Search

The association of melting Himalayan glaciers and planetary health is complex. Climate change has accelerated the melting of Himalayan glaciers, with profound impacts on the planetary health realms of the Himalayan region and that now threaten hundreds of millions of people. Using a complex adaptive systems framework based on a systematic literature review, this complexity has been captured and mapped in nine subsystem categories: ecological services, disaster, water security, food security, energy security, livelihood and culture, migration, conflict and public health. This mapping helps to explain linkages between melting glaciers and associated planetary health issues, which can be helpful in planning for better planetary health.

Catalysis of the hydrolysis of the organ phosphorus compound, quinalphos (Q) by (hydr) oxides was studied at pH 4.0, 7.0, and 10.0, and at 25oC. FeOOH and Al(OH)3 were the used solids for this research. Catalysis of quinalphos was followed by determining the disappearance of Q and the appearance of 2-hydroxyquinoxaline (HQ) product in the absence and presence of (hydr) oxides using HPLC with UV detector. Under these conditions, both hydroxides (FeOOH and Al(OH)3) have catalyzed the hydrolysis of quinalphos. In this study, FeOOH was found to be the best catalyst at the used pHs. It is apparent that at pH 10.0, Kobs for disappearance of Q is almost equal to that for the appearance of HQ, which indicates that hydrolysis of Q at pH 10.0 follows SN2 (P) pathway. On the other hand, at pH 4.0 and 7.0, hydrolysis of Q may have followed two pathways, SN2 (P) and SN2 (C), as Kobs for producing HQ is smaller than that for loss of Q.

COVID-19 can be characterized as an outcome of degraded planetary health drivers in complex systems and has wide-reaching implications in social, economic and environmental realms. To understand the drivers of planetary health that have influences of emergence and spread of COVID-19 and their implications for sustainability systems thinking and a narrative literature review are deployed. In particular, sixteen planetary health drivers are identified, i.e., population growth, climate change, agricultural intensification, urbanization, land use and land cover change, deforestation, biodiversity loss, globalization, wildlife trade, wet markets, non-planetary health diet, antimicrobial resistance, air pollution, water stress, poverty and weak governance. The implications of COVID-19 for planetary health are grouped in six categories: social, economic, environmental, technological, political, and public health. The implications for planetary health are then judged to see the impacts with respect to sustainable development goals (SDGs). The paper indicates that sustainable development goals are being hampered due to the planetary health implications of COVID-19.

Indicators for energy-use efficiency and levels of CO2 emissions were used to evaluate and compare a range of agricultural systems in coastal Bangladesh in order to identify the most energy efficient system. Using data collected by the authors, five different food production systems involving both agriculture and aquaculture in the coastal area of Bangladesh were studied. In particular, Bagda (shrimp), Bagda-rice, rice, Galda (prawn)-rice-vegetable, and traditional practice-based agricultural systems were thoroughly investigated. The findings revealed that the Galda (prawn)-rice-vegetable-based integrated agricultural system was the most energy-efficient system and released less CO2 than the other four systems.

Composite indicators for six key categories of agricultural sustainability are utilized within a Multi‐Criteria Decision Analysis (MCDA) structure to assess and compare the sustainability of different agricultural systems. Individual indicators – productivity, stability, efficiency, durability, compatibility and equity – were used to develop composite indicators. In this research, the major steps used to obtain the aggregated indicators and assess sustainability are: define sustainability; recognize sustainability issues; identify indicators; categorize sustainability; measure indicator values to develop composite indicators; give weighting to the categories of sustainability; aggregate composite indicators; and compare the sustainability of different agricultural systems. Using composite indicators, an MCDA structure is employed to evaluate and rank the agricultural systems of southwest coastal Bangladesh in terms of the level of agricultural sustainability of each one. The case study demonstrates that this MCDA approach has the potential to become a useful framework for agricultural sustainability assessment.

The sustainability of agricultural systems is of paramount concern in order to ensure the survival and wellbeing of humans throughout the world. Sustainability is a complex issue involving multiple factors that fit broadly within economic, social and environmental areas. Given its complexity, this paper examines the question of how sustainability can be assessed in a way that gives a holistic picture of the separate and interrelated factors. The paper then presents a literature review, field experience and the use of complex adaptive systems to identify the issues and concerns that need to be addressed during agricultural sustainability assessment and categorizes them into in seven groups: integration of capitals; maintaining resilience, adaptation and transformation; ensuring system performance; involving stakeholders; mixing interdisciplinary views; integration of scales; and practicing good governance. Based on these issues and concerns, a set of indicators are suggested that will assist with holistic agricultural sustainability assessment in a given area.

