Solute Sources in Stream Water during Consecutive Fall Storms in a Northern Hardwood Forest Watershed: A Combined Hydrological, Chemical and Isotopic Approach

Understanding the effects of climate change including precipitation patterns has important implications for evaluating the biogeochemical responses of watersheds. We focused on four storms in late summer and early fall that occurred after an exceptionally dry period in 2002. We analyzed not only the influence of these storms on episodic chemistry and the role of different water sources in affecting surface water chemistry, but also the relative contributions of these storms to annual biogeochemical mass balances. The study site was a well studied 135-ha watershed in the Adirondack Park of New York State (USA). Our analyses integrated measurements on hydrology, solute chemistry and the isotopic composition of NO₃⁻(δ¹⁵N and δ¹⁸O) and SO₄²⁻(δ³⁴S and δ¹⁸O) to evaluate how these storms affected surface water chemistry. Precipitation amounts varied among the storms (Storm 1: Sept. 14–18, 18.5 mm; Storm 2: Sept. 21–24, 33 mm; Storm 3: Sept. 27–29, 42.9 mm; Storm 4: Oct. 16–21, 67.6 mm). Among the four storms, there was an increase in water yields from 2 to 14%. These water yields were much less than in studies of storms in previous years at this same watershed when antecedent moisture conditions were higher. In the current study, early storms resulted in relatively small changes in water chemistry. With progressive storms the changes in water chemistry became more marked with particularly major changes in C_b (sum of base cations), Si, NO₃⁻, and SO₄²⁻, DOC and pH. Analyses of the relationships between Si, DOC, discharge and water table height clearly indicated that there was a decrease in ground water contributions (i.e., lower Si concentrations and higher DOC concentrations) as the watershed wetness increased with storm succession. The marked changes in chemistry were also reflected in changes in the isotopic composition of SO₄²⁻ and NO₃⁻. There was a strong inverse relationship between SO₄²⁻ concentrations and δ³⁴S values suggesting the importance of S biogeochemical redox processes in contributing to SO₄²⁻ export. The isotopic composition of NO₃⁻ in stream water indicated that this N had been microbially processed. Linkages between SO₄²⁻ and DOC concentrations suggest that wetlands were major sources of these solutes to drainage waters while the chemical and isotopic response of NO₃⁻ suggested that upland sources were more important. Although these late summer and fall storms did not play a major role in the overall annual mass balances of solutes for this watershed, these events had distinctive chemistry including depressed pH and therefore have important consequences to watershed processes such as episodic acidification, and the linkage of these processes to climate change.     

Effects of Watershed History on Dissolved Organic Matter Characteristics in Headwater Streams

Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver in aquatic ecosystem function. Climate, land use, and forest cover changes all impact stream DOM and alter biogeochemical cycles in terrestrial environments. We determined the temporal variation in DOM quantity and quality in headwater streams at a reference watershed (REF), a watershed clear-cut 30 years ago (CC), and a watershed converted to a white pine plantation 50 years ago (WP) at the US Forest Service, Coweeta Hydrologic Laboratory, in the Nantahala Mountains of western North Carolina, USA. Average stream dissolved organic carbon (DOC) concentrations in CC or WP were 60 and 80% of those in REF, respectively. Stream DOM composition showed that the difference was mainly due to changes in humic-like components in chromophoric DOM. In addition, excitation–emission matrix fluorescence data with parallel factor analysis indicate that although the concentration of protein-like components did not differ significantly among watersheds, their relative abundance showed an enrichment in CC and WP compared to REF. The ratio of humic acid-type to fulvic acid-type components was highest and lowest at REF and WP, respectively. Our data suggest that forest ecosystem disturbance history affects the DOM quantity and quality in headwater streams over decades as a result of changes in watershed soil organic matter characteristics due to differences in organic matter inputs.     

