Attraction of the potential biocontrol agent <Emphasis Type="Italic">Galerucella placida</Emphasis> (Coleoptera: Chrysomelidae) to the volatiles of <Emphasis Type="Italic">Polygonum orientale</Emphasis> (Polygonaceae) weed leaves

Galerucella placida Baly (Coleoptera: Chrysomelidae) is a potential biocontrol agent of the rice-field weed Polygonum orientale L. (Polygonaceae). The volatile organic compound (VOC) profiles from undamaged and mechanically damaged plants, and from plants 12- and 36-h following continuous feeding of female G. placida adults and 2nd instar larvae were identified and quantified by GC–MS and GC-FID analyses. Twenty-four and 21 compounds were identified in volatiles of undamaged and insect feeding plants, respectively; whereas 22 compounds were detected in volatiles of mechanically damaged plants. Decanal and 1-dodecanol were unique to undamaged plants, and linalool was detected in volatiles of undamaged and mechanically damaged plants, but not in volatiles of insect damaged plants. However, the beetles are not attracted by none of these volatile components, when tested individually in Y-shaped glass tube olfactometer bioassays. In all plants, methyl jasmonate was predominant. 1-Undecanol was the least amount in undamaged plants, and plants 12-h after feeding by G. placida adults and larvae; whereas 1-tridecanol was the least abundant in plants 36-h after feeding by G. placida adults and larvae, and mechanically damaged plants. The beetles showed significant preference to the whole volatile blends from plants 12-h after feeding by larvae and plants 36-h after feeding by either larvae or adults compared to those of undamaged plants. Further, G. placida responded to individual synthetic compounds, 3-hexanol, 1-octen-3-ol, nonanal, and geraniol at 7, 1.38, 3.75 and 4.5 µg/25 µL CH₂Cl₂, respectively, and provide a basis for attraction of the potential biocontrol agent in the field.     

Biosorbents for solid-phase extraction of toxic elements in waters

Some trace metals are highly toxic for the environment. There is therefore a need for reliable methods for the determination of metals at trace levels. To this end, new sample pretreatment methods such as separation, preconcentration and speciation prior to the determination of metal ions have developed rapidly. Biosorption has become a major tool for solid-phase extraction methods. This review covers selected biosorbents such as algae, bacteria, filamentous fungi and yeasts, as new sorbents used in the solid-phase extraction of metal ions from various water sample matrices. A survey of the literature over 2004-2014 shows possible applications of selected new sorbents available for use in trace metal analysis in waters using solidphase extraction. We highlight the preconcentration of the toxic elements prior to their determination by atomic spectrometry.     

High boron removal by functionalized magnesium ferrite nanopowders

Hydroxyl-enriched materials are promising boron adsorbents. However, the use of these materials is hampered by issues of separation, recovery, and selectivity, notably due to the presence of interfering ions. Therefore, we synthesized here a cheap magnetic nanopowder, which was further functionalized with polyvinyl alcohol and glycidol to produce boron-selective adsorbents. We studied their selectivity and removal efficiency using batch and fixed-bed systems. Sorption was studied at both concentrated and trace amounts of boron. Results show that nanopowders have 5.3–6.5 nm pore sizes and 145–203 m²/g surface areas, using Brunauer–Emmett–Teller analysis. Polyvinyl alcohol-functionalized particles removed 93 % of boron at 5 mg/L at pH 7 in 30 min, whereas only 68 % of boron was removed by glycidol-functionalized particles. However, at higher boron concentration, of 50 mg/L, glycidol-functionalized particles showed higher adsorption affinity of 68.9 mg/g. We conclude that internal hydroxyl groups of polyvinyl alcohol-functionalized particles are less accessible at higher boron concentration. This is the first report on magnesium ferrites for boron recovery. The spent adsorbents were separated easily from the aqueous media by an external magnet and repeatedly used. Overall, our findings demonstrated that the hydroxyl-enriched magnetic nanopowders are a better alternative to the existing boron adsorbents regarding magnetic separation, reusability, and selectivity.     

Simple model of sludge thickening process in secondary settlers

In wastewater treatment plants (WWTPs), a secondary settler acts as a clarifier, sludge thickener, and sludge storage tank during peak flows and therefore plays an important role in the performance of the activated sludge process. Sludge thickening occurs in the lower portions of secondary clarifiers during their operation. In this study, by detecting the hindered zone from the complete thickening process of activated sludge, a simple model for the sludge thickening velocity, u _s = aX ^b (a = 0.9925SSVI _3.5, b = 3.541ln(SSVI _3.5)+12.973), describing the potential and performance of activated sludge thickening in the hindered zone was developed. However, sludge thickening in the compression zone was not studied because sludge in the compression zone showed limited thickening. This empirical model was developed using batch settling data obtained from four WWTPs and validated using measured data from a fifth WWTP to better study sludge thickening. To explore different sludge settling and thickening mechanisms, the curves of sludge thickening and sludge settling were compared. Finally, it was found that several factors including temperature, stirring, initial depth, and polymer conditioning can lead to highly concentrated return sludge and biomass in a biologic reactor.     

