A review on completing arsenic biogeochemical cycle: Microbial volatilization of arsines in environment

Arsenic (As) is ubiquitous in the environment in the carcinogenic inorganic forms, posing risks to human health in many parts of the world. Many microorganisms have evolved a series of mechanisms to cope with inorganic arsenic in their growth media such as transforming As compounds into volatile derivatives. Bio-volatilization of As has been suggested to play an important role in global As biogeochemical cycling, and can also be explored as a potential method for arsenic bioremediation. This review aims to provide an overview of the quality and quantity of As volatilization by fungi, bacteria, microalga and protozoans. Arsenic bio-volatilization is influenced by both biotic and abiotic factors that can be manipulated/elucidated for the purpose of As bioremediation. Since As bio-volatilization is a resurgent topic for both biogeochemistry and environmental health, our review serves as a concept paper for future research directions.

Arsenic Speciation and Localization in Horticultural Produce Grown in a Historically Impacted Mining Region

A field and market basket study (similar to 1300 samples) of locally grown fruits and vegetables from historically mined regions of southwest (SW) England (Cornwall and Devon), and as reference, a market basket study of similarly locally grown produce from the northeast (NE) of Scotland (Aberdeenshire) was conducted to determine the concentration of total and inorganic arsenic present in produce from these two geogenically different areas of the U.K. On average 98.5% of the total arsenic found was present in the inorganic form. For both the market basket and the field survey, the highest total arsenic was present in open leaf structure produce (i.e., kale, chard, lettuce, greens, and spinach) being most likely to soil/dust contamination of the open leaf structure. The concentration of total arsenic in potatoes, swedes, and carrots was lower in peeled produce compared to unpeeled produce. For baked potatoes, the concentration of total arsenic in the skin was higher compared to the total arsenic concentration of the potato flesh, this difference in localization being confirmed by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS). For all above ground produce (e.g., apples), peeling did not have a significant effect on the concentration of total arsenic present.

Methylated Arsenic Species in Rice:Geographical Variation, Origin, and Uptake Mechanisms

Rice is a major source of inorganic arsenic (iAs) in the human diet because paddy rice. efficient at accumulating As Rice As speciation is dominated by iAs and dimethylarsinic acid (DMA). Here we review the global pattern in rice As speciation and the factors causing the variation. Rice produced in Asia shows a strong linear relationship between iAs and total As concentration with a slope of 0.78. Rice produced in Europe and the United States shows a more variable, but generally hyperbolic relationship with DMA being predominant in U.S. rice. Although there is significant genotypic variation in grain As speciation, the regional Variations are primarily attributed to environmental factors. Emerging evidence also indicates that methylated. As species in rice are derived from the soil, while rice plants lack the As methylation ability. Soil flooding and additions of organic matter increase microbial methylation of As, although the microbial community responsible for methylafion is poorly understood. Compared with iAs, methylated As species are taken up by rice roots less efficiently but are transported to the grain much, more efficiently, which may be an important factor responsible for the spikelet sterility disorder (straight head disease) in rice. DMA is a weak carcinogen, but the level of ingestion from rice consumption is much lower than that of concern. Questions that require further investigations are identified.

Arsenic in Rice Grown in Low-Arsenic Environments in Bangladesh

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 <50 mu g L-1. The As levels in soil samples collected from the Upazilas ranged between 0.2-4.0 mgkg(-1) in the sam-ples collected during the Boro season, and 0.4-5.7 mg kg(-1) in the samples collected in the Aman season. Levels of As in both Boro and Aman rice grain varied widely: in Boro 0.02-0.45 mg kg(-1), and in Aman 0.01-0.29 mg kg(-1). Additionally, a household survey of dietary habits was also conducted in one Upazila by estimating As ingestion by 15 head female members. On average, the women consumed 3.1 L of water, 1.1 kg of cooked rice, and 42 g dry weight of curry per day. The total As ingestion rates ranged from 31.1-129.3 mu g day(-1) (mean 63.5 mu g kg(-1)). These findings indicate that the major route of As ingestion in low groundwater As areas of Bangladesh is rice, followed by curry and then water.

Hydrogeochemistry and Arsenic Contamination of Groundwater in the Haor Basins of Bangladesh

Hydrogeochemical relationships and the level of arsenic (As) contamination of groundwater in the Haor Basin, a low-lying, semi-natural, region of remnant wetland environs to the northeast of Bangladesh, were studied to assess the As biogeochemical cycling. Most of the shallow and deep tubewells in the study area are contaminated with As (2-331 mu g/l). The relatively higher proportions of Na+ (8-156 mg/l) in groundwater suggest a mixing of connate marine water with freshwater aquifer. Non-significant association between As and PO43- has been found. Highly significant (P <0.001) relationship of As with DOC in groundwater indicates biodegradation of organic matter, creating an overall reducing environment in the aquifer sediments, which facilitates the release of As in the groundwater. The inverse As-Fe, As-Mn, As-Ca and As-Mg relationships in groundwater could be related to the precipitation of Fe-, Mn-, Ca-and Mg-minerals.