Land-Use Change and Stream Water Fluxes: Decadal Dynamics in Watershed Nitrate Exports

Stream water exports of nutrients and pollutants to water bodies integrate internal and external watershed processes that vary in both space and time. In this paper, we explore nitrate (NO₃) fluxes for the 326 km² mixed-land use Fall Creek watershed in central New York for 1972–2005, and consider internal factors such as changes in land use/land cover, dynamics in agricultural production and fertilizer use, and external factors such as atmospheric deposition. Segmented regression analysis was applied independently to dormant and growing seasons for three portions of the period of record, which indicated that stream water NO₃ concentrations increased in both dormant and growing seasons from the 1970s to the early 1990s at all volumes of streamflow discharge. Dormant season NO₃ concentrations then decreased at all flow conditions between the periods 1987–1993 and 1994–2005. Results from a regression-based stream water loading model (LOADEST) normalized to mean annual concentrations showed annual modeled NO₃ concentration in stream water increased by 34% during the 1970s and 1980s (from 1.15 to 1.54 mg l⁻¹), peaked in about 1989, and then decreased by 29% through 2005 (to 1.09 mg l⁻¹). Annual precipitation had the strongest correlation with stream water NO₃ concentrations (r = −0.62, P = 0.01). Among land use factors, corn production for grain was the variable most highly correlated to stream water NO₃ concentrations (r = 0.53, P = 0.01). The strongest associative trend determined using Chi-squared Automatic Interaction Detection (CHAID) was found between stream water NO₃ concentrations and N-equivalence of dairy production (Bonferroni adjusted P value = 0.0003). Large increases in dairy production were coincident with declining nitrate concentrations over the past decade, which suggest that dairy management practices may have improved in the watershed. However, because dairy production in the Fall Creek watershed has been fueled by large increases in feed imports, the environmental costs of feed production have likely been externalized to other watersheds.     

Simulation of Stream Water Alkalinity Concentrations using Coupled Models of Soil air CO2 and Stream Water Chemistry

The ability to predict stream alkalinity values over timescales shorter than monthly or annually is needed to understand the response of stream chemistry to acidic inputs which occur across short time scales (days). We develop and apply a coupled series of physically-based models which are able to predict daily stream alkalinity values by first calculating soil air CO₂ concentrations. We apply the model to a 9 year record of discharge and stream chemistry from a small catchment in the Shenandoah National park of Virginia. We find that we are able to accurately predict the minimum daily stream alkalinity values for all years and we are able to accurately predict the entire annual cycle for 6 of the 9 years (Nash–Sutcliffe criterion equals 0.26). For the 3 years which we overpredict summer stream alkalinity, summer precipitation was greater than normal and much greater than the period for which the model was calibrated.     

A Macrophyte-Based Rapid Biosurvey of Stream Water Quality: Restoration at the Watershed Scale

The restoration of chemically degraded rivers, lakes, and estuaries with large watersheds and pollution sources that are primarily diffuse in nature requires the grading of thousands of kilometers of tributary streams. Many population-and community-oriented biomonitoring methods have been developed that avoid the cost limitations of chemical/biomarker/bioassay approaches and the serious limitations of single-factor analysis as related to complex systems. In this study of the coastal plain and piedmont geomorphologic provinces of the Chesapeake Bay watershed, we have demonstrated a set of quantitative measures based on analysis of macrophyte populations that provide statistically significant separation of streams in accordance with their state-issued water quality rating. Macrophytes can be abundant and diverse in lower-order streams, and they demonstrate patterns of community structure and diversity similar to those of other organisms developed for biomonitoring of stream degradation. Unlike organisms previously and extensively used in biomonitoring techniques, however, macrophytes are considerably easier to identify and quantify. In addition, macrophyte techniques provide a range of measures of increasing sensitivity from species numbers at a few sites, to the presence/absence and abundance of indicator species, and, finally, to a diversity analysis based on easily identified species at an extended number of sites. We suggest that the ease of utilization of this methodology will allow repeated surveys of all streams in large watersheds with the invertebrate, fish and diatom biomonitoring to biomarking and chemical bioassays and finally analytical chemistry, progressively applied to verify and then identify specific pollution sources (“hot spots”) in a more limited number of problem streams.     

