Tropical tropospheric chemistry and climate change

A systematic programme of monitoring surface ozone and its precursor gases CH4, CO and NOx (NO + NO2) at some selected sites in the Indian region was started under ISRO's geosphere biosphere programme in 1991. Measurements have been made at Ahmedabad an urban polluted site, Gadanki a rural relatively clean site, Gurusikhar a high altitude site representative of the free troposphere and Trivandrum a coastal (relatively clean) site influenced by marine air. The data has been used to study different features of troposphere chemistry in the tropics. Some of the results from this programme relevant to the climate change problem are presented in this paper.

Presence and biodistribution of perfluorooctanoic acid (PFOA) in Paracentrotus lividus highlight its potential application for environmental biomonitoring

The first determination of presence and biodistribution of PFOA in ninety specimens of sea urchin Paracentrotus lividus from two differently contaminated sites along Palermo’s coastline (Sicily) is reported. Analyses were performed on the sea urchins’ coelomic fluids, coelomocytes, gonads or mixed organs, as well as on seawater and Posidonia oceanica leaves samples from the collection sites. PFOA concentration ranged between 1 and 13 ng/L in seawater and between 0 and 794 ng/g in P. oceanica. The analyses carried out on individuals of P. lividus from the least polluted site (A) showed PFOA median values equal to 0 in all the matrices (coelomic fluid, coelomocytes and gonads). Conversely, individuals collected from the most polluted site (B) showed median PFOA concentrations of 21 ng/g in coelomic fluid, 153 ng/g in coelomocytes, and 195 ng/g in gonads. Calculated bioconcentration factors of log10BCF > 3.7 confirmed the very bioaccumulative nature of PFOA. Significant correlations were found between the PFOA concentration of the coelomic fluid versus the total PFOA concentration of the entire sea urchin. PERMANOVA (p = 0.001) end Welch's t-test (p < 0.001) analyses showed a difference between specimens collected from the two sites highlighting the potential application of P. lividus as sentinel species for PFOA biomonitoring.

Relative gene expression, micronuclei formation, and ultrastructure alterations induced by heavy metal contamination in Pimelia latreillei (Coleoptera: Tenebrionidae) in an urban-industrial area of Alexandria, Egypt

The present research aims to evaluate the impact of industrial processes and anthropogenic activities on the beetle Pimelia latreillei inhabiting the polluted site at Zawya Abd El- Qader, Alexandria, Egypt. Beetles were collected from the vicinity of five factories. The genotoxic effects of environmental exposures to industrial heavy metals were monitored using a broad range of assays, including energy-dispersive X ray microanalysis and X-ray diffraction (SEM and EDX)), qRT-PCR gene expression assay, micronuclei formation, and transmission electron microscope (TEM). Energy dispersive X-ray microanalysis for the soil and testicular tissues of beetles collected from the polluted site revealed a higher percentage of heavy metals than the beetles collected from the reference site (Sidi Kirier, Alexandria, Egypt). To analyze/monitor genotoxicity in P. latreillei sampled from the polluted site, the transcription levels of levels of heat shock proteins (Hsps) and accessory gland seminal fluid protein (AcPC01) in testicular tissues were recorded. The incidence of micronuclei (MN) formation in the testicular cells was also observed. Quantitative RT-PCR (RT-qPCR) analysis was carried out to detect the changes in the gene expression of the aforementioned proteins. Genes encoding heat shock proteins (Hsp60, Hsp70, and Hsp90) were significantly overexpressed (> 2-fold) in specimens sampled from the polluted site; however, AcPC01 gene expression was under-expressed (<1.5-folds). The incidence of MN was significantly increased in specimens sampled from the polluted site. Ultrastructure anomalies (nuclear and cytoplasmic disruption) were also observed in the testicular cells of the beetles sampled from the polluted site compared to those sampled from the unpolluted site. Our results, therefore, advocate a need for adequate measures to reduce increasing environmental pollution in the urban-industrial areas.

Remediation of Hydrocarbon Polluted Soil Offsets Methanogenic Microbial Communities and Improves Soil Recovery of Crude Oil-Polluted Site