Levels of Arsenic and Other Trace Elements in Southern Libyan Agricultural Irrigated Soil and Non-irrigated Soil Projects

The levels of As and various other trace elements found in the irrigated agricultural soil (Tsoil) of southern Libya were compared with non-irrigated soil (Csoil) from the same sampling campaign collected between April and May 2008. The soil samples represented agronomic practice in the southern Libyan regions of Maknwessa (MAK), Aril (ARL) and Taswaa (TAS), and were analyzed by Inductively coupled plasma mass spectrometry (ICP-MS) for Co, Ni, Cu, Se, Mo, Zn, As, Pb, Cd and P. Concentrations of P and As in TAS and MAK were found to be higher in Tsoil compared to Csoil, while the opposite was true for ARL. In general, As concentrations in these areas were 2-3 times lower than the global average. In ARL, the average P concentrations of the Csoil samples were significantly higher than those of Tsoil samples: this site is composed mainly of pasture for animal production, where phosphate fertilizers are used regularly. Distance from the source of irrigation was found to be of an important influence on the heavy metal concentration of the soil, with greater concentrations found closer to the irrigation source. It can be concluded from the results that irrigation water contains elevated levels of As, which finds its way into the soil profile and can lead to accumulation of As in the soil over time.

Identification of quantitative trait loci for rice grain element composition on an arsenic impacted soil:Influence of flowering time on genetic loci

Elements in grain crops such as iron, zinc and selenium are essential in the human diet, whereas elements such as arsenic are potentially toxic to humans. This study aims to identify quantitative trait loci (QTLs) for trace elements in rice grain. A field experiment was conducted in an arsenic enriched field site in Qiyang, China using the Bala x Azucena mapping population grown under standard field conditions. Grains were subjected to elemental analysis by inductively coupled plasma mass spectroscopy. QTLs were detected for the elemental composition within the rice grains, including for iron and selenium, which have previously been detected in this population grown at another location, indicating the stability of these QTLs. A correlation was observed between flowering time and a number of the element concentrations in grains, which was also revealed as co-localisation between flowering time QTLs and grain element QTLs. Unravelling the environmental conditions that influence the grain ionome appears to be complex, but from the results in this study one of the major factors which controls the accumulation of elements within the grain is flowering time.

Bladder interstitial cells:an updated review of current knowledge

The field of bladder research has been energized by the study of novel interstitial cells (IC) over the last decade. Several subgroups of IC are located within the bladder wall and make structural interactions with nerves and smooth muscle, indicating integration with intercellular communication and key physiological functions. Significant progress has been made in the study of bladder ICs' cellular markers, ion channels and receptor expression, electrical and calcium signalling, yet their specific functions in normal bladder filling and emptying remain elusive. There is increasing evidence that the distribution of IC is altered in bladder pathophysiologies suggesting that changes in IC may be linked with the development of bladder dysfunction. This article summarizes the current state of the art of our knowledge of IC in normal bladder and reviews the literature on IC in dysfunctional bladder.

Urban/rural variation in the influence of widowhood on mortality risk: a cohort study of almost 300,000 couples

Death of a spouse is associated with increased mortality risk for the surviving partner (the widowhood effect). We investigated whether the effect magnitude varied between urban, rural and intermediate areas, assembling death records (2001-2009) for a prospective cohort of 296,125 married couples in Northern Ireland. The effect was greatest during the first six months of widowhood in all areas and for both sexes. Subsequently, the effect was attenuated among men in rural and intermediate areas but persisted in urban areas (HRs and 95% CIs: rural 1.09 [0.99, 1.21]; urban 1.35 [1.26, 1.44]). Among women the effect was attenuated in all areas (rural 1.06 [0.96, 1.17]; urban 1.09 [1.01, 1.17]). The impacts of spousal bereavement varied between urban and more rural areas, possibly due to variation in social support provided by the wider community. We identify men in urban areas as being in greatest need of such support and a possible target for health interventions.