Changes in Nutrient Loading in an Agricultural Watershed and Its Effects on Water Quality and Stream Biota

Non-point-sources of nitrogen (N) and phosphorus (P) are recognized as major causes of eutrophication of surface waters. Adoption of policies to reduce pollution in the former German Democratic Republic following re-unification of Germany in 1990 provided an opportunity to examine how taking agricultural land out of production affected nutrient loads and aquatic biota in a small rural watershed. Between 1994 and 1996, soluble reactive phosphorus (SRP) and dissolved inorganic nitrogen (DIN) loads in a first-order agricultural stream decreased by >90% while instream concentrations decreased by 89% for DIN and 40% for SRP. This reduction in nutrients coincided with a decrease in precipitation (from 760 to 440 mm between 1994 and 1996) and an increase in the area of land set aside from agricultural production (from 0.3% in 1990 to a maximum of 8% in 1994). The biomass of primary producers (episammic algae) showed no clear response to this decrease in nutrient concentrations. However, benthic invertebrate composition shifted from a chironomid–amphipod to an oligochaete–gastropod dominated community in response to the decrease in DIN and changes in episammic algal abundance and sediment organic carbon concentrations. Results from our 4-year study showed reductions in soil nutrient losses combined with less precipitation resulted in less P and N in a rural stream and a change in benthic invertebrate community composition and abundance.     

Relative Importance of Bacteria and Fungi in a Tropical Headwater Stream: Leaf Decomposition and Invertebrate Feeding Preference

Bacteria and fungi provide critical links between leaf detritus and higher trophic levels in forested headwater food webs, but these links in tropical streams are not well understood. We compared the roles of bacteria and fungi in the leaf decomposition process and determining feeding preference for two species of freshwater shrimp found in the Luquillo Experimental Forest, Puerto Rico, using experimental microcosms. We first tested the effects of four treatments on decomposition rates for leaves from two common riparian species, Cecropia scheberiana (Moraceae) and Dacryodes excelsa (Burseraceae), in laboratory microcosms. Treatments were designed to alter the microbial community by minimizing the presence of bacteria or fungi. The fastest decay rate was the control treatment for D. excelsa where both bacteria and fungi were present (k = −0.0073 day⁻¹) compared to the next fastest rate of k = −0.0063 day⁻¹ for the bacterial-conditioned D. excelsa leaves. The fastest decay rate for C. scheberiana was also the control treatment (k = −0.0035 day⁻¹), while the next fastest rate was for fungal-conditioned leaves (k = −0.0029 day⁻¹). The nonadditive effect for leaf decomposition rates observed in the control treatments where both fungi and bacteria were present indicate that bacteria and fungi perform different functions in processing leaf litter. Additionally, leaf types differed in microbial colonization patterns. We next tested feeding preference for leaf type and microbe treatment in microcosms using two species of freshwater shrimp: Xiphocaris elongata, a shredder, and Atya lanipes, a scraper/filterer. To estimate feeding preferences of individual shrimp, we measured change in leaf surface area and the amount of particles generated during 5-day trials in 16 different two-choice combinations. X. elongata preferred D. excelsa over C. scheberiana, and leaves with microbial conditioning over leaves without conditioning. There was no clear preference for fungal-conditioned leaves over bacterial-conditioned leaves. This lack of preference for which microbes were responsible for the conditioning demonstrates the importance of both bacterial and fungal resources in these tropical stream food web studies.     

The Role of Immunity and Seasonality in Cholera Epidemics

This paper presents a mathematical model for cholera epidemics which comprises seasonality, loss of host immunity, and control mechanisms acting to reduce cholera transmission. A collection of data related to cholera disease allows us to show that outbreaks in endemic areas are subject to a resonant behavior, since the intrinsic oscillation period of the disease (∼1 year) is synchronized with the annual contact rate variation. Moreover, we argue that the short period of the host immunity may be associated to secondary peaks of incidence observed in some regions (a bimodal pattern). Finally, we explore some possible mechanisms of cholera control, and analyze their efficiency. We conclude that, besides mass vaccination—which may be impracticable—improvements in sanitation system and food/personal hygiene are the most effective ways to prevent an epidemic.     

Trends in the Output of First-order Basins at Turkey Lakes Watershed, 1982–96

In 1981, we began to monitor the stream flow and chemistry of 13 first-order basins at the Turkey Lakes Watershed, with the objective of measuring the response of an undisturbed forested ecosystem to acid deposition. There was no trend in total annual precipitation received by the watershed, but the average annual water yield (percentage of annual precipitation) declined over the observation period. The proportion of runoff occurring in different seasons also changed, decreasing in the winter and increasing in the spring. In most streams the concentration of SO₄ ²⁻ has decreased coincident with the decline in precipitation inputs. Recovery of the basins from acid deposition (as evidenced by increased pH, increased alkalinity, and decreasing base cation fluxes) has not been uniform. Basins that do not show signs of recovery are characterized by deeper flowpaths and greater potential neutralizing capacity, which minimizes the impacts of acid deposition. Basins that are dominated by shallow flowpaths and lower levels of potential neutralizing capacity are showing some signs of recovery, but their recovery is not complete and it is possible that cation depletion may prevent or retard it. Received 5 October 1999; accepted 9 May 2001.     

