Duckweed has shown great potential for both energy and environmental applications, particularly in wastewater treatment and fuel ethanol production. A rhizobacterium, Exiguobacterium sp. MH3, has been reported to associate with the duckweed Lemna minor for symbiotic growth. The aim of this work is to study the effects of rhizobacterium MH3 on L. minor growth and chromium (Cr) remediation. It appeared to have a synergism between the rhizobacterium MH3 and duckweed; the presence of strain MH3 promoted the growth of duckweeds by increasing both the frond number and dry weight of duckweed by more than 30 %, while duckweed in turn provided essential carbon source and energy for the growth of rhizobacterium MH3. Under Cr(VI) exposure, particularly at higher Cr(VI) concentrations, Exiguobacterium sp. MH3 significantly alleviated the harmful effects of the stress on the duckweed by promoting duckweed growth and preventing duckweed from excessive uptake of Cr. Potential mechanisms were also discussed in light of the genome sequence of strain MH3, and it was speculated that siderophores and indole-3-acetic acid (IAA) secreted by strain MH3 might contribute to promoting duckweed growth.

This study aims to understand the mechanisms of nitrite appearance during wastewater denitrification by biofilters, focusing on the role of the carbon source. Experiments were carried out at lab-scale (batch tests) and full-scale plant (Parisian plant, capacities of 240,000 m³ day⁻¹). Results showed that the nature of the carbon source affects nitrite accumulation rates. This accumulation is low, 0.05 to 0.10 g N-NO₂ ⁻ per g N-NO₃ ⁻ eliminated, for alcohols such as methanol, ethanol, or glycerol. The utilization of glycerol leads to fungal development causing clogging of the biofilters. This fungal growth and consequent clogging exclude this carbon source, with little nitrite accumulation, as carbon source for denitrification. Whatever the carbon source, the C/N ratio in the biofilter plays a major role in the appearance of residual nitrite; an optimal C/N ratio from 3.0 to 3.2 allows a complete denitrification without any nitrite accumulation.

Thallium (Tl) is very toxic to mammals but little is known about its accumulation by plants, and it would be useful if prediction of Tl accumulation could be done using potassium (K) accumulation models. The objectives of this study were to compare the uptake kinetics of Tl⁺ and K⁺, and to determine how readily K⁺ can inhibit Tl⁺ uptake. Durum wheat (Triticum turgidum L.) and spring canola (Brassica napus L.) were grown hydroponically and exposed to 0–75 μM Tl or 0–250 μM K for up to 150 min (kinetics experiment), or to 0.1 or 10 μM Tl with Tl to K ratios of 1:1 to 1:10,000 for up to 300 min (competition experiment). The rate of uptake of Tl⁺ by canola was about three to five times faster than by wheat, while the rate of Tl⁺ uptake in wheat was the same as the rate of K⁺ uptake by either species. Uptake of Tl⁺ was more readily suppressed by K⁺ in wheat than in canola. When exposed to 0.1 uM Tl for 300 min with 100 or 1,000 uM K⁺, Tl⁺ uptake by wheat was reduced by 20 % and 50 %, respectively, while Tl⁺ uptake by canola was not reduced. Our results suggest that predicting Tl accumulation using a K accumulation model with a correction factor may be possible for canola, but would be much more difficult for wheat, since uptake of Tl⁺ is very sensitive to levels of K.

Increasing use of heavy metals in various fields, their environmental persistency, and poor regulatory efforts have significantly increased their fraction in river water. We studied the effect of Musi river water pollution on oxidative stress biomarkers and histopathology in rat after 28 days repeated oral treatment. River water analysis showed the presence of Zn and Pb at mg/l concentration and Ag, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Sn, and Sb at μg/l concentration. River water treatment resulted in a dose-dependent accumulation of metals in rat organs, being more in liver followed by kidney and brain. Metal content in both control and low-dose group rat organs was below limit of detection. However, metal bioaccumulation in high- and medium-dose group organs as follows: liver—Zn (21.4 & 14.5 μg/g), Cu (8.3 & 3.6 μg/g), and Pb (8.2 & 0.4 μg/g); kidney—Zn (16.2 & 7.9 μg/g), Cu (3.5 & 1.4 μg/g), Mn (2.9 & 0.5 μg/g), and Pb (2.6 & 0.5 μg/g); and brain—Zn (2.4 & 1.1 μg/g), and Ni (1 & 0.3 μg/g). These metals were present at high concentrations in respective organs than other metals. The increased heavy metal concentration in treated rat resulted significant increase in superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione S transferase enzymes activity, and lipid peroxidation in a dose-dependent manner. However, glutathione content and catalase activity were significantly decreased in treated rat organs. Histopathological examination also confirmed morphological changes in rat organs due to polluted river water treatment. In conclusion, the findings of this study clearly indicate the oxidative stress condition in rat organs due to repeated oral treatment of polluted Musi river water.

