Effects of increased deposition of atmospheric nitrogen on an upland moor: leaching of N species and soil solution chemistry

This study was designed to investigate the leaching response of an upland moorland to long-term (10 yr) ammonium nitrate additions of 40, 80 and 120 kg N ha(-1) yr(-1) and to relate this response to other indications of potential system damage, such as acidification and cation displacement. Results showed increases in nitrate leaching only in response to high rates of N input, in excess of 96 and 136 kg total N input ha(-1) yr(-1) for the organic Oh horizon and mineral Eag horizon, respectively. Individual N additions did not alter ammonium leaching from either horizon and ammonium was completely retained by the mineral horizon. Leaching of dissolved organic nitrogen (DON) from the Oh horizon was increased by the addition of 40 kg N ha(-1) yr(-1), but in spite of increases, retention of total dissolved nitrogen reached a maximum of 92% and 95% of 80 kg added N ha(-1) yr(-1) in the Oh and Eag horizons, respectively. Calcium concentrations and calcium/aluminium ratios were decreased in the Eag horizon solution with significant acidification mainly in the Oh horizon leachate. Nitrate leaching is currently regarded as an early indication of N saturation in forest systems. Litter C:N ratios were significantly lowered but values remained above a threshold predicted to increase leaching of N in forests.     

Innovative aspects of environmental chemistry and technology regarding air,water, and soil pollution

Environmental Science and Pollution Research -     

Simulating the long-term chemistry of an upland UK catchment: major solutes and acidification

CHUM-AM was used to investigate changes in soil and water chemical variables in four moorland sub-catchments in Cumbria UK, to which non-marine S deposition has declined by 65% since the 1970s. The principal processes represented in the model comprise N and S uptake and release, water movements, the binding of cations by soil organic matter, chemical interactions in solution, and chemical weathering. CHUM-AM reproduced reasonably well the current soil pH and pools of N and S, and changes in streamwater chemistry over the period 1970-2000, notably decreases in the concentrations of alkaline earth cations and sulphate, and increases in pH. The model also predicts streamwater pH-Al relationships in agreement with observations. Predictive calculations suggest that constant atmospheric deposition of N at present rates will lead to N saturation and re-acidification, whereas a 50% reduction in N would stabilise soil and streamwater pH at about the present levels.     

Copper and zinc retention by an organically amended soil

This paper describes changes in retention of Cu and Zn in laboratory experiments by a sandy soil that had been amended in the field with different composted wastes. The amounts of the metals retained increased as a result of the amendments, especially after two years. Desorption of the sorbed metals was always negligible, regardless of the treatment. The proportion of Cu retained was considerably higher than that of Zn, suggesting a higher affinity of the soil for the former. The greater sorption in the amended soils indicates a build-up of fresh sites for metal retention.The use of 'log(activity) vs. pH' plots showed that the nature of the surfaces retaining metals on the untreated and amended soils is different. At comparable pH values, the amended soils gave higher solution metal concentrations. Some of the possible environmental consequences of the use of these amendments for remediation purposes are discussed.     

Passive sampler derived air concentrations of PBDEs along an urban-rural transect: spatial and temporal trends

Passive air samplers consisting of polyurethane foam (PUF) disks housed in chambers were deployed at several sites along a approximately 75 km urban-rural gradient in Toronto and analyzed for polybrominated diphenyl ethers (PBDEs). Samplers were allowed to integrate gas-phase PBDEs over three consecutive seasons starting in the summer of 2000. PBDEs were fairly uniform along the transect with air concentrations in Toronto (10-30 pgm(-3)) about a factor of two greater than at rural sites. Lowest concentrations were observed during the winter and probably associated with reduced inputs from indoor sources of PBDEs and to a preference for PBDEs to partition to the particle-phase at colder temperatures. The composition of PBDEs in the air samples did not differ across the transect or for the different seasons.     