The Effect of Macroinvertebrate Exclusion on Leaf Breakdown Rates in a Tropical Headwater Stream1

The role of macroinvertebrates in the process of leaf breakdown is well studied in temperate streams, but less is known about their role in the tropics. We investigated the effect of reducing macroinvertebrate access to leaf material on leaf breakdown rates in a forested headwater stream in the Luquillo Experimental Forest, Puerto Rico. We measured leaf mass loss using fine and coarse mesh bags over 12 weeks for two common riparian species: Cecropia schreberiana (Moraceae) and Dacryodes excelsa (Burseraceae). Coarse mesh allowed freshwater shrimp and other macroinvertebrates to access leaf material, while fine mesh did not. Leaf breakdown rates did not differ between C. schreberiana and D. excelsa in coarse mesh bags (?0.0375/day vs. ?0.0395/day, respectively), but C. schreberiana breakdown was significantly slower than D. excelsa in fine mesh bags (?0.0159/day vs. ?0.0266/day). Additionally, breakdown in fine mesh bags was significantly slower compared to coarse mesh bags for C. schreberiana, but less so for D. excelsa. Breakdown rates for all treatments were fast relative to those in temperate‐zone streams indicating that both macroinvertebrates and macroinvertebrate‐independent processing can strongly influence leaf decomposition in tropical streams. The difference between C. schreberiana and D. excelsa indicates that the effect of macroinvertebrate exclusion can change with leaf type.     

Hydrologic Drivers and Seasonality of Dissolved Organic Carbon Concentration, Nitrogen Content, Bioavailability, and Export in a Forested New England Stream

We present the results of a full year of high-resolution monitoring of hydrologic event-driven export of stream dissolved organic matter (DOM) from the forested Bigelow Brook watershed in Harvard Forest, Massachusetts, USA. A combination of in situ fluorescent dissolved organic matter (FDOM) measurement, grab samples, and bioassays was utilized. FDOM was identified as a strong indicator of concentration for dissolved organic carbon (DOC, r ² = 0.96), dissolved organic nitrogen (DON, r ² = 0.81), and bioavailable DOC (BDOC, r ² = 0.81). Relationships between FDOM and concentration were utilized to improve characterization of patterns of hydrological event-driven export and the quantification of annual export. This characterization was possible because DOM composition remained relatively consistent seasonally; however, a subtle shift to increased fluorescence per unit absorbance was observed for summer and fall seasons and percent BDOC did increase slightly with increasing concentrations. The majority of export occurred during pulsed hydrological events, so the greatest impact of bioavailable exports may be on downstream aquatic ecosystems. Export from individual events was highly seasonal in nature with the highest flow weighted mean concentrations (DOC_FW) being observed in late summer and fall months, but the highest total export being observed for larger winter storms. Seasonal trends in DOC export coincide with weather driven changes in surface and subsurface flow paths, potential for depletion and rebuilding of a flushable soil organic matter pool, and the availability of terrestrial carbon sources such as leaf litter. Our approach and findings demonstrate the utility of high frequency FDOM measurement to improve estimates of intra-annual temporal trends of DOM export.     

Perfluorooctanoic Acid (PFOA): Environmental Sources,Chemistry, Toxicology,and Potential Risks

