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污染增加。污染物会对人类和野生动物造成危害，具体危害和暴露程度取决于复杂的社会生态因素。本研究调查了手工和小规模金矿（ASGM）场地释放的汞（Hg）所带来的环境风险。汞是一种有效的神经毒素，用于在全球范围内的ASGM背景下合并金。ASGM已成为全球汞排放的主要原因，当黄金被烧掉并以气态元素汞（GEM）的形式排放时尤其有害。然而，人们对ASGM活动中汞的命运知之甚少，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，所有这些都导致了实际和感知的环境风险。本研究提出了以下问题：(1)陆地生态系统中ASGM蒸发汞的局部和区域命运如何？(2)在ASGM附近种植的作物中汞的累积程度如何，景观和土壤特征如何影响作物汞浓度？(3)当地人如何理解汞污染和暴露，以及当地知识的空间性如何与环境污染变异性相表达？这项研究的结果将为最近批准的《关于汞的国际水俣公约》的目标提供直接的好处。该研究的重点是加纳ASGM系统中具有不同地质、采矿类型、气候和生态系统的汞。加纳拥有广泛的ASGM活动，在过去15年中急剧增加。为了查询研究问题，研究人员采用了混合方法，包括社区测绘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，大块沉积，贯穿物，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）。由于农民直接在ASGM场址附近种植作物，该项目模拟了汞的传播路径，以及汞如何在农田和两个社区种植的特定主要作物（如木薯、可可山药、车前草）中积累。该提案产生的数据将改进汞模型，从而更好地理解与局部ASGM活动相关的环境风险和污染动态（即汞的使用、大气运输、沉积、土壤储存和作物积累）。此外，本研究系统地调查了土壤和景观特征导致作物中汞的积累，以更好地了解除了职业接触和食用受污染的鱼类之外，人类接触汞的潜在途径。在项目结束时，将组织讲习班和培训，介绍减少危害的做法，包括农业和采矿做法，以减少作物中的汞积累和其他当地接触。这项研究将政治生态学和景观生态学的概念联系在一起，形成了社会环境系统的动态双向耦合，决定了污染物何时何地在景观上沉积和积聚。“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。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.