Bioaccumulation of arsenic(As) and phosphorous by transplanting Aman rice in arsenic-contaminated clay soils.

Arsenic pollution in soil and water has aroused a considerable attention. Inorganic species of arsenic are associated with various internal cancers and create other health problems. An experiment was conducted to investigate the effect of soil arsenic (As) concentration on arsenic and phosphorous accumulation in root, straw, husk and grain of rice (Oryza sativa). BRRI dhan 33 and BR 11 rice varieties were planted on six levels of As contaminated growth media (T1=3.2, T2=11.6, T3=18.7, T4=38.6, T5=57.8 and T6=80.3 ppm As) in a Completely Randomized Design (CRD) with six replications (Completely Randomized Design). Arsenic concentrations in root, straw, husk and grain were increased significantly with increasing soil As concentration. It was observed that As was highly concentrated in the roots, whereas, phosphorous was high in the grain. Among the treatments, T6 showed highest As accumulation. Arsenic contents in grain and husk of BR 11 were found higher than those of grain and husk of BRRI dhan 33. The straw and root of BRRI dhan 33 showed higher concentration of As than straw and root of BR 11. Phosphorous concentrations in straw, husk and grain were also increased with increase of soil As concentrations. Oryza sativa showed high bioconcentration factor (BCF) and low translocation factor (TF). Therefore, As content in grains did not exceed the maximum permissible limit of 1 mg As kg-1, but straw As is highly risky for animal health as well as human food-chain. It could be concluded that BRRI dhan 33 can be cultivated instead of BR11 in As contaminated soil

Yield and phosphorus efficiency of some lowland rice varieties at different levels of soil‐available phosphorus

A field experiment was conducted on an Aeric Haplaquept soil to study the effect of phosphorus (P) deficiency in soil on the P nutrition and yield of five modern varieties of rice, viz., Purbachi, BR1, BR3, BR14, and BR29, popular with the rice farmers of Bangladesh. Soil-available P in the different plots of the experimental field varied widely, from 2.8 to 16.4 ppm. This plot to plot variation in soil-available P content resulted from differences in the total amounts (0 to 480 kg ha -1) of P the plots had received over a period of 8 years in a long-term P fertilizer trial conducted previously in the same field. Phosphorus deficiency in soil drastically reduced the grain yield of all the rice varieties. In severely P deficient plots, where soil-available P was around 3 ppm, the yield was less than 1 ton ha -1 while in plots containing an adequate P level, i.e., >6 ppm, the yield was more than 4 t ha -1. Rice yield increased linearly with an increase in soil P content up to 6 ppm, and the highest grain yield for any variety, obtained at 6-7 ppm of soil-available P leveled off at this point. Soil P deficiency not only decreased rice yield severely but also decreased P content in straw and grain drastically. However, differences among rice varieties were noted in P nutrition, particularly at low soil P levels. The rice varieties differed markedly also in respect of internal P efficiency. The BR29 showed the highest internal P efficiency both at low and high soil P levels. In all the rice varieties, internal P efficiency decreased with an increase in soil P levels

Arsenic in the environment: Biology and Chemistry

Crown copyright © 2007 Published by Elsevier B.V.Arsenic (As) distribution and toxicology in the environment is a serious issue, with millions of individuals worldwide being affected by As toxicosis. Sources of As contamination are both natural and anthropogenic and the scale of contamination ranges from local to regional. There are many areas of research that are being actively pursued to address the As contamination problem. These include new methods of screening for As in the field, determining the epidemiology of As in humans, and identifying the risk of As uptake in agriculture. Remediation of As-affected water supplies is important and research includes assessing natural remediation potential as well as phytoremediation. Another area of active research is on the microbially mediated biogeochemical interactions of As in the environment. In 2005, a conference was convened to bring together scientists involved in many of the different areas of As research. In this paper, we present a synthesis of the As issues in the light of long-standing research and with regards to the new findings presented at this conference. This contribution provides a backdrop to the issues raised at the conference together with an overview of contemporary and historical issues of As contamination and health impacts.Prosun Bhattacharya, Alan H. Welch, Kenneth G. Stollenwerk, Mike J. McLaughlin, Jochen Bundschuh and G. Panaullahhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503360/description#descriptio

Hydrology: Indo-Gangetic Groundwater Threat

Increasing groundwater extraction supports hundreds of millions of people across the Indo-Gangetic Basin. Data suggests that despite the increase in withdrawals, groundwater depletion is localized and the most widespread threat is contamination

Baseline Soil Variation Is a Major Factor in Arsenic Accumulation in Bengal Delta Paddy Rice

Factors responsible for paddy soil arsenic accumulation in the tubewell irrigated systems of the Bengal Delta were investigated. Baseline (i.e., nonirrigated) and paddy soils were collected from 30 field systems across Bangladesh. For each field, soil sampled at dry season (Boro) harvest, i.e., the crop cycle irrigated with tubewell water, was collected along a 90 m transect away from the tubewell irrigation source. Baseline soil arsenic levels ranged from 0.8 to 21. mg/kg, with lower values found on the Pliestocene Terrace around Gazipur (average, 1.6 ± 0.2 mg/kg), and higher levels found in Holecene sediment tracts of Jessore and Faridpur (average, 6.6 ± 1.0 mg/kg). Two independent approaches were used to assess the extent of arsenic build-up in irrigated paddy soils. First, arsenic build-up in paddy soil at the end of dry season production (irrigated − baseline soil arsenic) was regressed against number of years irrigated and tubewell arsenic concentration. Years of irrigation was not significant (P = 0.711), indicating no year-on-year arsenic build-up, whereas tubewell As concentration was significant (P = 0.008). The second approach was analysis of irrigated soils for 20 fields over 2 successive years. For nine of the fields there was a significant (P < 0.05) decrease in soil arsenic from year 1 to 2, one field had a significant increase, whereas there was no change for the remaining 10. Over the dry season irrigation cycle, soil arsenic built-up in soils at a rate dependent on irrigation tubewell water, 35* (tubewell water concentration in mg/kg, ≡ mg/L). Grain arsenic rises steeply at low soil/shoot arsenic levels, plateauing out at concentratations. Baseline soil arsenic at Faridpur sites corresponded to grain arsenic levels at the start of this saturation phase. Therefore, variation in baseline levels of soil arsenic leads to a large range in grain arsenic. Where sites have high baseline soil arsenic, further additional arsenic from irrigation water only leads to a gradual increase in grain arsenic concentration