Global sourcing of low-inorganic arsenic rice grain

Arsenic in rice grain is dominated by two species: the carcinogen inorganic arsenic (the sum of arsenate and arsenite) and dimethylarsinic acid (DMA). Rice is the dominant source of inorganic arsenic into the human diet. As such, there is a need to identify sources of low-inorganic arsenic rice globally. Here we surveyed polished (white) rice across representative regions of rice production globally for arsenic speciation. In total 1180 samples were analysed from 29 distinct sampling zones, across 6 continents. For inorganic arsenic the global x ~ x~ was 66 μg/kg, and for DMA this figure was 21 μg/kg. DMA was more variable, ranging from < 2 to 690 μg/kg, while inorganic arsenic ranged from < 2 to 399 μg/kg. It was found that inorganic arsenic dominated when grain sum of species was < 100 μg/kg, with DMA dominating at higher concentrations. There was considerable regional variance in grain arsenic speciation, particularly in DMA where temperate production regions had higher concentrations. Inorganic arsenic concentrations were relatively consistent across temperate, subtropical and northern hemisphere tropical regions. It was only in southern hemisphere tropical regions, in the eastern hemisphere that low-grain inorganic arsenic is found, namely East Africa (x ~ x~  < 10 μg/kg) and the Southern Indonesian islands (x ~ x~  < 20 μg/kg). Southern hemisphere South American rice was universally high in inorganic arsenic, the reason for which needs further exploration

Rice grain cadmium concentrations in the global supply-chain

One of cadmium’s major exposure routes to humans is through rice consumption. The concentrations of cadmium in the global polished (white), market rice supply-chain were assessed in 2270 samples, purchased from retailers across 32 countries, encompassing 6 continents. It was found on a global basis that East Africa had the lowest cadmium with a median for both Malawi and Tanzania at 4.9 μg/kg, an order of magnitude lower than the highest country, China with a median at 69.3 μg/kg. The Americas were typically low in cadmium, but the Indian sub-continent was universally elevated. In particular certain regions of Bangladesh had high cadmium, that when combined with the high daily consumption rate of rice of that country, leads to high cadmium exposures. Concentrations of cadmium were compared to the European Standard for polished rice of 200 μg/kg and 5% of the global supply-chain exceeded this threshold. For the stricter standard of 40 μg/kg for processed infant foods, for which rice can comprise up to 100% by composition (such as rice porridges, puffed rice cereal and cakes), 25% of rice would not be suitable for making pure rice baby foods. Given that rice is also elevated in inorganic arsenic, the only region of the world where both inorganic arsenic and cadmium were low in grain was East Africa

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

Total calcium, copper, iron, manganese, phosphorus, silicon, sulphur and phosphorus concentrations in rice cooked using a coffee percolator compared to uncooked rice.

<p>Each point is the mean of 3 replicates. Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished.</p

As_<i>i</i> concentration and percentage in rice cooked using a coffee percolator compared to uncooked rice.

<p>Each point is the mean of 3 replicates. Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished.</p

Distribution of heavy metals and the exploration of potential indicators and hyperaccumulators in Jiang'an River, Chengdu, PR China

As a highly toxic contaminant, heavy metals have been proven to be widely distributed in the water and sediments of the global oceans, rivers, and lakes. Due to the functional differences in urban areas, the extent, characteristics, and hazards of heavy metal pollution in rivers are also different. To monitor and eliminate heavy metal pollution in rivers, indicators and hyperaccumulators perform crucial roles. In this study, heavy metal concentrations in the water, sediment, benthic faunae and aquatic plants of the Jiang'an River (which flows through Chengdu city, Sichuan Province, P.R. China) were investigated, followed by heavy metal correlation analysis of different media to identify potential bioindicator and hyperaccumulator. The results demonstrated that, none of the heavy metals were detected in the water. However, the 6 heavy metals in the surface sediments showed dramatic spatial regional differences, with Ni-As, Ni-Pb, Ni-Cr, Cr-Cu and Cr-Zn being highly significantly correlated. Furthermore, heavy metal contents in surface sediments were highly significantly correlated with the enrichment capacity of Eriocheir sinensis, Polypogon fugax, and Setaria viridis, and significantly correlated with Erigeron acer. Moreover, all plants were poorly enriched with Pb, which may be related to the morphology of Pb in the sediments. Besides, Eriocheir sinensis is a potential indicator of Zn and Cr in the sediments, and Erigeron acer is a possible Zn hyperaccumulator. This research confirms that heavy metals migrated in the water–sediment-benthic-plant system. Therefore, this study can provide a theoretical foundation for river monitoring and administration in Chengdu city and Sichuan Province

As_<i>i</i> concentration and percentage in rice that is either uncooked or has been cooked at different water: ratios.

