**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE WAYS THAT PEOPLE ARE ALTERING THE SULFUR (S) CYCLE ARE CHANGING--FROM MINING AND FOSSIL FUEL COMBUSTION TO AGRICULTURAL S ADDITIONS. PAST RESEARCH IN THE FLORIDA EVERGLADES LINKED HIGH CROP S APPLICATIONS TO METHYLMERCURY PRODUCTION, A NEUROTOXIN THAT BIOACCUMULATES IN THE FOOD CHAIN, PUTTING WILDLIFE AND PEOPLE AT RISK. THE LINK BETWEEN HIGH S APPLICATIONS TO CROPS AND METHYLMERCURY HAS NOT BEEN STUDIED IN UPLAND (NON-WETLAND) AGRICULTURAL SYSTEMS WHERE MANY CROPS ARE GROWN. THIS RESEARCH EXPLORES THE CONNECTION BETWEEN AGRICULTURAL S APPLICATIONS AND METHYLMERCURY PRODUCTIONIN THE NAPA RIVER WATERSHED (CALIFORNIA, US) -- A PERFECT REGIONAL CROP SYSTEM WHERE WINE GRAPES ARE GROWN EXCLUSIVELY AND HIGH S APPLICATIONS ARE USED BY MOST GRAPE GROWERS. THE INVESTIGATORS WILL DEVELOP APPROACHES USING STABLE ISOTOPE BIOGEOCHEMISTRY TO MEASURE RATES OF METHYLMERCURY PRODUCTIONAND DETERMINE WHETHER AGRICULTURAL S RUNOFF CAUSES METHYLMERCURY CONTAMINATION OF WETLANDS DOWNSTREAM FROM VINEYARD AGRICULTURE. THE RESEARCH INCLUDES STRONG COLLABORATIONS WITH GRAPE GROWERS, UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION, NAPA COUNTY OPEN SPACE, CALIFORNIA DEPARTMENT OF PESTICIDE REGULATION, AND THE STATE WATER BOARDS TO CONDUCT THE PROJECT AND USE ITS FINDINGS TO INFORM S MANAGEMENT. ITDIRECTLY ADDRESSES USDA/NIFA RESEARCH PRIORITIES IN THE BIOENERGY, NATURAL RESOURCES, AND ENVIRONMENT PROGRAM RELATED TO UNDERSTANDING AND IMPROVING SOIL HEALTH (A1401), INCREASING WATER QUANTITY AND QUALITY (A1411), AND REDUCING NUTRIENT LOADING TO SURFACE AND GROUNDWATER. ULTIMATELY, THE PROJECT WILL YIELD NEW INSIGHTS AND ANALYSIS APPROACHES THAT ARE BROADLY APPLICABLE TO AGRICULTURE IN THE US AND INTERNATIONALLY.