Boundary of ecosystem services: Differentiating between ecosystem services and geosystem services is needed.

Geosystem services (GSs) and ecosystem services (ESs) are interconnected, both representing nature's contributions to people. Whether GSs are a subset of ESs depends on the definition of ESs. The answer would be "not necessarily" (i.e., some GSs are, while other GSs are not), if ESs are the benefits humans derive from ecological functions, processes, or characteristics. The boundary proposed by Chen et al. (2023) to differentiate ESs from other ecosystem-related benefits adopted this definition, and suggested that ESs are renewable and affected by biotic elements to occur. Gray et al. (2024) criticized this boundary for separating out bits of nature and ignoring the contributions of GSs and abiotic elements to ESs and human wellbeing. In fact, highlighting that ESs are affected by biotic elements to occur does not deny that ESs' occurrence is also affected by abiotic elements. However, ESs' dependence on abiotic elements cannot be a criterion to differentiate ESs from other benefits because abiotic elements are integral to geosystems, ecosystems, and many other natural and artificial systems, as well as to these systems' services. Conversely, while geosystems might persist without biotic elements, ecosystems cannot. Chen et al. (2023) only excluded those (not the whole) abiotic benefits, such as wind energy, that may occur independently of biotic elements, while allowing for integrating certain GSs into ESs. For example, geological structures can offer flood protection and water storage as GSs, which can also be classified as ESs when their qualities or quantities are affected by biotic elements. Differentiation between GSs and ESs should not be misinterpreted as splitting their interconnections or undervaluing or dividing nature. Instead, such differentiation and classification of nature's benefits serve to facilitate communication, management, education, research, and policy-making associated with nature's benefits, while also highlighting the richness and diversity of nature's benefits.

Development, modification, and application of low-cost and available biochar derived from corn straw for the removal of vanadium(v) from aqueous solution and real contaminated groundwater.

In this work, a low-cost and available material for use as a permeable reactive barrier (PRB) to prevent vanadium in groundwater from leaking into river water was developed. Three modified biochars were prepared from available corn straw pretreated with CsCl, Zn(ii), and Zr(iv) to enhance ion exchange capacity (IEC) and specific surface area, and were designated as Cs-BC, Zn-BC, and Zr-BC, respectively. These materials were characterized via IEC, N2 adsorption-desorption, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The Langmuir isotherm model could be applied for the best fit for the adsorption data of Cs-BC and Zr-BC, indicating that vanadium(v) sorption occurred in a monolayer. The vanadium(v) adsorption capacities of Cs-BC, Zn-BC, and Zr-BC were 41.07, 28.46, and 23.84 mg g-1, respectively, which were 3.22-5.55 times higher than that of commercial activated carbon (AC) (7.40 mg g-1), probably because of their higher IECs and specific surface areas after modification. In addition, no heavy metal leaching was found from the modified biochars during the adsorption processes when pH > 2. According to the FTIR and XRD patterns, the adsorption mechanism of Cs-BC and Zr-BC was ion exchange, whereas for Zn-BC, it was mainly surface precipitation and electrostatic attraction. The adsorption of vanadium(v) onto the modified biochars was independent of pH in the range of 4.0 to 8.0. Furthermore, the removal efficiency of the vanadium(v) in real contaminated groundwater from the catchment of the Chaobei River by Zn-BC reached 100% at a dose of 4 g L-1. Hence, modified biochars are promising PRB filling materials for removing vanadium(v) from contaminated groundwater.