EVALUATING AZADIRACHTA INDICA AS A BIOLOGICAL SINK: A MULTI-ZONAL STUDY OF GEOCHEMICAL ANAYLSIS, PHOTOSYNTHETIC PIGMENTS, AND SECONDARY METABOLITES IN RELATION TO AIR POLLUTION IN ANTHRPOGENIC ENVIRONS OF CENTRAL GUJARAT, INDIA

Abstract

In the rapidly industrializing landscape of Central Gujarat, encompassing regions like Anand, Vadodara, and Ahmedabad, the interplay between soil geochemistry and plant health is critical for environmental management. This dataset provides a comparative analysis of three distinct environmental zones: a Control Zone (Botanical Garden), an Industrial Zone (GIDC Estates), and an Urban Road Zone (major crossroads). The study utilizes the Neem tree (Azadirachta indica) as a bio-monitoring tree species to evaluate how air and soil quality influence plant physiology and resilience. The baseline for fertile soil in Central Gujarat is established in botanical gardens, characterized by "Goradu" (sandy loam) and black cotton soils. Ideal soil parameters in these control zones include a pH of 6.5–7.5 and Total Organic Carbon (TOC) between 0.5%–0.8%, which ensures maximum nutrient bioavailability and high biodiversity. In contrast, Industrial GIDC zones exhibit "biological desertification," with TOC dropping to 0.2%–0.5% and sulphate levels spiking up to 500+ mg/kg due to atmospheric deposition and industrial discharge. Urban Road Zones present a unique profile of alkaline buffering (pH 7.2–8.4) caused by concrete dust and elevated nitrates from vehicular NOx emissions. The biochemical markers of A. indica fluctuate significantly across these zones. In the Control Zone, the tree exhibits high photosynthetic efficiency with Total Chlorophyll ranging from 2.50 to 3.80 mg/g. However, in Industrial Zones, chronic exposure to particulates (RSPM) and SO₂ leads to chlorophyll degradation (1.20–1.80 mg/g) as it is converted into phaeophytin. To counter this oxidative stress, the tree diverts energy from primary metabolism (proteins) to secondary metabolism, resulting in a "Defense Spike" where Total Phenols rise from a baseline of 8.0–15.0 mg/g to 18.0–30.0 mg/g in GIDCs. Roadside trees show a "starvation profile" due to dust accumulation, which physically blocks stomata and reduces energy reserves. The dataset links biological health to atmospheric quality through the Air Pollution Tolerance Index (APTI). A critical inverse relationship is observed: as the Air Quality Index (AQI) worsens from "Good" (0–50) in botanical gardens to "Poor vs. Very Poor" (201–300+) in GIDCs, the APTI of surviving Neem trees increases from ~11 to 26+. This indicates that only the most resilient individuals survive in toxic environments, making Neem an ideal "sink" for urban and industrial greenbelts. This research highlights that while soil nutrient stress is a factor, the physiological changes in Central Gujarat’s flora are primarily driven by air quality (SO₂, NOx, and RSPM). The high sulphate-to-nitrate ratio in industrial zones serves as the most telling indicator of an industrial footprint.