Arsenic in Rice Grown in Low-Arsenic Environments in Bangladesh ...

Water Qual Expo Health (2012) 4:197–208 DOI 10.1007/s12403-012-0079-6

Arsenic in Rice Grown in Low-Arsenic Environments in Bangladesh M.R. Islam · Hugh Brammer · G.K.M. Mustafizur Rahman · Andrea Raab · M. Jahiruddin · A.R.M. Solaiman · Andrew A. Meharg · Gareth J. Norton

Received: 28 June 2012 / Revised: 15 August 2012 / Accepted: 17 August 2012 / Published online: 14 September 2012 © Springer Science+Business Media B.V. 2012

Abstract It has previously been reported that rice grown in regions of Bangladesh with low-arsenic (As) concentrations in irrigation water can have relatively high concentrations of As within their grains. This study aims to determine how widespread this issue is, and determine the seasonal variation in grain As in these regions. Levels of As were measured in shallow tube well (STW) water, soils, and rice grains collected during the Boro (dry) and Aman (wet) seasons from six Upazilas (sub-districts) of Bangladesh where As levels in groundwater were known to be low. In all the Upazilas, the As concentrations in STW water were 0.15 µg g−1 ) in some of the samples from six districts (Dinajpur, Bogra, Gazipur, Mymensingh, Natore, Rangpur) where earlier surveys of groundwater quality for domestic use had shown low As concentrations. The shallow aquifer used for domestic water supply in these districts is widely used for irrigation of Boro (dry season) rice by means of shallow tube wells (STW). The aim of this study was to confirm and expand on the earlier observation by Williams et al. (2006), and to determine the As concentration in the soil in areas with low groundwater As to see if this is the source of the increased grain As concentration. Furthermore, the study aimed to quantify the contribution of rice, curry, and water on As ingestion for people living in regions with low As groundwater. This study was conducted, therefore, to measure the As content of irrigation water, soils, and rice grain in one Upazila (sub-district) in six districts of Dinajpur, Bogra, Gazipur, Mymensingh, Natore, and Rangpur during the Boro season (Fig. 1), taking samples from within physiographic regions with low reported As levels in groundwater. This was followed by analysis of the As contents of nail, hair, and urine samples collected from 15 families eating Boro rice grown in one of the sampled sites (Gouripur). In the following Aman (wet) season, samples were collected from five of the Upazilas where Boro rice was grown, together with Islampur Upazila where Boro rice was not

M.R. Islam et al.

Fig. 1 Location of the sampling sites in Bangladesh

grown. Samples were not collected from Natore Upazila after the Aman season as Aman rice does not follow Boro rice in this Upazila.

Methods Site Selection and Sampling The sample locations for the Boro rice survey were in the Dinajpur, Rangpur, Kahalu, Natore, Sripur, and Gouripur Upazilas of Bangladesh. A detailed map of As-contaminated areas of Bangladesh is given in Brammer and Ravenscroft (2009). The six Upazilas sampled were within areas where earlier groundwater surveys had indicated low As concentrations. The sampled areas of Dinajpur and Kahalu (in Bogra district) lie on the Barind Tract, an uplifted Pleistocene block underlain by Tertiary Dupi Tila sediments. In Natore the samples were taken in the northern part of the Upazila, where the Barind Tract has been shallowly buried by floodplain sediments in the Lower Atrai Basin. Sripur Upazila in Gazipur District, sampled during an earlier survey (Lu et al. 2009), is on the Madhupur Tract, an uplifted Pleistocene block similar to the Barind Tract. Gouripur Upazila in Mymensingh District is on the Old Brahmaputra Floodplain, and Rangpur Upazila is on the Tista Floodplain, both underlain by Holocene sediments. Detailed information on sediments and soils in the physiographic regions of Bangladesh

Arsenic in Rice Grown in Low-Arsenic Environments in Bangladesh

is given in Brammer (1996). A brief description of the soil properties is given in Supplementary Table 1. In each Upazila, five STW command areas were chosen. At all sites tubewell water was directly released into the field under study via a concrete or earthen channel straight from the STW. In each of the command areas three composite soil samples were collected at grain maturity during May 2009. One composite soil sample was collected from a rice field adjacent to the STW, and the other two composite samples were collected from the mid (approximately 100 m from STW) and far ends of the command area (approximately 200 m from STW). Soil was sampled to 15 cm depth using a 5 cm diameter auger. The GPS value was recorded at each sampling point. A bamboo stick was placed in the sampling point to mark the rice hill to be used for sampling the rice grains. The Boro rice cultivars sampled during the Boro season at each Upazila are listed in Supplementary Table 2. Field history was obtained from the farmer. In the same year, soil and Aman rice grain samples were collected from all the same Upazilas sampled during the Boro season, except Natore Upazila, where Aman rice was not cultivated due to deep flooding. Soil and rice grains were also collected from Islampur Upazila on the Old Brahmaputra Floodplain, where Aman rice was grown under rain-fed conditions. The rice cultivars sampled during the Aman season in each Upazila are listed in Supplementary Table 3. The soil samples were air dried and sieved (