soil. However, the effects of sewage irrigation on the pore characteristics of soil are not well understood. This study compares the effects of sewage irrigation and groundwater irrigation on computed tomography (CT)-measured pore parameters and examines the relationships between CT-measured pore parameters and soil physicochemical and microbial properties. Intact soil cores were collected from S1 irrigated with sewage for 25 years, S2 irrigated with sewage for 52 years, and CK irrigated with groundwater. Various soil pore characteristics were determined, including the total pore number, macropore number (>1 mm diam.), coarse mesopore number (0.264⁻1 mm diam.), total porosity, macroporosity, coarse mesoporosity, and circularity. The results indicated that sewage irrigation significantly affected soil pore number and porosity. Compared with S1 and S2, CK exhibited a higher average total pore number (91), macropore number (40), coarse mesopore number (51), total porosity (2.08%), macroporosity (1.90%), and coarse mesoporosity (0.18%) throughout the 50⁻350 mm layer. At depths of 200⁻350 mm, S2 exhibited the lowest average total pore number (33), macropore number (13), coarse mesopore number (21), total porosity (0.42%), macroporosity (0.35%), and coarse mesoporosity (0.07%) among the three sites. In addition, the average pore numbers and porosity at depths of 200⁻350 mm decreased with increasing sewage irrigation time. There were significant positive correlations between pore features (including pore numbers and porosity) and soil properties (phosphorus content and fungi numbers). Our results suggest that decreased macropore numbers and macroporosity in the sewage-irrigated farmland may strongly intensify the accumulation of metals and nutrients in the upper layer. The findings of this study are useful for understanding the negative effects of sewage irrigation on soil pore structure and are critical for developing sustainable strategies in agriculture.

Dimercapto-1-propanesulfonic acid (DMPS) induces metaphase II mouse oocyte deterioration

In light of the recent lead contamination of the water in Flint, Michigan and its potential adverse outcomes, much research and media attention has turned towards the safety profile of commonly used chelators. Dimercapto-1-propanesulfonic acid (DMPS) typically used in the treatment of lead, mercury and arsenic poisoning also displays a high affinity towards transition metals such as zinc and copper, essential for biological functioning. It is given in series of dosages (0.2-0.4g/day) over a long period, and has the ability to enter cells. In this work, we investigated the mechanism through which increasing concentrations of DMPS alter oocyte quality as judged by changes in microtubule morphology (MT) and chromosomal alignment (CH) of metaphase II mice oocyte. The oocytes were directly exposed to increasing concentration of DMPS (10, 25, 50, 100 and 300μM) for four hours (time of peak plasma concentration after administration) and reactive oxygen species (mainly hydroxyl radical and superoxide) and zinc content were measured. This data showed DMPS plays an important role in deterioration of oocyte quality through a mechanism involving zinc deficiency and enhancement of reactive oxygen species a major contributor to oocyte damage. Our current work, for the first time, demonstrates the possibility of DMPS to negatively impact fertility. This finding can not only help in counseling reproductive age patients undergoing such treatment but also in the development of potential therapies to alleviate oxidative damage and preserve fertility in people receiving heavy metal chelators.

Rationale for the Successful Management of EDTA Chelation Therapy in Human Burden by Toxic Metals

Exposure to environmental and occupational toxicants is responsible for adverse effects on human health. Chelation therapy is the only procedure able to remove toxic metals from human organs and tissue, aiming to treat damage related to acute and/or chronic intoxication. The present review focuses on the most recent evidence of the successful use of the chelating agent ethylenediaminetetraacetic acid (EDTA). Assessment of toxic-metal presence in humans, as well as the rationale of EDTA therapy in cardiovascular and neurodegenerative diseases, is reported.