10Atmospheric deposition is the major pathway for removal of organic carbon (OC) from the 11 atmosphere, affecting both atmospheric and landscape processes. Transfers of OC from the 12 atmosphere to land occur as wet deposition (via precipitation) and as dry deposition (via surface 13 settling of particles and gases). Despite current understanding of the significance of organic 14 carbon inputs with precipitation to carbon budgets, transfers of organic matter between the 15 atmosphere and land are not explicitly included in most carbon cycle models due to limited data, 16 highlighting the need for further information. Studies regarding the abundance of OC in 17 precipitation are relatively sparse, in part due to the fact that concentrations of organics in 18 precipitation and their associated rates of atmospheric deposition are not routinely measured as a 19 part of major deposition monitoring networks. Here, we provide a new data synthesis from 83 20 contemporary studies published in the peer reviewed literature where organic matter in 21 precipitation was measured around the world. We compiled data regarding the concentrations of 22 organic carbon in precipitation and associated rates of atmospheric deposition of organic carbon. 23 We calculated summary statistics in a common set of units, providing insights into the magnitude 24 and regional variability of OC in precipitation. A land to ocean gradient is evident in OC 25 concentrations, with marine sites showing lower values than continental sites. Our synthesis 26 highlights gaps in the data and challenges for data intercomparison. There is a need to 27 concentrate sampling efforts in areas where anthropogenic OC emissions are on the rise (Asia, 28 South America), as well as in remote sites suggesting background conditions, especially in 29Southern Hemisphere. It is also important to acquire more data for marine rainwater at various 30 distances from the coast in order to assess a magnitude of carbon transfer between the land and 31 the ocean. Our integration of the recent published information on OC in precipitation provides a 32 unique data set (shared here as supplemental information) and a regional perspective that will be 33 useful in carbon budgets, environmental modeling, and ecosystem studies. This can be used for 34 comparison with the past conditions and as a baseline toward exploring future changes, since 35 changes in emissions, land use, and climatic variability are reflected in the amount and quality of 36 OC deposited to ecosystems.37 38

We measured wet atmospheric deposition of dissolved organic carbon (DOC) over 6 years at a network of 12 monitoring sites across Pennsylvania, quantified rates of wet DOC deposition, and developed the first statewide estimates of inputs of DOC to watersheds via wet deposition. Average annual volume‐weighted concentration of DOC was 0.71 mg C L−1. Annual wet deposition fluxes of DOC varied between sites and years, ranging from 3 to 13 kg C ha−1 yr−1, with an average value of 8 kg C ha−1 yr−1 across all sites and years and are of the same order of magnitude as literature values for riverine organic carbon fluxes in the northeastern United States. The rates of wet DOC deposition showed a pronounced seasonality and spatial distribution, with highest deposition rates observed in the summer, especially at the sites located in western Pennsylvania. Significant links between DOC and inorganic constituents in precipitation, such as sulfate and inorganic nitrogen forms, point to the similarity of sources and atmospheric processing and suggest that DOC may potentially affect their atmospheric transport and ecological fate. Observational data resulting from this study underscore the potential significance of atmospheric deposition as an external input of reactive carbon species to watersheds and may be useful for constraining atmospheric carbon models and evaluating atmospheric influences on ecosystems.

The quantity and chemical composition of dissolved organic matter (DOM) in surface waters influence ecosystem processes and anthropogenic use of freshwater. However, despite the importance of understanding spatial and temporal patterns in DOM, measures of DOM quality are not routinely included as part of large‐scale ecosystem monitoring programs and variations in analytical procedures can introduce artifacts. In this study, we used consistent sampling and analytical methods to meet the objective of defining variability in DOM quantity and quality and other measures of water quality in streamflow issuing from small forested watersheds located within five Critical Zone Observatory sites representing contrasting environmental conditions. Results show distinct separations among sites as a function of water quality constituents. Relationships among rates of atmospheric deposition, water quality conditions, and stream DOM quantity and quality are consistent with the notion that areas with relatively high rates of atmospheric nitrogen and sulfur deposition and high concentrations of divalent cations result in selective transport of DOM derived from microbial sources, including in‐stream microbial phototrophs. We suggest that the critical zone as a whole strongly influences the origin, composition, and fate of DOM in streams. This study highlights the value of consistent DOM characterization methods included as part of long‐term monitoring programs for improving our understanding of interactions among ecosystem processes as controls on DOM biogeochemistry.

Spotted lanternfly (SLF; Lycorma delicatula White; Hemiptera: Fulgoridae) invaded the US from Asia and was first detected in 2014; currently, populations have established in 14 states primarily in the Northeast and Mid-Atlantic. It feeds voraciously on phloem sap from a broad range of host plants, with a preference for tree of heaven (Ailanthus altissima [Sapindales: Simaroubaceae]), grapevines (Vitis spp. [Vitales: Vitaceae]), and several common hardwood tree species. We evaluated the impacts of fourth instars and adults confined to a single branch or whole trees on gas exchange attributes (carbon assimilation [photosynthetic rate], transpiration and stomatal conductance), selected nutrients, and diameter growth using young saplings of four host tree species planted in a common garden. In general, the effects of adults on trees were greater than nymphs, although there was variation depending on tree species, pest density, and time post-infestation. Nymphs on a single branch of red maple (Acer rubrum [Sapindales: Sapindaceae]), or silver maple (Acer saccharinum [Sapindales: Sapindaceae]) at three densities (0, 15, or 30) had no significant effects on gas exchange. In contrast, 40 adults confined to a single branch of red or silver maple rapidly suppressed gas exchange and reduced nitrogen concentration in leaves; soluble sugars in branch wood were reduced in the fall for silver maple and in the following spring for red maple. Fourth instars confined to whole silver maple trees reduced soluble sugars in leaves and branch wood, and reduced tree diameter growth by >50% during the next growing season. In contrast, fourth instars in whole tree enclosures had no effects on black walnut (Juglans nigra [Fagales: Juglandaceae]). SLF enclosed on tree of heaven at 80 adults per tree suppressed gas exchange after two weeks of feeding, but did not alter non-structural carbohydrates, nitrogen concentrations, or tree growth. Results suggest that moderate to heavy feeding by SLF on young maple saplings may impair tree growth, which could have implications for production nurseries and forest managers.

Organic compounds are removed from the atmosphere and deposited to the Earth's surface via precipitation. In this study, we quantified variations of dissolved organic carbon (DOC) in precipitation during storm events at the Shale Hills Critical Zone Observatory, a forested watershed in central Pennsylvania (USA). Precipitation samples were collected consecutively throughout the storm during 13 events, which spanned a range of seasons and synoptic meteorological conditions, including a hurricane. Further, we explored factors that affect the temporal variability by considering relationships of DOC in precipitation with atmospheric and storm characteristics. Concentrations and chemical composition of DOC changed considerably during storms, with the magnitude of change within individual events being comparable or higher than the range of variation in average event composition among events. Although some previous studies observed that concentrations of other elements in precipitation typically decrease over the course of individual storm events, results of this study show that DOC concentrations in precipitation are highly variable. During most storm events, concentrations decreased over time, possibly as a result of washing out of the below‐cloud atmosphere. However, increasing concentrations that were observed in the later stages of some storm events highlight that DOC removal with precipitation is not merely a dilution response. Increases in DOC during events could result from advection of air masses, local emissions during breaks in precipitation, or chemical transformations in the atmosphere that enhance solubility of organic carbon compounds. This work advances understanding of processes occurring during storms that are relevant to studies of atmospheric chemistry, carbon cycling, and ecosystem responses.