ABSTRACT

Biosolarization is a fumigation alternative that combines solarization with organic amendments to suppress pests and pathogens in agricultural soils. The generation of volatile biopesticides in the soil, stemming from biodegradation of carbon-rich amendments, contributes to pest inactivation. The purpose of this study was to (1) profile volatiles that may contribute to pest control under field conditions and (2) measure volatile compounds that may present nuisance or exposure risks for humans near biosolarized fields where larger-scale anaerobic degradation of residues occurs. Biosolarization was performed using prominent agricultural waste products, hulls and shells from several almond varieties as soil amendments. After 8 days of biosolarization, soil samples were analyzed using solid phase microextraction-gas chromatography coupled to mass spectrometry. Volatile fatty acids and ketones made up 85% of biosolarized soil headspace, but terpenes, alcohols, aldehydes, esters, and sulfides were detected as well. Different almond variety residues produced distinct volatile profiles, and nonpareil-amended soils had a much richer and more diverse profile, as well as a fivefold greater VOC abundance, than pollinator-amended soil. Identified volatiles with low US recommended exposure limits were quantified via internal and external standards, including acetic acid, 2-butanone, butanal, hexanal, and phenylethyl alcohol. Across biosolarization treatments, headspace concentrations of selected compounds did not exceed 1 mg/m³. This study demonstrates that almond processing residues recycled into the soil as biosolarization substrates produce a high diversity of bioactive degradation compounds on a field scale, with low potential of non-target risks to humans.

Implications: This manuscript has implications for two policy goals in the state of California: to reduce landfill disposal of organic waste, and to reduce emissions from soil fumigants. Almond hulls and shells are an increasing source of organic waste, and novel recycling strategies must be developed. Here, recycling almond residues as soil amendments promoted the rapid formation of VOCs which may act as alternatives to chemical fumigants. Headspace concentrations of potentially deleterious VOCs produced from treated soil were low, on the order of parts per billion. These results will help achieve policy goals by expanding waste usage and fumigation alternatives.

摘要

生物日晒是一种熏蒸替代方法，将日晒与有机改良剂相结合，以抑制农业土壤中的害虫和病原体。土壤中挥发性生物农药的产生源于富碳改良剂的生物降解，有助于害虫灭活。本研究的目的是 (1) 分析在田间条件下可能有助于害虫控制的挥发物，以及 (2) 测量可能对人类在生物日晒田附近发生更大规模厌氧降解残留物的危害或暴露风险的挥发性化合物。使用来自几种杏仁品种的突出农业废物、外壳和壳作为土壤改良剂进行生物日晒。经过 8 天的生物日晒，使用固相微萃取-气相色谱与质谱联用对土壤样品进行分析。挥发性脂肪酸和酮占生物曝晒土壤顶空的 85%，但也检测到萜烯、醇、醛、酯和硫化物。不同的杏仁品种残留物产生了不同的挥发性特征，与授粉媒介改良的土壤相比，未经改良的土壤具有更丰富和更多样化的特征，以及高出五倍的 VOC 丰度。通过内部和外部标准，包括乙酸、2-丁酮、丁醛、己醛和苯乙醇，对确定的美国推荐接触限值低的挥发物进行量化。在生物日晒处理中，所选化合物的顶空浓度不超过 1 mg/m 挥发性脂肪酸和酮占生物曝晒土壤顶空的 85%，但也检测到萜烯、醇、醛、酯和硫化物。不同的杏仁品种残留物产生了不同的挥发性特征，与授粉媒介改良的土壤相比，未经改良的土壤具有更丰富和更多样化的特征，以及高出五倍的 VOC 丰度。通过内部和外部标准，包括乙酸、2-丁酮、丁醛、己醛和苯乙醇，对确定的美国推荐接触限值低的挥发物进行量化。在生物日晒处理中，所选化合物的顶空浓度不超过 1 mg/m 挥发性脂肪酸和酮占生物曝晒土壤顶空的 85%，但也检测到萜烯、醇、醛、酯和硫化物。不同的杏仁品种残留物产生了不同的挥发性特征，与授粉媒介改良的土壤相比，未经改良的土壤具有更丰富和更多样化的特征，以及高出五倍的 VOC 丰度。通过内部和外部标准，包括乙酸、2-丁酮、丁醛、己醛和苯乙醇，对确定的美国推荐接触限值低的挥发物进行量化。在生物日晒处理中，所选化合物的顶空浓度不超过 1 mg/m 与传粉媒介改良的土壤相比，未经改良的土壤具有更丰富、更多样化的特征，以及高出五倍的 VOC 丰度。通过内部和外部标准，包括乙酸、2-丁酮、丁醛、己醛和苯乙醇，对确定的美国推荐接触限值低的挥发物进行量化。在生物日晒处理中，所选化合物的顶空浓度不超过 1 mg/m 与传粉媒介改良的土壤相比，未经改良的土壤具有更丰富、更多样化的特征，以及高出五倍的 VOC 丰度。通过内部和外部标准，包括乙酸、2-丁酮、丁醛、己醛和苯乙醇，对确定的美国推荐接触限值低的挥发物进行量化。在生物日晒处理中，所选化合物的顶空浓度不超过 1 mg/m³ . 该研究表明，回收到土壤中的杏仁加工残留物作为生物日晒基质在田间范围内产生高度多样性的生物活性降解化合物，对人类的非目标风险的可能性很小。

影响：本手稿对加利福尼亚州的两个政策目标有影响：减少有机废物的填埋处理，以及减少土壤熏蒸剂的排放。杏仁壳是越来越多的有机废物来源，必须开发新的回收策略。在这里，回收杏仁残留物作为土壤改良剂促进了挥发性有机化合物的快速形成，这可能是化学熏蒸剂的替代品。从处理过的土壤中产生的潜在有害 VOC 的顶空浓度很低，约为十亿分之一。这些结果将有助于通过扩大废物使用和熏蒸替代方案来实现政策目标。