Spatial predictors and temporal forecast of total organic carbon levels in boreal lakes.

Browning of Fennoscandian boreal lakes is raising concerns for negative ecosystem impacts as well as reduced drinking water quality. Declined sulfur deposition and warmer climate, along with afforestation, other climate impacts and less outfield grazing, have resulted in increased fluxes of Total Organic Carbon (TOC) from catchments to freshwater, and subsequently to coastal waters. This study assesses the major governing factors for increased TOC levels among several catchment characteristics in almost 5000 Fennoscandian lakes and catchments. Normalized Difference Vegetation Index (NDVI), a proxy for plant biomass, and the proportions of peatland in the catchment, along with surface runoff intensity and nitrogen deposition loading, were identified as the main spatial predictors for lake TOC concentrations. A multiple linear model, based on these explanatory variables, was used to simulate future TOC concentration in surface runoff from coastal drainage basins in 2050 and 2100, using the forecasts of climatic variables in two of the Shared Socio-economic Pathways (SSP): 1-2.6 (+2 °C) and 3-7.0 (+4,5 °C). These scenarios yield contrasting effects. SSP 1-2.6 predicts an overall decrease of TOC export to coastal waters, while SSP 3-7.0 in contrast leads to an increase in TOC export.

Assessing Heavy Metal Pollution of the Largest Nature Reserve in Tianjin City, China.

Beidagang Wetland (BW) Nature Reserve is centrally situated in Tianjin City, experiencing an extreme industrial development. This study uses index characteristic analysis systems for assessing the individual and combined heavy metal pollution loading in the water during the spring and autumn seasons. By combining the pollution level of single pollutant, a more comprehensive evaluation of water quality in BW was achieved. Water quality was worst during autumn due to high level of Cd and Pb, which indicate the type of anthropogenic activities have a serious effect on heavy metal pollution in BW. In addition, high exchangeable amounts of Cd (> 40%) were found in the sediments of BW, indicating Cd pollution has emerged. There is a need for appropriate abatement actions curbing heavy metal loading and improving water quality of the BW Nature Reserve, thereby ensuring a sustainable management of its ecosystem services.

Riverine flux of dissolved phosphorus to the coastal sea may be overestimated, especially in estuaries of gated rivers: Implications of phosphorus adsorption/desorption on suspended sediments.

The flux of terrestrial dissolved inorganic phosphorous (DIP, i.e. PO43-) via rivers into coastal seas is usually calculated by simply multiplying its concentration with the corresponding water flow at the river mouth. Subsequent adsorption/desorption of DIP onto suspended sediment and the influence of salinity in the estuary are often overlooked. A series of DIP adsorption/desorption experiments under different salinities (0, 5, 15, 30) and suspended sediment concentrations (1-40 g L-1) were conducted in order to assess the potential influence of these factors on the overall DIP loading to the coastal zone. The effect of different sea-salt ions on DIP adsorption/desorption was also assessed by comparing different experimental solutions (NaCl solution, artificial seawater and real seawater). In estuaries, the adsorption of DIP to suspended sediments was greater than desorption, and the net adsorption increased with increasing concentration of suspended sediments and salinity. This enhanced DIP adsorption onto suspended sediment reduces the riverine discharge of DIP to coastal ecosystems. Disregarding this process, especially for the gated estuaries with high sediment resuspension, potentially leads to an overestimation of the terrestrial DIP input to the coastal region.

Polyethylene terephthalate and di-(2-ethylhexyl) phthalate in surface and core sediments of Bohai Bay, China: Occurrence and ecological risk.

Bohai Bay, a typical semi-enclosed bay, is close to the Beijing-Tianjin-Hebei Region, the economic center of north China. The release of emerging contaminants was considerably increasing with the fast urbanization and industrialization along the coastline. However, such data, e.g. plastic polymers, are still limited. Here, polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in surface sediments and sediment cores from the coastal area of Bohai Bay were investigated. The ranges of PET and DEHP concentrations in surface sediments are 1.49-13.90 mg/kg and 0.23-19.26 mg/kg, respectively. The relatively high contents of PET and DEHP were found near the Haihe River estuary, indicating the importance of riverine input. The PET and DEHP profiles in the cores dated by the 210Pb method showed increasing trends with time. The PET in Bohai Bay was low risk evaluated by the potential ecological risk assessment. Low ecological risks of DEHP to the benthic organisms were found in the sediments, using the environmental risk limits, risk quotient, threshold effect level and probable effect level methods. The pollution levels of PET and DEHP in Bohai Bay obtained in this study may provide important data for making pollution control strategies.