This paper describes the first study of the interactions of Ag+ with the organophosphorus (OP) insecticide diazinon, 1. Electrospray ionization mass spectrometry (ESI-MS) with corroborative collision-induced dissociation-mass spectrometry (CID-MS) demonstrates that 1 forms a bidentate chelate with Ag+. The hydrolysis products of 1, the pyrimidinol (PY) and O,O-diethylphosphorothioic acid (PA), are also found to bind to Ag+ via N (PY) and S (PA) Lewis base sites, respectively. 31P and 1H nuclear magnetic resonance (NMR) spectra in solution, followed over time with varying ratios of Ag+ to 1, confirm the MS evidence and show Ag+ catalysis of hydrolysis (e.g., complete hydrolysis of 1 in ∼5 min (first-order half-life = 3 × 10−4 d; kobs = 2 × 103 d−1)) with equimolar Ag+; this represents an approximate 150 000-fold enhancement in hydrolysis with Ag+ as compared to its absence. A mechanism for the enhanced hydrolysis is proposed in which bidentate binding of Ag+ to S of the P=S electrophilic site in tandem with binding to N of the leaving group stabilizes the SN2(P) transition state relative to the ground state; this effect is described by qualitative energy profiles.

Transformations of the agricultural systems have been taking place in the coastal zone of Bangladesh. In different settings, farmers have become involved in massive shrimp cultivation, shrimp–rice cultivation, rice-based improved agricultural systems or shrimp–rice–vegetable-integrated systems. The long-term livelihood, food security and adaptation of the coastal people largely depend on the sustainability of these agricultural practices. In this context, assessing the level of sustainability is extremely important. The present study attempts to examine the sustainability of agricultural practices in the coastal zone of Bangladesh. A field study was carried out in fiveupazilas(counties) in the coastal zone. The data were collected through in-depth questionnaire surveys, focus groups discussions, field observation, key informants and secondary materials. A comprehensive suite of indicators was developed considering productivity, efficiency, stability, durability, compatibility and equity related to the coastal agriculture. The categories and the indicators were aggregated using Multi-Criteria Decision Analysis to measure the sustainability level of five study sites. The integrated agricultural system (shrimp–rice–vegetables) of Dumuria appeared to be the most sustainable system among agricultural practices, and other integrated systems (rice-based) of Kalaroa were also found to show a good level of sustainability. The massive shrimp cultivation system of Shyamnagar and Kaliganj appears to be the least sustainable. A traditional agriculture system with some improved methods followed in Bhola Sadar also performed in a satisfactory manner. Measuring agricultural sustainability in this way produces a useful summary of sustainability issues. The information generated from the study may be used in formulating policies for this part of the country. The holistic and interdisciplinary approach employed here has the potential to a useful framework for sustainability assessment.

In order to enhance food production, India has adopted modern agriculture practices and achieved noteworthy success. This achievement was essentially the result of a paradigm shift in agriculture that included high inputs of agrochemicals, water, and widespread practice of monoculture, as well as bureaucratic changes that promoted these changes. There are very few comprehensive analyses of potential adverse health outcomes that may be related to these changes. The objective of this study is to identify health risks associated with modern agricultural practices in the southern Indian state of Karnataka. This study aims to compare high-input and low-input agricultural practices and the consequences for health of people in these communities. The fieldwork was conducted from May to August, 2009 and included a survey carried out in six villages. Data were collected by in-depth personal interviews among 240 households and key informants, field observations, laboratory analyses, and data from secondary sources. The study identified four major visible impacts: occupational hazards, vector borne diseases, changing nutritional status, and inequity in development. In the high-input area, mechanization has resulted in more occurrences of serious accidents and injuries. Ecological changes due to rice cultivation in this area have further augmented mosquito breeding, and there has been a surge in the incidence of Japanese encephalitis and malaria. The traditional coarse cereals (complex carbohydrates, high protein) have been replaced by mill-polished rice (simple carbohydrate, low protein). The prevalence of overweight (BMI>25) has emerged as a new public health challenge, and this is most evident in large-landholding households, especially in the high-input agriculture areas. In all agro-ecological areas, it was observed that women faced a greater risk of both extremes of under-nutrition and being overweight. Output-driven and market-oriented modern agricultural practices have changed the ecology and disease pattern in this area in India, and our survey indicated significant health effects associated with these changes. There is a need for more extensive epidemiological studies in order to know the full impact on diseases and to understand the complex causal relationships.