An intensive measurement campaign was undertaken to characterize eight fractions of organic carbon (OC) and elemental carbon (EC) in particulate matter (PM) at four urban sites with different pollution characteristics during summer, post-monsoon, and winter at Kanpur, India. Speciation samplers were used to collect particulate samples on quartz filters followed by analysis of OC and EC using Interagency Monitoring of Protected Visual Environments (IMPROVE)-based thermal/optical reflectance (TOR) method. Based on 24-h average results at each site, the highest levels of OC and EC were observed during winter as 96.7 ± 26.9 and 31.8 ± 9.8 μg/m³ at residential site and traffic site, respectively. The levels of OC at residential sites during winter appeared to be more than twice of that during summer. The site close to the road traffic had the least value of OC/EC, as 1.77 ± 0.28 during post-monsoon, and the site influenced by emissions of domestic cooking and heating had the highest value of OC/EC, as 4.05 ± 0.79 during winter. The average abundances of OC1, OC2, OC3, OC4, OP, EC1, EC2, and EC3 in total carbon (TC) at all sites for three seasons were 10.03, 19.04, 20.03, 12.32, 10.53, 33.39, 3.21, and 1.99 %, respectively. A sharp increase in levels of OC1 and EC1-OP during winter at two residential sites revealed that biomass burning could be a significant contributor to carbonaceous aerosols. From the application of EC-tracer method, it was observed that contribution of secondary organic carbon (SOC) to PM mass increased from 5 % during post-monsoon to 16 % during winter at residential sites and from 2 % during post-monsoon to 7 % during winter at traffic sites. Therefore, it could be inferred that increase in primary emissions coupled with unfavorable meteorological conditions could cause particle agglomeration and hygroscopic growth, leading to unpleasant pollution episode during winter.

During degradation of cyanobacterial blooms, some derived pollutants are released to the waters and last for a while before returning to normal levels. To assess whether the offspring of exposed Daphnia was affected by their maternal experience, we exposed mother Daphnia magna to mixtures of unionized ammonia (0, 0.30, and 0.48 mg L⁻¹) and microcystin-LR (0, 10, 30, and 100 μg L⁻¹) for 10 days and then immediately moved their offspring to a toxicant-free environment. The offspring were cultured for 21 days to record their survival, development, and reproduction. Results showed that the survival of the offspring of D. magna that experienced high doses of mixed toxicants decreased significantly, but there was no significant difference in development among the survivors of the offspring from different maternal treatments. However, reproductive performances significantly differed among the offspring from different maternal treatments, indicating that there existed a maternal effect in the offspring of D. magna that experienced high levels of mixed toxicants.

Nanofertilizers may be more effective than regular fertilizers in improving plant nutrition, enhancing nutrition use efficiency, and protecting plants from environmental stress. A hydroponic pot experiment was conducted to study the role of foliar application with 2.5 mM nano-silicon in alleviating Cd stress in rice seedlings (Oryza sativa L. cv Youyou 128) grown in solution added with or without 20 μM CdCl₂. The results showed that Cd treatment decreased the growth and the contents of Mg, Fe, Zn, chlorophyll a, and glutathione (GSH), accompanied by a significant increase in Cd accumulation. However, foliar application with nano-Si improved the growth, Mg, Fe, and Zn nutrition, and the contents of chlorophyll a of the rice seedlings under Cd stress and decreased Cd accumulation and translocation of Cd from root to shoot. Cd treatment produced oxidative stress to rice seedlings indicated by a higher lipid peroxidation level (as malondialdehyde (MDA)) and higher activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and a lower GSH content. However, those nano-Si-treated plants had lower MDA but higher GSH content and different antioxidant enzyme activities, indicating a higher Cd tolerance in them. The results suggested that nano-Si application alleviated Cd toxicity in rice by decreasing Cd accumulation, Cd partitioning in shoot and MDA level and by increasing content of some mineral elements (Mg, Fe, and Zn) and antioxidant capacity.