Distributions, temporal trends and ecological risks of polyethylene terephthalate (PET) and di-(2-ethylhexyl) phthalate (DEHP) in sediments of Jiaozhou Bay, China.

Spatiotemporal distribution and ecological risk of the polyethylene terephthalate (PET) plastic polymer and plasticizer di-(2-ethylhexyl) phthalate (DEHP) were investigated using both surface and core sediments in Jiaozhou Bay, China. The concentrations of PET and DEHP ranged 210.6-1929.7 µg/kg and 0-591.2 µg/kg, respectively. The depth profiles of PET and DEHP in the sediment cores indicated that PET and DEHP pollution increased since the 1970s, which is in accord with the regional PET and DEHP consumption history. The levels of PET in Jiaozhou Bay was found to represent low ecological risk based on the assessment models for Potential Ecological Risk factor and Potential Ecological Risk. The amounts of DEHP also posed a low risk to the aquatic organisms in the sediment phase as indicated by the Risk Quotient method.

A commonly available and easily assembled device for extraction of bio/non-degradable microplastics from soil by flotation in NaBr solution.

Soil microplastic pollution has caused widespread research attention worldwide. It is necessary to efficiently separate microplastic particles from soil matrixes in order to conduct studies of microplastic. And so far, few studies have described the separation and extraction devices of biodegradable microplastic. Here we present a commonly available device for extraction of non-degradable and biodegradable microplastics from soil samples in a NaBr solution based on density flotation. The device has a combined circulation and recovery system for the salt solution, which increases its environmental-friendliness. The accuracy and precision of the device was verified through spike and recovery experiments using three types of biodegradable microplastics (PBS, PBAT, PLA) and four types of non-degradable microplastics (LDPE, PS, PP, PVC), all with different particle sizes, and all microplastics are grinded autonomously, closer to reality. In despite of differences in particle size and density, for both biodegradable and non-degradable microplastics the device exhibited good extraction precision, with recovery rates ranging from 92% to 99.6%, over a wide range of particle densities and sizes. The recovery rates slightly increased with increased polymer density and microplastic particle size.

An optimized density-based approach for extracting microplastics from soil and sediment samples.

Microplastic pollution in the environment has received growing attention worldwide. A major impediment for accurate measurements of microplastics in environmental matrixes is to extract the particles. The most commonly-used method for separation from soil or sediment is flotation in dense liquid based on the relatively low density of plastic particles. This study provides an improved and optimized process for extraction of microplastic particles by modifying the floatation technique and floatation solution. Microplastics in soils and sediments are extracted by adding 200 g dry soil or sediment sample to 1.3 L mix of the saturated NaCl and NaI solutions in a volume ratio of 1:1 and aerating for 40 s then filtering the supernatant. The accuracy and precision of the new approach is validated by recovery experiments using soil and sediment samples spiked with six common microplastic compounds: polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and expanded polystyrene (EPS), and comparison with the previous method. The optimized approach is further compared with the previous approach using the real soil and sediment samples.

Soil sorption of two nitramines derived from amine-based CO2 capture.

Nitramines are potentially carcinogens that form from the amines used in post-combustion CO2 capture (PCCC). The soil sorption characteristics of monoethanol (MEA)- and dimethyl (DMA)-nitramines have been assessed using a batch experimental setup, and defined indirectly by measuring loss of nitramine (LC-MS/MS) from the aqueous phase (0.01 M CaCl2 and 0.1% NaN3) after equilibrium had been established with the soil (24 h). Nitramine soil sorption was found to be strongly dependent on the content of organic matter in the soil (r2 = 0.72 and 0.95, p < 0.05). Soil sorption of MEA-nitramine was further influenced by the quality of the organic matter (Abs254 nm, r2 = 0.93, p < 0.05). This is hypothesized to be due to the hydroxyl group on the MEA-nitramine, capable of forming hydrogen bonds with acidic functional groups on the soil organic matter. Estimated organic carbon normalized soil-water distribution coefficients (KOC) are relatively low, and within the same range as for simple amines. Nevertheless, considering the high content of organic matter commonly found in the top layer of a forest soil, this is where most of the nitramines will be retained. Presented data can be used to estimate final concentrations of nitramines in the environment following emissions from amine-based PCCC plants.

Reducing production of taste and odor by deep-living cyanobacteria in drinking water reservoirs by regulation of water level.