<p>Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished.</p

As_<i>i</i> concentration and percentage in rice cooked using a Soxhlet apparatus compared to uncooked rice.

<p>Squares are for wholegrain rice and circles for polished rice. Solid regression line is for wholegrain, dashed for polished.</p

Response of Soil Fauna to the Shift in a Riparian Landscape along an Urban&ndash;Rural Habitat Gradient

Urbanization is accelerating worldwide, resulting in drastic alterations of natural riverbanks, which seriously affects the ecological functions and services of riparian landscapes. Our understanding of how anthropogenic activities influence soil animal communities within riparian zones is scarce. The soil fauna represents an important biotic component of the soil ecosystem and greatly contributes to soil structure and fertility formation. We investigated the richness, abundance, diversity, and distribution of soil animal groups, including macro- and mesofauna, in different riparian landscapes along an urban&ndash;rural habitat gradient. In natural riparian zones with permeable revetments, the soil fauna was richest and most abundant, mainly because of the low levels of human disturbance and the more suitable habitat conditions. Different soil animal groups responded differently to revetment type and distance from the water flow. The hygrophilous soil mesofauna, requiring a more humid environment, was more sensitive to shifts in revetment types, the location on the riverbank, and the seasons. In summer, when precipitation in the study area was highest, the abundance of the hygrophilous soil mesofauna was significantly higher than in autumn. Distance from the water flow significantly affected the abundance of the hygrophilous soil mesofauna. Our results demonstrated that hygrophilous soil mesofauna can serve as a good indicator in riparian zones, reflecting the hydrological conditions. We also observed interactions between revetment type and distance from the water flow; the distance effect was stronger in the natural riparian zone with a permeable revetment type. Our results highlight the importance of anthropogenic effects on soil ecosystem processes and functions in riparian landscapes, and the necessity of protecting and retaining the natural riverbank and native vegetation patches in riparian landscape planning and construction

Integrative Metabolomic and Transcriptomic Analysis Reveals the Mechanism of Specific Color Formation in <i>Phoebe zhennan</i> Heartwood

Nanmu (Phoebe zhennan) is an extremely valuable tree plant that is the main source of famous “golden-thread nanmu” wood. The potential metabolites and gene regulation mechanisms involved in golden thread formation are poorly understood, even though the color change from sapwood to heartwood has been investigated in several tree plants. Here, five radial tissues from sapwood to heartwood were compared via integrative metabolomic and transcriptomic analysis to reveal the secondary metabolites and molecular mechanisms involved in golden thread formation. During heartwood formation, gradual starch grain loss is accompanied by the cell lumen deposition of lipids and color-related extractives. Extractives of 20 phenylpropanoids accumulated in heartwood, including cinnamic acids and derivatives, coumarin acid derivatives, and flavonoids, which were identified as being closely related to the golden thread. Phenylpropanoids co-occurring with abundant accumulated metabolites of prenol lipids, fatty acyls, steroids, and steroid derivatives may greatly contribute to the characteristics of golden thread formation. Additionally, the expression of nine genes whose products catalyze phenylpropanoid and flavonoids biosynthesis was upregulated in the transition zone, then accumulated and used to color the heartwood. The expression levels of transcription factors (e.g., MYB, bHLH, and WRKY) that act as the major regulatory factors in the synthesis and deposition of phenylpropanoid and flavonoids responsible for golden thread formation were also higher than in sapwood. Our results not only explain golden thread formation in nanmu, but also broaden current knowledge of special wood color formation mechanisms. This work provides a framework for future research focused on improving wood color