Surface Soil Concentrations Research Articles

An Assessment of Traditional Chemical Indicators of Atmospheric Pollution in Northern Saskatchewan Forest Soils

Core Ideas Concentrations of pollutants in Saskatchewan forest soils are low but are highly variable. Distinct spatial patterns in surface soil pollutant concentration are evident. Patterns in soil Hg and V and SO42− are strongly related to soil organic matter. Concentrations of Cu, Ni and Zn influenced by soil factors in addition to organic matter. Atmospheric deposition plays a minor role in pollutant levels in northern Saskatchewan soils. Long‐range transport and subsequent atmospheric deposition of pollutants has led to soil contamination around the globe. Northern Saskatchewan is downwind of major emissions of sulfur (S), nitrogen (N), and heavy metals vanadium (V) and nickel (Ni) associated with oil sands activities, leading to concerns over possible soil contamination. In this study we sampled 200 forested sites spanning five ecoregions of Saskatchewan. Surface (A‐horizon) soils were measured for a suite of traditional chemical indicators of atmospheric pollution (e.g., SO42–, NO3−, Hg, heavy metals). In general, metal concentrations in surface soils were among the lowest reported in the literature indicating low levels of soil contamination. Despite the remote location of the sites there was a large range in pollution soil indicators in surface soil. For example, Hg concentrations were between 0.6 and 53.3 μg g−1, V concentrations varied from <0.02 to 161 mg kg−1, and extractable SO42– was between 0.2 and 52.2 mg kg−1 and distinct spatial patterns were evident. Higher concentrations of pollutants were observed in southern, eastern and northern parts of the study area. Much of the variability in surface soil chemistry was explained by soil factors and in particular organic matter as the dominant controls of these pollution indicators. Lower values of these indicators were found in sandy soils low in organic matter such as those occurring in the Athabasca Plain located south of Lake Athabasca closest to oil sands activities.

Soil–atmosphere exchange of carbonyl sulfide in a Mediterranean citrus orchard

Abstract. Carbonyl sulfide (COS) is used as a tracer of CO2 exchange at the ecosystem and larger scales. The robustness of this approach depends on knowledge of the soil contribution to the ecosystem fluxes, which is uncertain at present. We assessed the spatial and temporal variations in soil COS and CO2 fluxes in a Mediterranean citrus orchard combining surface flux chambers and soil concentration gradients. The spatial heterogeneity in soil COS exchange indicated net uptake below and between trees of up to 4.6 pmol m−2 s−1 and net emission in sun-exposed soil between rows of up to 2.6 pmol m−2 s−1, with an overall mean uptake value of 1.1±0.1 pmol m−2 s−1. Soil COS concentrations decreased with soil depth from atmospheric levels of ∼450 to ∼100 ppt at 20 cm depth, while CO2 concentrations increased from ∼400 to ∼5000 ppm. COS flux estimates from the soil concentration gradients were, on average, -1.0±0.3 pmol m−2 s−1, consistent with the chamber measurements. A soil COS flux algorithm driven by soil moisture and temperature (5 cm depth) and distance from the nearest tree, could explain 75 % of variance in soil COS flux. Soil relative uptake, the normalized ratio of COS to CO2 fluxes was, on average, -0.4±0.3 and showed a general exponential response to soil temperature. The results indicated that soil COS fluxes at our study site were dominated by uptake, with relatively small net fluxes compared to both soil respiration and reported canopy COS fluxes. Such a result should facilitate the application of COS as a powerful tracer of ecosystem CO2 exchange.