Agriculture including crop production and animal husbandry provides for the food, fodder, and fuel needs in rural regions of many countries such as India. Using the knowledge pertinent to complex mixed cropping-livestock systems at the village level, the goal of this study is to develop a rational method for crop selection, such that the capacity for production of food, fodder and biomass fuel can be examined under various cropping patterns. An agricultural survey is carried out in November 2007 for three villages located in the dryland agro-ecozone of Karnataka State, India. Various demands, including human food energy and protein requirements, and constraints, including land area, are modeled for optimal cropping pattern. A clear recommendation of the study is that a substantial shift in village-wide area planted to cereal crops, in all cases over 50%, is necessary to satisfy human and livestock demands. Additionally, there are visible and growing population pressures on the resources in the dryland, se...

This study investigates food production and agrobiodiversity in the Tarikhet and Ukhimath blocks in Uttarakhand, India, located in the middle ranges of the Himalayas. On the small patches of terraced land available to the average household in these areas, the cultivation of a wide range of traditional and high-yielding varieties of grains, legumes, vegetables, and fruits is a positive feature in terms of sustainability. Some villages also supplement plant-based food production and income by incorporating animal husbandry into the overall agroecosystem. It was found, however, that the output of the average farm provides only about half of the household energy requirements, forcing most families to resort to off-farm activities to support a large proportion of their food and other requirements. There is therefore a need to develop policies that will continue to support the rich agrobiodiversity of these areas, while providing for the nutritional and economic needs of the population.

31P NMR and ESI-MS structural studies have been carried out for O,O-dimethylphosphorothioate anion (PA–) interacting with Ag+, Hg2+, and Na+ cations. Evidence is presented for the formation of PA–···Ag+ and PA–···Hg2+ metal complexes and for ionic PA–Na+, with 31P chemical shift values of 43, 40, and 65 ppm, respectively. The 31P chemical shifts for PA–···Ag+ and PA–···Hg2+ complexes exhibit an initial sharp rise as the [Ag+]/[PA] and [Hg2+]/[PA] ratio increases from 0 to 1.0 and 0 to 0.5, respectively, and remain almost constant beyond these ratios. These results indicate the formation of 1:1 PA–···Ag+ and 2:1 (PA–)2···Hg2+ complexes. Electrospray ionization mass spectroscopy (ESI-MS) revealed peaks corresponding to [O-P(=S)(OCH3)2 + Ag + H]+ and {2[O-P(=S)(OCH3)2] + Hg + H}+ for PAH interacting with Ag+ and Hg2+, supporting the 1:1 PA–···Ag+ and 2:1 (PA–)2···Hg2+ stoichiometry. The experimental results support the predominance of species with greater P=O double bond and P–S single bond character, relative to P-O/P=S. Our results on 31P NMR chemical shifts have a bearing on the use of 31P chemical shifts as a tool for organophosphorus pesticide identification.

Complexation of the organophosphorus pesticide, diazinon, with α-, β- and γ- cyclodextrin has been investigated through NMR and computational methodologies. Binding constants (Kb) determined by 1H and 31P NMR follow the order γ-CD > α-CD = β-CD, in contrast with reported Kb data for other pesticides and thus indicative of steric encumbrance by the isopropyl group in diazinon being an important factor influencing binding constants. The interaction of diazinon with the CDs has also been investigated through computational studies via molecular dynamics – molecular mechanics (MD–MM2) and density functional theory (DFT), B3LYP/6-31G*. It is shown that the most favorable orientation in binding corresponds to the hydrophobic heterocyclic residue of diazinon being pulled deepest into the CD cavity, in agreement with the experimentally determined order of binding constants. Moreover, the computations show that it is only with γ-CD that the heterocyclic residue of diazinon and the phosphoryl residue are both largely encrypted in the CD cavity, marking a clear differentiation with α-CD and β-CD where the phosphoryl residue is located largely outside the cavity. Thus, the computational results are in essential agreement with the experimental binding constants where γ-CD stands out with the highest Kb value. Our work could point to the potential usefulness of computational studies to be undertaken in tandem with experimental work in environmental situations such as soil remediation.Key words: organophosphorus pesticides, diazinon complexation, cyclodextrins, computational studies, molecular mechanics.