Abatement and control of algae, producing toxins and creating taste & odor (T&O) in drinking water sources, is a major challenge for water supply. In this study we proposed a strategy based on water level regulation for the control of odor-producing cyanobacteria in source water. Miyun Reservoir, the main surface water source for Beijing, has been suffering from 2-methylisoborneol (2-MIB) induced T&O problems caused by deep-living Planktothrix sp. since 2002. The biomass of deep-living Planktothrix in Miyun Reservoir was found to be mainly governed by the water depth above its sediment habitat. An algorithm for water level regulation aiming to minimize the risk for T&O in different types of reservoirs is proposed. The study demonstrates that risk for T&O can be minimized by increasing the water level in Miyun Reservoir. The high-risk area can be reduced by about 2.91% (0.61% to 5.76%) of surface area for each meter increase in the water level, when the water level is lower than 145m. More specifically, the water level needs to be raised to higher than 147.7ma.s.l. from 131.0m in order to obtain an acceptable risk level (ARL) of 10%. This management strategy to abate T&O problems is simpler and cheaper to implement compared to traditional physical, chemical and biological techniques. Moreover, it has no apparent negative impact on water quality and aquatic organisms.

Environmental values and attitudes among farmers in China - a case study in the watershed of Yuqiao reservoir of Tianjin Municipality, China.

Failure to curb water pollution in China brings to the fore the issue of environmental values and attitudes among Chinese farmers. Applying the New Ecological Paradigm Scale this study finds that the pro-environmental value of New Ecological Paradigm (NEP) Worldview has a stronger standing among the studied Chinese farmers than the Dominant Social Paradigm (DSP) Worldview.

Responses of Organic Phosphorus Fractionation to Environmental Conditions and Lake Evolution.

Geochemical fractionation is used to assess the significance of environmental factors on organic phosphorus (OP) pools in sediments. Labile, moderately labile, and nonlabile OP pools in the sediments from Lake Hulun, Inner Mongolia, were fractionated, and their responses to environmental conditions and lake evolution were investigated based on the spatial and vertical distribution of OP fractionations. In light of the recalcitrant characteristics of organic matter (OM) in different environmental conditions, the pH presents significant negative effects on the amount of labile OP, while water depth shows an important role in regulating the distribution between the moderately labile and nonlabile OP pools. A latitudinal zonation in the distribution of OP pools in surface sediments from different lakes was apparent with this zonation likely linked to the gradient effects of climate and anthropogenic activities on OM decomposition and thereby on the sediments capacity to hold phosphorus. These results show that OM plays a role in governing the impacts of weather and environmental factors on OP fractionation in aquatic environments. This work suggests that OP pools in the sediment core could be used as an archive for environmental conditions and lake evolution.

Processes and their explanatory factors governing distribution of organic phosphorous pools in lake sediments.

The amount of organic phosphorus (OP) and its distribution among different pools in lake sediments depends on biotic and abiotic processes driving the OP fractionation. Key environmental factors governing these transformations processes between OP fractionations in sediments were studied on the basis of geochemical characteristics of OP pools in relation to environmental factors in the sediments. The results illustrate that the factors influencing the accumulation or depletion of different OP pools were intrinsically dependent on the composition of the deposited organic matter (OM). During the mineralization of the OM the microorganisms excrete the enzyme alkaline phosphatase, accelerating the OP hydrolysis, and thereby setting the grounds for the bacterially-mediated oxidation of OM. There are two main degradation products of the labile OP pool (LOP) and the moderately labile OP pool (MLOP): Either the OP is transformed to a dissolved organic or inorganic P form, and thereby released to water column, or OP is transformed to a non-labile OP pool and stored in the sediments. A comparative study showed that oxy-hydroxides of iron (Fe) and aluminum (Al) only played an important role in influencing OP fractionation in Lake Wuliangsuhai, while the complexation reactions of OP with calcium ions and sorption to its minerals are key factors governing the OP fractionation in the two alkaline lakes. It is worth noting that a significant correlation between the Fe-P pool and the pools of LOP and MLOP indicates that the degradation of the rather labile OP pools are highly dependent on the iron redox reaction.

Biochar amendment to soil changes dissolved organic matter content and composition.

Amendments of biochar, a product of pyrolysis of biomass, have been shown to increase fertility of acidic soils by enhancing soil properties such as pH, cation-exchange-capacity and water-holding-capacity. These parameters are important in the context of natural organic matter contained in soils, of which dissolved organic matter (DOM) is the mobile and most bioavailable fraction. The effect of biochar on the content and composition of DOM in soils has received little research attention. This study focuses on the effects of amendments of two different biochars to an acidic acrisol and a pH-neutral brown soil. A batch experiment showed that mixing biochar with the acrisols at a 10 wt.% dose increased the pH from 4.9 to 8.7, and this resulted in a 15-fold increase in the dissolved organic carbon concentration (from 4.5 to 69 mg L(-1)). The pH-increase followed the same trend as the release of DOM in the experiment, causing higher DOM solubility and desorption of DOM from mineral sites. The binding to biochar of several well-characterised reference DOM materials was also investigated and results showed a higher sorption of aliphatic DOM to biochar than aromatic DOM, with DOM-water partitioning coefficients (Kd-values) ranging from 0.2 to 590 L kg(-1). A size exclusion occurring in biochar's micropores, could result in a higher sorption of smaller aliphatic DOM molecules than larger aromatic ones. These findings indicate that biochar could increase the leaching of DOM from soil, as well as change the DOM composition towards molecules with a larger size and higher aromaticity.