Consequences of Mercury Used by Artisanal and Small-Scale Gold Mining Processes – A Case of River Nile State Sudan

On the discovery of gold reserves in 14 states in Sudan, traditional gold mining suddenly started to flourish and hundreds of thousands of laymen became engaged in gold extraction. The use of mercury in gold extraction poses much threat to the environment and general health of miners and the surrounding areas. The investigation includes: The effects of extraction methods on the environment and general health, The level of education and its distribution within the miners and how it affected the awareness of the miners about the dangers of mining activities, The period of stay that miners spend in the mining area and its contribution on the awareness about the dangers and diseases inflicted on the miners, The effects of traditional gold mining activities on natural environmental and The effects of the meteorological and topographical factors, the distribution and concentration of mercury in the area and their effects on the environment and general health. The research adopted the techniques of using random sampling and quantitative qualitative in addition to the analytical techniques. The research finally concluded that the mercury has potential to distribution and transport from study area to neighboring places by two meteorological and topographical factors, the wind directions and speed, those two meteorological elements affect the transport of pollutants from the highest to the lowest boundary layers. The area is characterized by high temperatures during most of year for ten months (50c) and low temperatures during winter months to (5c). Mercury starts to evaporate at temperature exceeding (25c). hence areas of higher temperatures are subjected to higher mercury concentration than other area of low temperatures. The study area is located at a height of (372 meters) above sea level, and that the River Nile to the West is located at an altitude of (340 meters), Topographically contour lines retreat towards in the River Nile, the fact which means that the surface run-off water will flow towards in River Nile and carry mercury concentration because of the natural slope of the area. But a portion of the Western area slopes towards the residents within the surrounding communities. Artisanal and small-scale gold mining has positive effects on the economic side and negative effects on the environment and general health. Keywords: artisanal and small-scale gold mining, Workers occupationally exposed (WOE), Residents in surrounding communities (RSC), Distribution of mercury concentration in surface soil and surface water, Meteorological and topographical factors.

Long-term sustaining crop productivity and soil health in maize–chickpea system through integrated nutrient management practices in Vertisols of central India

Long-term sustainability concerns are growing in agriculture owing to over and under application of fertilizers and poor management of available resources which are resulting into soil health deterioration and declining crop productivity. Balanced and integrated use of organic and inorganic fertilizers is the most logical concept for managing and sustaining long term soil health and crop productivity. Hence, a long-term field experiment was conducted from 2012 to 2017 to develop integrated nutrient management (INM) practices for sustaining crop productivity and maintaining soil health under maize (Zea mays L.) chickpea (Cicer arietinum L.) cropping system in Vertisols of central India. Twelve treatments that comprised of various combinations of general recommended dose (GRD) of NPK, farmyard manure (FYM), poultry manure (poultry manure), urban compost (UC), maize residue (MR), glyricidia loppings (GL) and soil test crop response (STCR) based NPK with target yield 5.0 and 1.50 Mg ha1 in maize and chickpea, respectively were tested. The experiment was conducted following a Randomized Complete Block Design (RCBD) set up with three replications and Simple Random Sampling (SRS) technique of sampling. The results indicated that the grain yield and system yield were observed to be significantly higher with 75% NPK of STCR + FYM at 5 Mg ha1 treatment and recorded an increase of 20.9% and 13.08% in mean grain yield of maize and chickpea, respectively over GRD. The combined analysis results illustrated significant (P < 0.0001) year x nutrient management interaction effect on grain yield with N input (R2 = 0.80) and N uptake (R2 = 0.91). Stepwise multiple regression model also showed that the N input and N uptake significantly (P < 0.05) influenced the system yield under different INM practices. However, apparent nutrient balance was negative for N and K in all treatments except higher level of FYM treatment (FYM at 20 Mg ha1) while P balance was positive under balanced and complete nutrition through organic and inorganic treatments over the years. A significant increase was observed in the various soil health indicators (physical, chemical and biological) under balanced and integrated use of organic and inorganic fertilizers. FYM, poultry manure and urban compost improved the physical properties of soil like mean weight diameter (MWD), water stable aggregates (WSA), bulk density and porosity. The application of higher level of FYM (20 Mg ha1) significantly increased the soil organic carbon (SOC) (6.30 g kg1), SOC stock (11.8 Mg ha1), carbon sequestration rate (213.1 kg ha1 year1), KMnO4-N (121.7 mg kg–1), Olsen-P (23.8 mg kg–1) and NH4OAc-K (273.5 mg kg–1) concentration in surface soil as compared to GRD and control treatments. The soil enzymes, dehydrogenase (DHA), alkaline phosphates (Alk-P) and fluorescein diacetate (FDA) were enhanced significantly with the application of FYM at 20 Mg ha1 and STCR based 75% NPK + FYM at 5 Mg ha1. The STCR based 75% NPK along with FYM at 5 Mg ha1 treatment recorded highest sustainable yield index (SYI) 0.84 and 0.92 with maximum guaranteed yield of 6.19 and 1.99 Mg ha1 in maize and chickpea, respectively. The results indicate that the chickpea yield was more sustainable as compared to the maize.