Attention regarding perfluoroalkyl and polyfluoroalkyl substances (PFAS) has increased in recent years, due to recognition of widespread environmental presence, recognition of a chemical structure that confers resistance to degradation, and reported health concerns. Historical common exposure sources include food, drinking water, occupational circumstances, and products in commerce (e.g., carpeting, clothing, paper products). Early-2000’s data showed perfluorooctanoic acid (PFOA) was present in blood samples from nearly all the U.S. general population (>99%). Alterations in industrial manufacturing processes, increased regulatory scrutiny, and advanced water treatment options have reduced the reported human body burden of PFAS in the U.S., including for PFOA. Human serum concentrations of PFOA, which do not identify the source(s) of exposure, have exhibited a substantial decrease (~63%) between the 1999–2000 and the 2013–2014 NHANES monitoring by the Centers for Disease Control and Prevention (CDC). With respect to both noncancer and potential cancer effects that may be associated with reported serum levels of PFOA, conclusions regarding an absence of effects, or insufficient information to suggest adverse effects, prevent a consistent conclusion about the occurrence and magnitude of human health effects. In the last several years, a number of state and federal agencies have developed health advisories or guideline values for drinking water exposure that are in the sub-ppb range. In 2016, a USEPA Health Advisory of 0.07 ppb was released, which stands in contrast to 2016 Health-based Values from Health Canada ranging from 0.2 ppb (PFOA) to 30 ppb, and a few other U.S. states with values even less than that of USEPA (e.g., MN, NJ, VT). Further work is necessary to distinguish in transparent fashion between drinking water levels that intentionally are set on a conservative basis to protect human health vs exposure levels that may be associated with tangible adverse effects.     

Comparisons of Macrophyte Breakdown,Associated Plant Chemistry,and Macroinvertebrates in a Wastewater Dominated Stream

Replacement of native macrophyte species with exotic or invasive ones affects the quality of detritus entering streams and can alter nutrient cycles and community structure in aquatic ecosystems. Decomposition of air‐dried native hardstem bulrush (Schoenoplectus acutus), invasive southern cattail (Typha domingensis), and exotic common reed (Phragmites australis) were studied in an urban stream (Las Vegas, Nevada, USA) using litter bags. Samples were analyzed for dry mass, lignin, nutrients, trace elements, and macroinvertebrates. Litter type and sediment deposited on plant material influenced material loss. Trace elements arsenic and selenium increased in plant material to concentrations considered marginal for ecosystem contamination by exposure day 76. Mercury increases were inconsistent across plant species and did not exceed limits. Bulrush decomposed faster, and tended to have higher selenium concentrations, than did invasive southern cattail and exotic common reed. Macroinvertebrate communities colonizing litter bags were similar across plant litter types, but differed from mesh‐only bags and samples collected with a kick‐net. Macroinvertebrate exclusion resulted in significantly lower loss rates, but functional feeding groups such as shredders were not associated with decomposition differences. The caddisfly, Smicridea, physically modified stem material and aided in processing, but microbes appeared most important in biological material breakdown. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sources and Species of Cryptosporidium Oocysts in the Wachusett Reservoir Watershed

Understanding the behavior of Cryptosporidium oocysts in the environment is critical to developing improved watershed management practices for protection of the public from waterborne cryptosporidiosis. Analytical methods of improved specificity and sensitivity are essential to this task. We developed a nested PCR-restriction fragment length polymorphism assay that allows detection of a single oocyst in environmental samples and differentiates the human pathogen Cryptosporidium parvum from other Cryptosporidium species. We tested our method on surface water and animal fecal samples from the Wachusett Reservoir watershed in central Massachusetts. We also directly compared results from our method with those from the immunofluorescence microscopy assay recommended in the Information Collection Rule. Our results suggest that immunofluorescence microscopy may not be a reliable indicator of public health risk for waterborne cryptosporidiosis. Molecular and environmental data identify both wildlife and dairy farms as sources of oocysts in the watershed, implicate times of cold water temperatures as high-risk periods for oocyst contamination of surface waters, and suggest that not all oocysts in the environment pose a threat to public health.     

溪流两边的湿地对其含氮量的贡献（英）

本文对美国科罗拉多洛基山国家公园内Loch Vale小流域溪流两边的湿地土壤水溶液中的含氮量进行了研究,并比较了与其相邻的溪流中的含氮量。结果发现,溪流中的硝态氮含量显著高于3个湿地土壤水溶液中的,而氨态氮则并没有显著差异;溪流水中的pH值要显著高于土壤水溶液中的,而电导率又显著低于后者。同时,还发现取自不同地点的溪流水分的化学性质也显著的不同,采自溪流支流水分的pH,电导率和硝态氮都要显著高于取自主溪流中的水分的。另外,还分析比较了3个湿地样地的地上部分生产力以及土壤和生物量中的碳和全氮含量。最后,我们认为溪流两边的湿地对溪流中的氮的含量并没有显著的影响。     

