Low Environmental Risk Research Articles

Fractionation, molecular composition, and biological effects of organic matter in bio-stabilization sludge with implication to land utilization

Bioactive organic compounds (BOCs) contained in bio-stabilized products of waste activated sludge (WAS) have attracted considerable attention, as they can enhance the fertilizing effect of WAS in land applications. This study investigated the molecular composition and plant-growth-promoting mechanisms of various BOCs in the bio-stabilized products of WAS. After stepwise fractionation, aerobic composting sludge (ACS) and anaerobic digestion sludge (ADS) were chemically fractioned into five subcomponents, namely dissolved organic matter (DOM) (C1), weakly interacted organic matter (OM) (C2), metal-bonded OM (C3), NaOH-extracted OM (C4), and strongly interacted OM (C5), in sequence. The results showed that fatty acids and carboxylic acid (CAs) present in ACS C2 promoted plant growth and enhanced the ability of plants against stresses by upregulating pathways related to “carbohydrate metabolism,” “lipid metabolism,” “amino acid metabolism,” and “phenylpropanoid biosynthesis.” However, in ACS C4, plenty of amino acids could promote plant growth via upregulating “carbohydrate metabolism” and “amino acid metabolism” pathways. As an important precursor, aromatic amino acids inside ACS C4 also stimulated the production of indoleacetic acids. In ADS C1, amino sugar and phytohormone were the major BOCs causing the up-regulation of “carbohydrate metabolism” and AAA catabolism in “amino acid metabolism” pathways. CAs enriched in ADS C2 stimulated plant growth through “amino acid metabolism” pathway. In summary, alkali extraction can recycle a large proportion of BOCs with low environmental risk from the bio-stabilization products of WAS. The results from this study provide scientific guidance for safe and value-added resource utilization of bio-stabilization products of WAS in land applications.

Environmental processes and fate of PAHs at a shallow and enclosed bay: West Nanao Bay, Noto Peninsula, Japan

From August 2019 to August 2020, particulate and dissolved polycyclic aromatic hydrocarbons concentrations (PAHs) were analyzed in the water body of West Nanao Bay, Japan, to determinate their levels, environmental pathways, and ecological risks at this remote but shallow and semi-enclosed bay. The 14 targeted PAHs were analyzed by high performance liquid chromatography-fluorescence detector. Even when water column stratifies, the summatory of 14 targeted dissolved PAHs did not follow significantly change with depth. Results agreed with our previous findings in the surface distribution at the bay and can be attributed to long retention time of the water mass of the semi-enclosed bay. Suspended solids start precipitating according to their size; with biggest particles rapidly settling in the proximities of river mouths. Partition coefficients (Kp) varied from 103 to 107, according to molecular weights. In general, highest Kp were found in the nepheloid layer. The risk quotients, RQ∑14 PAHs (NCs) (1.04-174.08), indicated that PAHs represented a very low to low environmental risks.

Optimization of Extraction of Natural Antimicrobial Pigments Using Supercritical Fluids: A Review

It has become increasingly popular to replace chemically synthesized compounds with natural counterparts mostly found in natural sources, such as natural pigments. The conventional extraction processes for these compounds are limited by the toxicity and flammability of the solvents. To obtain pure extracts, it is always a longer process that requires several steps. Supercritical fluid extraction (SFE) is a cutting-edge green technology that is continuously increasing and expanding its fields of application, with benefits such as no waste produced, shorter extraction time, automation, and lower solvent consumption. The SFE of natural pigments has high potential in food, textiles, cosmetics, and pharmaceuticals; there are a number of other applications that can benefit from the SFE technique of natural pigments. The pigments that are extracted via SFE have a high potential for application and sustainability because of their biological and antimicrobial properties as well as low environmental risk. This review provides an update on the SFE technique, specifically as it pertains to the optimization of health-promoting pigments. This review focuses on antimicrobial pigments and the high efficiency of SFE in extracting pure antimicrobial pigments. In addition, the optimal conditions, biological activities, and possible applications of each category are explained.

Estimating the Effects of a Complex, Multidimensional Moderator: An Example of Latent Class Moderation to Examine Differential Intervention Effects of Substance Use Services.