Phytoremediation assessment of Gomphrena globosa and Zinnia elegans grown in arsenic-contaminated hydroponic conditions as a safe and feasible alternative to be applied in arsenic-contaminated soils of the Bengal Delta

Several agricultural fields show high contents of arsenic because of irrigation with arsenic- contaminated groundwater. Vegetables accumulate arse- nic in their edible parts when grown in contaminated soils. Polluted vegetables are one of the main sources of arsenic in the food chain, especially for people living in rural arsenic endemic villages of India and Bangladesh. The aim of this study was to assess the feasibility of floriculture in the crop rotation system of arsenic en- demic areas of the Bengal Delta. The effects of different arsenic concentrations (0, 0.5, 1.0, and 2.0 mg As L−1) and types of flowering plant (Gomphrena globosa and Zinnia elegans) on plant growth and arsenic accumula- tion were studied under hydroponic conditions. Total arsenic was quantified using atomic absorption spec- trometer with hydride generation (HG-AAS). Arsenic was mainly accumulated in the roots (72 %), followed by leaves (12 %), stems (10 %), and flowers (<1 %). The flowering plants studied did not show as high phytoremediation capacities as other wild species, suchas ferns. However, they behaved as arsenic tolerant plants and grew and bloomed well, without showing any phytotoxic signs. This study proves that floriculture could be included within the crop rotation system in arsenic-contaminated agricultural soils, in order to im- prove food safety and also food security by increasing farmer’s revenue.

Physical map and cosmid contig encompassing a new interstitial deletion of the X-linked lymphoproliferative syndrome region

The X-linked lymphoproliferative syndrome (XLP) is an inherited immuno-deficiency to Epstein-Barr virus infection that has been mapped to chromosome Xq25. Molecular analysis of XLP patients from ten different families identified a small interstitial constitutional deletion in 1 patient (XLP-D). This deletion, initially defined by a single marker, DF83, known to map to interval Xq24-q26.1, is nested within a previously reported and much larger deletion in another XLP patient (XLP-739). A cosmid minilibrary was constructed from a single mega-YAC and used to establish a contig encompassing the whole XLP-D deletion and a portion of the XLP-739 deletion. Based on this contig, the size of the XLP-D deletion can be estimated at 130 kb. The identification of this minimal deletion, within which at least a portion of the XLP gene is likely to reside, should greatly facilitate efforts in isolating the gene.

Rethinking Rice Preparation for Highly Efficient Removal of Inorganic Arsenic Using Percolating Cooking Water

A novel way of cooking rice to maximize the removal of the carcinogen inorganic arsenic (Asi) is presented here. In conventional rice cooking water and grain are in continuous contact, and it is known that the larger the water:rice cooking ratio, the more Asi removed by cooking, suggesting that the Asi in the grain is mobile in water. Experiments were designed where rice is cooked in a continual stream of percolating near boiling water, either low in Asi, or Asi free. This has the advantage of not only exposing grain to large volumes of cooking water, but also physically removes any Asi leached from the grain into the water receiving vessel. The relationship between cooking water volume and Asi removal in conventional rice cooking was demonstrated for the rice types under study. At a water-to-rice cooking ratio of 12:1, 57±5% of Asi could be removed, average of 6 wholegrain and 6 polished rice samples. Two types of percolating technology were tested, one where the cooking water was recycled through condensing boiling water steam and passing the freshly distilled hot water through the grain in a laboratory setting, and one where tap water was used to cook the rice held in an off-the-shelf coffee percolator in a domestic setting. Both approaches proved highly effective in removing Asi from the cooking rice, with up to 85% of Asi removed from individual rice types. For the recycled water experiment 59±8% and 69±10% of Asi was removed, on average, compared to uncooked rice for polished (n=27) and wholegrain (n=13) rice, respectively. For coffee percolation there was no difference between wholegrain and polished rice, and the effectiveness of Asi removal was 49±7% across 6 wholegrain and 6 polished rice samples. The manuscript explores the potential applications and further optimization of this percolating cooking water, high Asi removal, discovery.

Arsenic & Rice

Rice is the staple food for half of the world's population. Consumption of rice is the major exposure route globally to the class one, non-threshold carcinogen inorganic arsenic. This book explains the sources of arsenic to paddy soils and the biogeochemical processes and plant physiological attributes of paddy soil-rice ecosystems that lead to high concentrations of arsenic in rice grain. It presents the global pattern of arsenic concentration and speciation in rice, discusses human exposures to inorganic arsenic from rice and the resulting health risks. It also highlights particular populations that have the highest rice consumptions, which include Southern and South East Asians, weaning babies, gluten intolerance sufferers and those consuming rice milk. The book also presents the information of arsenic concentration and speciation in other major crops and outlines approaches for lowering arsenic in rice grain and in the human diet through agronomic management.