Impact of anthropogenic land uses on soil microbiological activity in a peri-urban landscape.

Land use and land cover patterns impact soil properties and negatively affect soil microbial community and related processes. However, the information regarding the influence of urban land use on soil microbial composition and functioning is limited. Here, we investigated the impact of urban land use patterns on soil microbiological parameters by comparing five contrasting anthropogenic land use classes, i.e. agriculture, park, roadside plantation, street green, and bare land. Soil physicochemical properties, basal respiration (BR), microbial biomass carbon (MBC), and enzyme activities were estimated and correlated. The results revealed that soil physicochemical and microbiological properties greatly varied across the five land use classes. Among all the land use types, the roadside plantation had the highest nutrient content, i.e. soil organic carbon (SOC), total nitrogen (TN), and mineral nitrogen (MN) (1.33%, 0.13%, 84.0 mg kg-1, respectively), while the soil functional capacities measured in terms of BR, MBC, microbial quotient (QCO2), soil microbial activity (SMA), and dehydrogenase activity (DHA) (9.90 C µg g-1 h-1, 300 µg g-1, 0.045 µg h-1/ µg MBC, 9.0 µg ml-1, 1.30 TPF g-1 h-1, respectively) were highest in the park. Disturbed street greens were markedly nutrient depleted and apparently exhibited lower microbial activity. Variations in soil BR, MBC, and enzyme activity were revealed to be primarily influenced by soil moisture, available phosphorus, and SOC content. We concluded that the negative impacts of anthropogenic land use soil quality and microbiological functioning can be managed by integrating proper management approaches for various land use classes in urban systems.

Urban dust pollution tolerance indices of selected plant species for development of urban greenery in Delhi.

The rise in urbanization has led to an increase in dust pollution which is hazardous to the health of living beings. The role of roadside plant species in intercepting particulate matter and improving air quality is well reported. Hence, this study was carried out to determine the ability of various plant species to intercept atmospheric dust and withstand the abiotic stress triggered by dust deposition. In the present investigation, three sites (viz., control, commercial, and industrial) differing in anthropogenic activities and vegetation were selected. Sixteen plant species entailing both trees and shrubs that are commonly occurring at all three sites were selected to estimate their dust interception capacity (DIC). The impact of dust pollution on foliage biochemistry and their tolerance in winter and summer seasons were analyzed. Based on biochemical, biological, and socio-economic parameters, air pollution tolerance index (APTI) and anticipated performance index (API) were evaluated. Both dust load and DIC were found to be two times higher in winter than in the summer season. Terminalia arjuna, Ficus benghalensis, and Plumeria alba were the best dust accumulators, while Prosopis juliflora accumulated least. The highest DIC was observed at the industrial site, for Terminalia arjuna (0.025 mg/cm2/d) in winter and Plumeria alba (0.023 mg/cm2/d) in the summer season. Photosynthetic pigments showed a negative correlation with dust load, while pH, ascorbic acid, electrolytic leakage (E.L.), and proline content showed a positive correlation. In the present study, APTI and API values were highest for Ficus religiosa, Ficus benghalensis, Alstonia scholaris, Dalbergia sissoo, and Terminalia arjuna. Such plant species with wide canopy, large and rough leaf surface area with perforated veins are found to be more suitable and, hence, recommended for the development of greenery to improve air quality in urban areas like Delhi.

Heavy metal accumulation in leaves of selected plant species in urban areas of Delhi.

Heavy metals beyond their permissible limits are major contaminants and causes of concern due to their persistent nature and health hazards. Several studies validated the utilization of plants as biomonitors and bioaccumulators for heavy metal pollution. Therefore, this study was conducted to examine the proficiency for heavy metal monitoring and mitigation by commonly found plant species in urban areas of Delhi. For this objective, four sites (viz., control, residential, commercial, and industrial) and sixteen usually growing plant species were selected. Four heavy metals, i.e., lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn), were analysed for soil and dust from each site, and leaf samples from each plant, at all sites, and various other parameters were calculated. Among the four elements, Pb and Cd showed maximum geoaccumulation and contamination at all sites. Pollution load index (PLI) values for both soil and dust indicated that industrial sites (1.78, 2.15) were most contaminated followed by commercial (1.52, 1,87), residential (1.41, 1.67), and control (1.22, 1.37) sites. Concentrations of Pb, Cu, and Zn were found to be highest in Morus alba, while Cd concentrations were found to be highest in Millettia pinnata (L.) Panigrahi. From various analyses, we concluded that commonly found plant species such as Ficus religiosa L., Terminalia arjuna (Roxb. Ex DC.) Wight &Arn., Morus alba L., Prosopis juliflora (Sw.) DC., and M. pinnata proved to be exceptional biomonitors and bioaccumulators for heavy metals in urban areas. Therefore, these plant species are highly recommended for plantation in urban areas for decontamination of the air and soil by mitigating heavy metal pollution.

Impact of dust accumulation on the physiological functioning of selected herbaceous plants of Delhi, India.

Plants are now widely recognized for their potential role in improving the air quality by dispersion and deposition of atmospheric dust particles. However, suspended dust particles negatively affect plant growth and physiological development. The present study aims to assess the amount of dust accumulation on the leaf surface and to evaluate the effect of foliar dust on leaf gas exchange parameters, photosynthetic pigment, and metabolite content of five roadside herbaceous plant species (Amaranthus viridis, Achyranthes aspera, Acalypha indica, Parthenium hysterophorus, Trianthema portulacastrum). Two sites (site I and site II) were selected that differed in their surrounding anthropogenic activities and dust pollution levels. Results showed that the average amount of dust accumulated on the leaf surface was significantly greater in plants grown at the polluted site. Among the five species examined, the highest amount of foliar dust load was observed for A. aspera (0.49 mg cm-2). Dust accumulation caused substantial changes in plant physiology as indicated by the significant decline in chlorophyll content, photosynthetic rate, stomatal conductivity, and transpiration rate in plants grown at the polluted site. Moreover, an increase in antioxidant activity, total ascorbate, and metabolite content, responsible for maintaining plant defense, was higher in plants at polluted site. Biochemical response of the individual plants studied was variable, which suggests that different plants adopted different mechanisms to cope with the stress induced by dust particles.