Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD, USA.
Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA; Department of Biology, Hood College, Frederick, MD, USA.
Sci Total Environ. 2022 Oct 15;843:156976. doi: 10.1016/j.scitotenv.2022.156976. Epub 2022 Jun 27.
Climate change is stressing irrigation water sources, necessitating the evaluation of alternative waters such as harvested rainwater to determine if they meet water quality and food safety standards. We collected water, soil, and produce samples between June and August 2019 from two vegetable rain garden (VRG) sites in Frederick, Maryland that harvest rainwater using a first flush system, and deliver this water to produce through subsurface irrigation. The raised VRG beds include layers of gravel, sand, and soil that act as filters. We recorded the average surface soil moisture in each bed as well as antecedent precipitation. All water (n = 29), soil (n = 55), and produce (n = 57) samples were tested for generic E. coli using standard membrane filtration, and water samples were also tested for Salmonella spp. and Listeria monocytogenes by selective enrichment. No Salmonella spp. or L. monocytogenes isolates were detected in any water samples throughout the study period. Average E. coli levels from all harvested rainwater samples at both sites (1.2 and 24.4 CFU/100 mL) were well below the Good Agricultural Practices food safety guidelines. Only 7 % (3/44) of produce samples from beds irrigated with harvested rainwater were positive for E. coli. E. coli levels in soil samples were positively associated with average surface soil moisture (r = 0.13, p = 0.007). Additionally, E. coli presence in water samples was marginally associated with a shorter length of antecedent dry period (fewer days since preceding rainfall) (p = 0.058). Our results suggest that harvested rainwater collected through a first flush system and applied to produce through subsurface irrigation meets current food safety standards. Soil moisture monitoring could further reduce E. coli contamination risks from harvested rainwater-irrigated produce. First flush and subsurface irrigation systems could help mitigate climate change-related water challenges while protecting food safety and security.
气候变化正在给灌溉水源带来压力，需要评估替代水源，如集雨，以确定它们是否符合水质和食品安全标准。我们于 2019 年 6 月至 8 月在马里兰州弗雷德里克的两个蔬菜雨水花园 (VRG) 收集了水、土壤和农产品样本，这些 VRG 采用初次冲洗系统收集雨水，并通过地下灌溉将水输送到农产品。抬高的 VRG 床包括砾石、沙子和土壤层，这些层起到了过滤作用。我们记录了每个床的平均表层土壤湿度和前期降水。对所有水 (n = 29)、土壤 (n = 55) 和农产品 (n = 57) 样本进行了常规大肠杆菌检测，采用标准膜过滤法，并对水样进行了沙门氏菌和单增李斯特菌的选择性富集检测。在整个研究期间，在任何水样中均未检测到沙门氏菌或单增李斯特菌。两个地点所有集雨样本的平均大肠杆菌水平 (1.2 和 24.4 CFU/100 mL) 均远低于良好农业规范食品安全指南。仅 7%（3/44）的从用集雨灌溉的床收获的农产品样本呈大肠杆菌阳性。土壤样本中的大肠杆菌水平与平均表层土壤湿度呈正相关 (r = 0.13, p = 0.007)。此外，水样中大肠杆菌的存在与前期干燥期 (降雨量之前的天数) 较短呈边缘相关 (p = 0.058)。我们的结果表明，采用初次冲洗系统收集并通过地下灌溉应用于农产品的集雨符合当前的食品安全标准。土壤湿度监测可以进一步降低集雨灌溉农产品的大肠杆菌污染风险。初次冲洗和地下灌溉系统可以帮助缓解与气候变化相关的水资源挑战，同时保护食品安全和保障。