Amendment of a soil slurry with low concentrations of a cyclodextrin, hydroxypropyl-b-cyclodextrin (HPCD), (0.05–0.5 g l 1 ) increased the phenanthrene mineralization rate of a microbial consortium by 25% under Fe(III)-reducing conditions. Although a higher concentration (5.0 g l 1 ) resulted in a faster initial rate of mineralization, mineralization ceased after 25 days with maximum mineralization 17% lower than the control (no HPCD). At lower HPCD concentrations, mineralization was still taking place at day 76. Although pH should affect Fe(III) solubility, mineralization rates at pH 6.0 and 8.0 were comparable. Decreasing the temperature reduced the extent and rate of mineralization, but mineralization rates at 10 � C were still 60% of that obtained at 30 � C. � 2005 Elsevier Ltd. All rights reserved.

This paper evaluates the possibility of using cyclodextrins (CDs) as solubility-enhancing agents that could be employed to increase the rate of the mass delivery of trichloroethylene (TCE) to an iron wall where dechlorination will occur. Dechlorination of TCE by zero-valent iron was performed in the absence and in the presence of CDs in batch (static) and column (dynamic) systems. The presence of CDs slowed the overall degradation of TCE. The effect of various concentrations of different CDs on the rate of TCE degradation was evaluated, and it was found that as the CD concentration increased, reaction rate decreased. However, the overall decrease in reaction rate could not be explained solely on the basis of TCE:CD host-guest complexation. A novel mechanism involving CD binding to the iron surface, in addition to TCE:CD complexation, was proposed, and this enabled satisfactory interpretation of the kinetic data. A central feature of the proposal is that Fe:CD binding impedes electron transfer from the underlying iron metal to the TCE molecule. The overall rate of TCE degradation by zero-valent Fe in the presence of CDs is governed by several factors: the extent of binding of CD with the iron surface, the binding constant between CD and TCE, and the degradation of complexed TCE (TCE:CD), where CD is, in turn, associated with the iron surface. It appeared that CD binding to the iron surface depends largely on the type of substituent groups present in the β-CD derivatives as well as their degree of substitution. Association constants for the Fe:CD interaction were determined. The new hypothesis explained well both batch and column data, and the magnitude of Fe:CD binding constants was found to be similar in the two systems. Key words: cyclodextrin, trichloroethylene, zero-valent iron, reductive dechlorination.

The speciation of aluminum in solutions of alum and various prehydrolyzed, aluminum-based water treatment coagulants was investigated by 27 Al NMR at 5°C and 25°C. Alum solutions were seen to contain only mononuclear species including an AlSO 4 + complex, while the prehydrolyzed coagulant solutions contained polynuclear aluminum species, as well. The relative proportions of both polynuclear species and AlSO 4 + complex decreased in cold water. The presence of organic matter had little effect on the speciation of aluminum in diluted alum, but markedly reduced the relative proportion of the tridecamer species in the prehydrolyzed coagulant solutions. The relationship between Al speciation in the coagulants and organic matter removal during jar tests was considered, and the possible role of sulfate in both the formation of the tridecamer species and the effect of organic matter on coagulation efficiency was discussed.

This paper describes a systematic study for the evaluation of different substituted β-cyclodextrins (β-CDs), as agents for the enhancement of the aqueous solubility of two major organic pollutants, trichloroethylene (TCE) and perchloroethylene (PCE). The aqueous solubility enhancement occurs through the formation of host–guest inclusion complexes between the CD molecule (host) and the polychloroethylene (guest) and is driven primarily by hydrophobic forces. The CDs evaluated are: methyl-β-CD (Mβ-CD), hydroxypropyl-β-CD (HPβ-CD), carboxymethyl-β-CD (CMβ-CD1, CMβ-CD2), and sulfated-β-CD (Sβ-CD1, Sβ-CD2); the degree of substitution was also varied. Using a 5% (w/v) aqueous CD solution, solubility enhancement factors (St/So) up to 5.5 and 14 were determined for TCE and PCE, respectively. Binding constants (K11) for TCE with the substituted CDs were evaluated using an 1H NMR technique; these were found to range from 3 to 120 M–1. It was shown that solubility enhancement, as well as the binding constant, is dependent on the type and degree of substitution of the β-CD molecule; the determining factors are discussed. The CDs are also capable of effective removal of PCE and TCE retained by soil organic matter. Thus, a suitably substituted β-CD may be a valuable additive in pump-and-treat protocols for site remediation of polychlorinated organics. Key words: Cyclodextrin, trichloroethylene, perchloroethylene, solubility enhancement, binding constant, soil and water remediation.

