DISES Investigating mercury biogeochemical cycling via mixed-methods in complex artisanal gold mining landscapes and implications for community health

人类活动导致陆地和水生生态系统的污染增加。污染物可对人类和野生动物造成危害，具体危害和暴露取决于复杂的社会生态因素。本研究调查了个体和小规模采金场汞排放的环境风险。汞是一种强有力的神经毒素，在全球小规模手工开采金矿的情况下，汞齐化黄金。手工和小规模采金业已成为全世界汞排放的主要原因，尤其是在焚烧黄金和以气态元素汞（GEM）的形式排放时，危害更大。然而，人们对手工和小规模采金业活动中汞的去向知之甚少，包括汞是否以及如何在作物中积累，或当地对汞危险和接触途径的了解，所有这些都会造成实际和感知的环境风险。本研究的问题是：（1）小规模手工开采金矿蒸发的汞在陆地生态系统中的地方和区域归宿是什么？(2)在小规模手工开采金矿附近种植的作物中，汞的积累程度如何？地貌和土壤特征如何影响作物中的汞浓度？(3)当地人如何理解汞污染和汞暴露，当地知识的空间性如何与环境污染的可变性相联系？这项研究的结果将为最近批准的《国际汞问题水俣公约》的目标提供直接惠益。研究重点是加纳小规模手工开采金矿系统中的汞，这些系统具有不同的地质、采矿类型、气候和生态系统。加纳开展了广泛的手工和小规模采金业活动，在过去15年中大幅增加。为了查询研究问题，研究人员采用混合方法，包括社区制图活动和半结构化访谈，生物地球化学数据收集（被动空气样本，大量沉积，穿透，凋落物，土壤和作物）和建模（经验约束的质量预算，拉格朗日羽流模型）。由于农民在手工和小规模采金业场地附近种植作物，该项目模拟了汞的移动位置，以及汞如何在农田和两个社区种植的特定主食作物（如木薯、可可山药、大蕉）中积累。该提案产生的数据将改进汞模型，从而更好地了解环境风险和污染动态（即，汞的使用、大气迁移、沉积、土壤储存和作物积累）。此外，本研究还系统地调查了导致作物中汞积累的土壤和景观特征，以更好地了解人类在职业暴露和食用受污染鱼类之外的潜在汞暴露途径。在项目结束时，将组织讲习班和培训，以宣传减少危害的做法，包括减少作物中汞积累的农业和采矿做法，以及其他当地接触。这项研究将政治生态学和景观生态学的概念联系在一起，在社会环境系统的动态双向耦合中确定污染物存款和积累在景观上的位置和时间。“环境风险景观”的概念可以进一步发展，以评估其他社会环境背景下的环境风险，包括美国的环境不公正。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估。

Human activities lead to increased contamination in both terrestrial and aquatic ecosystems. Contaminants can pose harm to both people and wildlife, with specific harms and exposures dependent on complex socio-ecological factors. This study investigates environmental risk vis-a-vis mercury (Hg) released from artisanal and small-scale gold mining (ASGM) sites. Mercury is a potent neurotoxin used to amalgamate gold in ASGM contexts globally. ASGM has become the leading cause of mercury emissions worldwide and is particularly harmful when burned off gold and emitted as gaseous elemental mercury (GEM). However, little is known about the fate of mercury from ASGM activities, including if and how mercury accumulates in crops, or local knowledge of mercury dangers and exposure routes, all of which contribute to actual and perceived environmental risk. This research asks: (1) What is the local and regional fate of Hg vaporized from ASGM in terrestrial ecosystems? (2) To what extent is Hg accumulating in crops grown near ASGM, and how do landscape and soil characteristics impact crop Hg concentrations? (3) How do local people understand Hg contamination and exposure, and how do spatialities of local knowledge articulate with environmental contamination variability? Results from this research will provide direct benefits related to the goals of the recently ratified International Minamata Convention on Mercury. The research focuses on mercury in Ghanaian ASGM systems with contrasting geology, mining type, climate, and ecosystem. Ghana possesses extensive ASGM activities, which increased dramatically in the last 15 years. To query the research questions, the researchers employ mixed methods including community mapping activities and semi-structured interviews, biogeochemical data collection (passive air samples, bulk deposition, throughfall, litterfall, soil, and crop) and modeling (empirically constrained mass budgets, Lagrangian plume models). As farmers grow crops directly adjacent to ASGM sites, this project models where mercury travels, and how it accumulates in agricultural fields and specific staple crops grown in both communities (e.g. cassava, cocoa yam, plantain). The data generated from this proposal will improve Hg models, allowing for better understanding of environmental risks and contamination dynamics (i.e., Hg use, atmospheric transport, deposition, soil storage, and crop accumulation) associated with localized ASGM activity. Furthermore, this research systematically investigates what soil and landscape features lead to the accumulation of Hg within crops to better understand potential human exposure pathways to Hg beyond occupational exposure and consumption of contaminated fish. At the end of the project, workshops and training will be organized to inform harm reduction practices, including agricultural and mining practices to reduce mercury accumulation in crops, and other local exposures. This research links together concepts from political ecology and landscape ecology in a dynamic bi-directional coupling of socio-environmental systems that determines where and when contaminants deposit and accumulate on the landscape. The concept of “environmental risk landscape” can be further developed to evaluate environmental risk in other socio-environmental contexts, including environmental injustice in the U.S.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.