Solar distillation system depends on adhesion of water molecules inside the glass cover of solar stills. Regular glass surfaces are prone to adsorbing other unwanted compounds and in turn lower the percentage of recovery of pure distilled water. In this study, the production of purified distilled water was compared with and without the use of graphene-based surface modifiers. In areas where salt content is high, the first pass is still usually laden with salts. Hence, to improve adhesion of water and rejection of salts, both the inside glass cover surfaces and the metal absorber plates were modified using oxygen plasma treatment and graphene surface enhancement. Results showed a 48.9% improvement of distilled water recovery from an initial recovery of 2.90 L/m² per day to an average of 4.32 L/m² per day. In addition, the resulting distilled water passes the World Health Organization drinking water standards such as pH, electrical conductivity (EC), and salinity. The average reduction in EC was 96.52%, an average increase of 5.06% of pH, and an average reduction of salinity of 96.52%, all measured at the highest brine salinity of 5%. The reported value of EC was 23.33 μS/cm, a lowest and near-neutral pH of 6.85, and an average salinity of 12.10 ppm.

The lack of an available particulate matter (PM) PM_2.5 emission factor for almond harvesting operations has become a challenge for particulate matter regulations and emissions inventory in California. Low-dust harvesters are viewed as one of the strategies to reduce PM emissions and help achieve the state’s PM_2.5 attainment targets. This paper evaluates the potential emission reduction from using low-dust harvesters compared to the conventional. Orchard boundary measurements of PM concentrations were collected to back-calculate emission rates using inverse dispersion modeling. Emissions from four low-dust harvesters (Flory 850, Exact E3800, Weiss-McNair 9800 and Jack Rabbit) were compared to those from a conventional harvester (Flory 480) in two orchards, located in the Fresno County. Emissions of PM_2.5, PM₁₀ and total suspended particles were observed to be lower for all new harvesters compared to the conventional harvester. The range of reductions varies from about 40% to 77% in PM_2.5 emissions based on emission factors generated. The average ratio of PM₁₀ to PM_2.5 emissions is about 12.5%. The results of these tests imply that these new low-dust harvesters are capable of reducing PM emissions without affecting product quality. Therefore, the San Joaquin Valley Air Pollution Control District should consider including the use of these new harvesters in the conservation management practices (CMP) for the reduction of PM emissions in the valley. Implications: The results of this research indicate that almond low-dust harvesters could potentially reduce PM emissions over traditional harvesters without any negative effect on product quality. Therefore, the use of these new harvesters should be considered as part of almond best management practices and updating of emissions inventory in the San Joaquin Valley.

Particulate matter (PM) emissions from dairies and feedlot sources require regular emission factor update. Likewise, development of simple measurement technique to accurately measure pollution concentration is warranted to limit the impact of air pollution and take necessary actions. During June of 2020, a dairy facility from central Texas and a feedlot from the Texas Panhandle region, titled as Dairy B and Feedlot C, respectively, were chosen for measurement of PM emissions in the state of Texas to represent dairy facilities and cattle feedlots PM emission rates. Four stations, each assigned with an EPA-approved Federal Reference Method (FRM) sampler, Texas A&M University (TAMU) designed sampler and handheld non-FRM AEROCET (MET One Instruments) sampler for collocation, were selected within each sampling locations. Drones were also utilized mounted with a handheld AEROCET sampler for simultaneously sampling at a certain height. PM_2.5 emissions of Dairy B were all below 24-h PM_2.5 standard of 35 μg m⁻³ as specified by National Ambient Air Quality Standards (NAAQS) even at the 98th percentile. The PM ratio between regulated PM₁₀ to PM_2.5 was determined to make an estimate of relative percentage of coarser particles to fine particles in both feedlot and the dairy representative animal facilities. The maximum mean emission factor determined using AERMOD for PM_2.5 and PM₁₀ was found to be 0.53 and 7.09 kg 1000-hd⁻¹ d⁻¹, respectively, for the dairy facility while 8.93 and 33.42 kg 1000-hd⁻¹ d⁻¹, respectively, for the feedlot. A conversion factor and correlation matrix were developed in this study to relate non-FRM sampler data from the handheld AERCET samplers with FRM samplers. Cheaper handheld samplers (AEROCETs) may play a potential role in quick and relatively instant measurement of PM emissions to initiate necessary preventive actions to control PM emission from dairy facility and feedlot sources.

Peak ambient dusts levels in the San Joaquin Valley (SJV) are often coincident with peak agricultural harvest seasons, particularly for nut orchards. Federal reference methods (FRMs), consist of mass-based sampling techniques, are designated to measure and analyze ambient dust concentrations. However, FRMs generally require meticulous attention to sampling details, tedious labor and logistics, and time-consuming dispersion calculations. This study used opacity-based techniques - the U.S. Environmental Protection Agency (EPA) Method 9 and the Digital Compliance Opacity Technique (DCOT) - to quickly measure relative dust intensity at different harvester settings, and to evaluate visible dust emission reductions using a new/low-dust nut harvester. Results indicate that old/conventional harvester at standard settings (3 mph ground speed and 900 rpm blower speed) produced visible dusts with opacities ranging from 23.3% - 29.0%. The dust plume generated from new/low-dust harvesters at similar settings registered lower opacity readings, with an average of 13.94%. The lowest average dust opacity (7.8%) was achieved when the separation fan was turned off. The present results validated the previous FRM emission findings that an old/conventional harvester has the highest PM emissions, but with a potential to achieve 50% reduction by adopting new/low-dust harvesters. Compared to an old harvester, the relative intensity of dusts was reduced by 40% - 51% for low-dust harvesters operated at lower ground speeds. Further dust reductions could be achieved by lowering the fan speed (58%) and operating at no fan/blower setting (66.4%). Both visible emission evaluation (VEE) techniques were able to provide rapid quantitative feedback on the effects of operational changes on emitted harvest dusts. At this stage, opacity-based techniques can potentially be adapted as a screening tool for identifying best management practices (BMP) in reducing harvest dusts, rather than to solely rely on FRM mass-based techniques.

This study demonstrates the feasibility of a mobile aerial drone particle monitoring system (DPMS) to measure and detect changes in harvest dust levels based on moderate adjustments to harvester settings. When compared to an earlier harvester, a new harvester operated at standard settings produced 35% fewer PM2.5s, 32% fewer PM10s, and 42% fewer TSPs. Increasing the ground speed had an adverse effect on dust mitigation, while reducing it by half only offered a slightly more favorable margin. The mutual effects of some meteorological factors were found to be slightly correlated with PM10 and TSP readings and caused significant variability in PM2.5 readings. The current findings show similar trends to PM reduction estimates of previous studies, with only a nominal difference of 10 to 15% points. Overall, the DPMS was found to perform well within an acceptable statistical confidence level. The use of DPMSs could reduce the logistical needs, complexity issues, and feedback times often experienced using the Federal Reference Method (FRM). Further investigation is needed to verify its robustness and to develop potential correlations with the FRM under different orchard location and management practices. At this stage, the current aerial DPMS should be considered a rapid screening tool not to replace the FRM, but rather to complement it in evaluating the feasibility of dust abatement strategies for the almond industry.