Hydrochemical modelling of the retention and transport of metallic radionuclides in the soils of an upland catchment

The CHemistry of the Uplands Model (CHUM) describes the transport of chemicals through upland catchments with acid, organic-rich soils, by a combination of sub-models for equilibrium soil chemistry, hydrology, weathering, and nitrogen cycling. CHUM was used to simulate the retention and transport of metallic radionuclides (Co, Sr, Cs, UO(2), U(IV), Th, Am), in the soils of a small catchment in Cumbria, UK, for 2 years after their atmospheric deposition in a single hypothetical precipitation event. Export of radionuclides to streamwater is calculated to occur most readily following deposition of the dissolved elements at high water saturation of the catchment, when little incoming rainwater is required to make up the small moisture deficit of the organic surface horizon, and solutes can move to greater depths in the soil profile. Deposition when the catchment is drier, or of particulate radionuclides, leads to stronger retention. Radionuclide retention or transport depends on the strength of chemical interaction with the solid phases of the different soil horizons; this varies among the elements, and also with oxidation state, U(IV) species being more strongly retained than UO(2). For purely organic soils, the least strongly retained radionuclide is Cs, but the presence in the mineral soil horizon of small amounts of clay mineral with high selectivity towards Cs can markedly increase with high selectivity towards Cs can markedly increase its retention. For the actinides, binding by dissolved organic matter is important; for example, the rate of transport of Th to the stream is increased by more than two orders of magnitude by complexation with dissolved fulvic acid. The model assumptions suggest that, in the longer term, losses from the catchment of Co, Sr and Cs would take place on a time-scale of decades, whereas the actinides would be much more persistent.     

Seasonal variations of nitrogen and phosphorus retention in an agricultural drainage river in East China

Background, aim, and scope  

Riverine retention decreases loads of nitrogen (N) and phosphorus (P) in running water. It is an important process in nutrient cycling in watersheds. However, temporal riverine nutrient retention capacity varies due to changes in hydrological, ecological, and nutrient inputs into the watershed. Quantitative information of seasonal riverine N and P retention is critical for developing strategies to combat diffuse source pollution and eutrophication in riverine and coastal systems. This study examined seasonal variation of riverine total N (TN) and total P (TP) retention in the ChangLe River, an agricultural drainage river in east China.     

Effects of clearfelling on stream and soil water aluminium chemistry in three UK forests

Data are presented demonstrating how clearfelling has changed soil and stream water aluminium chemistry. For soil waters, a strong empirical relationship was observed between inorganic aluminium (Al(inorg)) and total inorganic anion (TIA) concentrations. Before felling, chloride and sulphate accounted for the largest proportion of the TIA concentration. After felling, in soils where nitrification was active, nitrate became increasingly important. Where this led to an increase in TIA, Al(inorg) concentrations increased. Over five years, nitrate concentrations have fallen, along with TIA, resulting in a sympathetic decline in Al(inorg). Streams draining clearfelled areas initially became more acid, although chloride and sulphate concentrations decreased. Stream water nitrate concentrations increased soon after felling and remained higher than controls for up to four years. While nitrate concentrations were high, Al(inorg) remained unchanged. Subsequently, as nitrate and TIA decreased, Al(inorg) also declined to concentrations below those in the control stream. Clearfelling upland forests will not necessarily result in immediate improvements in water quality, although long-term benefits may be seen before canopy-closure of the next crop.     

Polychlorinated biphenyls (PCBs) in soils of the Moscow region: concentrations and small-scale distribution along an urban-rural transect

In soils of the Moscow region, we examined PCB concentrations in bulk samples and aggregate fractions. Topsoils under grassland and forest at five locations along a southeast-bound transect from Moscow and at a northeastern background location (grassland only) were analysed. We collected aggregates >1 cm and fractionated them into interior and exterior portions and also analysed the remaining soil without the aggregates >1 cm. The concentrations of the sum of 17 PCBs (sigma17PCBs) in 35 bulk soil samples ranged from 3.1 to 42 microg kg(-1). This was 48-61% of the sigma33PCBs determined in 23 selected samples. The congeners 138(+158), 101 and 52 were most abundant. All PCB concentrations and the degree of chlorination declined with increasing distance from Moscow. The PCBs were accumulated in the aggregate exterior (on average 146% of the sigma17PCBs in bulk soil). We conclude that the ecotoxicological risk of PCBs in soils may not be properly assessed with the conventional bulk soil analysis.     