Improvements in substance use disorder recovery may be achieved by recognizing that effective interventions do not work equally well for all individuals. Heterogeneity of intervention effects is traditionally examined as a function of a single variable, such as gender or baseline severity. However, responsiveness to an intervention is likely a result of multiple, intersecting factors. Latent class moderation enables the examination of heterogeneity in intervention effects across subgroups characterized by profiles of characteristics. This study analyzed data from adolescents (aged 13 to 18years old) who needed treatment for cannabis use (n = 14,854) and participated in the Global Appraisal of Individual Needs to evaluate differential effects of substance use services on cannabis use outcomes. We demonstrate an adjusted three-step approach using weights that account for measurement error; sample codes in Mplus and Latent Gold are provided and data are publicly available. Indicators of the latent class moderator comprised six contextual (e.g., recovery environment risk) and individual (e.g., internal mental distress) risk factors. The latent class moderator comprised four subgroups: low risk (21.1%), social risk (21.1%), environmental risk (12.5%), and mixed risk (45.2%). Limited moderation of associations between level of care and any past 90-day cannabis use were observed. In predicting number of cannabis use-days, compared to individuals with low risk, those with environmental risk showed improved outcomes from intensive outpatient care whereas individuals with social risk and mixed risk showed improved outcomes from residential care (all compared to early intervention/outpatient care). Latent class moderation holds potential to elucidate heterogeneity in intervention effectiveness that otherwise may go undetected.

Sustainable water and nitrogen optimization to adapt to different temperature variations and rainfall patterns for a trade-off between winter wheat yield and N2O emissions

Optimizing irrigation and nitrogen (N) fertilizer applications is essential to ensure crop yields and lower environmental risks under climate change. The DeNitrification-DeComposition (DNDC) model was employed to investigate the impacts of irrigation regime (RF, rainfed; MI, minimum irrigation; CI, critical irrigation; FI, full irrigation) and N fertilizer rate (N60, N90, N120, N150, N180, N210, N240, N270, and N300 kg ha−1) on yield and nitrous oxide (N2O) emissions from winter wheat growing season under different temperature rise levels (+0, +0.5, +1.0, +1.5, and +2.0 °C scenarios) and precipitation year types (wet, normal, and dry seasons) in the North China Plain. Model evaluations demonstrated that simulated soil temperature, soil moisture, daily N2O flux, yield, and cumulative N2O emissions were generally in close agreement with measurements from field experiment over three growing seasons. By adopting simulation scenarios analysis, the model was then used to explore the effects of irrigation and N fertilizer inputs to balance yield and N2O emissions from winter wheat growing season. Based on reduced water and fertilizer inputs and N2O emissions with little yield penalty, recommended management practices included application of MI-N150 in wet season, CI-N120 in both normal and dry seasons, and CI-N150 for +0 to +2.0 °C scenarios. Recommended practices in different precipitation year types reduced irrigation amount by 75–150 mm, N rate by 75–105 kg N ha−1, yield by 0.16–0.86 t ha−1, cumulative N2O emissions by 0.13–0.64 kg ha−1, and yield-scaled N2O emissions by 15.5–85.0 mg kg−1 compared with current practices. The corresponding metrics for different elevated temperature levels decreased by 75 mm, 75 kg N ha−1, 0.09–0.50 t ha−1, 0.12–0.52 kg ha−1, and 13.7–72.3 mg kg−1, respectively. The proposed management practices can help to maintain high agronomic productivity and alleviate environmental pollution from agricultural ecosystems, thereby providing an important basis for mitigation strategies to adapt to climate change.

Development of Carbon-based N Fertilizer for Reducing N Loss and Improving Nitrogen Availability

