Determination of heavy metals and their availability to plants in soil fertilized with different waste substances

Occurrence, Source and Dietary Exposure of Toxic and Essential Elements in the Indian Food Basket

In this study, representative urban and peri-urban Indian food baskets have been studied for the presence of toxic and essential elements. The concentration of target toxic and essential elements was used to estimate dietary intakes (EDIs) and health risks. Across all food matrices, toxic elements like Cd and Pb were dominant. The highest concentrations of the target elements were found in vegetables, with Cd, Pb, and Ni being beyond permissible limits of the Food and Agriculture Organization of the United Nations and the World Health organization (0.05 mg/kg, 0.1 mg/kg, and 1.5 mg/kg, respectively) in okra, spinach, and cauliflower. The sum of concentrations of the toxic elements (As, Ni, Hg, Cr, Cd, Pb) in vegetables had a range of 0.54-12.08 mg/kg, the highest sum was found in spinach (median 12.08 mg/kg), followed by okra (median 1.68 mg/kg). The EDI was observed for vegetables with a contribution as high as 92% for Cd. Dairy products were found with the highest loading for Ni with a dietary intake of 3.1 mg/kg/day for adults and twice as much for children. Carcinogenic risk for Ni was the highest and found above the threshold for all food categories, as was the case with As. Cumulative carcinogenic and non-carcinogenic risks were mostly contributed by milk and vegetables, in particular, spinach.

Stabilization of metals in sludge-amended soil using red mud and its effects on yield and oil quality of Brassica juncea cultivar Kranti

Prolonged application of sewage-sludge may cause excessive accumulation of metal(oid)s in soil, leading to phytotoxic effects. Spread of contaminants in soil can probably be hindered by using an effective metal(oid) stabilizer. Pot experiment in open field conditions was conducted for five months to evaluate the metal(oid) (Al, Cu, Zn, Cd and Cr) stabilization potential of red mud (RM) in sludge-amended soil and its effects on growth, yield, oil quality parameters and metal(oid) accumulations in Brassica juncea cultivar Kranti. The test plant was grown at different RM concentrations (0, 5, 10 and 15% w/w) in sludge-amended soil (soil/sludge: 2:1 w/w). As the total and phytoavailable metal(oid) concentrations in sludge were high, its application increased their concentrations in soil compared to the control (no RM and sludge). Increasing RM concentrations in sludge-amended soil effectively stabilized Cd followed by Cr, Cu, Zn and Al, leading to their reduced contents in plants coupled with enhanced growth performance and yield. Maximum plant (root and shoot) biomass (14.9%) and seed yield (40.4%) were found in 10% RM treatment, whereas oil content showed substantial increase with increasing RM treatments in sludge-amended soil. Mustard oil showed low rancidification, high long-chain fatty acids, saturated and polyunsaturated (ω-3 and ω-6) fatty acids within FAO ranges for edible oils under varying RM treatments compared to sludge-amended soil. Furthermore, high oleic and low erucic acid contents in mustard oil indicated a better oil quality under different RM treatments. Metal(oid) contents in seeds under different red mud treatments were within FAO/WHO limits for consumption. Thus, RM applications preferably 5 and 10% (w/w) in sludge-amended soil might be effective in stabilization of metal(oid)s using B. juncea cultivar Kranti coupled with better yield, improved oil quality and metal(oid)s within limits for human consumption.

Effects of Cu and Zn contamination on chicken manure-based bioponics: Nitrogen recovery, bioaccumulation, microbial community, and health risk assessment

In bioponics, although chicken manure is an efficient substrate for vegetable production and nitrogen recovery, it is often contaminated with high Cu and Zn levels, which could potentially cause bioaccumulation in plants and pose health risks. The objectives of this study were to assess nitrogen recovery in lettuce- and pak choi-based bioponics with Cu (50-150 mg/kg) and Zn (200-600 mg/kg) supplementation, as well as their bioaccumulation in plants, root microbial community, and health risk assessment. The supplementation of Cu and Zn did not affect nitrogen concentrations and plant growth (p > 0.05) but reduced nitrogen use efficiency. Pak choi showed higher Cu and Zn bioconcentration factors than lettuce. Bacterial genera Ruminiclostridium and WD2101_soil_group in lettuce roots and Mesorhizobium in pak choi roots from Cu and Zn supplemented conditions were significantly higher (p < 0.05) than controls, suggesting microbial biomarkers in plant roots from Cu and Zn exposure bioponics depended on plant type. Health risk assessment herein revealed that consumption of bioponic vegetables with Cu and Zn contamination does not pose long-term health risks (hazard index <1) to children or adults, according to the US EPA. This study suggested that vegetable produced from chicken manure-based bioponics has low health risk in terms of Cu and Zn bioaccumulation and could be applied in commercial-scale system for nutrient recovery from organic waste to vegetable production; however, health risk from other heavy metals and xenobiotic compounds must be addressed.