Reduced European emissions of S and N--effects on air concentrations, deposition and soil water chemistry in Swedish forests

Changes in sulphur and nitrogen pollution in Swedish forests have been assessed in relation to European emission reductions, based on measurements in the Swedish Throughfall Monitoring Network. Measurements were analysed over 20 years with a focus on the 12-year period 1996 to 2008. Air concentrations of SO₂ and NO₂, have decreased. The SO₄-deposition has decreased in parallel with the European emission reductions. Soil water SO₄-concentrations have decreased at most sites but the pH, ANC and inorganic Al-concentrations indicated acidification recovery only at some of the sites. No changes in the bulk deposition of inorganic nitrogen could be demonstrated. Elevated NO₃-concentrations in the soil water occurred at irregular occasions at some southern sites. Despite considerable air pollution emission reductions in Europe, acidification recovery in Swedish forests soils is slow. Nitrogen deposition to Swedish forests continues at elevated levels that may lead to leaching of nitrate to surface waters.     

Polybrominated diphenyl ethers (PBDEs) in soils along a rural-urban-rural transect: sources, concentration gradients, and profiles

This study reports concentrations of PBDEs in surface soil samples collected along a 140 km transect across Kuwait to assess the role of urban centers as sources of persistent organic pollutants to the surrounding environment. The ΣPBDE concentrations varied by a factor of ∼250 and ranged from 289 to 80,078 pg g⁻¹ d.w. The concentrations of PBDEs in Kuwait City were significantly higher (p < 0.01) than those collected from sites outside the city supporting the hypothesis that urban centers are sources of PBDEs. The congener profiles were dominated by BDE-209, accounting for 93% of the PBDEs in the soil samples. The concentrations of all congeners (except BDE-209) were highly correlated with percent organic carbon (%OC) (p > 0.05) when the data from Kuwait City was omitted from the analysis. These findings suggest that soil concentrations outside the urban centers were close to equilibrium with the atmosphere.     

Research on ecosystem services of water conservation and soil retention: a bibliometric analysis

Environmental Science and Pollution Research - Water conservation and soil retention are two essential regulating services that are closely related, and their relationship might produce synergies...     

Shade and flow effects on ammonia retention in macrophyte-rich streams: implications for water quality

Controlled releases of NH4-N and conservative tracers (Br- and Cl-) to five reaches of four streams with contrasting macrophyte communities have shown differing retentions, largely as a result of the way plants interact with stream flow and velocity. First-order constants (k) were 1.0-4.8 d(-1) and retention of NH4-N was 6-71% of amounts added to each reach. Distance travelled before a 50% reduction in concentration was achieved were 40-450 m in three streams under low-flow conditions, and 2400-3800 m at higher flows. Retention (%) of NH4-N can be approximated by a simple function of travel time and k, highlighting the importance of the relationship between macrophytes and stream velocity on nutrient processing. This finding has significant management implications, particularly with respect to restoration of riparian shade. Small streams with predominantly marginal emergent plants are likely to have improved retention of NH4-N as a result of shading or other means of reducing plant biomass. Streams dominated by submerged macrophytes will have impaired NH4-N retention if plant biomass is reduced because of reduced contact times between NH4-N molecules and reactive sites. In these conditions water resource managers should utilise riparian shading in concert with unshaded vegetated reaches to achieve a balance between enhanced in-stream habitat and nutrient processing capacity.     

Metal ion and other key water quality constituent attenuation in soil columns

A set of soil columns was constructed to simulate discharge of disinfected tertiary treated wastewater to a river via nearby land application or indirect discharge. The system was primarily designed to observe the fate of metal ions and nutrients. The following three experiments were conducted: (1) flow through saturated soils only, which simulates indirect discharge where water is directly applied to groundwater; (2) flow through unsaturated soil followed by saturated flow, which simulates vadose then saturated zone transport; and (3) saturated flow only using ethylene diamine tetraacetic acid-metal chelates, which determined effects of metal organic complexes on metal mobility through the soil. Metal ion attenuation was substantial but not complete in experiments 1 and 2 (removal: 68% Cu2+, 43% Ni2+, 98% Pb2+, and 96% Hg2+), which was somewhat contrary to modeling results. Cyanide attenuation was also monitored (92% removal). In experiment 3, lead attenuation was somewhat reduced (92% removal) and delayed (requiring additional residence time); copper attenuation was significantly reduced (38% removal) and delayed; and nickel concentrations were higher in the 28-day sample (> 80 microg/L) than in the column feed water (58 microg/L). Near-complete denitrification and total phosphorus attenuation were observed. For the water quality constituents studied, unsaturated (vadose zone) transport did not appear to add additional benefit.     