Distribution characteristics of organic phosphorus in sediments from Lake Hulun, China.

The amount of organic phosphorus (OP) and its distribution among different pools in lake sediments depend on biotic and abiotic processes driving OP fractionation. The key abiotic factors governing these transformation processes between different OP fractions in sediments were studied on the basis of distribution characteristics of OP pools in sediments from Lake Hulun (HLH). The results showed the order of the size of OP pools in the surface sediments from Lake Hulun to be: Re-OP (residual OP) ≫ FAOP (fulvic acid fraction) ≥ HCl-OP (OP extracted by HCl) > HAOP (humic acid fraction) ≫ LOP (labile OP); lower concentrations of LOP were found in lake surface sediments with high pH (pH > 9) of lake overlying water indicating a governing role of pH in LOP degradation in an aquatic environment. The pattern of total OP (TOP) spatial distribution showed an obvious decreasing trend from the west to the east lake districts in surface sediments from HLH, which was attributed to the inputs of dust and dry grass driven by the prevailing wind and the finer grain size in the west lake districts. However, the spatial distribution pattern of dissolved OP (DOP) in overlying water, which presented different trends with TOP and total organic carbon (TOC) in surface sediments, indicated that the biological factors and terrestrial inputs showed a joint influence on DOP distribution in HLH. The higher levels of Re-OP and lower levels of HCl-OP observed in HLH may reveal that calcium ions and their minerals were the key governing factors of OP fractionation in sediments from HLH. This work revealed the main abiotic process or mechanism driving OP fractionation in the aquatic environment helping to understand the geochemical information archived in OP pools in lake sediments.

Land use as an explanatory factor for potential phosphorus loss risk, assessed by P indices and their governing parameters.

The total level of phosphorus (P) and the distribution of P pools in the topsoil are significantly affected by the excessive application of mineral and organic fertilizers connected with intensive agriculture. This leads to an increased potential risk for P loss, and then contributes to freshwater eutrophication. Soil test P (STP), P sorption index (PSI) and degree of P saturation (DPS) are commonly applied as proxies for assessing the risk of P loss. Although conceptually based, the empirical relationships between these operationally defined proxies and the actual P flux exhibit large spatial variations. Herein, a comprehensive synoptic study and monitoring of soil has been conducted in a watershed in north-eastern China. A set of conventional indicators for soil P loss risk were measured along with the main P pools, P sorption indices, texture, organic matter, as well as Fe and Al oxides and other mineral compositions. Moreover, detailed soil P speciation was conducted using phosphorus nuclear magnetic resonance ((31)P NMR) spectroscopy. In addition, phosphatase activities in the soils were determined for each land use soil category. The results reflected that the soil content of total P, total inorganic P and STP increased significantly following the order of increasing management intensity. STP, being strongly coupled to the application of P fertilizers, was a strong explanatory factor for the spatial differences in DPS - both between and within different land uses. The dominant inorganic and organic P species in the soils were orthophosphate and monoester-P, respectively. Their contents were oppositely correlated with the degree of management influence, with the amount of orthophosphate positively related. Alkaline phosphomonoesterase (AlP) represented the highest activities among the four representative phosphatases, i.e. enzymes that hydrolyze organic P - releasing labile orthophosphate. Orchard soils were found to contain the highest levels of monoester P as well as high AlP activities. This indicates a strong capacity to produce labile orthophosphate. Our results suggest that the type of land use can be employed as a general explanatory factor for considering the potential high risk of loss of P. Regionalized P loss parameters will further improve the accuracy of risk assessment.

MIB-producing cyanobacteria (Planktothrix sp.) in a drinking water reservoir: distribution and odor producing potential.