Long-term leaching of arsenic from pressure-treated playground structures in the northeastern United States

Wood used in playground structures built prior to 2004 was pressure-treated with chromated copper arsenate (CCA) which has been associated with negative health and environmental impacts. Given the prevalence and lack of maintenance of these aging play structures in rural northeastern US, the aim of this study was to determine the distribution of As (total, speciated and bioaccessible) in surface soil collected near and underneath four CCA-treated playground structures 16- and 26-years following installation. Note that one playground in southeastern MA was studied where surface soil samples were collected at various distances from the structures (0, 5, 15, and 30 cm). Total As in surface soil was measured by graphite furnace atomic absorption spectroscopy, whereas As speciation and bioaccessible As were determined by HPLC-ICPMS and in vitro SBRC-gastric assay, respectively. Near (≤5 cm) and underneath CCA-treated structures total As concentration in surface soil ranged from 143.4–213.5 mg/kg after 26 years of installation compared to 101.3–166.6 mg/kg ten years earlier. These concentrations exceeded the Massachusetts Residential Risk-Based Soil Standard by 5–10 times. In comparison, total As in background soil samples ranged from 4.6–6.6 mg/kg during the two study periods. While most of the As in surface soil were in the form of As(V), ≤29% was bioaccessible. Overall, our findings demonstrated that arsenic accumulation in soil surrounding aging playground structures continues to be a source of elevated exposure to children through contact with contaminated soil.

Congener-specific C10[sbnd]C13 and C14[sbnd]C17 chlorinated paraffins in Chinese agricultural soils: Spatio-vertical distribution, homologue pattern and environmental behavior

A comprehensive spatio-vertical survey of short-chain (SCCPs, C10-13) and medium-chain (MCCPs, C14-17) chlorinated paraffins (CPs) was performed in surface and core soils from Chinese nation-wide agricultural lands in 2016, and a total of 48 congener groups were measured. The shorter carbon chain C10-11 in SCCP and C14-15 in MCCP homologue groups, and the lower chlorinated congeners (Cl5-7) for both CP groups were predominant. The ∑SCCP and ∑MCCP concentrations in surface soils ranged from 39 to 1609 ng/g and 127–1969 ng/g, dry weight (dw), respectively. The spatial distribution trend showed that SCCP congener groups with relatively low octanol-water partition coefficient (KOW) and octanol-air partition coefficient (KOA) are uniformly distributed across surface soils compared to MCCP congener groups. Significant relationships were observed between the spatial variation of SCCP concentrations and the driving factors responsible for dispersion and deposition. The distribution behavior of SCCPs and MCCPs in highland and plain surface soils showed an increasing trend of MCCP concentrations with elevation, indicating the “mountain cold-trapping effect”. Vertical distribution profile revealed similar homologue group composition patterns of SCCP and MCCP congener groups as those of surface soils. Furthermore, the penetration potential ratios (r) of chlorine and carbon atoms of CPs demonstrated that the lower chlorinated (Cl5-7) and the shorter carbon chain (C10-13) congener groups are more prone to vertical movement into deeper soil layers compared to the longer carbon chain (C14-17) and highly chlorinated (Cl8-10) congener groups.