This research is a continuation of a study on the behavior of hydrophobic organic compounds in the environment and describes the simultaneous abiotic degradation and sorption of pirimiphos-methyl (O-2-diethylamino-6-methylpyrimidin-4-yl O,O-dimethylphosphorothioate) under controlled conditions in soil/water slurries. A microfiltration-HPLC technique was employed to follow these processes in two well-characterized soils from the Middle Belt region of Nigeria. Rapid sorption of the pesticide occurs during the first 10 min of equilibration and accounted for 37% of the original pirimiphos-methyl in the Rhodic Kandiustalf soil and for 41% of the original concentration in Aquic Ustropept soil. Subsequent slow processes were followed during the remaining 30 days of the experiment. During this time, first-order rate constants for disappearance from solution of pirimiphos-methyl were found to have values of 6.1 x 10(-)(7) and 9.8 x 10(-)(7) s(-)(1) for the Rhodic and Aquic soils, respectively. Similarly, rate constants for production of the product, pyrimidinol, were calculated to be 6.0 x 10(-)(7) and 9.4 x 10(-)(7) s(-)(1) for the Rhodic and Aquic soils, respectively, giving pesticide degradation half-lives of 13 and 8.5 days. Disappearance of the pesticide is discussed in terms of a scheme involving both sorptive uptake by the soil and degradation by hydrolysis in the presence of the soil matrix. The labile sorption capacities for pirimiphos-methyl in the Rhodic and Aquic soils were found to be 0.75 and 0.90 micromol g(-)(1), respectively.

In the present world context, there is a need to assess the sustainability of agricultural systems. Various methods have been proposed to assess agricultural sustainability. Like in many other fields, Multi-Criteria Decision Analysis (MCDA) has recently been used as a methodological approach for the assessment of agricultural sustainability. In this paper, an attempt is made to apply Elimination, a MCDA method, to an agricultural sustainability assessment, and to investigate its benefits and drawbacks. This article starts by explaining the importance of agricultural sustainability. Common MCDA types are discussed, with a description of the state-of-the-art method for incorporating multi-criteria and reference values for agricultural sustainability assessment. Then, a generic description of the Elimination Method is provided, and its modeling approach is applied to a case study in coastal Bangladesh. An assessment of the results is provided, and the issues that need consideration before applying Elimination to agricultural sustainability, are examined. Whilst having some limitations, the case study shows that it is applicable for agricultural sustainability assessments and for ranking the sustainability of agricultural systems. The assessment is quick compared to other assessment methods and is shown to be helpful for agricultural sustainability assessment. It is a relatively simple and straightforward analytical tool that could be widely and easily applied. However, it is suggested that appropriate care must be taken to ensure the successful use of the Elimination Method during the assessment process.

• Modern agriculture (known as the Green Revolution) has significantly improved India's food production.

The rates of displacement of 3-methyl-4-nitrophenoxide ion from the pesticide, fenitrothion, by alkali metal ethoxides in anhydrous ethanol were followed spectrophotometrically. Through product analysis experiments, which included 31P NMR and GC-MS, as well as spectrophotometric analysis, three reaction pathways were identified: nucleophilic attack at the phosphorus centre, attack at the aliphatic carbon, and a minor SNAr route ([Formula: see text]7%). Furthermore, a consecutive process was found to occur on the product of attack at the phosphorus centre. For purposes of kinetic treatment, the processes at the aliphatic and aromatic carbon were combined (i.e., the minor SNAr pathway was neglected), and the observed reaction rate constants were dissected into rate coefficients for nucleophilic attack at phosphorus and at aliphatic carbon. Attack at phosphorus was found to be catalyzed by the alkali metal ethoxides in the order KOEt > NaOEt > LiOEt. Catalysis arises from alkali metal ethoxide aggregates in the base solutions used (0–1.8 M); treatment of the system as a mixture of free ethoxide, ion-paired metal ethoxide, and metal ethoxide dimers resulted in a good fit with the kinetic data. An unexpected dichotomy in the kinetic behaviour of complexing agents (e.g., DC-18-crown-6, [2.2.2]cryptand) indicated that the dimers are more reactive than free ethoxide anions, which are in turn more reactive than ion-paired metal ethoxide. The observed relative order of reactivity is explained in the context of the Eisenman theory in which the free energy of association of the metal ion with the rate-determining transition state is largely determined by the solvent reorganization parameter. In contrast with displacement at the phosphorus centre, attack at the aliphatic carbon was not found to be catalyzed by alkali metals. In this case, the free ethoxide anion was more reactive than either the ion-paired metal ethoxide or the dimeric aggregate. The differing effects of alkali metals on the two pathways is ascribed largely to the leaving group pKa. For carbon attack, the pKa value estimated for demethyl fenitrothion, 2.15, is sufficiently low that metal ions are not required to stabilize the rate-determining transition state. In contrast, for phosphorus attack, 3-methyl-4-nitrophenoxide, with a pKa of 7.15, requires stabilization by metal ion interactions. Hence, alkali metal ions catalyze attack at phosphorus, but not attack at the carbon centres.Key words: organophosphorothioate, pesticide, fenitrothion, ethanolysis, alkali metal ethoxide, ion-pair reactivity, dimers, catalysis, competitive pathways.

