Hydroxyl Radical Generation and Contaminant Removal from Water by the Collapse of Microbubbles Under Different Hydrochemical Conditions

The present study addresses the mechanism of hydroxyl radical (·OH) generation by the collapse of microbubbles in water solution. The influence of gas supply and flow rate, solution pH, and ionic strength on the aeration efficiency, free radical generation, and contaminant removal (take methylene blue as an example) are elucidated. The results showed that the degradation rate of methylene blue by ·OH increased with flow rate as well as in acidic or alkaline solutions compared to that in neutral conditions. ·OH was shown to be produced by the reaction between protons and oxygen radicals generated by the decomposition of O₂ rather than water molecules. A greater concentration of O₂ or H⁺ thus promoted the reaction, resulting in effective removal at a high flow rate or low pH. Nevertheless, there was considerable methylene blue removal at high pH, driven by the production of the dye cation through the dissociation of methylene blue and the high electronegativity of bubbles at high pH, thus enhancing interface adsorption and degradation, as well as by the high ionic strength of the solution helping to generate ultrafine bubbles and maintaining them through ionic shielding. The current work provides useful insights into the application of microbubble as a promising technique.     

Prevalence of Concentrated Flow Paths in Agricultural Fields in Southern Illinois

Literature on prevalence of concentrated flow paths (CPFs) in agricultural fields are limited at field scale with only few studies that address occurrence of CFPs at large geographic extent. This study used high-resolution Light Detection and Ranging (LiDAR) data to identify CFPs in agricultural fields and calculate the percentage of the fields drained by CFPs at a county scale. In 389 agricultural fields across Jackson County, southern Illinois, this study also investigated the association between field characteristics and CFP formation using multiple regression and CART analysis. The mean number of CFPs in a field was 5 with a minimum of 0 and maximum of 17 CFPs. The majority of the CFPs fell under the large category for CFP length and drainage area that corresponds with high mean percent (81%) of field area drained by the CFPs. Further, 85% of the fields had more than 70% of their area drained by CFPs. The multiple regression and CART analysis showed slope as an important factor influencing CFP characteristics such as number of CFPs and CFP length. Both analyses also indicated physical soil properties such as bulk density, soil erodibility factor, saturated hydraulic conductivity, LS factor, organic matter, and percent sand were also predictors of the CFP characteristics. However, these factors explained only 2 to 12% of the variation observed. The significant presence of CFP’s has important implications for water quality since current conservation practices such as riparian buffers were not designed to address concentrated flow from agricultural fields.     

Peroxicoagulation and Solar Peroxicoagulation for Landfill Leachate Treatment Using a Cu–Fe System

Leachates, particularly those from mature landfills, are difficult to treat by biological processes because of their high toxicity and low biodegradability. Therefore, the development of new treatment technology is necessary. The treatment of landfill leachate by peroxicoagulation and solar peroxicoagulation using a batch electrolytic reactor with a Fe cathode and a Cu anode is proposed. The tested operational variables included pH (2.8 and 8.2), current density (11 and 16 mA cm^?2), treatment time (5, 10, 15, 20, 25, and 30 min), and presence of solar ultraviolet (UV) light and were collected using a compound parabolic collector. The optimum conditions were a pH, current density, and treatment time of 2.8, 16 mA cm^?2, and 10 min, respectively. The presence of UV did not have a significant effect. The chemical oxygen demand and biochemical oxygen demand removed were 62.3% and 55.5%, respectively. The results of UV-visible absorption, fluorescence, and Fourier transform infrared spectroscopy measurements confirm the oxidation process.     

Small Area Estimation of Proportions with Constraint for National Resources Inventory Survey

Motivated by the need to produce small area estimates for the National Resources Inventory survey, we develop a spatial hierarchical model based on the generalized Dirichlet distribution to construct small area estimators of compositional proportions in several mutually exclusive and exhaustive landcover categories. At the observation level, the standard design-based estimators of the proportions are assumed to follow the generalized Dirichlet distribution. After proper transformation of the design-based estimators, beta regression is applicable. We consider a logit mixed model for the expectation of the beta distribution, which incorporates covariates through fixed effects and spatial effect through a conditionally autoregressive process. In a design-based evaluation study, the proposed model-based estimators are shown to have smaller root-mean-square error and relative root-mean-square error than design-based estimators and multinomial model-based estimators. Supplementary materials accompanying this paper appear online.     

Assessment of genetic variability in the endangered <Emphasis Type="Italic">Citrus macroptera</Emphasis> Mont. (“hatkora”) from Mizoram,north-east India

Assessment of genetic variability in the available germplasm is the prerequisite for development of improved genotypes through planned breeding programmes. In view of this, 39 “hatkora” (Citrus macroptera Mont.) genotypes collected from different locations of Mizoram, India were evaluated for physico-chemical characteristics during 2013–2015. The study reveals that there was significant variation among the collections in these particular traits. Individual fruit weight ranged from 277.78 to 617.69 g; fruit diameter 9.32–12.52 cm; fruit length 7.74–10.19 cm, fruit volume 238.33–583.33 cc; pulp weight 153.75–320.94 g; pulp:peel ratio 1.50–3.24 and seed number 9.33–23.6. Similarly, the chemical parameters also varied significantly among different germplasms. The juice content varied from 13.45 to 32.53 %, ascorbic acid 34.81–73.64 mg/100 mL, TSS 6.15–9.10 %, acidity 5.03–8.75 %, total sugars 5.16–7.97 % and sugar:acid ratio 0.75–1.52. From the analysis of genetic parameters, it could be concluded that characters like fruit weight, fruit length, fruit diameter, fruit volume, pulp weight, pulp–peel ratio, juice, Total soluble solids (TSS), acidity, ascorbic acid, total sugars, and sugar–acid ratio could be used as selection criteria for development of effective and productive plant types in “hatkora”. Wide range of variation in physico-chemical parameters of “hatkora” fruits indicated the great scope of individual plant selection based on these characters for future genetic improvement programme.     