Mercury Sourcing and Sequestration in Weathering Profiles at Six Critical Zone Observatories

AbstractMercury sequestration in regolith (soils + weathered bedrock) is an important ecosystem service of the critical zone. This has largely remained unexplored, due to the difficulty of sample collection and the assumption that Hg is predominantly sequestered within surface soils (here we define as 0–0.3 m). We measured Hg concentrations and inventories in weathering profiles at six Critical Zone Observatories (CZOs): Boulder Creek in the Front Range of Colorado, Calhoun in the South Carolina Piedmont, Eel River in coastal northern California, Luquillo in the tropical montane forest of Puerto Rico, Shale Hills of the valley and ridges of central Pennsylvania, and Southern Sierra in the Sierra Nevada range of California. Surface soils had higher Hg concentrations than the deepest regolith samples, except for Eel River, which had lower Hg concentrations in surface soils compared to regolith. Using Ti normalization, CZOs with &lt;12% rock‐derived Hg (Boulder Creek, Calhoun, and Southern Sierra) had Hg peaks between 1.5 and 8.0 m in depth. At CZOs with &gt;50% rock‐derived Hg, Eel River Hg concentrations and pools were greatest at &gt;4.0 m in the weathering profile, while Luquillo and Shale Hills had peaks at the surface that diminished within 1.0 m of the surface. Hg and total organic C were only significantly correlated in regolith at Luquillo and Shale Hills CZOs, suggesting that Hg sorption to organic matter may be less dominant than clays or Fe(II) sulfides in deeper regolith. Our results demonstrate the importance of Hg sequestration in deep regolith, below typical soil sampling depths.

Measurements of radon gas concentration in surface soil in Baghdad city

In the present work, radon gas concentrations in different surface soil samples in Baghdad governorate were measured using RAD-7 detector. The results have been shown that, the Radon gas concentrations ranged between (41.67±1.78Bq/m3), to (185.67±4.22Bq/m3), a map showing the distribution of the concentration of radon in selected areas was defined to identify areas with high pollution level. The reason for the high concentration of radon is that these surface soil samples are taken from agricultural areas. It is also known that fertilizers contain uranium levels as well as areas bombed in wars in the country. It is worth noting that all radon concentrations in Baghdad governorate are below the recommended minimum of 200-300Bq/m3) (International Commission on Radiation Protection, ICRP, 2009).

Phosphorus Application Rates Affected Phosphorus Partitioning and Use Efficiency in Tomato Production

Core Ideas The partitioning of P uptake to fruit was maximized at 72 kg ha−1 in 2014. Increasing P rate linearly increased P concentrations in both soil and leachate. Efficiency of converting P fertilizer into yield decreased with increasing P rate. The rate 56 kg ha−1 was considered the sufficient P rate based on tomato yield. Understanding P accumulation and partitioning is essential for improving phosphorus use efficiency (PUE) and minimizing environmental impact. A 2‐yr study was conducted to determine P distribution and PUE in tomato (Solanum lycopersicum L.) production as influenced by P application rates in a calcareous soil. Phosphorus was applied at 0, 29, 49, 78, 98, and 118 kg ha−1 as pre‐plant dry fertilizers. At 95 d after transplanting, total phosphorus uptake (TPU) was not significantly affected by P rates in either year. In 2014, the highest proportion of TPU was accumulated in fruits and the maximum partitioning of TPU to fruits occurred at 72 kg ha−1. A higher or similar percentage of TPU was allocated to leaves comparing with fruits in 2015, which was probably due to the higher rainfall accumulation. Positive soil P budgets occurred with P rates ranging from 29 to 118 kg ha−1 in both years. Phosphorus concentrations in surface soil and subsurface leachate increased linearly with increasing P rate. Tomato marketable yield at the first and second combined harvest was not affected in 2014, whereas the yield increased linearly and attained a plateau at 56 kg ha−1 in 2015. There were no significant differences among treatments in the total season marketable yields in either year, thus, the partial factor productivity decreased with increasing P rate. Consequently, in the calcareous soils with 37 to 51 mg kg−1 of Mehlich‐3 extractable P, 56 kg ha−1 can be the sufficient P rate for tomato production.