Formulation and evaluation of organo-mineral fertilizers based on sewage sludge optimized for maize and sunflower crops

The depletion of natural resources, energy consumption and environmental issues relating to fertilizer production processes are driving a move towards a more sustainable use of resources and the recycling of nutrients. With regard to the fertilizer industry, this gives the opportunity to use the fertilizing potential of alternative raw materials. This paper evaluates the possibility of using dried sewage sludge in the manufacture of organo-mineral fertilizers. Fertilizers based on sewage sludge with an addition of poultry litter ash and mineral fertilizers were developed and characterized in the study. It was possible to produce multicomponent organo-mineral fertilizers with optimized compositions for maize and sunflower crops, characterized by total nutrient content over 20%. Moreover, they contained beneficial secondary nutrients and micronutrients originated from waste materials. The fertilizers were free of pathogens and fulfilled the requirements related to heavy metal content according to Polish legislation. The method of manufacturing organo-mineral fertilizers based on waste materials is a simple waste management solution offering organic matter and nutrient recycling in line with the circular economy and reducing reliance on imported raw materials.

Availability of Trace Elements in Soil with Simulated Cadmium, Lead and Zinc Pollution

The research was based on a pot experiment in which the impact of increasing Cd, Zn and Pb doses on the content of available trace elements in soil was compared. Seven series of trials were designed: 1 (Cd), 2 (Pb), 3 (Zn), 4 (Cd + Pb), 5 (Cd + Zn), 6 (Pb + Zn), 7 (Cd + Pb + Zn). Aside from the control one (without the metals), three increasing levels of contamination were considered within each series. Mobile forms of trace elements (Cd, Pb, Zn, Fe, Mn, Cu, Ni, Co, and Cr) in soil were determined, in addition to which selected physicochemical soil properties—reaction (pH), salinity (EC), hydrolytic acidity (HAC), total exchange bases (TEB)—were identified while cation exchange capacity (CEC), base saturation (BS) and availability factor (AF) were calculated. The application of Cd and Pb to soil resulted in an increase in the share of potentially available forms of these metals in their total content. The availability factor (AF) in the pots polluted with these metals was higher than in the control, in the range 17.5–20.0% for Cd, and 62.8–71.5% for Pb. In turn, the share of Zn mobile forms was comparable in most experimental objects, oscillating around 30%. Moreover, addition to soil of Cd, Pb and Zn usually caused a significant decrease in the content of available forms of Fe, Mn and Cu, and resulted in significantly higher content of available forms of Cr in the soil.

Sustainable utilization of biowaste compost for renewable energy and soil amendments

Acceleration of urbanization and industrialization has resulted in the drastic rise of waste generation with majority of them being biowaste. This constitutes a global challenge since conventional waste management methods (i.e., landfills) present environmental issues including greenhouse gases emissions, leachate formation and toxins release. A sustainable and effective approach to treat biowaste is through composting. Various aspects of composting such as compost quality, composting systems and compost pelletization are summarized in this paper. Common application of compost as fertilizer or soil amendment is presented with focus on the low adoption level of organic waste compost in reality. Rarely known, compost which is easily combustible can be utilized to generate electricity. With the analysis on critical approaches, this review aims to provide a comprehensive study on energy content of compost pellets, which has never been reviewed before. Environmental impacts and future prospects are also highlighted to provide further insights on application of this technology to close the loop of circular bioeconomy.

