Spatial Variability of Cadmium and Lead in Surface Soils in-relation to Landuse and Topography

Accumulation of trace elements in soils has become an environmental concern. Understanding spatial variability of trace elements in relation to point and non-point sources is important to identify threats and monitoring mechanisms. Objectives of this study were to explore the spatial variability of cadmium (Cd) and lead (Pb) in relation to the land-use and topography. One hundred and thirty seven surface soil (0-15 cm) samples were collected from a tropical Ultisol soil scape in up-and mid-country in wet zone in Sri Lanka, representing tea, forest, and urban land uses. Total Cd and Pb concentrations were determined by digesting the soils using aqua regia (Trace-metal grade) and analysed using Graphite Furnace Atomic Absorption Spectrophotometer, following USEPA method 7010.Extractable concentrations of Cd and Pb were determined using Mehlich 3 extraction. Soil pH, electrical conductivity, cation exchange capacity, available P, total P, amorphous Fe, total Fe and Mn were determined using standard methods. Total and Mehlich 3 concentrations of trace elements showed positively skewed data distributions. Across all the land uses, the total Cd and Pb concentrations ranged from 0.05 to 0.40 mg kg-1 (median: Tea=16, Urban=13, Forest=19) and 3 to 37 mgkg-1 (median: Tea=0.13, Urban=0.14, Forest=0.16) respectively. Mehlich 3 Cd and Pb concentrations were low and ranged from 0.01 to 0.62 mgkg-1and 1 to 26 mgkg-1, respectively. Potential bioavailability of Cd in tea, urban and forest land uses was 40%, 32% and 32% respectively, meanwhile for Pb it was 40%, 60% and 40% respectively. Regression analysis explained that the relationship of total Pb and Mehlich 3 extractable Pb concentrations with elevation was significant (p<0.05); However, only about 4-7% of variation of them was explained by elevation. Cd concentration was not significantly related to elevation. Variability of concentrations of Cd and Pb were not related to land use. Soil associations were also not related to spatial variability of total concentrations of Cd and Pb in soils. Spatial variability of total concentrations of Cd and Pb will be presented with maps including land use, soil association and elevation distribution.Keywords: Potential bioavailability, Spatial variability, Topography, Trace element

Bioaccessibility of Lead in Long-Term Vegetable Grown Urban Soil

Vegetable cultivation has been practiced for more than fifty years in the up-country of Sri Lanka providing about 60% of country’s vegetable requirement. Often, vegetable cultivations are distributed in urban areas. Moreover, agricultural inputs, gasoline and paints can contribute for lead (Pb) contamination in soils. Direct soil ingestion is the major exposure pathway of soil Pb to organisms. The risk of direct ingestion of soil Pb can be assessed by using in-vitro bioaccessibility tests. Objectives of the study were to assess bioaccessibility of Pb in long-term vegetable grown urban soils by using in-vitro bioaccessibility tests and to investigate the potential of Mehlich 3 extractable Pb as a measure of bioaccessible Pb. Simplified physiologically based in-vitro extraction test was conducted for extracting bioaccessible Pb in 42 surface soil samples collected from vegetable grown fields located in urban areas in Nuwaraeliya. Total Pb concentrations in soils were determined by digesting the soils using aqua regia (trace metal-grade) and analysing using Graphite Furnace Atomic Absorption Spectrophotometer. Total Pb concentration in soils ranged from 10 to 110 mg/kg. The Mehlich 3 Pb and bioaccessible Pb concentrations were low, which ranged from 2 to 12 mg/kg and 1 to 3 mg/kg, respectively. High available P (47 to 757 mg/kg) and organic C content (1.1 to 3.8%) in soils may have contributed to low bioaccessibility of Pb. The regression analysis revealed that only 44% of variation of bioaccessible Pb and 22% of variation of total Pb can be explained by Mehlich 3 Pb (p<0.001). Effect of total Pb on bioaccessible Pb is low. Strong relationship (p<0.001) was observed between bioaccessible Pb and Mehlich 3 Pb expressed as percentages of total Pb [bioaccessibility of Pb=0.17*(availability of Pb)+0.38, R2=0.71]. Thus, less laborious Mehlich 3 and total Pb measurements can be used to estimate bioaccessibility of Pb. Low bioaccessibility suggested that the risk of direct exposure for soil Pb is minimal in the tested long-term vegetable grown urban soil. Keywords: Lead, Bioaccessibility, Urban soil, Vegetable, Mehlich 3 extractio

Identification and antimicrobial susceptibility of bacteria isolated from corneal ulcers of dogs Identificação e susceptibilidade antimicrobiana de bactérias isoladas de úlceras de córnea em cães

A total of 22 clinical specimens were obtained from 19 dogs with corneal ulcer (16 unilateral and three bilateral) for isolation and antimicrobial susceptibility evaluation of the isolated bacteria. Bacterial growth was observed in 100% of the samples (n=22). Staphylococcus intermedius was the predominant species (35.5%), followed by Corynebacterium xerosis (19.3%). Gentamicin, ciprofloxacin, chloramphenicol and tobramycin had a high efficacy against all of the isolated bacteria. The results evidenced that 80.7% of the isolates were Gram positive cocci and Gram positive bacilli, and that those microorganisms were sensitive to gentamicin, ciprofloxacin, chloramphenicol and tobramycin.<br>Utilizaram-se 22 amostras de material, obtidas de 19 cães com úlcera de córnea, sendo 16 unilaterais e três bilaterais, para isolamento e avaliação da susceptibilidade antimicrobiana das bactérias isoladas. Observou-se crescimento bacteriano em 100% das amostras (n=22). A espécie predominante foi Staphylococcus intermedius (35,5%) seguido de Corynebacterium xerosis (19,3%). Gentamicina, ciprofloxacina, cloranfenicol e tobramicina apresentaram alta eficácia contra todas as bactérias isoladas. Os resultados evidenciam que 80,7% dos isolados foram cocos e bacilos Gram positivos e que estes microrganismos foram sensíveis à gentamicina, ciprofloxacina, cloranfenicol e tobramicina

Bifidobacteria as indicators of faecal contamination along a sheep meat production chain

Aims: The potential use of bifidobacteria as indicators for faecal contamination was studied along a sheep meat production and processing chain. The levels of bifidobacteria were compared with those of Escherichia coli. Total viable counts were followed along the chain (244 samples). Methods and Results: Forty-three per cent of the samples contained bifidobacteria, of which 15% were solely detected using a PCR method based on the hsp60 gene and not by a culture-based method. Bifidobacteria were detected in only three of nine sheep faeces samples using one or the other method. However, carcasses (types C and E) were highly contaminated. These sample types (30% and 28%, respectively) were positive for bifidobacteria and negative for E. coli. The species Bifidobacterium pseudolongum and Bif. thermophilum, isolated from faecal samples, were predominant. Bifidobacterium choerinum were found in C, D, E and F sample types. Conclusions: Bifidobacteria were shown more efficient than E. coli in carcasses samples. The presence of Bif. choerinum suggested a faecal pork contamination. Significance and Impact of the Study: Detection and identification of bifidobacteria, in correlation with E. coli counting, should improve hygiene quality of mutton processing chains.BIFI