Aims: Synthesis and characterization of carbon-based nitrogen fertilizer and assess the nitrogen releasing pattern of newly synthesized N fertilizer.
 Study Design: The experiment was laid out in Completely Randomized Design (CRD) with seven treatments in three replications.
 Place and Duration of Study: The incubation study was conducted in the Soils and Environment post-graduate laboratory at Agriculture College and Research Institute, Tamil Nadu Agricultural University, Madurai, India from February 2022 to April 2022.
 Methodology: Seven treatments were tested with various combinations of N fertilizers viz., Absolute control-No nitrogen (C), Soil test crop response-based N as urea (STCR- U), Soil test crop response-based N as ammonium chloride (STCR-AC), Carbon-tailored N fertilizer from urea (100% N) (CNF-U100), Carbon-tailored N fertilizer from urea (75% N) (CNF-U75), Carbon-tailored N fertilizer from ammonium chloride (100% N) (CNF-AC100) and Carbon-tailored N fertilizer from ammonium chloride (75% N) (CNF-AC75). The characterization of carbon-tailored N fertilizers and their impact on soil available N were analyzed.
 Results: When compared to STCR urea and ammonium chloride, carbon-tailored N fertilizers generated a greater result in terms of sustained release pattern of nitrogen over 10 weeks. Among the N fertilizers, carbon-tailored N fertilizer from urea 75% N (CNF-U75) demonstrated the sustained release of N (104.0 mg kg-1), when compared to the STCR-U (108.9 mg kg-1) and STCR-AC (110.0 mg kg-1) fertilizers.
 Conclusion: A novel carbon-based N fertilizer was tailored by intercalating urea and ammonium chloride with carbon material. The N releasing pattern of CNF-U75 implied that carbon-based N fertilizer is a novel product for sustained N release with higher nitrogen utilization efficiency and lower environmental risks. This study result could be used as a beneficial source of information on the current needs and future perspectives of carbon-based N fertilizer (CNF) in precision farming.

Comprehensive Meta-Analysis of Pathways to Increase Biogas Production in the Textile Industry

The textile industry is one of the largest environmental polluters in the world. Although waste management via anaerobic digestion (AD) is a sustainable strategy to transform waste into clean energy and water recovery, the efficiency of the AD process is reduced by the presence of recalcitrant materials, chemicals, and toxic contents. This study aims to investigate the performance of several chemical, physical, and biological pretreatments applied to improve the biodegradability of textile waste. We performed a meta-analysis with 117 data extracted from 13 published articles that evaluated the efficiency of pretreatments applied to textile waste prior to AD to increase biogas production measured as methane (CH4) yield. Even though the majority of the studies have focused on the effect of chemical and physical pretreatments, our results showed that the application of biological pretreatments are more efficient and eco-friendlier. Biological pretreatments can increase CH4 yield by up to 360% with lower environmental risk and lower operating costs, while producing clean energy and a cleaner waste stream. Biological pretreatments also avoid the addition of chemicals and favor the reuse of textile wastewater, decreasing the current demand for clean water and increasing resource circularity in the textile industry.

A Systematic Review and Meta-Analysis of the Inhibitory Effects of Plant-Derived Sterilants on Rodent Population Abundance.

Owing to their low minimal environmental risk and other ethical considerations, plant-derived sterilants are used to control rodent populations. However, the effects of plant-derived sterilants are not immediate, and their efficacy on rodent control is controversial, which negatively affects sterilant research and application. Here, a meta-analysis of the available literature was conducted to evaluate the effects of two plant-derived sterilants, triptolide and curcumol, on rodent populations. Using a random-effects and a fixed-effects model, we calculated the weighted mean difference (WMD) and relative risk (RR) and their corresponding 95% confidence intervals (95% CIs). After the application of plant-derived sterilants, the rodent population density tended to decrease. Three outcome-related measures in rodents, i.e., capture rate (RR = 0.31, 95% CI [0.20, 0.47]), pregnancy rate (RR = 0.49, 95% CI [0.40, 0.61]), and sperm survival rate (WMD = −17.53, 95% CI [−28.96, −6.06]), significantly decreased, as shown by a significant reduction of ovarian, uterine, and testicular organ coefficients. However, the number of effective rodent holes did not change significantly after the interventions, indicating that the studied sterilants did not directly eradicate the rodent populations. This study provides a theoretical basis for elucidating the inhibitory mechanisms of plant-derived sterilants on rodent populations and for the rational use of these sterilants.