Foliar Application of Low Concentrations of Titanium Dioxide and Zinc Oxide Nanoparticles to the Common Sunflower under Field Conditions

Nano-fertilisers have only recently been introduced to intensify plant production, and there still remains inadequate scientific knowledge on their plant-related effects. This paper therefore compares the effects of two nano-fertilisers on common sunflower production under field conditions. The benefits arising from the foliar application of micronutrient-based zinc oxide fertiliser were compared with those from the titanium dioxide plant-growth enhancer. Both the zinc oxide (ZnO) and titanium dioxide (TiO₂) were delivered by foliar application in nano-size at a concentration of 2.6 mg·L⁻¹. The foliar-applied nanoparticles (NPs) had good crystallinity and a mean size distribution under 30 nm. There were significant differences between these two experimental treatments in the leaf surfaces’ trichomes diversity, ratio, width, and length at the flower-bud development stage. Somewhat surprisingly, our results established that the ZnO-NPs treatment induced generally better sunflower physiological responses, while the TiO₂-NPs primarily affected quantitative and nutritional parameters such as oil content and changed sunflower physiology to early maturation. There were no differences detected in titanium or zinc translocation or accumulation in the fully ripe sunflower seeds compared to the experimental controls, and our positive results therefore encourage further nano-fertiliser research.

The contribution of water extractable forms of plant nutrients to evaluate MSW compost maturity: a case study

The object of the experiment was to evaluate municipal solid waste (MSW) compost. Composting was carried out in a pile under aerobic conditions. Total content as well as water-extractable forms of macro and microelements were analysed during composting. Nutrient solubility indices were calculated for samples taken at various stages of maturity. The soluble forms of C, P, K, Ca and Mg decreased relatively to their total forms following maturation phases. For all micronutrients tested, a significant reduction in the proportion of soluble forms in relation to their total content was observed with an increase in composting time. In mature compost, low solubility were found for nitrogen, potassium, sodium and magnesium, which may indicate that the final product is a good source of these nutrients. The solubility index (percentage share of water-extractable forms of macro- and micronutrients in the total content) for iron indicates that the composting process does not affect its degree of solubility. Solubility index instead of the content of water-extractable forms of chosen macro- and microelements could be taken into account in determining the degree of MSW compost maturity.

The Availability and Accumulation of Heavy Metals in Greenhouse Soils Associated with Intensive Fertilizer Application

In China, greenhouse agriculture, which provides abundant vegetable products for human consumption, has been rapidly developed in recent decades. Heavy metal accumulation in greenhouse soil and products obtained have received increasing attention. Therefore, the availability and accumulation of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) and their association with soil pH, soil organic matter (SOM), inorganic nitrogen (IN), total nitrogen (TN), available phosphorus (AP), and planting year (PY) in greenhouse soils were analyzed. The results showed that the mean concentrations of available Cd, Cu, Ni, Pb, and Zn were 17.25 μg/kg, 2.89, 0.18, 0.36, and 5.33 mg/kg, respectively, while their suggested levels in China are 0.6, 100, 100, 120, and 250 mg/kg. Cd, Cu, and Zn might be mainly originated from fertilizer application. A lower soil pH significantly increased the available Cu, Ni, and Zn concentrations and reduced Cd, Cu, Ni, and Zn accumulation. A higher AP significantly increased the proportions of available Cu, Ni, and Zn and elevated Cd, Cu, and Zn accumulation. There was a strong positive correlation between Cd, Pb, and Zn availability and TN, while IN was negatively related to the availability and accumulation of Cu and Zn. It was concluded that chemical fertilizer application increased the availability of Cu, Ni, Pb, and Zn and the accumulation of Cd, Cu, and Zn. Manure application clearly elevated the accumulation and availability of Cd and Zn in greenhouse soil.

Geoassessment of heavy metals in rural and urban floodplain soils: health implications for consumers of Celosia argentea and Corchorus olitorius vegetables in Sagamu, Nigeria

Vegetable gardening in floodplains in western Nigeria has assumed economic significance but with attendant pressure on urban field in the dry season. This study assessed soil properties and bioconcentration of cadmium (Cd), iron (Fe) and lead (Pb), in edible parts of Celosia argentea and Corchorus olitorius grown in floodplains. Soil and vegetable samples were collected at 20 m intervals from rural (Atoyo and Ewuga) and urban (GRA Rd. and Lafarge) floodplain gardens in Sagamu. Six samples were collected per location making a total of 24 samples each of soil and vegetable. Samples were analyzed for soil properties and heavy metal concentration in the vegetables. Transfer factor (TF), contamination factor (CF), daily intake of metals (DIM), health risk index (HRI) and geoaccumulation index (I_geo) were also determined. Soil properties varied significantly, with the highest soil concentration of Cd (0.91 mg kg^-1) and Fe (208.20 mg kg^-1) recorded at Lafarge. The highest soil Pb (223.77 mg kg^-1) was at Atoyo. Bioaccumulation of Fe was significantly (p ≤ 0.05) higher in C. argentea than C. olitorius. Heavy metal bioaccumulation beyond allowable limits was recorded for Cd (0.46 mg kg^-1) and Pb (49.30 mg kg^-1) by C. argentea and C. olitorius, respectively. Soil contamination was dominated by Cd at Lafarge and by Pb at Atoyo. The DIM and HRI indices indicated no risk of Cd, Fe and Pb consumption in the vegetables. Geoaccumulation index revealed that Lafarge and Atoyo soils were extremely contaminated with Cd and Pb, respectively. Leafy vegetables grown in urban and rural floodplain soils adjacent to waste dumpsite are accumulators of Cd and Pb with food poisoning as the consequence.

