BayCEER Workshop 2023

canceled

Climate change effects on arsenic speciation in a paddy soil chronosequence: health and agricultural risks

Previous studies have shown that climate change will exacerbate environmental, health and food safety risks related to soils used for rice cultivation under flooded conditions, known as paddy soils. In paddies, arsenic (As) is a relevant contaminant as soil management favors its release and consequent uptake by rice plants, affecting either yield or human health, depending on As speciation. Rising temperatures due to climate change will affect the dynamics of As in porewater since it is related to other biogeochemical processes, which are strongly driven by temperature. These effects, however, have not yet been studied among paddy soils of different age which exhibit pedologic characteristics depending on their development stage (i.e., how long they have been used as paddies). Here, we studied, in a microcosm experiment, the changes in As speciation in porewater under the influence of rising temperatures and soil age, based on future climate scenarios projected by the IPCC using a 2000-year-old paddy soil chronosequence. We determined that under higher temperatures, “middle-aged” paddy soils (100 and 300 years) reached higher concentrations of phytotoxic methylated As. In the oldest paddy (2000 years), the highest peaks of carcinogenic inorganic oxyarsenic concentration were observed at increased temperatures. Possible explanations for the different dynamics of As species could be the stimulation of certain groups of microbes, changes in the structure and abundance of microbial communities, changes in Fe mineralogy, and the diverse complexity of carbon substrates, as these factors define other processes related to As, such as S and Fe redox reactions. Overall, rising temperatures related to climate change could be a key driver of intensifying health risks due to higher exposure of rice to inorganic arsenic species in older paddies; whereas, in younger paddies, due to higher concentrations of methylated As, higher risks for crop production could be expected.