Hydrocarbon pollution amplified by artisanal refining has led to the devastating destruction of farmlands and fishing settlements of subsistence farmers in the Niger Delta. The relatively slow natural attenuation of these polluted sites is the motivation for this study. The natural response and the influence of intermittent tillage and nutrient addition on bacterial community ecological functions were investigated using 16S rRNA metabarcoding. Representative soil samples were drawn from the surface (0 – 15cm) and subsurface (1m and 1.5m depths) of the polluted site pre-remediation and during remediation on Days 0, 14, 49, 70 and 91. Nutrient in the form of poultry droppings was added to the polluted soil while aeration was improved by tillage at 3-weeks interval throughout the duration of remediation. Total petroleum hydrocarbon was reduced from 93,720 mg kg–1 on timepoint zero to 9,029.76 mg kg–1 on day 91. Alpha diversity analysis revealed that the proportionality (evenness) of bacterial species significantly reduced during remediation. The bacterial community structure during remediation was significantly different compared to the structure pre-remediation. Spearman’s rank correlation revealed that soil pH, total phosphorus and total potassium were the chemical factors that influenced diversity. During remediation, the most responsive bacterial phyla were Proteobacteria and Cyanobacteria while Hydrogenedentes and Spirochaetes were among biomarkers pre-remediation. PICRUSt2-based functional prediction revealed that pre-remediation, pathways for methanogenesis and terpenoids biosynthesis were differentially abundant while high energy-yielding TCA cycle and pathways for both fatty acid biosynthesis and the degradation of aromatic hydrocarbons were differentially abundant during remediation. Overall, the addition of poultry droppings and intermittent tillage improved nutrient availability and this subsequently led to a significant change in the bacterial community structure and the rate of hydrocarbon sequestration. The authors concluded that incorporation of poultry droppings by tillage may serve as a suitable remediation method to reduce hydrocarbon in oil-polluted Niger Delta soils.

Assessment of Air Pollution Impact on Micro-Morphological and Biochemical Properties Of Callistemon citrinus (Curtis) Skeels And Lagerstroemia indica L.

The urban air pollution is a major environmental concern, particularly in the developing countries and in their major cities. In the present study an attempt has been made to assess the air pollution effect on micromorphological and biochemical parameters of Callistemon citrinus and Lagerstroemia indica. Biochemical parameters were analyzed by using standard protocol. one-way analysis of variance was performed with SPSS software, v. 20.0, and Duncan test (p ≤ 0.05) was used to compare averages of all measured biochemical parameters and micromorpholgical features. There was a decrease in number of stomata of both species at highly polluted site compared to less polluted site (control). Stomatal index of both species was found to be reduced in polluted site when compared to control. The number of clogged stomata was less in control area samples when compared to polluted sample. A number of epidermal cells were significantly decreased at heavily polluted site. Total chlorophyll content and leaf extract pH in both the plants were found to be significantly higher in control sites than in heavily polluted sites. Ascorbic acid, relative water content, and Air Pollution Tolerance Index (ATPI) was found to be significantly higher at more polluted plants than at control. Based on the present study results, Callistemon citrinus emerged as the most tolerant species with the highest APTI. Hence, Callistemon citrinus can be suggested for plantations along the roadside of urban areas for green belt development.

Effects of road traffic on photosynthetic pigments and heavy metal accumulation in tree species of Kumasi Metropolis, Ghana

This study was undertaken to examine changes in the content of pigments and accumulation of metals from vehicular pollution in selected species of roadside trees under vehicular pollution. A major arterial road with heavy vehicle emissions in the Kumasi Metropolis was designated as the polluted site, while Kwame Nkrumah University of Science and Technology Campus was designated as the control site. Four tree species (Terminalia catappa, Mangifera indica, Ficus platyphylla and Polyalthia longifolia) selected for the study were well distributed and abundant in the polluted and control sites. Photosynthetic pigments and levels of heavy metals (Pb, Cu, Cd and zinc) were assessed in their leaves. Chlorophyll and carotenoid contents were determined by absorption spectrometry, while the metal accumulation index (MAI) was used to determine the total metal accumulation capacity of the tree species. We observed a reduction in photosynthetic pigments in the leaf samples from the polluted site. Ficus platyphylla had the maximum reduction in total chlorophyll (49.34%), whereas Terminalia catappa recorded the lowest reduction (33.88%). Similarly, the largest decrease (31.58%) of carotenoid content was found in Terminalia catappa trees and the lowest in Polyalthia longifolia (16.67%). The Polyalthia longifolia, Ficus platyphylla and Terminalia catappa leaf samples collected at the polluted site recorded a higher ratio of chlorophyll a/b. Heavy metal (Cu, Pb, Zn and Cd) accumulation in leaf samples was higher in the polluted site than in the control, as expected. The highest metal MAI value was recorded in Mangifera indica (5.35) followed by Polyalthia longifolia with 4.30. The findings from this study specifically demonstrate that air contamination induced by vehicles decreases the level of photosynthetic pigments in trees subjected to roadside emissions. It is clear that both chlorophyll a/b and chlorophyll/carotenoid ratios will act as very useful stress-level markers. Elevated heavy metal levels in the tree species along arterial roadsides indicate that they serve as heavy metals sink. The change in MAI resulting from different pollution burden is an indication that the removal capabilities of the tree species differ from each other. We therefore suggest M. indica and P. longifolia as potential species to be used in air pollution reduction plans in the city.