Fate and exposure risk of florfenicol, thiamphenicol and antibiotic resistance genes during composting of swine manure

Livestock manure is an important source of antibiotic resistance genes (ARGs) spreading to the environment, posing a potential threat to human health. Here, we investigated the dissipation of florfenicol (FF) and thiamphenicol (TAP), and their effects on the bacterial community, mobile genetic elements (MGEs), and ARGs during composting. The results indicated that FF and TAP dissipated rapidly in compost, with half-life values of 5.1 and 1.6 d, respectively. However, FF could not be completely removed during composting. The FF and TAP residues in manure could reduce the elimination of ARGs and MGEs during composting, and had a negative effect on the physicochemical factors of the compost. Significant correlations were found between floR and intI1, indicating that floR in manure may more easily diffuse to the soil environment. Meanwhile, the presence of FF in manure could increase the abundance of floR. Network analysis showed that Proteobacteria and Firmicutes were the dominant bacterial communities and important potential pathogen hosts carrying ARGs. The predicted environmental concentration of FF in the soil was over 100 μg kg−1, which indicates that FF poses a potential risk to the natural environment, and we verified this result through field experiments. The results showed that FF dissipated in the soil after it migrated from manure to soil. In contrast, TAP in manure posed lower environmental risk. This study highlights that changed in composting conditions may control the rate of removal of ARGs. Further studies are needed to investigate the best environmental conditions to achieve a faster degradation of FF and a more comprehensive elimination of ARGs during composting.

Assessing the environmental risk and mobility of cobalt in sediment near nonferrous metal mines with risk assessment indexes and the diffusive gradients in thin films (DGT) technique

The Jialing River is the tributary of the Yangtze River with the largest drainage area. In recent years, the Jialing River has suffered a series of environmental problems, such as discharge of industrial effluent and sand mining activities, which have severely threatened the aquatic ecosystem of the river. In the present study, we employed risk assessment indexes, sequential extraction and the diffusive gradients in thin films (DGT) technique to assess environmental risks and study the remobilization of cobalt (Co) in sediments. The potential ecological risk index and risk assessment code results demonstrated that Co may pose a low environmental and ecological risk to the local aquatic environment. However, BCR sequential extraction showed that the sum of the F1, F2 and F3 fractions of Co still accounted for over 50% of the Co in the study areas, indicating that sediments may be a source of Co release. The DGT results showed an increasing trend for DGT-labile Co in deep sediments (−8 cm to −12 cm), and the calculated flux values ranged from 0.08 to 15.54 ng cm2·day−1, indicating that Co tends to transfer across the sediment-water interface at all sampling sites. Correlation analysis showed that F1–Co, F2–Co and F3–Co are the fractions readily captured by DGT and can be used for predicting Co remobilization in sediment. Sand mining activities contribute substantially to the release of Co from the F1 and F3 fractions as a result of strong stirring of sediments and introduction of oxygen into the sediments. The reductive dissolution of iron (Fe) and manganese (Mn) hydroxides or oxides causes the release of Co and Fe/Mn in the sediment, which leads to Co release from the reducible fraction. The above work suggests that sand mining in the Jialing River should be reasonably regulated to prohibit illegal sand mining activities.

Efficiency of heterogeneous chelating agents on the phytoremediation potential and growth of Sasa argenteostriata (Regel) E.G. Camus on Pb-contaminated soil

Ethylenediaminetetraacetic acid (EDTA) is one of the most effective chelating agents for enhancing lead (Pb) accumulation in various plant organs. However, it has a higher risk of causing secondary pollution than other chelating agents. To reduce such environmental risks and increase remediation efficiency, EDTA can be combined with degradable chelating agents for use in phytoremediation, but there are few reports on the combination of EDTA and nitrilotriacetic acid (NTA). This study evaluated the effects of combined EDTA and NTA application at different concentrations (900, 1200, or 1500 mg/kg) and with different methods (1 application or 3 applications) on dwarf bamboo (Sasa argenteostriata (Regel) E.G. Camus) growth and phytoremediation efficiency and on the soil environment in pot experiments with Pb-contaminated soil. Applying EDTA and NTA together resulted in lower soil water-soluble Pb concentrations than applying EDTA alone and therefore resulted in lower environmental risk. The increased availability of soil Pb produced a stress response in the dwarf bamboo plants, which increased their biomass significantly. Moreover, under the chelating treatments, the soil Pb availability increased, which promoted Pb translocation in plants. The Pb content in the aerial parts of the dwarf bamboo increased significantly in all treatments (translocation factors increased by 300~1500% compared with that in CK). The Pb content increase in the aerial parts caused high proline accumulation in dwarf bamboo leaves, to alleviate Pb toxicity. Maximum Pb accumulation was observed in the EN1500 treatment, which was significantly higher than that in the other treatments except the EN900 treatment. This study elucidates the choice of remediation techniques and the physiological characteristics of the plants used in such studies. In conclusion, the EN900 treatment resulted in the lowest environmental risk, greatest biomass production, and highest phytoremediation efficiency of all treatments, indicating that it has great potential for application in phytoremediation with dwarf bamboo in Pb-contaminated soil.

