Crops are the main source of toxic cadmium for humans due to uptake from naturally or anthropogenically polluted soils. Chronic Cd ingestion causes kidney, liver, and skeletal damage along with an increased risk of cancer. Cacao is known to accumulate Cd and may therefore be potentially harmful to human health. Consequently, cocoa production on intensely polluted soils should be avoided. Cocoa products from South America in particular often exceed the limits for Cd, but the factors that drive Cd uptake are as yet poorly studied. In this study, we measured Cd concentrations in defatted cocoa powder from unfermented seeds of 40 different trees on 20 farms in the Huánuco Region, Peru, and associated the Cd levels with the farms’ soil, field management, and nearby vegetation diversity. The mean Cd concentration found in cocoa of the study region was 2.46 mg kg⁻¹ with a range of 0.2–12.56 mg kg⁻¹. The maximum content measured was an order of magnitude higher than the allowed limit of 1.5 mg kg⁻¹ and was the highest reported so far in the literature. Soil Cd content was the most relevant driver of Cd concentration in cacao. In addition, fertilizer use caused significantly higher Cd concentration in cocoa. Higher biodiversity of herbs was positively correlated with Cd contents in cocoa. The study shows that, apart from the known correlation of soil conditions with Cd accumulation in cacao seeds, changes in fertilization and plant composition may be promising measures to counteract Cd contamination in regions with high soil Cd content.

Biotemplating method is a promising way to obtain hierarchical materials with unique morphology and property. In the current work, a novel hierarchically porous ZnAl-CLDH (calcined layered double hydroxides)/FeWO₄ had been successfully synthesized by a facile biotemplated method. The obtained samples were characterized in detail via FESEM-EDX, TEM, XRD, IR, TGA, and BET techniques. The as-synthesized ZnAl-CLDH/FeWO₄ hierarchical microspheres were composed of ZnAl-CLDH nanosheets and FeWO₄ nanoparticles. The obtained sample exhibited both high adsorption and visible-light photocatalytic activity toward Congo Red (CR) in water. It was found that the adsorption process was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model, while the photocatalytic degradation process was well fitted to the first-order kinetics model. The enhanced photocatalytic performance was mainly due to the hierarchically porous structure that could offer more exposed active sites, as well as the unique energy band structure of heterostructures, that facilitated the efficient separation and transfer of photoinduced carriers and enhanced light harvesting. In addition, the as-prepared sample had quickly magnetic response and could be easily separated from water under an external magnetic field after wastewater treatment.

External carbon source was usually added to enhance denitrification efficiency for nitrogen removal in wastewater treatment. In this study, waster sludge alkaline fermentation liquid was successfully employed as an alternative carbon source for biological denitrification. The denitrification performance was studied at different C/Ns (carbon-to-nitrogen ratios) and HRTs (hydraulic retention times). A C/N of 7 and an HRT of 8 h were the optimal conditions for denitrification. The nitrate removal efficiency of 96.4% and no obvious nitrite accumulation in the effluent were achieved under the optimal conditions with a low soluble chemical oxygen demand (SCOD) level. The sludge carbon source utilization was analyzed and showed that the volatile fatty acids (VFAs) were prior utilized than proteins and carbohydrates. The excitation-emission matrix (EEM) spectroscopy with fluorescence regional integration (FRI) was adopted to analyze the compositional and variations of dissolved organic matters (DOM). Moreover, a high denitrification rate (VDN) and potential (PDN) with low heterotroph anoxic yield (YH) was exhibited at the optimal C/N and HRT condition, indicating the better denitrification ability and organic matter utilization efficiencies.