Arsenic accumulation in paddy plants at different phases of pre-monsoon cultivation

Geogenic arsenic (As) contamination in Bengal Delta Plain is a growing environmental and research concern. Cultivation of staple crops like paddy on these contaminated fields is one of the major routes for human dietary exposure. The present study investigates changes of arsenic concentrations in paddy plant parts, root soil and surface soil throughout the various phases of pre-monsoon (boro) cultivation. Arsenic uptake property of paddy plants collected from 10 fields was found to be dependent on the variety of paddy plant (like Minikit, Jaya) rather than arsenic levels in groundwater (0.074–0.301 mg/l) or soil (25.3–60 mg/kg). Arsenic is translocated from root to aerial parts in descending order. Leaf, stem, root, root soil and surface soil showed a similar trend in their change of arsenic concentration throughout the cultivation period. Arsenic concentration was highest in vegetative phase; sharply declined in reproductive phase; followed by moderate increase in ripening phase. The young root tissues in vegetative (primary) phase could uptake arsenic at a much faster rate than the older tissues in later phases. With the growth of the plant, higher concentrations of iron in root soil in the reproductive phase confirmed the formation of iron plaques on the surface of the root, which sequester arsenic and prevented its uptake by plants. Finally, co-precipitation of arsenic with iron released from crystallized iron plaques results in loosening of the iron plaques from root surface. Thus, soil arsenic concentration increases in the final phase of cultivation which in turn contributes to increased concentration in plant parts.

Radionuclide distribution in soil and undecayed vegetative litter samples in a riparian system at the Savannah River Site, SC

The aim of this study is to comprehensively investigate radionuclide concentrations in surface soil and un-decayed vegetative litter along four stream systems (i.e. Fourmile Branch, Lower Three Runs, Pen Branch, and Steel Creek) at the Savannah River Site (SRS), Aiken, South Carolina. Soil and litter samples from systematically spaced 12 pairs (contaminated or uncontaminated) of plots along the four streams were analyzed for 16 distinct radionuclide activities. Lower radionuclide concentrations were observed in soil and litter samples collected along Pen Branch compared to the other 3 streams. The anthropogenic radionuclide with the highest activity was 137Cs in soil (10.6–916.9 Bq/kg) and litter (8.0–222.3 Bq/kg), while the naturally occurring radionuclides possessing the highest concentration in the samples were 40K (33.5–153.7 Bq/kg and 23.1–56.0 Bq/kg in soil and litter respectively) and 226Ra (55.6–159.9 Bq/kg and 30.2–101.8 Bq/kg in soil and litter respectively). A significant difference (p < 0.05) of radionuclide concentrations between paired-plots across four streams was observed for 241Am, 137Cs, 238Pu, 239Pu, and 226Ra in both contaminated and non-contaminated samples. 137Cs and uranium isotopes had the highest litter-to-soil correlation in contaminated (rho = 0.70) and uncontaminated plots (rho = 0.31–0.41), respectively. 90Sr was the only radionuclide with higher radioactive concentrations in litter (12.65–37.56 Bq/kg) compared to soil (1.61–4.79 Bq/kg). The result indicates that 1) historical discharges of anthropogenic 137Cs was the most important contributor of radiation contamination in the riparian environment at SRS, 2) 90Sr was the only radionuclide with higher concentration in litter than in soil, and 3) no apparent pattern in deposition density in soil or litter along downstream was observed for the radionuclides measured in this study.

IMPACTO DE LA MINERÍA DEL ORO ASOCIADO CON LA CONTAMINACIÓN POR MERCURIO EN SUELO SUPERFICIAL DE SAN MARTÍN DE LOBA, SUR DE BOLÍVAR (COLOMBIA)

Human activities have increased mercury (Hg) contamination of terrestrial environments, especially gold mining areas. The aim of this study was to evaluate total Hg concentrations (T-Hg) in surface soil samples of San Martin de Loba, south of Bol i var (Colombia), to determine their Hg contamination level. For that purpose, 202 surface soil samples were collected. T-Hg levels were measured by electrothermal atomization and atomic absorption spectroscopy. The T-Hg surface soil concentrations ranged between 0.002 and 23.83 μg/g, with a median value of 3.40 ± 0.36 μg/g, which is slightly higher than the international Hg soil levels. The geoaccumulation index (I geo ) for soils reached values greater than 5, indicating extreme pollution (Class 6) in 17 % of samples, while 70 % was Class 5 (strongly to extremely polluted). This study also provides a risk map to evaluate potential negative repercussions. In conclusion, the municipality of San Martin de Loba can be considered as a strongly polluted area with high Hg content. Technology used to extract gold through amalgamation processes causes a high degree of Hg pollution around this gold mining area. Therefore, alternative extraction methods should be considered to reduce Hg levels that can be released into the environment and affect human health.

