Assessment of trace metal contamination in a historical freshwater canal (Buckingham Canal), Chennai, India

The present study was done to assess the sources and the major processes controlling the trace metal distribution in sediments of Buckingham Canal. Based on the observed geochemical variations, the sediments are grouped as South Buckingham Canal and North Buckingham Canal sediments (SBC and NBC, respectively). SBC sediments show enrichment in Fe, Ti, Mn, Cr, V, Mo, and As concentrations, while NBC sediments show enrichment in Sn, Cu, Pb, Zn, Ni, and Hg. The calculated Chemical Index of Alteration and Chemical Index of Weathering values for all the sediments are relatively higher than the North American Shale Composite and Upper Continental Crust but similar to Post-Archaean Average Shale, and suggest a source area with moderate weathering. Overall, SBC sediments are highly enriched in Mo, Zn, Cu, and Hg (geoaccumulation index (Igeo) class 4– 6), whereas NBC sediments are enriched in Sn, Cu,Zn, and Hg (Igeo class 4–6). Cu, Ni, and Cr show higher than Effects-Range Median values and hence the biological adverse effect of these metals is 20%; Zn, which accounts for 50%, in the NBC sediments, has a more biological adverse effect than other metalsfound in these sediments. The calculated Igeo, Enrichment Factor, and Contamination Factor values indicate that Mo, Hg, Sn, Cu, and Zn are highly enriched in the Buckingham Canal sediments, suggesting the rapid urban and industrial development of Chennai MetropolitanCity have negatively influenced on the surrounding aquatic ecosystem

Division S-8 - Nutrient management & soil & plant analysis: Estimation of nitrate leaching in an entisol under optimum citrus production

Leaching of fertilizer nutrients and widespread NO3-N contamination of drinking water wells in proximity to citrus growing regions of central Florida are a serious concern. We evaluated NO3-N distribution in soil solution at various depths in the vadose zone, and N leaching below the root zone for two cropping seasons under the canopy of 21-yr-old Hamlin orange [Citrus sinensis (L.) Osbeck] trees on Cleopatra mandarin (Citrus reticulata Blanco) rootstock, on an entisol of central Florida. The treatments included 112, 168, 224, and 280 kg N ha-1 yr-1 as either dry granular fertilizer (DGF; broadcast, in 4 equal doses) or fertigation (FRT; 15 applications yr-1), and 56, 112, and 168 N kg ha-1 yr-1 as controlled-release fertilizer (CRF; single application yr-1). Irrigation was scheduled using recommended tensiometer set points as guidelines, with a target wetting depth of 90 cm. The NO3-N was measured in soil solutions bi-weekly at 60-, 120-, and 240-cm depths using suction lysimeters (SLs) installed under the tree canopy. The 240-cm depth sample represented soil solution below the rooting depth of the trees, and the NO3-N at this depth could contaminate groundwater. At the 60- or 120-cm depths, the NO3-N concentrations occasionally peaked at 12 to 100 mg L-1, but at 240 cm NO3-N concentrations mostly remained below 10 mg L-1. The careful irrigation management, split fertilizer application, and timing of application contributed to the low leaching of NO3-N below the root zone. Calculated NO3-N leaching losses below the rooting depth increased with increasing rate of N application and the amount of water drained, and accounted for 1 to 16% of applied fertilizer N

Fate of nitrate and bromide in an unsaturated zone of a sandy soil under citrus production

Understanding water and nutrient transport through the soil profile is important for efficient irrigation and nutrient management to minimize excess nutrient leaching below the rootzone. We applied four rates of N (28, 56, 84, and 112 kg N ha-1; equivalent to one-fourth of annual N rates being evaluated in this study for bearing citrus trees), and 80 kg Br- ha-1 to a sandy Entisol with \u3e25-yr-old citrus trees to (i) determine the temporal changes in NO3-N and Br- distribution down the soil profile (2.4 m), and (ii) evaluate the measured concentrations of NO3-N and Br- at various depths with those predicted by the Leaching Estimation and Chemistry Model (LEACHM). Nitrate N and Br- concentrations approached the background levels by 42 and 214 d, respectively. Model-predicted volumetric water content and concentrations of NO3-N and Br- at various depths within the entire soil profile were very close to measured values. The LEACHM data showed that 21 to 36% of applied fertilizer N leached below the root zone, while tree uptake accounted for 40 to 53%. Results of this study enhance our understanding of N dynamics in these sandy soils, and provide better evaluation of N and irrigation management to improve uptake efficiency, reduce N losses, and minimize the risk of ground water nitrate contamination from soils highly vulnerable to nutrient leaching

Constituents of high altitude Himalayan herb <i>Angelica glauca</i>

2452-2455(Z)-ligustilide, (Z)-butylidine phthalide, methyl octadecadinoate, caryophyllene and caryophyllene oxide have been isolated from the n-hexane extracts of root of Angelica glau ca, collected from the high altitude region of Kumaun Himalayas in Uttaranchal

1, 5-Dihydroxy-3, 8-dimethoxyxanthone from <i>Swertia cuneata</i>^†

953-955A new tetraoxygenatedxanthone 1, 5-dihydroxy-3, 8-dimethoxyxanthone 1 has been isolated from Swertia cuneata (Gentianaceae) and identified by means of chemical and UV, 1H NMR, 13C NMR and mass spectral data

Nitrogen and irrigation management practices to improve nitrogen uptake efficiency and minimize leaching losses

Nitrogen (N) is the most important nutrient for plant growth and production. Nitrogen uptake efficiency is dependent on a number of factors. Water management influences the transformation of N sources applied to the soil and transport of the nitrate form of N in the soil. Nitrate-N is the final product of N transformations and is quite mobile in soils with the water front. Leaching of nitrate below the rootzone is an economic loss and contributes to non-point source pollution of groundwater. In this chapter we summarize the factors influencing the N uptake efficiencies for various crops and production systems, and chemical and biological processes that influence the N transformation or losses. Recent advances leading to development of N and irrigation best management practices that support sustainable crop production and net returns while minimizing the non-point source nitrate pollution of groundwater are also discussed. © 2005 by The Haworth Press, Inc. All rights reserved

Numerical modeling to study the fate of nitrogen in cropping systems and best management case studies

Nitrogen (N) availability for crop uptake is dependent on various factors that influence the transformation of N sources and transport of N forms in soils. The fate and transport of N is site specific. Therefore evaluation of N dynamics under each condition is neither practical nor feasible. Simulation models which are adequately calibrated and tested can be used to estimate the fate and transport of N as well as crop responses under different production systems. These evaluations provide some guidelines as how to manage N and water efficiently to maximize the N uptake efficiency and minimize the losses. Thus, they contribute to the development of N and water best management practices. In this chapter, we discuss recent information on experimentally measuring the water and nutrient transport in soils as well as performing estimations using simulation models. The development and application of different simulation models for different production systems have been summarized. Some case studies on nitrogen and water best management practices are also discussed. © 2005 by The Haworth Press, Inc. All rights reserved