Baseline sensitivity and bioactivity of tetramycin against Sclerotium rolfsii isolates in Huanghuai peanut-growing region of China

Peanut stem rot caused by Sclerotium rolfsii is a serious soil-borne disease and poses a threat to the peanut production. The antibiotic fungicide tetramycin has a broad antifungal spectrum against multiple pathogens and possess low environmental risks. In current study, a total of 250 isolates collected from Huanghuai peanut-growing region of China (Henan, Shandong and Hebei Province) were used to establish the baseline sensitivity of S. rolfsii to tetramycin. The baseline sensitivity curve was unimodal and distributed from 0.01 to 0.36 mg/L, with a mean EC50 (50% effective concentration) value of 0.11 ± 0.06 mg/L. Tetramycin also had strong inhibitory activity on the formation and germination of sclerotia. There was no significant correlation of S. rolfsii sensitivity to tetramycin and other commonly used SDHI (succinate dehydrogenase inhibitor), QoI (quinone outside respiration inhibitor) and DMI (demethylation inhibitor) fungicides. Moreover, tetramycin significantly increased the cell membrane permeability and reduced the oxalate acid content. Greenhouse experiments showed that tetramycin has both protective and curative efficacy against S. rolfsii, while protective efficacy was higher than curative efficacy. Anyhow, the bioactivity of tetramycin is similar (curative efficacy) or higher (protective efficacy) than the control fungicide validamycin. In terms of application method, root drench may be more suitable for tetramycin than spraying, because root drench of tetramycin obtained a higher efficacy. These results indicated that tetramycin may be a potential alternative fungicide for the efficient control of peanut stem rot.

Effect of sewage sludge-derived amendments on the nutrient uptake by Chinese cabbage from Mediterranean soils

The utilization of sewage sludge (SS) as a fertilizer for agricultural land is increasingly seen by many as the best option for recycling. This study investigates the effects of SS-derived compost (SSC) or biochar (SSB) amendments on N, P, K, Ca, Mg, Na, Fe, Mn and Mo uptake by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) from terra rossa and rendzina soils. A two-factorial experiment was performed under greenhouse conditions whereby elemental concentrations (substrate, leachates and plants), edible tissue uptake (ETU), concentration ratios (CR) and soil characteristics were determined. The pH (7.03 to 7.32) and P content (286 to 421 mg/kg d.w.) in SSC- and SSB-amended soils increased, while EC (450 to 253 μS/cm) decreased. Phosphorous levels were higher in SSB-amended soils, although P leaching indicates a low environmental risk in both soils. In leaves, P (1.02 to 4.15 g/kg d.w.), K (12.8 to 21.8 g/kg d.w.), Mg (1.05 to 1.55 g/kg d.w.), Na (660 to 1350 mg/kg d.w.), and Mo (1.20 to 2.65 mg/kg d.w.) levels increased with amendment rate and were higher in SSC-amended soils. Nutrient bioavailability also increased with amendment rate, while cabbage biomass production increased proportionally to the dose. The P, K, and Mg levels were higher in leaves, while roots contained more Ca, Fe, and Mn. Despite amendment rates 10x the permitted dose of SS, they did not affect soil leachate, plant growth and biomass yield. Overall, adopting the cautionary principle is advised until the long-term effects are better understood.

