Nitrate is a worldwide pollutant in aquifers. Shallow aquifer nitrate concentrations generally display vertical stratification, with a maximum concentration immediately below the water level. The concentration then gradually decreases with depth. Different techniques can be used to highlight this stratification. The paper aims at comparing the advantages and limitations of three open hole multilevel sampling techniques (packer system, dialysis membrane samplers and bailer), chosen on the base of a literary review, to highlight a nitrate vertical stratification under the assumption of (sub)horizontal flow in the aquifer. The sampling systems were employed at three different times of the year in a shallow aquifer piezometer in northern Italy. The optimal purge time, equilibration time and water volume losses during the time in the piezometer were evaluated. Multilevel techniques highlighted a similar vertical nitrate stratification, present throughout the year. Indeed, nitrate concentrations generally decreased with depth downwards, but with significantly different levels in the sampling campaigns. Moreover, the sampling techniques produced different degrees of accuracy. More specifically, the dialysis membrane samplers provided the most accurate hydrochemical profile of the shallow aquifer and they appear to be necessary when the objective is to detect the discontinuities in the nitrate profile. Bailer and packer system showed the same nitrate profile with little differences of concentration. However, the bailer resulted much more easier to use.

Salicylic acid (SA) mediates tolerance mechanisms in plants against a wide spectrum of biotic and abiotic stresses. Therefore, the present study was carried out to determine how SA regulates the plant protection mechanisms in two cultivars of oilseed rape (Brassica napus L.) under chromium (Cr) stress. Exogenously applied SA enhanced plant growth, increased dry biomasses, and strengthened the reactive oxygen scavenging system by improving cell organelles that were severely damaged via Cr toxicity. The contents of Cr were significantly enhanced in both root and leaf of cultivar Zheda 622 (yellow color) compared with cultivar ZS 758 (black color). Exogenous application of SA significantly reduced the Cr contents in both plant organs as well as enhanced the SA contents under Cr stress. A dose-dependent increase was observed in reactive oxygen species (ROS) generation under Cr stress. To ease the inimical effects of ROS, plants’ defense systems were induced under Cr stress, and SA further enhanced protection. Further, TEM micrographs results showed that Cr stress alone significantly ruptured the plant cell organelles of both cultivars by increasing the size of starch grain and the number of plastoglobuli, damaging the chloroplast and mitochondrion structures. However, exogenously applied SA significantly recovered these damages in the plant cells of both cultivars. It was also observed that cultivar ZS 758 was proved to be more tolerant under Cr toxicity. Gene expression analysis revealed that combined treatments of Cr and SA increased antioxidant-related gene expression in both cultivars. Findings of the present study demonstrate that SA induces the enzymatic antioxidant activities and related gene expression, secondary metabolism, and improves the cell structural changes and the transcript level of specific stress-associated proteins in root and leaf of two oilseed rape cultivars under Cr toxicity.

Reverse osmosis concentrate (ROC) from municipal wastewater reclamation reverse osmosis (mWRRO) contains elevated concentrations of contaminants which pose potential risks to aquatic environment. The treatment of ROC from an mWRRO using granular activated carbon (GAC) combined pretreatment of coagulation was optimized and evaluated. Among the three coagulants tested, ferric chloride (FeCl₃) presented relatively higher DOC removal efficiency than polyaluminium chloride and lime at the same dosage and coagulation conditions. The removal efficiency of DOC, genotoxicity, and antiestrogenic activity concentration of the ROC could achieve 16.9, 18.9, and 39.7 %, respectively, by FeCl₃ coagulation (with FeCl₃ dosage of 180.22 mg/L), which can hardly reduce UV₂₅₄ and genotoxicity normalized by DOC of the DOM with MW <5 kDa. However, the post-GAC adsorption column (with filtration velocity of 5.7 m/h, breakthrough point adsorption capacity of 0.22 mg DOC/g GAC) exhibited excellent removal efficiency on the dominant DOM fraction of MW <5 kDa in the ROC. The removal efficiency of DOC, UV₂₅₄, and TDS in the ROC was up to 91.8, 96, and 76.5 %, respectively, by the FeCl₃ coagulation and post-GAC adsorption. Also, the DOM with both genotoxicity and antiestrogenic activity were completely eliminated by the GAC adsorption. The results suggest that GAC adsorption combined pretreatment of FeCl₃ coagulation as an efficient method to control organics, genotoxicity, and antiestrogenic activity in the ROC from mWRRO system.

