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 5-fold 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 statement

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

生化法是一种熏蒸替代品，它结合了日光化和有机改良剂，以抑制农业土壤中的有害生物和病原体。由于富含碳的改良剂的生物降解而在土壤中产生挥发性生物农药，导致有害生物灭活。这项研究的目的是（1）在田间条件下分析可能有助于有害生物控制的挥发性物质，以及（2）测量可能对发生大规模厌氧降解残留物的生物隔离田地附近的人类造成滋扰或暴露风险的挥发性化合物。生物增盐作用是使用著名的农业废品，几种杏仁品种的壳和贝壳作为土壤改良剂进行的。经过8天的生物增溶处理，固相微萃取-气相色谱-质谱联用分析土壤样品。挥发性脂肪酸和酮占生物固溶土壤顶空的85％，但也可以检测到萜烯，醇，醛，酯和硫化物。不同的杏仁品种残留物会产生不同的挥发性特征，而未经pareil改良的土壤具有比传粉媒介改良的土壤更丰富，更多样化的特征，并且VOC丰度高出5倍。通过内部和外部标准（包括乙酸，2-丁酮，丁醛，己醛和苯乙醇）对已确定的具有低美国推荐暴露极限的挥发物进行定量。在整个生物增盐处理中，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固溶土壤顶空的85％，但也可以检测到萜烯，醇，醛，酯和硫化物。不同的杏仁品种残留物会产生不同的挥发性特征，而未经pareil改良的土壤具有比传粉媒介改良的土壤更丰富，更多样化的特征，并且VOC丰度高出5倍。通过内部和外部标准（包括乙酸，2-丁酮，丁醛，己醛和苯乙醇）对已确定的具有低美国推荐暴露极限的挥发物进行定量。在整个生物增盐处理中，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固溶土壤顶空的85％，但也可以检测到萜烯，醇，醛，酯和硫化物。不同的杏仁品种残留物会产生不同的挥发性特征，而未经pareil改良的土壤具有比传粉媒介改良的土壤更丰富，更多样化的特征，并且VOC丰度高出5倍。通过内部和外部标准（包括乙酸，2-丁酮，丁醛，己醛和苯乙醇）对已确定的具有低美国推荐暴露极限的挥发物进行定量。在整个生物增盐处理中，所选化合物的顶空浓度不超过1 mg / m 与未经授粉改良的土壤相比，与传粉媒介改良的土壤相比，土壤具有更丰富，更多样化的特征，并且VOC丰度高出5倍。通过内部和外部标准（包括乙酸，2-丁酮，丁醛，己醛和苯乙醇）对已确定的具有低美国推荐暴露极限的挥发物进行定量。在整个生物增盐处理中，所选化合物的顶空浓度不超过1 mg / m 与未经授粉改良的土壤相比，与传粉媒介改良的土壤相比，土壤具有更丰富，更多样化的特征，并且VOC丰度高出5倍。通过内部和外部标准（包括乙酸，2-丁酮，丁醛，己醛和苯乙醇）对已确定的具有低美国推荐暴露极限的挥发物进行定量。在整个生物增盐处理中，所选化合物的顶空浓度不超过1 mg / m³。这项研究表明，杏仁加工残留物作为生物增溶基质再循环到土壤中，在田间规模上产生高多样性的生物活性降解化合物，对人类的非目标风险低。

影响陈述

该手稿对加利福尼亚州的两个政策目标产生了影响：减少垃圾掩埋对有机废物的处置，并减少土壤熏蒸剂的排放。杏仁壳和贝壳是越来越多的有机废物来源，必须开发新颖的回收策略。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，而挥发性有机化合物可以替代化学熏蒸剂。经处理的土壤产生的潜在有害VOC的顶空浓度很低，约为十亿分之几。这些结果将通过扩大废物使用量和熏蒸替代方案来帮助实现政策目标。