Evaluation of environmental and anthropogenic influences on ambient background metal and metalloid concentrations in soil

There has been a global shift in environmental risk assessment towards quantifying ambient background concentrations of metals/metalloids in soil. Whilst bedrock has been shown to be a key driver of metal/metalloid variability in soil, few researchers have assessed controls of ambient background concentrations in soils of similar bedrock. A soil survey was undertaken ofGreater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia for elements of potential environmental concern: As, Cd, Cr, Cu, Ni, Hg, Pb and Zn. Samples (n=622) were collected from surface (0 to 0.1m) and sub-surface (0.3 to 0.6m) soils, overlying Tertiary-Quaternary basalt, Tertiary sediments and Silurian siltstone and sandstone. In addition, background soil data from open-source environmental assessment reports (n=5512) were collated to support the understanding of natural enrichment, particularly at depths >0.6m. Factor analysis, supported by correlation analysis and auxiliary geo-spatial data, provided an improved understanding of where and how background metal/metalloid enrichment occurs in the environment. Weathering during paleoclimates was the predominant influence of background metal/metalloid variability in soils overlying similar bedrock. Other key influences of metal/metalloid variability in soil included hydraulic leaching of alkali elements, biological cycling, topography and alluvial transfer of silt and sand from mineralised regions. In addition, urbanisation positively correlated with Pb and Zn concentrations in surface soils suggesting that anthropogenic activities may have resulted in diffuse Pb and Zn contamination of urban soil.

Relationship between Pb and Cd accumulations in house crow, their habitat, and food content from Klang area, Peninsular Malaysia.

Heavy metal pollution has become a global concern due to accumulation in tissue and transferable effects to humans via the food chain. This study focused on monitoring the accumulation of cadmium (Cd) and lead (Pb) in surface soil and body content: bone, heart, brain, liver, lung, muscle, kidney, feathers, feces, and gizzard contents of house crow Corvus splendens in the Klang region, Malaysia. The results revealed the occurrence of Pb and Cd in all biological samples from house crows, food contents, and surface soil samples. Heart and kidney accrued high amounts of Cd, while high amounts of Pb were found to accumulate in bones and feathers. Major discrepancies were also discovered in the concentrations of metals between juvenile and adults, as well as female and male bird samples. Concentrations of Pb and Cd in house crow internal tissues correlated significantly with that of bird feathers, but none could be established with that of surface soil. In addition, a significant correlation was observed between Pb concentration in the internal tissues to that of the feces, but the same was not the case when compared with the surface soil concentration. Metal accrual in the house crows feathers and feces may be through a long-term transmission via the food chain, which are eliminated from feathers via molting. This may suggest the utility of molted breast feathers of house crow in the bio-monitoring of Cd and Pb contamination, whereas feces of house crow appear only to be suitable for the bio-monitoring of Pb contamination.

Potassium fertilisation reduces radiocesium uptake by Japanese cypress seedlings grown in a stand contaminated by the Fukushima Daiichi nuclear accident

We analysed suppressive effects of potassium (K) fertilisation on radiocesium (137Cs) uptake by hinoki cypress (Chamaecyparis obtusa) seedlings from soils contaminated after the Fukushima Daiichi Nuclear Power Plant accident. Three-year-old seedlings were planted in a clear-cut forest (ca. 4 ha) during June–July 2014, and potassium chloride fertiliser (83 kg K ha−1) was applied twice (August 2014 and April 2015). 137Cs concentrations in the needles in the fertilised plots were one-eighth of those in the control (unfertilised) plots at the end of the second growing season (October 2015). Our results clearly indicated that K fertilisation reduced radiocesium transfer from soil to planted cypress seedlings. A linear mixed model analysis revealed that 137Cs concentrations in the needles were significantly affected by 137Cs inventory in the soil (Bq m−2) adjacent to the sampled seedlings, exchangeable K concentrations in surface mineral soils (0–5 cm) and fertilisation. The exchangeable K concentrations in surface soils in October 2015 did not differ from those in August 2014 (before fertilisation) in the fertilised plots and in the control plots. These results suggested that the levels of exchangeable K would temporarily increase by fertilisation during the growing season, and radiocesium uptake by tree roots was suppressed.