Interactions of entomopathogens with insect growth regulators for the control of Spodoptera littoralis (Lepidoptera: Noctuidae)

Agriculture is currently expected to establish different pest insect control alternatives that have less impact and involve a lower environmental risk. New legislative regulations on the use of plant protection products give priority to biological control measures over the use of chemical insecticides. One of the potential control alternatives to be included in integrated pest management is the combination or simultaneous use of chemical agents, in low doses, with insecticides of microbial origin, seeking to maximize their potential and at the same time reduce the environmental impact that chemical control can cause. This work evaluates the effects of three microbial agents to control Spodoptera littoralis: Bacillus thuringiensis var. aizawai; a native isolate of Beauveria bassiana; and the S. littoralis nucleopolyhedrovirus (SlNPV). These have been used both as individual treatments and in combination with low doses of lufenuron and tebufenozide, synthetic compounds that act as Insect Growth Regulators (IGRs). The median lethal concentrations (LC50) of SlNPV, lufenuron, and tebufenozide on third instar S.littoralis larvae were 6.6 × 105 OB/ml, 0.26 mg a.i./L, and 13.92 mg a.i./L, respectively. The results of simultaneous treatments showed additive effects for B. thuringiensis and B. bassiana with each of the IGRs tested. An antagonistic effect occurred when SlNPV and tebufenozide were administered simultaneously. In contrast, the combination of SlNPV and lufenuron resulted in a significantly higher larval mortality rate than treatments using each agent alone. It is concluded that simultaneous applications of these entomopathogens together with low concentrations of the IGRs can be included in Integrated Pest Management (IPM) programmes, exception of the combination SlNPV and tebufenozide. A product based on lufenuron and the SlNPV is presented as a potential candidate for commercial development.

Fabrication of ultrafine sporopollenin particles and its application as pesticide carrier

Control release formulation is of great interest to pesticide researchers due to its programmable release of active ingredients with low environmental risk. The carrier is a dominant factor affecting the performance of the preparation. In this work, a copper-based fungicide is developed using plant sporopollenin materials as a control release carrier. Although sporopollenin is regarded as the toughest natural material, sporopollenin was broken down into nano- and micro- particles along with the modified surface chemistry by a facile oxidation treatment. The surface chemistry of sporopollenin is characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS) and Boehm titration. The resulting ultrafine sporopollenin particles (USPs) show a high copper(II) loading capacity of 435 mg/g, owing to the electrostatic effect. Furthermore, copper(II) can be released from copper(II)–sporopollenin complex (Cu-USPs) in a pH-dependent manner. As a proof of concept, Cu-USPs show very promising activity against a plant-specific pathogen-Pectobacterium carotovorum. Overall, this paper shed light on developing sporopollenin-derived functional materials for pesticide delivery.

Organic micropollutants, heavy metals and pathogens in anaerobic digestate based on food waste

Anaerobic digestate based on food waste is increasingly used as fertilizer in food production. This study examined the characteristics of anaerobic digestate based on food waste from three biogas plants in Sweden. The characterization included measurements of heavy metals (n = 7), chemicals of emerging concern (CECs), such as currently used drugs and pesticides (n = 133), and an extended range of food-borne pathogens, including two notable sporeformers and some widespread antibiotic-resistant bacteria. The amounts of Escherichia coli, enterococci, and Salmonella and the concentrations of the target heavy metals were all below the maximum accepted levels at all three locations studied. However, the spore-forming Bacillus cereus was found to be present at high levels in samples from all three biogas plants. Among the 133 CECs investigated, 48 were detected at least once, and the highest concentrations were found for pyroxidine, nicotine, caffeine, theobromine, and nicotine. The biofertilizers from the different biogas plants had similar CEC profiles, which indicate similarities in household waste composition and thorough mixing in the biogas plants. If this profile is found to be spatially and temporally consistent, it can help regulators to establish priority lists of CECs of top concern. Assuming increasing use of biofertilizers for food production in the future, it would be beneficial to have concentration limits for CECs Risk estimation based on risk quotients (RQs) indicated generally low environmental risks associated with application of biofertilizer to soils for food crop production. However, the toxicity of CEC mixtures needs to be considered when estimating the risks from application of biofertilizers on agricultural land or in other production systems.

Application of natural hydroxyapatite in the treatment of polluted water: Utilization of dromedary bone as bioadsorbent

AbstractIn this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X‐ray diffraction, elemental analysis X‐ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo‐second‐order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.

Development of a Preemergent Nanoherbicide: From Efficiency Evaluation to the Assessment of Environmental Fate and Risks to Soil Microorganisms.