For remediating polluted soils, phytoextraction of metals received considerable attention in recent years, although slow removal of metals remained a major constraint in this approach. We, therefore, studied the effect of selected organic and inorganic amendments on the solubility of zinc (Zn), cadmium (Cd), and lead (Pb) in polluted soil and enhancing the efficacy of phytoextraction of these metals by Indian mustard (Brassica juncea cv. Pusa Vijay). For this purpose, a greenhouse experiment was conducted using a metal-polluted soil to evaluate the effect of amendments, viz. green manure (T2), EDTA (T3), sulfur (S)+S oxidizing bacteria (Thiobacillus spp.) (T4), metal-solubilizing bacteria (Pseudomonas spp.) (T5), and green manure + metal-solubilizing bacteria (T6), on solubility and bioavailability of Zn, Cd, and Pb. Distribution of metals in different soil fractions revealed that Cd content in water soluble + exchangeable fraction increased to the extent of 34.1, 523, 133, 123, and 75.8% in T2, T3, T4, T5, and T6 treatments, respectively, over control (T1). Cadmium concentrations in soil solution as extracted by Rhizon sampler were recorded as 3.78, 88.1, 11.2, 6.29, and 4.27 μg L⁻¹in T2, T3, T4, T5, and T6, respectively, whereas soil solution concentration of Cd in T1 was 0.99 μg L⁻¹. Activities of Cd (pCd²⁺) in Baker soil extract were 12.2, 10.9, 6.72, 7.74, 7.67, and 7.05 for T1, T2, T3, T4, T5, and T6, respectively. Cadmium contents in shoot were recorded as 2.74, 3.12, 4.03, 4.55, 4.68, and 4.63 mg kg⁻¹ in T1, T2, T3, T4, T5, and T6 treatments, respectively. Similar trend in Zn and Pb content with different magnitude was also observed across the different amendments. Cadmium uptake by shoot of mustard was enhanced to the extent of 125, 62.5, 175, 175, and 212% grown on T2-, T3-, T4-, T5-, and T6-treated soil, respectively, over T1. By and large, free ion activity of metals as measured by Baker soil test proved to be the most effective index for predicting Zn, Cd, and Pb content in shoot of mustard, followed by EDTA and DTPA. Among the metal fractions, only water soluble + exchangeable metal contributed positively towards plant uptake, which explained the variation in shoot Zn, Cd, and Pb content to the extent of 74, 81, and 87%, respectively, along with other soil metal fractions. Risk to human health for intake of metals through the consumption of leafy vegetable (mustard) grown on polluted soil in terms of hazard quotient (HQ) ranged from 0.64 to 1.10 for Cd and 0.11 to 0.34 for Pb, thus rendering mustard unfit for the human consumption. Novelty of the study mainly consisted of the use of natural means and microorganisms for enhancing solubility of metals in soil with the ultimate aim of hastening the phytoremediation.

This study was conducted to assess the proximate analysis (protein, carbohydrate, lipid, and moisture content) and concentration levels of metals (Zn, Cu, Cd, Pb, and Cr) in the muscles of selected shellfish (Portunus reticulatus, P. segnis, P. sanguinolentus, Scylla olivaceae, Penaeus monodon, and P. indicus) species. The concentration of metals showed significant difference (p > 0.05) among species. The detected concentrations of the analyzed heavy metals were below the daily intake and legal limits set by national and international standards. The THQs and CR index were calculated to evaluate the risk estimation of the metal contamination associated with the human health. The THQ values of all metals were below 1 in all species, indicated that there is no risk of adverse health effect, but the risk of elevated intakes of heavy metals adversely affecting food safety for the studied species. The CR index indicated that Cd and Pb caused the greatest cancer risk. The correlation and multivariate (principle component analysis) among metal concentration and nutritional quality were also evaluated. The carbohydrate and moisture showed the positive correlation (p > 0.05) with metals. The biochemical results of the present work clearly indicate that there was a significant difference in the muscles of shellfish. It was concluded that more effective controls should be focused on Cd and Pb to reduce pollution for quality and seafood safety concern.

