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AbstractEssential oil (EO) allelopathy has been considered as potential applications in organic agriculture and weed management, where the EOs can be used as eco-friendly natural herbicides. Rhazya strictais a widely distributed dwarf shrub in the Arabian Peninsula and is characterized by its toxicity. The present study aimed to investigate the chemical composition of the R. strictaEO using quantitative and qualitative analysis via Gas chromatography/ mass spectroscopy (GC-MS) and GC-flame ionization detection (GC-FID) as well as assess its phytotoxicity on weeds. Fifty-four volatile components were identified, representing 97.5% of total oil. The terpenes were found as the backbone of the oil constituents including mono- (55.28%) and sesqui-terpenes (27.35%), alongside non-terpenoid constituents (13.63%). From the overall identified oil constituents, trans-chrysanthenyl acetate (31.57%), cis-verbenol (11.84%), octadecenoic acid, methyl ester (4.84%), cubenol (4.82%), davana ether (4.79%), (E)-9-octadecenoic acid ethyl ester (3.93%) represented the abundant compounds. The EO exhibited strong phytotoxicity on the germination and seedling growth of weeds Dactyloctenium aegyptiumand Chenopodiastrum muralecompared to the crop Triticum aestivum. The EO showed an IC50of 6.66, 7.75, and 6.45 mg/L for seed germination, shoot growth, and root growth, respectively for the weed D. aegyptium, while it showed 5.41, 8.33, and 6.82 mg/L for C. muralecompared to 16.9, 18.5, and 19.5 for T. aestivummg/L for seed germination, shoot growth, and root growth, respectively. The observed strong phytotoxicity could be ascribed to the higher content of the oxygenated terpenoid compounds, whereas, further study is recommended to evaluate the phytotoxicity of the major compounds either singularly or in combination against weeds and determine their mode(s) of action as bioherbicides.

The groundwater systems of northwest India and central Pakistan are among the most heavily exploited in the world. However, recent, and well-documented, groundwater depletion has not been historically contextualized. Here, using a long-term observation-well dataset, we present a regional analysis of post-monsoon groundwater levels from 1900 to 2010. We show that human activity in the early twentieth century increased groundwater availability before large-scale exploitation began in the late twentieth century. Net groundwater accumulation in the twentieth century, calculated in areas with sufficient data, was at least 420 km3at ~3.6 cm yr–1. The development of the region’s vast irrigation canal network, which increased groundwater recharge, played a defining role in twentieth-century groundwater accumulation. Between 1970 and 2000, groundwater levels stabilized because of the contrasting effects of above-average rainfall and the onset of tubewell development for irrigation. Due to a combination of low rainfall and increased tubewell development, approximately 70 km3of groundwater was lost at ~2.8 cm yr–1in the first decade of the twenty-first century. Our results demonstrate how human and climatic drivers have combined to drive historical groundwater trends.

Groundwater abstraction from the transboundary Indo-Gangetic Basin comprises 25% of global groundwater withdrawals, sustaining agricultural productivity in Pakistan, India, Nepal and Bangladesh. Recent interpretations of satellite gravity data indicate that current abstraction is unsustainable, yet these large-scale interpretations lack the spatio-temporal resolution required to govern groundwater effectively. Here we report new evidence from high-resolution in situ records of groundwater levels, abstraction and groundwater quality, which reveal that sustainable groundwater supplies are constrained more by extensive contamination than depletion. We estimate the volume of groundwater to 200 m depth to be >20 times the combined annual flow of the Indus, Brahmaputra and Ganges, and show the water table has been stable or rising across 70% of the aquifer between 2000 and 2012. Groundwater levels are falling in the remaining 30%, amounting to a net annual depletion of 8.0 ± 3.0 km3. Within 60% of the aquifer, access to potable groundwater is restricted by excessive salinity or arsenic. Recent groundwater depletion in northern India and Pakistan has occurred within a longer history of groundwater accumulation from extensive canal leakage. This basin-wide synthesis of in situ groundwater observations provides the spatial detail essential for policy development, and the historical context to help evaluate recent satellite gravity data.

Abstract: Cd-enriched cadmium telluride (CdTe) polycrystalline films were grown on corning glass substrates by close spaced sublimation (CSS) technique. To our knowledge, Cd-enriched CdTe thin films by CSS have not been reported earlier. The structural investigations performed by means of X-ray diffraction (XRD) technique, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX) showed that the deposited films exhibit a polycrystalline structure with 〈111〉 as preferred orientation. The structural, optical, and electrical properties of these films were analyzed as a function of the Cd concentration. For the films having an excess of Cd, the electrical resistivity dropped several orders of magnitude. The deposited films also showed that the value of resistivity decreased with increasing temperature manifesting the semiconducting behavior of the films. The results showed that using this deposition technique, n-type Cd-enriched CdTe polycrystalline film could be produced.