Rate constants for the reaction of the title compound, 1, with a number of oxygen nucleophiles, including structurally related phenoxides and oxygen-based α-nucleophiles, have been measured in aqueous solution at 25 °C. A significant α-effect was observed, confirming participation of the nucleophile in the rate-limiting step of the reaction as well as indicating different transition states (TS) for the reaction of α-nucleophiles compared to normal ones. The Bronsted-type correlation of log kNuvs. pKa of nucleophiles shows a linear plot for the series of structurally related phenoxides in the pKa range 5.4–10.0, straddling the pKa of the leaving group (3-methyl-4-nitrophenoxide, pKa 7.20), but is curved in the highly basic region corresponding to CF3CH2O− and HO− as nucleophiles. The slope of the linear portion of the plot (βNu) is 0.49 (R2 0.988). The linearity of the plot for the series of structurally related phenoxides is consistent with a concerted mechanism for nucleophilic attack at the P center of the substrate. A value of βlg −0.39 (R2 0.973) is measured for the reaction of PhO− with substituted phenyl dimethyl phosphorothioate esters. Combining the values of βNu and βlg gives βeq = 0.88; these parameters when considered together with the effective charge distribution in the TS, demonstrate that the TS for the symmetrical reaction (in which nucleophile = leaving group = 3-methyl-4-nitrophenoxide) has no significant phosphorylium ion character. The Leffler index points to a concerted reaction in which bond formation is slightly ahead of bond rupture in the TS. Data from the present study are compared with literature data for (thio)phosphoryl group transfer. We propose that, unless special structural and/or environmental features prevail, (thio)phosphoryl transfers between phenoxides are more likely to occur via a concerted mechanism. It is shown that the TS for the concerted transfer of (EtO)2PO between two PhO− moieties shows more pentacoordinate intermediate character than the symmetrical reaction of 1 due to differences in (i) basicity of PhO−versus 3-CH3,4-NO2PhO−, and (ii) abilities of O and S in the PX (X = O, S) moiety to stabilize the incoming negative charge.

This study examined removal of organic matter (OM) by coagulation in drinking water treatment. First, the ability of three coagulants to simultaneously reduce turbidity and remove OM from water was determined. The coagulants tested were the commercial products alum and polyaluminum chloride (PACl) and a polyaluminum hydroxysulfate (PAHS) synthesized in the authors' laboratory. Tannic, humic, lignosulfonic, and salicylic acids (SAL) were used as model organic compounds in cold and warm water. The effect of the concentration of tannic acid was also examined, and semiquantitative relationships between OM concentration and coagulant dosage required were determined. In cold water, PACl and PAHS were efficient coagulants for all organic compounds except SAL (which was not itself removed, although it did not inhibit turbidity reduction). However, alum was a poor coagulant in the presence or absence of OM. In warm water, alum and PACl were the more efficient coagulants. OM had approximately the same effect on alum at both temperatures, but its effect on PACl was somewhat increased in warm water. Although PAHS effectively reduced turbidity in the absence of OM or in the presence of SAL, the presence of the other organic substances greatly increased the coagulant demand in warm water.

Ferron reagent and FTIR spectroscopy were used for the identification and characterization of the aluminum species formed during dephosphorization of simulated wastewater with and without organic matter. Evidence from FTIR spectroscopy showed the formation of aluminum hydroxyphosphate, hydroxy-Al–tannate and aluminum complexes containing both phosphorus and tannic acid. The surface reactivity of the solid products is proportional to the rate of reaction with ferron. The measured reactivities indicate that aluminum solid species with different surface properties were formed depending on solution components and method of precipitation. Tannic acid was found to inhibit phosphorus removal and the extent of inhibition increased with increasing concentration. When prehydrolyzed aluminum is exposed to tannic acid, the organic matter forms a coating on the surface of the inorganic solid during the aging process. Coprecipitation of aluminum, phosphate and tannic acid, which is synonymous with the addition of alum before or in the aerator, produces some soluble complex and some hydroxy-Al–phosphate–tannate complex, in the form of solid with very small particle size. This system gives high residual aluminum. The results suggest that it is advantageous to add at least a portion of the alum at the exit of the aerator. This enhances phosphorus removal by coprecipitation under conditions where the concentration of organic matter is relatively low and enhances removal of organic matter by postprecipitation onto the recycled sludge in the aerator.