The effects of elevated ozone (O₃) levels (80 ppb and 120 ppb) on photosynthetic efficiency and growth of canola plants were studied in open-top chambers. The chlorophyll a polyphasic fluorescence rise kinetics OJIP, stomatal conductance and Chlorophyll Content Index (CCI) were measured after 15 and 30 days of O₃ fumigation, as well as in control plants; biomass measurements were done only after 30 days with and without fumigation. Analysis of the OJIP kinetics by the JIP-test led to the calculation of several photosynthetic parameters and the total Performance Index (PIₜₒₜₐₗ). The decline of PIₜₒₜₐₗ under the 80 ppb O₃ treatment was due to a lower density of reaction centres (RC/ABS), while the notable decline under the 120 ppb treatment was found to be due both to a further decline of RC/ABS and to a pronounced lowering of the efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end acceptors (δRₒ). Stomatal conductance was affected by both treatments. Biomass was found to be affected by O₃ fumigation (for 30 days), decreasing by 40% at 80 ppb and by more than 70% under 120 ppb. Our findings indicate that biomass decline is due both to the lowering of CCI and the lowering of photosynthetic efficiency parameters. They thus suggest that two simple, non-invasive and rapid methods, namely, the analysis of OJIP fluorescence transients and the measurement of CCI, can be used to screen the effect of elevated O₃ on biomass of canola plants.

Biogas reactors are now a common part of wastewater treatment systems. The quality of produced biogas is the result of many factors, mainly the input substrate and microbial composition of the bioreactor. The aim of this research was to evaluate the microbial community of the Modřice biogas reactor together with the possible changes in biogas composition. The key microbial groups and their content in anaerobic digester were identified by sequencing techniques. The most dominant group were sulphate-reducing (45%), followed by methanogenic (19%), acetate (6%) and hydrogen-producing (11%) microorganisms. The remaining microorganisms were identified only to their order (19%). Phylogenetic trees were constructed to show evolutionary relationships of detected microorganisms. The volume of methane in biogas content was 60%, which corresponds with literature data regarding sewage digesters. None of the detected impurities have crossed the safe limits and their volume remained stable during the measurement period. Despite sulphate-reducing bacteria being the dominant group, their produced hydrogen sulphide (H₂S) was detected only in a small quantity (2.43–7.46 ppm) and had no inhibitory effect on the methane production. The mechanism of inhibition by H₂S and the perspective of its biological removal were discussed. Application of phototrophic sulphur bacteria, especially Chlorobiaceae and Chromatiaceae family, and the creation of new photobioreactor systems can be a promising pathway for hydrogen sulphide treatment in biogas plants.

Two nonionic POEA surfactants (CAS No. 61791-26-2), TA15 and TH30, were tested to establish their acute pathological effects and lethal concentrations (LC₅₀) in Piaractus brachypomus. Both compounds are nonionic surfactants produced by the alkoxylation of ethylene oxide with tallow amine, and they are used in variety of industries such as textiles, paints, metal working, agriculture, and polish manufacture. Fish were exposed to six concentrations of TA15 (0.2–4.0 mg/L) or TH30 (8–140 mg/L) for 96 h. The LC₅₀ for TA15 was 2.08 mg/L and for TH30 47.32 mg/L. The main clinical signs observed in fish exposed to 4 mg/L of TA15 and 32 to 140 mg/L of TH30, were lethargy, loss of shoaling behavior, respiratory distress, changes in swimming pattern, such as, loss of balance and abnormal buoyancy, prolapse of the lower lip and superior location in the water column. The highest concentrations of these compounds induced nervous signs and collapse. The relevant macroscopic lesions were skin and fins erosions with necrotic lysis of the caudal peduncle. In addition, hemorrhages in mouth, branchial arches, and petechial hemorrhages in skin were observed. An increased fluid in the celomic cavity and meningeal hemorrhages were also evident. Organs as gills, liver, brain, and anterior kidney presented severe lesions at the highest concentrations of each compound. For the first time, it is reported lesions in interrenal tissues and choroidal bodies, as well as severe telencephalic lesions associated with the POEA toxicity. These last lesions were more severe in fish exposed to TA15 than to TH30, although the pattern of injuries was similar with both substances. According to the Global Harmonized System of Classification and Labelling of Chemical (GHS) by the United Nations, we reported that TA15 is classified as Acute Category 2 and TH30 is Acute Category 3 for white cachama. Due to the low LC₅₀ and the highly toxic effects of both POEA compounds for neotropical fish, a revision of the regulation of the use of herbicide mixtures by Colombian legislation is necessary.