Nitrate (NO₃ ⁻) pollution is a severe problem in urban aquatic systems especially within megacity undergoing rapid urbanization, and mostly, sewage is supposed as the prevailing NO₃ ⁻ source. A dual isotope approach (δ ¹⁵N-NO₃ ⁻ and δ ¹⁸O-NO₃ ⁻) was applied to explore the variation in NO₃ ⁻ isotopic signatures in sewage processed by wastewater treatment plants (WWTPs) in Beijing from 2014 to 2015. We found that the raw and treated sewage owned the different NO₃ ⁻ isotopic signatures, including δ ¹⁵N from 1.1 to 24.7 ‰ and δ ¹⁸O from 1.6 to 22.8 ‰ in raw sewage, as well as δ ¹⁵N from 6.1 to 22.8 ‰ and δ ¹⁸O from 1.6 to 13.2 ‰ in treated effluents. The WWTP processing would result in the enrichment of NO₃ ⁻ isotopic compositions in discharged effluents with NO₃ ⁻ concentrations increasing. Besides, advanced sewage treatment technology with more pollutant N reduction may raise the heavier NO₃ ⁻ isotopic compositions further. The NO₃ ⁻ isotope value ranges of urban sewage and manure should be separated, and the seasonal and tighter NO₃ ⁻ isotope value ranges are supposed to improve the accuracy of source apportionment. The NO₃ ⁻ isotope value ranges conducted in this study might provide useful information for tracing NO₃ ⁻ sources towards the implementation of efficient water pollution control in Beijing.

The land disposal of waste and wastewater is a major source of N₂O emission. This is due to the presence of high concentrations of nitrogen (N) and carbon in the waste. Abattoir wastewater contains 186 mg/L of N and 30.4 mg/L of P. The equivalent of 3 kg of abattoir wastewater-irrigated soil was sieved and taken in a 4-L plastic container. Abattoir wastewater was used for irrigating the plants at the rates of 50 and 100 % field capacity (FC). Four crop species were used with no crop serving as a control. Nitrous oxide emission was monitored using a closed chamber technique. The chamber was placed inside the plastic container, and N₂O emission was measured for 7 days after the planting. A syringe and pre-evacuated vial were used for collecting the gas samples; a fresh and clean syringe was used each time to avoid cross-contamination. The collected gas samples were injected into a gas chromatography device immediately after each sampling to analyse the concentration of N₂O from different treatments. The overall N₂O emission was compared for all the crops under two different abattoir wastewater treatment rates (50 and 100 % FC). Under 100 % FC (wastewater irrigation), among the four species grown in the abattoir wastewater-irrigated soil, Medicago sativa (23 mg/pot), Sinapis alba (21 mg/pot), Zea mays (20 mg/pot) and Helianthus annuus (20 mg/pot) showed higher N₂O emission compared to the 50 % treatments—M. sativa (17 mg/pot), S. alba (17 mg/pot), Z. mays (18 mg/pot) and H. annuus (18 mg/pot). Similarly, pots with plants have shown 15 % less emission than the pots without plants. Similar trends of N₂O emission flux were observed between the irrigation period (4-week period) for 50 % FC and 100 % FC. Under the 100 % FC loading rate treatments, the highest N₂O emission was in the following order: week 1 > week 4 > week 3 > week 2. On the other hand, under the 50 % FC loading rate treatments, the highest N₂O emission was recorded in the first few weeks and in the following order: week 1 > week 2 > week 3 > week > 4. Since N₂O is a greenhouse gas with high global warming potential, its emission from wastewater irrigation is likely to impact global climate change. Therefore, it is important to examine the effects of abattoir wastewater irrigation on soil for N₂O emission potential.

Traditionally, a few processes have to be employed in sequence for multi-dye removal, due to the different physical and chemical characteristics of the dyes. In this study, we innovatively developed an integrated adsorption and Fenton oxidation fluidized bed reactor (FBR) based on the hydraulic classification theory, which could efficiently remove dispersed red, acid yellow, and reactive brilliant dyes. The fluidized solids such as ceramsite and activated carbon could be separately fluidized at the bottom and the top part of the FBR, respectively. As a result, Fenton oxidization of dyes was promoted by the fluidization of ceramsite and activated carbon. Besides, adsorption of activated carbon could synergistically act on the dyes. The results showed that the removal efficiencies of acid yellow 2G, disperse red 60, and reactive brilliant blue X-BR could reach 100, 79.8, and 84.9 % in 10 min, respectively. Lots of intermediates with unsaturated bonds were generated during Fenton reaction, which was further removed by adsorption of activated carbon. Consequently, a high COD removal of 93 % was obtained. Interestingly, some of Fe³⁺ produced during Fenton reaction was further precipitated and crystallized as FeO(OH) or Fe(OH)₃ on the surface of activated carbon and ceramsite, which could be potentially recycled for further utilization as a heterogeneous catalyst. Meanwhile, the other Fe³⁺ might be removed in the form of ferro-organic complexes by adsorption onto the activated carbon. Thus, only a little iron hydroxide sludge was generated in the FBR. This novel FBR gave us an effective clue to realize multi-reactions for textile wastewater treatment by employing hydraulic classification fluidization.