Potential bacterial bioindicators of urban pollution in mangroves

Despite their ecological and socioeconomic importance, mangroves are among the most threatened tropical environments in the world. In the past two decades, the world's mangrove degradation and loss were estimated to lie between an 35% and >80%. However, appropriate bioindicators for assessing the impact of external factors, and for differentiating polluted from unpolluted areas are still scarce. Here, we determine the physicochemical profiles of the soils of two mangroves, one exposed to and one not exposed to anthropogenic factors. By metagenomic analysis based on 16S rRNA, we generated the bacterial diversity profiles of the soils and estimated their functional profiles. Our results showed that the two examined mangrove forests differed significantly in the physicochemical properties of the soils, especially regarding organic carbon, phosphorus and metal content, as well as in their microbial communities, which was likely caused by anthropogenic pollution. The physicochemical differences between the soils explained 76% of the differential bacterial composition, and 64% depended solely on gradients of phosphorus, metal ions and potassium. We found two genera JL-ETNP-Z39 and TA06 exclusively in polluted and non-polluted mangroves, respectively. Additionally, the polluted mangrove was enriched in Gemmatimonadetes, Cyanobacteria, Chloroflexi, Firmicutes, Acidobacteria, and Nitrospirae. A total of 77 genera were affected by anthropic contamination, of which we propose 33 as bioindicators; 26 enriched, and 7 depleted upon pollution.

Biosolids and sludge management

The advancements in the field of sludge and biosolids have been made over the past year. This review outlines the major contributions of researchers that have been published in peer-reviewed journals and conference proceedings throughout 2018. The review is organized in sections including regulatory developments and market analysis; analysis and quantification of characteristics including microconstituents and metals; treatment advances for the conversion of sludge to biosolids including pretreatment and sludge minimization, conditioning and dewatering, digestion, composting, and innovative technologies; product development and reuse including adsorbents and thermal products, agricultural and other uses, and innovative uses; odor and air emissions; and energy factors. PRACTITIONER POINTS: Summary of advances in the field of residuals and biosolids research in 2018. This review outlines the major contributions of researchers that have been published in peer-reviewed journals and conference proceedings. Topics covered range from regulation to innovation.

Investigation of pesticide exposure by genotoxicological, biochemical, genetic polymorphic and in silico analysis

Soybean farmers are exposed to various types of pesticides that contain in their formulations a combination of chemicals with genotoxic and mutagenic potential. Therefore, the objective of this paper was to evaluate the genetic damages caused by this pesticide exposure to soybean producers in the state of Mato Grosso (Brazil), regarding biochemical, genetic polymorphic and in silico analyses. A total of 148 individuals were evaluated, 76 of which were occupationally exposed and 72 were not exposed at all. The buccal micronucleus cytome assay (BMCyt) detected in the exposed group an increase on DNA damage and cell death. No inhibition of butyrylcholinesterase (BchE) was observed within the exposed group. The detection of inorganic elements was made through the particle-induced X-ray emission technique (PIXE), which revealed higher concentrations of Bromine (Br), Rubidium (Rb) and Lead (Pb) in rural workers. A molecular model using in silico analysis suggests how metal ions can cause both DNA damage and apoptosis in the exposed cells. Analysis of the compared effect of X-ray Repair Cross-complement Protein 1 (XRCC1) and Paraoxonase 1 (PON1) genotypes in the groups demonstrated an increase of binucleated cells (exposed group) and nuclear bud (non-exposed group) in individuals with the XRCC1 Trip/- and PON1 Arg/- genes. There was no significant difference in the telomere (TL) mean value in the exposed group in contrast to the non-exposed group. Our results showed that soybean producers showed genotoxic effect and cell death, which may have been induced by exposure to complex mixtures of agrochemicals and fertilizers. In addition, XRCC1 Arg/Arg could, in some respects, provide protection to individuals.