The aim of the present experimental study was to perform a technical-economic evaluation of a combined treatment system, consisting of coagulation-flocculation or rapid sand filtration as pre-treatment followed by column adsorption, for reducing the arsenic concentration from approximately 1 mg/L to below the limit set for groundwater remediation and drinking water, i.e., 0.01 mg/L, according to the legislation in force. A wide number of operating conditions were experimentally evaluated in the different tests. In the coagulation-flocculation study, it was initially investigated if the iron contained in a mining drainage co-mixed with the groundwater would be able to achieve a better As content reduction by adsorption/precipitation, thus avoiding fresh coagulant addition. Then, different polyelectrolyte dosages were tested varying the mixing ratio. None of the tested conditions allowed to improve the arsenic removal so significantly to warrant the consequent incremental costs. Therefore, the optimal condition was considered any mixing with a different liquid stream and any polyelectrolyte dosage. The iron content naturally present in the groundwater and contact with air was capable alone of reducing As concentration of about 80%. Sand filtration reached approximately the same removal efficiency (about 80%) at the lower surface loading rate among the values tested. Between coagulation and sand filtration, in terms of costs, the latter showed to be more convenient than coagulation-flocculation, at the same removal efficiency: therefore, it was considered the optimal pre-treatment. The following adsorption column plant was capable of further reducing As concentration up to the required value of 0.01 mg/L. Among the two iron-based commercial adsorbents applied in the adsorption column tests, the hybrid media consisting of an exchange resin with iron oxides showed to be preferable under the selected operating conditions: it offered higher adsorption capacity at breakthrough and, after exhaustion, could be regenerated for a number of cycles. The influent pH showed to have a great influence on the duration of the adsorbent media, and values around neutrality were considered preferable. The estimated cost of the full treatment was computed to be about 0.50 €/m³ of purified water. Therefore, the capacity of achieving the required remediation goal, the limited cost, and simplicity of operation make the proposed combined treatment being potentially suitable for real application.

In this study, we investigated the Sb(V) adsorption on ferrihydrite (Fh) at different pH values, in the presence and absence of common competing anions in soil such as phosphate (P(V)) and arsenate (As(V)). Batch adsorption experiments, carried out at pH 4.5, 6.0, and 7.0, showed a greater affinity of Fh towards P(V) and As(V) with respect to Sb(V), especially at higher pH values, while the opposite was true at acidic pH. The capacity of Fh to accumulate greater amounts of phosphate and arsenate in the 6.0–7.0 pH range was mainly linked to the different acid properties of P(V), As(V), and Sb(V) oxyanions. The Sb(V) adsorption on Fh was highly pH-dependent and followed the following order: pH 4.5 (0.957 mmol·g⁻¹ Fh) > pH 6.0 (0.701 mmol·g⁻¹ Fh) > pH 7.0 (0.583 mmol·g⁻¹ Fh). Desorption of antimonate from Sb(V)-saturated Fh, treated with citric and malic acid solutions, was ~equal to 55, 68, and 76% of that sorbed at pH 4.5, 6.0, and 7.0, respectively, while phosphate, arsenate, and sulfate were able to release significantly lower Sb(V) amounts. The FT-IR spectra revealed substantial absorbance shifts related to the surface hydroxyl groups of Fh, which were attributed to the formation of Fe-O-Sb(V) bonds and supported the formation of inner-sphere bonding between Sb(V) and Fh.