Using inductively coupled plasma mass spectrometry (ICP-MS), the lead concentrations and isotope ratios of 32 kinds of seafood collected from local markets of China were measured. Among these seafoods, the highest concentrations of lead were found in Patinopecten yessoensis and Mugil cephalus, which were 2.94 ± 0.40 and 2.02 ± 0.26 μg g⁻¹ of dry weight, respectively. Pb concentration was found to be higher in benthic fish than in other fish. The result indicated that lead concentrations in some seafood exceeded the maximum levels of Pb in foods proposed by European Commission (EC). Nine species of cooked seafood were chosen to feed mice (35–38 g). The result showed that Pb oral bioavailability of cooked seafood in vivo was below 10 %. Furthermore, oral bioavailability of the same lead-containing seafood increased greatly in pregnant mice compared with non-pregnant mice.

The breakage and regrowth of flocs formed by sweep flocculation were investigated on different flocculation mechanisms using additional dosage coagulant of poly aluminium chloride (PACl) and non-ionic polyacrylamide (PAM) to explore the reversibility after floc breakage. The optimal dosage of PACl was 0.15 mM (as alum), and zeta potential exceeding 1 mV meant that sweep flocculation was dominant in the pre-flocculated process. Re-coagulation efficiency increased with additional coagulants dosing, and sedimentation rates of flocs re-formed by small additional dosage of non-ionic PAM are faster than that of flocs re-formed by additional PACl. For additional inorganic coagulant (PACl) during regrowth processes, few negatively charged particles that existed in water sample restricted the effect of charge neutralization. An amorphous aluminum hydroxide precipitation could re-activate the weaker points on the broken floc surface, but regrown flocs have loose structure indicating worse settleability. For additional non-ionic PAM dosing, lower dosage showed large values of fractal dimension and average size, probably due to that unfolded curly molecular chain and exposed amide groups of non-ionic PAM which provide superb conditions for amide group interacting with particles. The use of non-ionic PAM in flocculation has advantage of being more effective than the cationic PACl, probably because it may avoid the re-stabilization of broken flocs by polymer adsorption driven by electrostatic attraction. Hence, appropriate dosing of PAM after breakage could improve the flocs characteristics with large size and compact structure.

Due to chemical and biochemical similarities between cadmium (Cd) and zinc (Zn), application of Zn may minimize Cd uptake by plants and ameliorate its toxicity. However, there is poor understanding of the comparative effectiveness of the foliar Zn application at different growth stages on Cd toxicity and accumulation in wheat. The present study was carried out to compare the effectiveness of foliarly applied Zn at different stages of plant growth to minimize Cd accumulation in wheat grains. Wheat (cv AARI-2011) was grown at three levels of soil Cd (0, 2.5, and 5.0 mg kg⁻¹). Foliar application of Zn was carried out at either tillering, jointing, booting, heading, or grain filling stage using 0.05 % w/v aqueous solution of ZnSO₄ · 7H₂O. Increasing soil Cd had a negative effect on growth and yield attributes, including tiller production, root length and dry weight, plant height, 100-grain weight and grain and straw yield. Zinc foliar spray increased grain yield by increasing tiller production; importantly, an application at booting was more effective than at other stages. Foliarly applied Zn decreased Cd concentration in the roots, straw, and grain. Similar to grain yield, the largest decrease (74 %) in Cd concentration was associated with Zn foliar spray at booting. Grain yield was negatively related to grain Cd concentration which in turn showed a negative relationship with Zn concentration in leaves and grains. It is concluded that the booting stage is the suitable time for foliar application of Zn to (i) effectively minimize a Cd-induced loss in grain yield and (ii) decrease grain Cd concentration.

A novel approach to improve the efficiency of Fenton treatment for sludge reduction through the implication of a deflocculating agent citric acid, for the exclusion of extracellular polymeric substances (EPS) from waste-activated sludge (WAS), was investigated. Deflocculation was achieved with 0.06 g/g suspended solids (SS) of citric acid dosage. Fenton optimization studies using response surface methodology (RSM) revealed that 0.5 and 0.0055 g/g SS were the optimal dosages of H₂O₂ and Fe²⁺. The addition of a cation-binding agent set the pH value of sludge to 5 which did not affect the Fenton efficiency. The results presented in this study shows the advantage of deflocculating the sludge as SS and volatile suspended solids (VSS) reductions were found to be higher in the deflocculated (53 and 63 %, respectively) than in the flocculated (22 and 34 %, respectively) sludges. Kinetic investigation of the treatment showed that the rate of the reaction was four times higher in the deflocculated sludge than control. The methodology reported in this manuscript was successfully applied to a real case were the deflocculated mediated Fenton process reduced the sludge disposal cost from 297.8 to 61.9 US dollars/ton of sludge.