The production of odorant 2-methylisoborneol (MIB) in water bodies by Planktothrix sp. have not been understood very well. Through a four-year investigation in Miyun Reservoir, a huge mesotrophic drinking water reservoir known to have the MIB episodes, we found that the Planktothrix sp. bloomed during September and October causing the high levels of MIB in the reservoir. The concentration of MIB and the biomass of MIB-producing cyanobacteria Planktothrix were measured (n = 887) at different sites and depths during different seasons. The results indicated that the shallow region of the reservoir is the major habitat for Planktothrix sp. due to that the light is able to penetrate down to the relatively high concentrations of nutrients close to the sediments. Quantile regression analysis between Planktothrix biomass and MIB concentration shows that the risk of MIB exceeding the odor threshold (15 ng L⁻¹) in water was as high as 90% when the Planktothrix density was more than 4.0 × 105 cells L⁻¹, while the risk was reduced to 10% when the Planktothrix density remained below 1.6 × 104 cells L⁻¹. This study will improve the understanding of the environmental behaviors of Planktothrix sp., and can provide useful information for better management of drinking water lakes/reservoirs experiencing the taste and odor (T&O) problems caused by deep living cyanobacterial species.

Soil fertility and plant diversity enhance microbial performance in metal-polluted soils.

This study examined the effects of soil physicochemical properties (including heavy metal pollution) and vegetation parameters on soil basal respiration, microbial biomass, and the activity and functional richness of culturable soil bacteria and fungi. In a zinc and lead mining area (S Poland), 49 sites were selected to represent all common plant communities and comprise the area's diverse soil types. Numerous variables describing habitat properties were reduced by PCA to 7 independent factors, mainly representing subsoil type (metal-rich mining waste vs. sand), soil fertility (exchangeable Ca, Mg and K, total C and N, organic C), plant species richness, phosphorus content, water-soluble heavy metals (Zn, Cd and Pb), clay content and plant functional diversity (based on graminoids, legumes and non-leguminous forbs). Multiple regression analysis including these factors explained much of the variation in most microbial parameters; in the case of microbial respiration and biomass, it was 86% and 71%, respectively. The activity of soil microbes was positively affected mainly by soil fertility and, apparently, by the presence of mining waste in the subsoil. The mining waste contained vast amounts of trace metals (total Zn, Cd and Pb), but it promoted microbial performance due to its inherently high content of macronutrients (total Ca, Mg, K and C). Plant species richness had a relatively strong positive effect on all microbial parameters, except for the fungal component. In contrast, plant functional diversity was practically negligible in its effect on microbes. Other explanatory variables had only a minor positive effect (clay content) or no significant influence (phosphorus content) on microbial communities. The main conclusion from this study is that high nutrient availability and plant species richness positively affected the soil microbes and that this apparently counteracted the toxic effects of metal contamination.

Modelling transport and transformation of mercury fractions in heavily contaminated mountain streams by coupling a GIS-based hydrological model with a mercury chemistry model.

Many heavily polluted areas are located in remote regions that lack routine hydrologic monitoring. A modelling method that can produce scenarios of water chemistry trends for regions that lack hydrological data is therefore needed. The Wanshan mining area, in Guizhou province in south-western China, is such a region, as it is heavily polluted with mercury (Hg). In order to model Hg transport in a stream draining the Wanshan mining area, a Geographic Information System (GIS) hydrologic model (HEC-HMS) was coupled with a simulation model for Hg fractions in water (WASP Hg). Hydrological variations in the stream flow can thereby be simulated based on readily available precipitation data. The WASP 7 MERC Hg model was used for simulating variations in total Hg, dissolved Hg and methyl-Hg concentrations. The results of HEC-HMS modelling of flow show clear seasonal variation. Winter (Oct-Dec) constitutes the dry season with low flow, while the summer season (Jun-Aug) is rainy with high flow. 48% of total annual precipitation happens in the three summer months. The stream flows at the high flow events were several times higher than normal flow. The modelled total suspended solids and Hg concentrations were tested against monitoring data from two sampling campaigns conducted in September 2007 and August 2008. The model produced reasonable simulations for TSS, THg, DHg and MeHg, with relative errors generally around 10% for the modelled parameters. High flow events are the main contributors for release of both suspended particles and Hg. The three high flow events account for about 50% of annual discharge of THg. The annual total discharge of Hg was 8.8 kg Hg high up in the stream and 2.6 kg where the stream meets a large river 20 km downstream of the pollution source. Hence, about 70% of Hg is retained in the stream through sedimentation.

Transport and fate of mercury under different hydrologic regimes in polluted stream in mining area.

Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated runoff. Samples were taken during different flow regimes in the Wanshan Hg mining area in Guizhou Province, China. In its headwaters the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The concentrations of major anions (e.g., Cl-, F-, NO3- and SO4(2-)) were lower during higher flow due to dilution. Due to both sedimentation of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within 10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60% for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction (DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved phase in surface waters in Wanshan (over 95%).