The detect limit of each sample (Figure 1) using the Low-resolution mid-infrared reflection spectrometer (S/N = 3).

Table 4: The detect limit of each sample (Figure 1) using the Low-resolution mid-infrared reflection spectrometer (S/N = 3).

Sample	Detectability
	Percentage of the field of view	Area (mm²)
New module tarp	43.2%-31.2%	14.3-10.4
Yellow bale bag	49.0%-36.0%	16.3-12.0
Color shopping bag	46.3%-31.4%	15.4-10.4
JD module out	39.8%-28.4%	13.2-9.4
JD module inner	42%-32.7%	14.0-10.9
JD module middle	32.2%-25.6%	10.7-8.5
White bale bag	50.6%-40.7%	16.8-13.5
White shopping bag	48.4%-32.2%	16.1-10.7
Bale twine	55.7%-39.9%	18.5-13.3
Old module tarp	39.7%-24.2%	13.2-8.0
Hard green	60.7%-26.5%	20.1-8.8
Black plastic	31.4%-11.7%	10.4-3.9
Oil	58.9%-33.5%	19.6-11.1
Grease	45.6%-27.0%	15.1-9.0