Spectrophotometry, voltammetry and electrospray mass spectrometry have been used to examine dilute aqueous solutions containing pyocyanine and manganous ions. Spectrophotometry shows no evidence of complex formation between the two constituents in either non-buffered (pH ∼5) or buffered (pH 6.4) media at concentrations up to 100 μ mol l −1 pyocyanine and 150 μ mol l −1 Mn 2+ . Direct voltammetry with buffered solutions confirms the spectrophotometric results, however the results obtained with non-buffered solutions, although significantly different from those for the buffered solutions, do not provide unambiguous evidence of complex formation. Complexes of Mn 2+ with one, two and three pyocyanine molecules are present in high intensity in the electrospray mass spectra obtained with unbuffered aqueous solutions but are almost entirely absent with the buffered solutions. It is concluded that the concentrations of complexes in the solutions are extremely low and that their mass spectrometric observation is due to their formation in the electrospray process and not to their pre-formation in the solutions.

The reactions of two members of the dinitroaniline class of herbicides, N,N-di-n-propyl-2,6-dinitro-4- (trifluoromethyl)aniline (trifluralin; 1) and N-ethyl-N-n-butyl-2,6-dinitro-4-(trifluoromethyl)aniline (benefin; 2), along with their analogue, N-phenyl-2,6-dinitro-4-(trifluoromethyl)aniline (3), with the nucleophiles, OD- and SO32- , have been investigated using 400 MHz 1H NMR spectroscopy. The reactions of both 1 and 2 with OD- result in formation of Meisenheimer anionic σ -complexes according to a K3T1 (kinetic preference for formation of the C-3 adduct with thermodynamic preference for formation of the C-1 adduct) reaction sequence while the reaction of 3 with OD- and that of 1 with SO32- follow a K3T3 (kinetic and thermodynamic preference for formation of the C-3 adduct) sequence. There was no observation of the C-1 adducts of 1 and 2 with OD-, but the products of SNAr displacement at C-1 were observed as the final thermodynamic products. Geometry optimization calculations support our hypothesis of n –> σ * stabilization of the C-1 adduct leading to SNAr displacement. In the reaction of 3 with OD-, initial N-deprotonation to form the anion, 3a, is followed by σ -complex formation. The final thermodynamic product observed in this system is 3,5-dinitro-4-(N-phenylamino)benzoic acid formed through hydrolysis of the trifluoromethyl group on the anion, 3a. Aryl H-D exchange has been found for the systems of 1 and 2 with OD-, but not for the SO32- system and neither for the reaction of 3 with OD-. Since dimethylpicramide showed significantly slower H-D exchange under identical conditions, it is argued that this discrepancy has as origin the ability of the amino N lone electron pair to interact with the π -system of the ring. With both 1 and 2 the larger size of the amino alkyl chains prevent the amino N lone pair from aligning with the π -system of the ring, thus hindering electron density donation to the electron-deficient ring carbons.Key words: trifluralin, benefin, herbicides, Meisenheimer complexes, stereoelectronic effects.

A sensitive voltammetric stripping procedure for trace measurement of chromium (VI) and (III) in aqueous samples is reported. The method is based on the preconcentration of a chromium(VI)–pyrocatechol violet complex at HMDE from an acetate buffered solution. The adsorbed complex is then reduced, producing a well defined peak at a potential of −0.73 V. Total chromium was determined after oxidation of chromium (III) to chromium (VI) by UV irradiation in an oxygen-saturated solution. Therefore, total chromium was also determined as chromium (VI). Optimal conditions for the determination of chromium (VI) and total chromium at the nmol L−1level have been established. A preconcentration time of 1 min provided a detection limit of 3 nmol L−1.

