A combination of methods needed to assess the actual use of provisioning ecosystem services

Failure to recognize that potential provisioning ecosystem services are not necessarily collected and used by people may have important consequences for management of land and resources. Accounting for people's actual use of ecosystem services in decision making processes requires a robust methodological approach that goes beyond mapping the presence of ecosystem services. But no such universally accepted method exists, and there are several shortcomings of existing methods such as the application of land use/cover as a proxy for provisioning ecosystem service availability and surveys based on respondents' recall to assess people's collection of e.g. wild food. By combining four complementary methods and applying these to the shifting cultivation systems of Laos, we show how people’s actual use of ecosystem services from agricultural fields differs from ecosystem service availability. Our study is the first in Southeast Asia to combine plot monitoring, collection diaries, repeat interviews, and participant observation. By applying these multiple methods borrowed from anthropology and botany among other research domains, the study illustrates that no single method is sufficient on its own. It is of key importance for scientists to adopt methods that can account for both availability of various services and actual use of those services

Application of Biochar for Cadmium Stabilization in Contaminated Paddy Soil

Cadmium contamination in rice fields near zinc mines in Mae Sot District, Tak Province has been a persistent problem for decades. The contamination covers a vast area, making several soil remediation methods, such as soil washing or excavation impractical. Phytoremediation would also take several years and interfere with farming. However, there are recent reports on the potential of biochar in cadmium stabilization which resulted in reduced cadmium uptake by rice. Therefore, in this study, several biomaterials were investigated to produce the most suitable biochar for cadmium stabilization in paddy soil in Mae Sot. Rice husk, rice straw and bagasse were selected because of their availability in Mae Sot. Cadmium adsorption efficacy of biochar made from these biomaterials were analyzed using the adsorption isotherm. The results showed that cadmium adsorption by biochar from bagasse, rice husk, and rice straw were in accordance with Freundlich adsorption isotherm equation. By comparing the distribution coefficient, the adsorption efficacy of the biochar was ranked as rice straw> bagasse> rice husk. Therefore, rice straw biochar, which had the highest cadmium adsorption efficacy, was selected for stabilization experiments. After 30 days of incubating contaminated soil with rice straw biochar, the amount of extractable Cd using CaCl2 and EDTA were reduced significantly. The optimal application rate of rice straw biochar was 5% with the incubation period of 20 days. This warrants the next phase of this study which will be conducted in the field experiments in Mae Sot

Mobility of Polyethylene Glycol-Modified Urethane Acrylate (PMUA) Nanoparticles in Soils

Engineered nanoparticles (ENPs) have been reported for their potential to enhance in situ soil remediation due to their size and stability in water. These properties allow them to pass through soils with minimal loss in soil flushing or pump-and-treat process. The success of nanoparticle-facilitated soil flushing depends on the mobility of nanoparticles in the soil matrix. However, organic carbon content and soil texture can affect the mobility of nanoparticles in soils. This study compared the mobility of polyethylene glycol-modified urethane acrylate (PMUA) nanoparticles in three types of soils with varying organic contents. The results of two consecutive injection experiments showed that the recovery of injected nanoparticles through a soil column were 91 and 97% for sandy soil with carbon content of 0.01%, 81 and 85% for clay loam soil with organic carbon content of 1.20% and 67 and 73% for clay soil with organic carbon content of 3.25%. Furthermore, the batch experiments showed that the distribution coefficient (Kd) of PMUA nanoparticles between water and sandy soil, clay loam soil, and clay soil were 1.86, 2.34 and 3.01 mL/g, respectively. This conforms to the column experiment results and confirms that the increase in organic carbon content in soils increases the adsorption of PMUA nanoparticles, and therefore decreases the mobility of the nanoparticles through soils. Moreover, the distribution coefficient from batch experiments could be used to predict the mobility of PMUA nanoparticles in soils, and the viability of in situ PMUA-facilitated soil flushing method for specific contaminated soils