The sludge settleability is of prime importance for the activated sludge process. The effect of calcium ion on the biological performance of sludge was investigated in a lab-scale activated sludge system with varying Ca2+ concentration. Results indicated that addition of 150mg/L Ca2+ to the influent significantly improved the settling characteristics and metabolic reactivity of activated sludge in the bioreactors. Analyses using denaturing gradient gel electrophoresis (DGGE) and 16S rRNA sequencing showed that a significant difference in the presence of certain bacterial groups between the sludge systems with 150mg/L Ca2+ and those with 0–100mg/L Ca2+ addition. Ca2+ also increased the production of the extracellular polymeric substance (EPS) and facilitated the development of microbial cluster in the bioreactor. Study showed that an addition of 150mg/L Ca2+ to the influent provides a simple approach to improve the settling properties of activated sludge and maintain high pollutant removal efficiency.
Archived wheat ( Triticum aestivum L.) grain and straw, and soil samples from the control plot of the Rothamsted Broadbalk Experiment, located in southeastern England and established in 1843, were used to investigate the effects of dramatically changing SO 2 pollution inputs on the concentrations and stable isotope ratios (δ 34 S) of S in the samples. Representative coal samples from UK major coal fields were also determined for δ 34 S. Concentrations of S showed no clear trends in either grain or straw over the 155 years from 1845 to 1999. However, grain and straw δ 34 S decreased rapidly from 6 to 7‰ in 1845 to −2 to −5‰ in the early 1970s, and since then have increased to 0.5 to 2‰ in the late 1990s. This pattern mirrored the trend of UK SO 2 emissions over the 155 years. Both grain and straw δ 34 S correlated strongly and negatively with UK SO 2 emissions ( R 2 > 0.89), but the relationships were different for the pre‐ and post‐1970 data sets. Soil δ 34 S also decreased considerably, from 8.2‰ in 1865 to 3.7 to 4.5‰ during 1965–1999. A negative δ 34 S value was inferred for the anthropogenic S deposited at the experimental site before 1970, and further confirmed by negative δ 34 S values (−6 to −10‰) found in the coal samples from southeastern England and southern Wales. Based on the S isotope ratios, we estimated that anthropogenic S contributed 62 to 78% of the S uptake by wheat at the peak of SO 2 emissions, and accounted for 28 to 37% of the topsoil S in 1965.
No abstract is provided for this article.
The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report. While the authors have worked on the best information available to them, neither HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based.
No abstract is provided for this article.
The family Rhizobiaceae includes many genera of soil bacteria, often isolated for their association with plants. Herein, we investigate the genomic diversity of a group of Rhizobium species and unclassified strains isolated from atypical environments, including seawater, rock matrix or polluted soil. Based on whole-genome similarity and core genome phylogeny, we show that this group corresponds to the genus Pseudorhizobium. We thus reclassify Rhizobium halotolerans, R. marinum, R. flavum and R. endolithicum as P. halotolerans comb. nov., P. marinum comb. nov. , P. flavum comb. nov. and R. endolithicum comb. nov., respectively, and show that P. pelagicum is a synonym of P. marinum . We also delineate a new chemolithoautotroph species, P. banfieldiae sp. nov., whose type strain is NT-26 T (= DSM 106348 T = CFBP 8663 T ). This genome-based classification was supported by a chemotaxonomic comparison, with gradual taxonomic resolution provided by fatty acid, protein and metabolic profiles. In addition, we used a phylogenetic approach to infer scenarios of duplication, horizontal transfer and loss for all genes in the Pseudorhizobium pangenome. We thus identify the key functions associated with the diversification of each species and higher clades, shedding light on the mechanisms of adaptation to their respective ecological niches. Respiratory proteins acquired at the origin of Pseudorhizobium are combined with clade-specific genes to encode different strategies for detoxification and nutrition in harsh, nutrient-poor environments. Finally, we predict diagnostic phenotypes for the distinction of P. banfieldiae from other Pseudorhizobium species, including autotrophy and sensitivity to the azo dye Congo Red, which we experimentally validated.
Ten United Kingdom laboratories participated in a study to evaluate variability of analysis for total concentrations of sulphur (S) and nitrogen (N) in plant materials and extractable S in soil samples. Four plant and two soil samples were prepared and distributed to the participants. Results show that laboratories were in reasonable agreement for analysis of total N in plant materials, with coefficients of variation (CVs) in the range of 2.7–5.4%. In contrast, the inter-laboratory variability for total S was much higher, with CVs varying from 8.2 to 20.3%. The inter-laboratory variability for plant N:S ratio was similar to that for total S, indicating that the reliability of N:S was limited by the accuracy of the S analysis. Large differences (5-fold) between laboratories were reported for extractable S in soil, with CVs of 36–45%. The laboratories used different analytical methods for both soil and plant analyses, but method bias does not seem to explain the large inter-laboratory variability. Diagnosis of S deficiency based on S analysis may be of questionable validity if S analyses results for plant and soil samples are not accurate. To improve analytical reliability, more method development and standardization are needed.
The unique archived samples from the Rothamsted Broadbalk Experiment, England, were used to evaluate long‐term effects of changing S inputs from atmospheric deposition and fertilization on soil S pools and soil S isotope ratio since 1843. The effects of changing land uses were also investigated. Large S inputs from atmospheric deposition and from sulfate fertilizers did not result in any significant accumulation of soil organic or inorganic S in the arable plots where organic C remained stable. Inputs of sulfate in excess of crop uptake were lost mainly through leaching. Organic S accumulated markedly in the arable plot receiving farmyard manure (FYM) or where arable land was allowed to revert to woodland or grassland. In the latter two systems soil organic C accumulated faster than organic S. In all soils investigated the S isotope ratio (δ 34 S) decreased substantially during the last 150 yr. The decrease in δ 34 S was greater in the woodland, grassland, and the arable FYM plot than in other arable plots receiving either inorganic fertilizers only or no fertilizers. The results indicate that atmospheric S was more depleted in 34 S than the soil native S at the experimental site, and that atmospheric S was incorporated into the organic pool to varying degrees depending on the C pool. In conclusion, land use had a large effect on the S cycling in soils, which is driven mainly by soil organic C cycling. Without accumulating soil organic C, there appears to be little scope for S retention in temperate soils with neutral pH.
No abstract is provided for this article.
Arsenic is a metalloid which is toxic to living organisms. Natural occurrence of arsenic and human activities have led to widespread contamination in many
• Pteris vittata is the first plant reported to be a hyperaccumulator of arsenic (As), and little is known about the mechanisms of As hyperaccumulation in this plant. • Arsenic distribution at the whole plant (fronds) and cellular level was investigated using chemical analyses and energy dispersive X-ray microanalyses (EDXA). Speciation of As in the fronds was determined using X-ray absorption near edge spectroscopy (XANES) analyses. • The majority of As was found in the pinnae (96% of total As). The concentration of As in pinnae decreased from the base to the apex of the fronds. Arsenic concentrations in spores and midribs were much lower than in the pinnae. EDXA analyses revealed that As was compartmentalized mainly in the upper and lower epidermal cells, probably in the vacuoles. The distribution pattern of potassium was similar to As, whereas other elements (Ca, Cl, K, Mg, P and S) were distributed differently. • XANES analyses showed that approximately 75% of the As in fronds was present in the As(III) oxidation state and the remaining as As(V).
No abstract is provided for this article.
No abstract is provided for this article.