The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Ice-nucleating particles (INPs) play a significant role in the climate and hydrological cycle by triggering ice formation in supercooled clouds, thereby causing precipitation and affecting cloud lifetimes and their radiative properties. However, despite their importance, INP often comprise only 1 in 10³–10⁶ ambient particles, making it difficult to ascertain and predict their type, source, and concentration. The typical techniques for quantifying INP concentrations tend to be highly labour-intensive, suffer from poor time resolution, or are limited in sensitivity to low concentrations. Here, we present the application of microfluidic devices to the study of atmospheric INPs via the simple and rapid production of monodisperse droplets and their subsequent freezing on a cold stage. This device offers the potential for the testing of INP concentrations in aqueous samples with high sensitivity and high counting statistics. Various INPs were tested for validation of the platform, including mineral dust and biological species, with results compared to literature values. We also describe a methodology for sampling atmospheric aerosol in a manner that minimises sampling biases and which is compatible with the microfluidic device. We present results for INP concentrations in air sampled during two field campaigns: (1) from a rural location in the UK and (2) during the UK’s annual Bonfire Night festival. These initial results will provide a route for deployment of the microfluidic platform for the study and quantification of INPs in upcoming field campaigns around the globe, while providing a benchmark for future lab-on-a-chip-based INP studies

Monsoon rain chemistry and source apportionment using receptor modeling in and around National Capital Region (NCR) of Delhi, India

Studies on monsoon precipitation chemistry were carried out to understand the nature of rainwater and sources of pollution at eight different locations in and around the National Capital Region (NCR) of Delhi during southwest monsoon in the years 2003-2005. These sites were Bulandshahr (BUL), Garhmuktesar (GAR), Muradnagar (MUR), Sardhana (SAR), Panipat (PAN), Charkhi Dadri (CHA), Hodal (HOD) and Bahror (BAH). The rainwater samples, collected at these locations, were analyzed for major anions, cations and pH. The data were assessed for its quality. In general, the order of concentrations of major ions was observed to be: Ca 2+>SO 4 2->HCO 3 ->NH 4 +>Cl ->NO 3 ->Na +>Mg 2+>K +> F -. The average pH of rainwater at these stations was observed to be 6.39, ranging from 5.77 to 6.62, indicating alkaline nature. However, a few rain events, 31 at Panipat, 12 at Muradnagar and 29 at Sardhana, were observed to be acidic (pH<5.6). Acidity observed at Panipat and Muradnagar is attributed to industrial influence but at Sardhana to weak organic acids contributed by surrounding vegetation. No definite trends are found for most of the components at all the sites. However, concentrations of Cl - at Bulandshahr; NO 3 - at Muradnagar and Hodal; F - at Panipat and Bahror; Na + at Bulandshahr; K + at Bahror and Bulandshahr; Ca 2+ at Bulandshahr, Muradnagar, Charkhi Dadri and Sardhana; Mg 2+ at Panipat, Bahror, Bulandshahr, Hodal and Sardhana have increased from 2003 to 2005. For source identification, principal component analysis (PCA) was made, which showed that in general, at all the sites; suspended soil-dust and sea salts which are natural sources, were identified as the most dominating. Sources like agriculture including cattle, brick kilns and industries were reflected in third or fourth PC indicating moderate influence of anthropogenic activities in this region

Quality characteristics of Ohmic heated Aonla<i> </i><span style="mso-bidi-font-style:italic">(<i>Emblica</i><span style="font-size:14.0pt; color:black;mso-bidi-font-weight:bold" lang="EN-US"> <i>officinalis</i><span style="font-size:14.0pt; color:black;mso-bidi-font-weight:bold" lang="EN-US"> <span style="font-size:14.0pt;color:black;mso-bidi-font-weight:bold" lang="EN-US">Gaertn.) pulp </span></span></span></span>

670-676Present investigation deals with quality characteristics of aonla pulp subjected to ohmic heating at 11, 13, 15, 17 v/cm voltage gradients. The time and temperature were the process variables which were kept fixed on the basis of preliminary experiments. The product characteristics were evaluated for vitamin C, tannin content, titrable acidity, colour and microbial counts. Results indicated that all the quality parameters were influenced by treatment and KMS addition significantly. Per cent loss for all quality parameter was found to be least in aonla pulp ohmically treated at 17V/cm voltage gradient followed by 15, 13 and 11V/cm while the losses were maximum in conventionally prepared aonla pulp. Ohmically heated aonla pulp at 90°C for 1 minute was observed to be sufficient for safe storage of aonla pulp with little quality losses. In terms of quality, ohmically treated aonla pulp was found to be superior than conventionally prepared one. The quality losses in terms of vitamin C, tannin, titrable acidity and colour lightness were positively correlated to each other. Within the experimental range investigated in this study, aonla pulp ohmically heated at 17V/cm voltage gradients was found to be best in terms of all the quality parameters