Removal of elemental mercury by KI-impregnated clay

This study described the use of clay impregnated by KI in gas phase elemental mercury (Hg^o) removal in flue gas. The effects of KI loading, temperature, O₂, SO₂ and H₂O on Hg^o removal were investigated using a fixed bed reactor. The Hg^o removal efficiency of KI-clay with 3% KI loading could maintain at a high level (approximately 80 %) after 3 h. The KI-clay demonstrated to be a potential adsorbent for Hg^o removal when compared with activated carbon based adsorbent. O₂ was found to be an important factor in improving the Hg^o removal. O₂ was demonstrated to assist the transfer of KI to I₂ on the surface of KI-clay, which could react with Hg^o directly. NO and SO₂ could slightly improve Hg^o removal, while H₂O inhibited it greatly. The results indicated that after adsorption, most of the mercury escaped from the surface again. Some of the mercury may have been oxidized as it left the surface. The results demonstrated that the chemical reaction primarily occurred between KI and mercury on the surface of the KI-clay.     

A photolysis coefficient for characterizing the response of aqueous constituents to photolysis

UV photolysis and UV based advanced oxidation processes (AOPs) are gaining more and more attention for drinking water treatment. Quantum yield (ø) and molar absorption coefficient (ε) are the two critical parameters measuring the effectiveness of photolysis of a compound. The product of the two was proposed as a fundamental measure of a constituent’s amenability to transformation by photolysis. It was shown that this product, named the photolysis coefficient, k _p , can be determined using standard bench tests and captures the properties that govern a constituent’s transformation when exposed to light. The development showed the photolysis coefficient to be equally useful for microbiological, inorganic and organic constituents. Values of k _p calculated by the authors based on quantum yield and molar absorption coefficient data from the literature were summarized. Photolysis coefficients among microorganisms ranged from 8500 to more than 600000 and are far higher than for inorganic and organic compounds, which varied over a range of approximately 10 to 1000 and are much less sensitive to UV photolysis than the microorganisms.     

Characterization of the genes involved in nitrogen cycling in wastewater treatment plants using DNA microarray and most probable number-PCR

To improve nitrogen removal performance of wastewater treatment plants (WWTPs), it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods:most probable number-polymerase chain reaction (MPN-PCR) and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional activated sludge processes (CAS) are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern:the nirS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectively. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes (AO), whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.

Open image in new window

     

Characteristics and mixing state of S-rich particles in haze episodes in Beijing

Direct individual analysis using Scanning Electron Microscopy combined with online observation was conducted to examine the S-rich particles in PM_2.5 of two typical polluted haze episodes in summer and winter from 2014 to 2015 in Beijing. Four major types of S-rich particles, including secondary CaSO₄ particles (mainly observed in summer), S-rich mineral particles (SRM), S-rich water droplets (SRW) and (C, O, S)-rich particles (COS) were identified.We found the different typical morphologies and element distributions of S-rich particles and considered that (C, O, S)-rich particles had two major mixing states in different seasons. On the basis of the S-rich particles’ relative abundances, S concentrations and their relationships with PM_2.5 as well as the seasonal comparison, we revealed that the S-participated formation degrees of SRM and SRW would enhance with increasing PM_2.5 concentration. Moreover, C-rich matter and sulfate had seasonally different but significant impacts on the formation of COS.

Open image in new window

     

Environmental deterioration of farmlands caused by the irrational use of agricultural technologies

Without considering the ecosystem-dependence of agricultural production, irrational use of agricultural technologies could bring only short-term economic benefits but leave long-term environmental deterioration. If some agricultural lands have to be abandoned because of these technologies such as chemical films or groundwater depletion, it will aggravate the burden of remaining lands for maintaining or enhancing production. Thus, agricultural production should be a part of public services, requiring the consideration of interests of different stakeholders and sustainability.     

Improved blending strategy for membrane modification by virtue of surface segregation using surface-tailored amphiphilic nanoparticles

Membrane modification is one of the most feasible and effective solutions to membrane fouling problem which tenaciously hampers the further augmentation of membrane separation technology. Blending modification with nanoparticles (NPs), owing to the convenience of being incorporated in established membrane production lines, possesses an advantageous viability in practical applications. However, the existing blending strategy suffers from a low utilization efficiency due to NP encasement by membrane matrix. The current study proposed an improved blending modification approach with amphiphilic NPs (aNPs), which were prepared through silanization using 3-(Trimethoxysilyl)propyl methacrylate (TMSPMA) as coupling agents and ZnO or SiO₂ as pristine NPs (pNPs), respectively. The Fourier transform infrared and X-ray photoelectron spectroscopy analyses revealed the presence of appropriate organic components in both the ZnO and SiO₂ aNPs, which verified the success of the silanization process. As compared with the pristine and conventional pNP-blended membranes, both the ZnO aNP-blended and SiO₂ aNP-blended membranes with proper silanization (100% and 200%w/w) achieved a significantly increased blending efficiency with more NPs scattering on the internal and external membrane surfaces under scanning electron microscope observation. This improvement contributed to the increase of membrane hydrophilicity. Nevertheless, an extra dosage of the TMSPMA led to an encasement of NPs, thereby adversely affecting the properties of the resultant membranes. On the basis of all the tests, 100% (w/w) was selected as the optimum TMSPMA dosage for blending modification for both the ZnO and SiO₂ types.

Open image in new window