The Role of Stream Water Carbon Dynamics and Export in the Carbon Balance of a Tropical Seasonal Rainforest,Southwest China

A two-year study (2009 ∼ 2010) was carried out to investigate the dynamics of different carbon (C) forms, and the role of stream export in the C balance of a 23.4-ha headwater catchment in a tropical seasonal rainforest at Xishuangbanna (XSBN), southwest China. The seasonal volumetric weighted mean (VWM) concentrations of total inorganic C (TIC) and dissolved inorganic C (DIC) were higher, and particulate inorganic C (PIC) and organic C (POC) were lower, in the dry season than the rainy season, while the VWM concentrations of total organic C (TOC) and dissolved organic C (DOC) were similar between seasons. With increased monthly stream discharge and stream water temperature (SWT), only TIC and DIC concentrations decreased significantly. The most important C form in stream export was DIC, accounting for 51.8% of the total C (TC) export; DOC, POC, and PIC accounted for 21.8%, 14.9%, and 11.5% of the TC export, respectively. Dynamics of C flux were closely related to stream discharge, with the greatest export during the rainy season. C export in the headwater stream was 47.1 kg C ha⁻¹ yr⁻¹, about 2.85% of the annual net ecosystem exchange. This finding indicates that stream export represented a minor contribution to the C balance in this tropical seasonal rainforest.     

Grazing Increases Soil Warming in Headwater Wetlands: Importance to Land Managers and Water Users

Ecosystems - The earth’s mountains continue to lose water. Glaciers are melting and mountain snow/rain balance tilts increasingly liquescent. Water is running off sooner—sometimes...     

Effect of Seasonality on Distribution of Macroalgae in a Stream System （Xin＇an Spring）in Shanxi Province, North China

A survey of the seasonal distribution of macroalgae in a stream system in Shanxi Province, north China, was undertaken from July 2004 to April 2005. The relative abundance and percentage cover of macroalgae, and several environmental factors were monitored along a 20-m stretch at each of four sites, at intervals of approximately three months （one sampling per season）. Several stream conditions were relatively constant over the sampling period （pH, maximum width and maximum depth）, whereas others exhibited a distinct seasonal pattern （water temperature and specific conductance）, and some fluctuated with no discernable seasonal pattern （current velocity and dissolved oxygen）. Forty-two species of macroalgae were found, with a predominance of Chlorophyta （26 species, 61.9%）. Rhodophyts and Charophyta represented the smallest proportion （1 species each, 2.38%）. Six macroalgae species were the most widespread, occurring in all four sampling sites. Twelve species were found at only one site each. In terms of seasonality, eight species occurred throughout the year, whereas 16 species were found in only one season each. The macroalgal community at Xin＇an Spring was species rich relative to other streams. Species richness per sampling site was negatively correlated with pH. Principal component analysis revealed that no single variable had much influence on the macroalgal seasonal dynamics. We calculated Sorensen similarity indices to compare our study with other continent-wide surveys of stream macroalgae, but the similarity indices were all very low. This study also shows that macroalgae in different locations have significant reproductive isolation.     

Watershed Deforestation and Down-Estuary Transformations Alter Sources,Transport, and Export of Suspended Particles in Panamanian Mangrove Estuaries

We identified eight Panamanian watersheds in which conversion from wet tropical forest to pastures differed and assessed the effects of degree of deforestation, and down-estuary transformations, on the suspended particulate matter discharged from the watersheds, entering, traversing through mangrove estuaries, and emerging into coastal waters. Deforested watersheds discharged larger concentrations of suspended particulate matter, with lower % C and N, higher mineral content, and heavier isotopic signatures into fresh reaches of estuaries. Down-estuary, sediment entrainment increased non-organic content of particulates, and watershed-derived imprints of deforestation on composition of particulate matter were mostly erased by within-estuary transformations. Isotopic signatures of C, N, and S in particulate matter demonstrated strong land-sea couplings, and indicated that the direction of the coupling was asymmetrical, with terrestrial and estuarine sources delivering particulate materials to coastal waters and sediments. Mangrove estuaries therefore both act as powerful modulators of human activities on land, while also exporting particulate materials to sea.