High-resolution solid-state 27Al and 31P MAS NMR has been used to investigate the nature of aluminium- and phosphorus-containing solids formed during wastewater treatment. Although difficult to characterize by conventional techniques, these amorphous solids can be characterized by MAS NMR, providing information about their short-range ordering. In the present study, most of the solids were precipitated under conditions of high alkalinity, similar to those encountered during wastewater treatment. The ageing time of the aluminum hydroxide prior to the addition of phosphate (t1), the ageing time of the aluminum hydroxyphosphates after the addition of phosphate (t2), and the phosphorus to aluminum molar ratio were controlled while the effects of changing the parameters were examined. It was found that the aluminum MAS NMR chemical shift was related to the amount of phosphate present in the solid, which in turn was related to t1, t2, and the P:Al molar ratio. The results also lend support to the hypothesis that phosphate removal occurs through an adsorption process onto amorphous aluminum hydroxide, rather than through direct precipitation of aluminum phosphate. The increased understanding of aluminum and phosphate chemistry and the species formed during wastewater treatment will be useful in optimizing wastewater treatment processes. Keywords: aluminum, phosphate, NMR, activated sludge, wastewater treatment.

This study examined the solid degradation products formed in partially neutralized aluminum sulfate (PNAS) solutions. The PNAS, which has superior properties as a coagulant for treatment of some waters, suffers from instability as is evidenced by a precipitate which forms with age. The precipitate was found to contain aluminum and sulfate, but the ratio of these two species changed over time. It is suggested that the observed increase in sulfate content in the solids is consistent with the view that polymeric aluminum species are preferentially precipitated during the initial stages followed by monomeric species as degradation continues.

Global hunger is on the rise (FAO, 2009). The number of those that are undernourished has increased steadily over the past decade reaching 1.02 billion people in 2009 (FAO, 2009), and remaining near this total over the past two years. The Millennium Development Goal to reduce world hunger by half by 2015 will likely not be met with current observed trends according to a recent UN report on food insecurity and world hunger (FAO, 2009). Limited land and growing population (Gerbens-Leenes and Nonhebel, 2005), global yield decline (Alston et al., 2009), financial resources and the economic downturn in 2008 are a few reasons that have led to the recent trend in world hunger.

The chemical behaviour of aluminum and phosphorus is examined at various stages in an activated sludge wastewater treatment facility which uses alum as a coagulant. It is found that most of the phosphorus leaving the plant is in the form of unsettled particulates associated with residual aluminum. This result is in agreement with numerous other studies and has led us to postulate that by optimizing conditions under which coagulants are added to the wastewater stream, improved settling of the resulting flocculant material would occur and this would be indicated by lower total phosphorus and turbidity. The hypothesis was tested on batch samples in the laboratory and at the plant, and also using a bench-scale continuous model plant. The data indicate that addition of alum using moderate mixing after the effluent leaves the aerator could result in a final effluent with significantly lower turbidity and phosphorus.

Characterization by the ferron method of the solid formed during hydrolysis of aqueous aluminum(III), under conditions of water and wastewater treatment, is the focus of the present study. It has been found that the rate of reaction (later referred to as aluminum reactivity) between freshly precipitated amorphous aluminum hydroxide and the reagent containing a reduced form of ferron may be used to characterize the precipitate. With increasing age between 1 min and 45 d, the reactivity of aluminum in the precipitate was found to steadily decrease. For example, a t 50 value (indicating the time for 50% recovery of the added aluminum) for a 1-min aged aluminum hydroxide was found to be near 10 min, while for the 10 000-min aged sample the t 50 value was near 100 min

New sensitive stripping voltammetric procedures for trace measurements of titanium in various samples are reported. The first method is based on the interfacial accumulation of the titanium-pyrocatechol violet complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed complex. The limit of detection is 0.55 nmol/L titanium after a 30 s collection with a stirred solution at pH 4.9. The procedure is extremely selective with respect to other metals and has been applied in analyzing various samples. Based on this, a catalytic method involving the chlorate ion was developed and the sensitivity was enhanced by more than an order of magnitude. In this way, analysis for Ti in aqueous solutions at the picomolar (part per trillion) level is possible.

The determination of cobalt and nickel in aqueous solutions by stripping voltammetry after adsorptive preconcentration is an established procedure. The method is highly sensitive, but there is some controversy concerning the reasons for the excellent sensitivity. Using a variety of voltammetric techniques, we have determined that the reduction of nickel dimethylglyoximate in an ammonia buffer is consistent with an overall process involving 16 or possibly 18 electrons. This hypothesis is confirmed by independently measuring the total quantity of metal adsorptively deposited on the mercury electrode and comparing the amount with the quantity of electricity required for its reduction.