A detailed gamma ray spectrometry survey was carried out to make an action in environmental impact assessment of urbanization and industrialization on Port Said city, Egypt. The concentrations of the measured radioelements U-238, Th-232 in ppm, and K-40 %, in addition to the total counts of three selected randomly dumping sites (A, B, and C) were mapped. The concentration maps represent a base line for the radioactivity in the study area in order to detect any future radioactive contamination. These concentrations are ranging between 0.2 and 21 ppm for U-238 and 0.01 to 13.4 ppm for Th-232 as well as 0.15 to 3.8 % for K-40, whereas the total count values range from 8.7 to 123.6 uR. Moreover, the dose rate was mapped using the same spectrometer and survey parameters in order to assess the radiological effect of these radioelements. The dose rate values range from 0.12 to 1.61 mSv/year. Eighteen soil samples were collected from the sites with high radioelement concentrations and dose rates to determine the activity concentrations of Ra-226, Th-232, and K-40 using HPGe spectrometer. The activity concentrations of Ra-226, Th-232, and K-40 in the measured samples range from 18.03 to 398.66 Bq kg⁻¹, 5.28 to 75.7 Bq kg⁻¹, and 3,237.88 to 583.12 Bq kg⁻¹, respectively. In addition to analyze heavy metal for two high reading samples (a₁and a₁₀) which give concentrations of Cd and Zn elements (a₁40 ppm and a₁₀42 ppm) and (a₁0.90 ppm and a₁₀0.97 ppm), respectively, that are in the range of phosphate fertilizer products that suggested a dumped man-made waste in site A. All indicate that the measured values for the soil samples in the two sites of three falls within the world ranges of soil in areas with normal levels of radioactivity, while site A shows a potential radiological risk for human beings, and it is important to carry out dose assessment program with a specifically detailed monitoring program periodically.

In the West African savanna zone, traditional subsistence farming increasingly shifts to cash crop farming and in particular to cotton cultivation, which is accompanied by application of pesticides. Increasing use of pesticides by smallholder farmers is suspected to have negative effects on non-target organisms. In this study, possible pesticide impact on the development of tadpoles was investigated. Two insecticide formulations used in cotton cultivation in Benin were compared: Cotofan® (active ingredient (a.i.): α- and β-endosulfan) and Tihan® (a.i.: spirotetramat and flubendiamide). Tadpoles of the widespread species Amietophrynus maculatus were kept in small water basins with increasing insecticide concentrations (1, 10 and 100 μg a.i./L) over a period of 28 days. Tadpoles showed reduced survival at the highest endosulfan concentrations (100 μg/L). Survival of tadpoles undergoing metamorphosis was not influenced by Tihan®. Endosulfan in concentrations of 10 and 100 μg/L negatively impacted the movement of the tadpoles which was not the case for the mixture of spirotetramat and flubendiamide. Time to metamorphosis was not significantly different in the various treatments. Tail length of tadpoles was significantly shorter in Cotofan® treatments compared to controls. Pesticide residues in the tadpoles were relatively low after keeping them in concentrations of 1 and 10 μg a.i./L (25 and 26 μg/kg wet weight (w/w) for the sum of α-endosulfan, β-endosulfan and endosulfan sulphate and below the detection limits for flubendiamide and spirotetramat). For the 100 μg a.i./L treatments, 1,600 μg/kg w/w was found of α-endosulfan, β-endosulfan and endosulfan sulphate together in the survived tadpoles and 21 μg/kg w/w of flubendiamide.

The present investigation deals with the prediction of the performance of simultaneous anaerobic sulfide and nitrate removal in an upflow anaerobic sludge bed (UASB) reactor through an artificial neural network (ANN). Influent sulfide concentration, influent nitrate concentration, S/N mole ratio, pH, and hydraulic retention time (HRT) for 144 days’ steady-state condition were the inputs of the model; whereas output parameters were sulfide removal percentage, nitrate removal percentage, sulfate production percentage, and nitrogen production percentage. The prediction performance was evaluated by calculating root mean square error (RMSE), mean absolute error (MAE), mean absolute relative error (MARE), and determination coefficient (R ²) values. Generally, the ANN model exhibited good prediction of the simultaneous sulfide and nitrate removal process. The effect of five input parameters to the performance of the reactor was quantified and compared using the connection weights method, Garson’s algorithm method, and partial derivatives (PaD) method. The results showed that HRT markedly affects the performance of the reactor.