Genetic relationships among improved varieties of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) in Indonesia over the last 60 years as revealed by morphological traits and DNA markers

Morphological traits and two kinds of molecular markers were employed to study the genetic relationships among improved rice (Oryza sativa ) varieties of Indonesia since 1943. Dendrograms based on morphological traits and both molecular markers (simple sequence repeats, SSR and single nucleotide polymorphism, SNP) agreed in separating the varieties into two primary groups. Based on the morphological traits, a larger group (>60 %) contains varieties with smaller sizes compared with those in the smaller group (<40 %). SSR and SNP markers revealed that most of the varieties belonged to indica (88; 89 %) and japonica (9; 8 %) subspecies, and 3 % of varieties were not involved in two subspecies. The molecular markers revealed that the genetic diversity (H) stagnated between stage II (1967–1985) and stage III (1986–2003). However, during stage I (1943–1966), H was higher than in the other stages as revealed by SNP markers, while H in stage I was lower than in the other stages as revealed by SSR markers. In this study, the two molecular data sets were positively correlated and positive correlations between the phenotypic and molecular data depended on the kind of molecular marker: SNP had higher Mantel r values than SSRs. Besides, SSR markers seem to be appropriate for pedigree studies, while SNP markers could be used to reveal genomic relationships. These findings were attributable to the different properties of these two different markers. These results suggested that the diversity and differentiation of both the phenotypic and molecular marker variations were probably resulted from the crossing and selection in rice breeding in Indonesia. We suggest that Indonesia needs another strategy to improve new varieties to avoid a reduction in genetic diversity and similarity.     

Geographical distribution and diversity of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L. subsp. <Emphasis Type="Italic">mays</Emphasis>) races in Mexico

The center of origin of maize is in Mexico and maize diversity is very high in many parts of the country. Here we describe and analyze the geographic distribution and diversity of maize using a database of 18,176 georeferenced observations of maize races. The number of observations by race follows the common “hollow curve” distribution, with six races comprising 54 % of the records and 37 races only 10 %. Few races are widespread, and some have a highly localized distribution. The average maximum distance (D _max) between two records of the same race was 1169 km, but seven races had a D _max lower than 200 km. The average circular area range size (CA₂₅) was 51, but 14 races had a CA₂₅ lower than 10. Some races have very few observations but were found over a large area. These races may not be valid and their classification should be reviewed. Areas of high race richness and diversity are in mountainous northwest, south central, and southern Mexico in the states of Oaxaca, Jalisco, Michoacán and Chiapas. Six contiguous maize regions were defined using hierarchical clustering. Despite the high sample size, further sampling could improve estimates of race diversity in several regions.     

Variation in tuber mineral concentrations among accessions of <Emphasis Type="Italic">Solanum</Emphasis> species held in the Commonwealth Potato Collection

The variation in tuber mineral concentrations amongst accessions of wild tuber-bearing Solanum species in the Commonwealth Potato Collection (CPC) was evaluated under greenhouse conditions. Selected CPC accessions, representing the eco-geographical distribution of wild potatoes, were grown to maturity in peat-based compost under controlled conditions. Tubers from five plants of each accession were harvested, bulked and their mineral composition analysed. Among the germplasm investigated, there was a greater range in tuber concentrations of some elements of nutritional significance to both plants and animals, such as Ca, Fe and Zn (6.7-fold, 3.6-fold, and 4.5-fold, respectively) than others, such as K, P and S (all less than threefold). Significant positive correlations were found between mean altitude of the species’ range and tuber P, K, Cu and Mg concentrations. The amount of diversity observed in the CPC collection indicates the existence of wide differences in tuber mineral accumulation among different potato accessions. This might be useful in breeding for nutritional improvement of potato tubers.     

Experimental Study of Tidal Effects on Coastal Groundwater and Pollutant Migration

The problem of current urban groundwater pollution is very serious, which has influenced social development and people’s daily life. Around the land-sea interface, tide obviously changes nearshore the groundwater flow regime and makes the pollutant migration process become more complex. In the present study, the effect of tide-induced groundwater table fluctuations and on the pollutants migration in beach aquifers is investigated by constructing a two-dimensional sand trough physical experimental model. The model considered brackish-water density differences and the tide by controlling experimental medium properties and boundary conditions. The results showed that the groundwater table fluctuation cycle is the same as the tidal cycle and the fluctuation lag time increases linearly with the increase of the offshore distance. Tidal fluctuation flattens brackish-freshwater interface, widens the dispersion zone, and generates the upper saline and the freshwater belt. Time lag corresponding relationships between saline water and tidal fluctuation was observed. With the pollutant approaching the saline water area, the profile of the pollutant migration is gradually developed into a spindle shape until the strip shape, and the pollutant enters the saline water body along the curved edge of the upper part of the saline water. The transverse dispersion of pollutants is larger than the longitudinal dispersion in a tidal cycle and its outline presents a strip shape development. No mixing or exchange between the pollutants and the saline water body happened during the whole process. This study can provide scientific references for nearshore groundwater pollution prevention and control in the future.