Three-fluid retention in porous media involving water, PCE and air

A classical way to obtain three-fluid retention curves in porous media from measured two-fluid retention curves is based on the Leverett concept, which states that the total volumetric liquid content in a water-wet porous medium, containing water, a nonaqueous-phase liquid (NAPL) and air, is a function of the capillary pressure across the interface between the continuous NAPL and air. This functional relationship results from the assumed condition that in a three-fluid porous medium, the intermediate wetting fluid spreads over the water-air interface. Application of Leverett's concept may not be valid, however, for nonspreading NAPLs like perchloroethylene (PCE). This paper discusses measurements of both PCE-air and water-PCE-air retention curves using a long vertical column in conjunction with a dual-energy gamma radiation system. The data indicate that the Leverett concept was applicable only until a critical PCE saturation had been reached.     

Heavy metal contamination and risk assessment in water,paddy soil,and rice around an electroplating plant

Purpose  

The objective of this paper is to assess the impact of long-term electroplating industrial activities on heavy metal contamination in agricultural soils and potential health risks for local residents.     

Amending greenroof soil with biochar to affect runoff water quantity and quality

Numbers of greenroofs in urban areas continue to grow internationally; so designing greenroof soil to reduce the amount of nutrients in the stormwater runoff from these roofs is becoming essential. This study evaluated changes in extensive greenroof water discharge quality and quantity after adding biochar, a soil amendment promoted for its ability to retain nutrients in soils and increase soil fertility. Prototype greenroof trays with and without biochar were planted with sedum or ryegrass, with barren soil trays used as controls. The greenroof trays were subjected to two sequential 7.4cm/h rainfall events using a rain simulator. Runoff from the rain events was collected and evaluated. Trays containing 7% biochar showed increased water retention and significant decreases in discharge of total nitrogen, total phosphorus, nitrate, phosphate, and organic carbon. The addition of biochar to greenroof soil improves both runoff water quality and retention.     

Interactive effects of nitrogen deposition and fire on plant and soil chemistry in an alpine heathland

The response of alpine heathland vegetation and soil chemistry to N additions of 0, 10, 20 and 50 kg N ha⁻¹ year⁻¹ in combination with simulated accidental fire (+/−) was monitored over a 5-year period. N addition caused rapid and significant increases in plant tissue N content and N:P and N:K of Calluna vulgaris, suggesting increasing phosphorus and potassium limitation of growth. Soil C:N declined significantly with N addition, indicating N saturation and increasing likelihood of N leakage. Fire further decreased soil C:N and reduced potential for sequestration of additional N. This study shows that alpine heathlands, which occupy the headwaters of many rivers, have limited potential to retain deposited N and may rapidly become N saturated, leaking N into downstream communities and surface waters.     

Changes in bryophyte and lichen communities on Scots pines along an alkaline dust pollution gradient

Environmental Science and Pollution Research - Dust pollution can cause a significant damage of environment and endanger human health. Our study aimed to investigate epiphytic lichens and...     

Physicochemical forms of technetium in surface water covering paddy and upland fields

The behavior of an element in the environment depends on its physicochemical form. Basic data for the behavior of technetium in an agricultural environment were obtained by determining the physicochemical forms of Tc in 28 surface water samples from paddy and upland fields. Most of the (95m)Tc was present as TcO(4)(-) in the samples. The relative amount of this chemical form was 72% on average. A significant amount of insoluble Tc (particles more than 0.2 microm in size), however, was found in some samples. The maximum amount of the insoluble Tc was 91%. Other forms were found in insignificant amounts. The amount of insoluble Tc was relatively high in paddy soil samples. Paddy soils, gley soils and gray lowland soils were particularly effective in the insolubilization of Tc. Among the soil characteristics studied, cation exchange capacity, anion exchange capacity, and active aluminum showed significant correlations with the relative amount of insoluble Tc. When microorganisms were eliminated from the surface water samples before the addition of (95m)TcO(4)(-), little insoluble Tc was found, suggesting that microorganisms cause the physicochemical transformation. These results showed that the physicochemical form of Tc changes from TcO(4)(-) to insoluble forms in surface water covering paddy fields. The insoluble forms would restrict the mobility of Tc in paddy fields.