Nanoparticles based on biodegradable polymers have been shown to be excellent herbicide carriers, improving weed control and protecting the active ingredient in the crop fields. Metribuzin is often found in natural waters, which raises environmental concerns. Nanoencapsulation of this herbicide could be an alternative to reduce its losses to the environment and improve gains in its efficiency. However, there is a paucity of information about the behavior of nanoformulations of herbicides in environmental matrices. In this study, the stability of nanoencapsulated metribuzin in polymeric nanoparticles (nanoMTZ) was verified over time, as well as its dissipation in different soils, followed by the effects on soil enzymatic activity. The physiological parameters and control effects of nanoMTZ on Ipomoea grandifolia plants were investigated. No differences were verified in the half-life of nanoencapsulated metribuzin compared to a commercial formulation of the herbicide. Moreover, no suppressive effects on soil enzymatic activities were observed. The retention of nanoMTZ in the tested soils was lower compared to its commercial analogue. However, the mobility of nanoencapsulated metribuzin was not greatly increased, reflecting a low risk of groundwater contamination. Weed control was effective even at the lowest dose of nanoMTZ (48 g a.i. ha-1), which was consistent with the higher efficiency of nanoMTZ compared to the conventional herbicide in inhibiting PSII activity and decreasing pigment levels. Overall, we verified that nanoMTZ presented a low environmental risk, with increased weed control.

INTERACTIONS BETWEEN GREEN MANURE AND ROCK PHOSPHATE ON SOIL NUTRIENT CYCLING ON FAMILY FARMS

ABSTRACT Family farming is important for the production of food for human consumption, but it lacks resources to invest in the soil fertility of its crops. The objective of this study was to analyze whether the use of green manures increases soil fertility in terms of the nutrients N, P and K with low environmental risk for family agricultural production. An experiment was set up in the State of Mato Grosso (Brazil), in randomized complete block design, with a 6 x 3 factorial scheme, four replications, corresponding to 6 types of plants and 3 doses of phosphorus. Leguminous green manure plants were: velvet bean, Crotalaria juncea, Crotalaria ochroleuca and dwarf pigeon pea, in addition to plots with pearl millet and weedy fallow control. Rock phosphate (i.e., reactive natural phosphate) was applied as a source of phosphorus at 0, 50 and 100 kg P2O5 ha-1. The species used as green manure were cut in full bloom and the levels of N, P, K and C in plants and soil were determined. Leguminous green manure plants, after mineralization, increased the stocks of N, P and K in the soil. Crotalaria juncea was the one that reached the highest N accumulation in its constitution, being recommended in the intercropping with species with C/N ratio > 30 to minimize risks of contamination with nitrate in the soil. This work concluded that the managements with green manure plants, especially Crotalaria ochroleuca, are recommended and environmentally safe technical alternatives for family farming.

Geochemical and hydrological evolution of mine impacted waters at the Argyle Diamond Mine, Western Australia

The lamproite ore body at the recently closed Argyle diamond mine is geochemically benign, but the surrounding sedimentary sequence contains two thin pyritic black shale beds that are prone to acidification. Although the waste rock is on average net neutralizing, some localized acidification and sulfate release was first observed in 1999 after 15 years of open pit mining. Contact and receiving water quality have been actively managed and monitored for 20 years to further limit the already low environmental risks posed by nitrate, nickel, magnesium and sulfate. All four solutes exhibited increasing concentrations across the monitoring network during or shortly after the period of peak waste rock production from 1999 to 2004. Since open pit mining and associated rock blasting ended in 2013, concentrations of nitrate have declined by 50%–90% at most locations. Nickel concentrations have also declined by 30% at the two acidic waste rock seeps which account for 80% of the dissolved nickel load. Sulfate and magnesium concentrations generally peaked between 2010 and 2013 and have not exhibited any significant increasing or decreasing trends since then. Annual offsite sulfate release since 2014 has averaged about 0.4% of the total sulfur inventory stored on site. Future sulfate concentrations and loads are predicted to gradually decline as the remaining sulfur inventory is depleted. Even during the 2005 to 2008 period, when all solute release rates were near their maximum, the receiving aquatic ecosystems remained intact with only subtle changes to some invertebrate communities. It is clear that peak release rates have already passed. The geochemical evolution at Argyle is much more rapid than at most other large mines. This is likely due to several factors including: 1. the low mean sulfur concentrations in the black shales; 2. the short geochemical lag time in the reactive units; 3. the high annual rainfall; and 4. a black shale segregation program that was initiated in roughly 1996.