Arsenic in soils contaminated by arsenic-containing chemical weapons in a site of Jilin, China: fraction and bioaccessibility

Effect of freeze-thaw frequency plus rainfall on As and Sb metal(loid)s leaching from the solidified/stabilized soil remediated with Fe-based composite agent

The composite agent of ferrous sulfate, fly ash, and calcium lignosulfonate (FFC) can remediate the soil contaminated by As and Sb under cyclic freeze-thaw (F-T) via stabilization/solidification (S/S). However, the impact of high-frequency F-T cycles on the leaching behavior and migration of As and Sb in FFC-treated soils remains unclear. Here the leaching concentrations, heavy metal speciation (Wenzel's method), and Hydrus-1d simulations were investigated. The results showed that FFC effectively maintained the long-term S/S efficiency of arsenic remediation subject to an extended rainfall and freeze-thaw cycles, and stabilized the easily mobile form of As. The short-term S/S effect on Sb in the remediated soils suffering from F-T cycles was demonstrated in the presence of FFC. In a 20-year span, the mobility of Sb was affected by the number of F-T cycles (FT60 > FT20 > FT40 > FT0) in soil with a depth of 100 cm. As leaching progressed, FFC slowed the upward proportion of adsorbed As fractions but converted parts of the residual Sb to the form of crystalline Fe/Al (hydro) oxide. Moreover, the adsorption rate and capacity of As also preceded that of Sb. Long-term curative effects of FFC could be observed for As, but further development of agents capable of remedying Sb under cyclic F-T and long-term rainfall was needed. The predictive results on the migration and leaching behavior of heavy metals in S/S remediated soils may provide new insight into the long-term assessment of S/S under natural conditions.

Arsenic pollution cycle, toxicity and sustainable remediation technologies: A comprehensive review and bibliometric analysis

Arsenic pollution and its allied impacts on health are widely reported and have gained global attention in the last few decades. Although the natural distribution of arsenic is limited, anthropogenic activities have increased its mobility to distant locations, thereby increasing the number of people affected by arsenic pollution. Arsenic has a complex biogeochemical cycle which has a significant role in pollution. Therefore, this review paper has comprehensively analysed the biogeochemical cycle of arsenic which can dictate the occurrence of arsenic pollution. Considering the toxicity and nature of arsenic, the present work has also analysed the current status of arsenic pollution around the world. It is noted that the south of Asia, West-central Africa, west of Europe and Latin America are major hot spots of arsenic pollution. Bibliometric analysis was performed by using scopus database with specific search for keywords such as arsenic pollution, health hazards to obtain the relevant data. Scopus database was searched for the period of 20 years from year 2003-2023 and total of 1839 articles were finally selected for further analysis using VOS viewer. Bibliometric analysis of arsenic pollution and its health hazards has revealed that arsenic pollution is primarily caused by anthropogenic sources and the key sources of arsenic exposure are drinking water, sea food and agricultural produces. Arsenic pollution was found to be associated with severe health hazards such as cancer and other health issues. Thus considering the severity of the issue, few sustainable remediation technologies such as adsorption using microbes, biological waste material, nanomaterial, constructed wetland, phytoremediation and microorganism bioremediation are proposed for treating arsenic pollution. These approaches are environmentally friendly and highly sustainable, thus making them suitable for the current scenario of environmental crisis.

A review on arsenic in the environment: contamination, mobility, sources, and exposure

Arsenic is one of the regulated hazard materials in the environment and a persistent pollutant creating environmental, agricultural and health issues and posing a serious risk to humans. In the present review, sources and mobility of As in various compartments of the environment (air, water, soil and sediment) around the World are comprehensively investigated, along with measures of health hazards. Multiple atomic spectrometric approaches have been applied for total and speciation analysis of As chemical species. The LoD values are basically under 1 μg L-1, which is sufficient for the analysis of As or its chemical species in environmental samples. Both natural and anthropogenic sources contributed to As in air, while fine particulate matter tends to have higher concentrations of arsenic and results in high concentrations of As up to a maximum of 1660 ng m-3 in urban areas. Sources for As in natural waters (as dissolved or in particulate form) can be attributed to natural deposits, agricultural and industrial effluents, for which the maximum concentration of 2000 μg L-1 was found in groundwater. Sources for As in soil can be the initial contents, fossil fuel burning products, industrial effluents, pesticides, and so on, with a maximum reported concentration up to 4600 mg kg-1. Sources for As in sediments can be attributed to their reservoirs, with a maximum reported concentration up to 2500 mg kg-1. It is notable that some reported concentrations of As in the environment are several times higher than permissible limits. However, many aspects of arsenic environmental chemistry including contamination of the environment, quantification, mobility, removal and health hazards are still unclear.

Study on the composition and distribution characteristics of As in As-containing agent contaminated soil

In recent years, China and Japan are cooperating in the destruction of the Japanese army abandoned chemical weapons in China (JACWs). During the long-term burial of JACWs, As-containing agents leaked into the environment due to the corrosion of the shell, resulting in soil As pollution. This paper studied the fraction, speciation, and composition of As in the soil polluted by the As-containing agent in Jilin, China. The results showed that As was mainly distributed in the forest soil in the study area, with the highest concentration of 110 mg/kg, and had the trend of migration to the downhill farmland soil. As mainly accumulated in the amorphous Fe/Al oxides bounded fraction and residual states, the proportion of potentially risky fractions in the soil of downhill farmland is higher than that of uphill farmland. The speciation of As in the soil is mainly As(V), with an average content of 25.02 mg/kg. The transformation behavior of As in the horizontal migration of topsoil is mainly the oxidation of As (III). The residual organic As in soil mainly includes 2-chlorovinylarsonic acid, triphenylarsine, phenylarsine oxide, and diphenylarsonic acid. Similar to the influence factors of As, both speciation and organic compounds of As are significantly affected by Fe/Al/Mn-oxides, and degradation and transformation reactions such as redox occur during migration.

Application of iron oxyhydroxide to stabilize As(V) and phenylarsonic acid in contaminated soil: adsorption and the relevance to bioavailability

The leaked arsenic-containing chemical warfare agent has caused severe contamination to the surrounding soil and water. In this study, iron oxyhydroxide (FeOOH) with different crystalline phases was used to stabilize arsenic. The results revealed that α/β- mixed crystalline iron oxyhydroxide (MIX-FeOOH) had better adsorption performance for As(V) and phenylarsonic acid (PAA) in water, with the adsorption capacity 71.4 and 54.7 mg g^-1 at 50 mg L^-1 equilibrium concentration, respectively. The adsorption mechanism was proved to be inner-sphere complexation, electrostatic interaction, and hydrogen bonding. Meanwhile, the oxygen vacancies on FeOOH could increase the isoelectric point and further promote the adsorption capacity through inner-sphere complexation. In arsenic contaminated soil, when the addition amount of MIX-FeOOH was 5%, the bioavailability of arsenic in As(V) and PAA contaminated soil was significantly reduced after 28 days, and the stabilization rate reached 77.2% and 76.5%, respectively. After 7 days of remediation, 17.1% and 11.9% of the most mobile portions of As(V) and PAA could be converted into poorly mobile portions, respectively. The stabilization mechanism includes inner-sphere complexation, mineral adsorption, and coprecipitation. In summary, this study can provide technical support for the remediation practice of arsenic-containing warfare agent contaminated sites.