Improving human health outcomes with a low-cost intervention to reduce exposures from lead acid battery recycling: Dong Mai, Vietnam

This study details the first comprehensive evaluation of the efficacy of a soil lead mitigation project in Dong Mai village, Vietnam. The village's population had been subject to severe lead poisoning for at least a decade as a result of informal Used Lead Acid Battery (ULAB) recycling. Between July 2013 to February 2015, Pure Earth and the Centre for Environment and Community Development (Hanoi, Vietnam) implemented a multi-faceted environmental and human health intervention. The intervention consisted of a series of institutional and low-cost engineering controls including the capping of lead contaminated surface soils, cleaning of home interiors, an education campaign and the construction of a work-clothes changing and bathing facility. The mitigation project resulted in substantial declines in human and environmental lead levels. Remediated home yard and garden areas decreased from an average surface soil concentration of 3940mg/kg to <100mg/kg. One year after the intervention, blood lead levels in children (<6 years old) were reduced by an average of 67%—from a median of 40.4μg/dL to 13.3μg/dL. The Dong Mai project resulted in significantly decreased environmental and biological lead levels demonstrating that low-cost, rapid and well-coordinated interventions could be readily applied elsewhere to significantly reduce preventable human health harm.

Conservation agriculture effects on crop and water productivity, profitability and soil organic carbon accumulation under a maize-wheat cropping system in the North-western Indo-Gangetic Plains

The Indo-Gangetic Plains (IGP) of India is dominated with rice − wheat cropping system that occupies almost 10.5 million ha area. The sustainability of rice-wheat system is under threat due to numerous water-, nutrients-, weeds- and environment-related problems, mainly, due to the cultivation of rice. Suitable crop and soil management practices with a bias to conservation agriculture (CA) that can sustain soil and environmental health as well as improve crop and water productivity, are required for the Indian IGP. Maize can be a viable alternative to rice and a potential driver for diversification of rice-wheat system. The acreage of maize is on the increase in conventional and conservation agriculture-based cereal systems of India in recent years. Therefore, a field experiment, involving a maize (Zea mays L.)-wheat cropping system was undertaken on a sandy clay loam soil for three years (2010–11 to 2012-13) in New Delhi to evaluate the impacts of CA on crop and water productivity, profitability and soil organic carbon (SOC) accumulation. There were five CA-based treatments in first year, and two treatments were introduced in second year (2011-12) onwards. The experiment was laid out in a randomized complete block design with three replications. In all the residue retention plots, wheat residue was retained in maize crop and maize residue was retained in wheat crop under zero till conditions. Results showed that the plots under permanent broad bed with residue (PBB+R) and without residue (PBB) resulted in ∼29 and ∼26% higher maize grain yield, respectively than conventional tillage (CT) (2.6tha−1), but wheat grain yields were comparable in all the treatments in first year. Maize grain yield in second year under PBB+R and zero tillage with residue (ZT+R) were 55 and 43% higher than CT plots (2.8tha−1). Three-year mean maize yields due to PBB+R and permanent narrow bed with residue (PNB+R) were 28 and 15% higher than that in CT plots (3.3tha−1). The PBB+R resulted in 11% higher two-year mean water productivity in maize than PBB (∼without residue), but both these treatments were comparable in this regard in wheat. The ZT+R plots resulted in 14% and 22% higher two-year mean water productivity, respectively in maize and wheat than ZT plots. Overall, the plots under PBB+R had 57% and 19% higher mean water productivities in maize and wheat, respectively compared with CT plots. Again, the PBB+R plots gave 12% higher two-year mean net returns compared with CT plots. With regard to net returns, the plots under permanent narrow bed with and without residue (PNB+R; PNB) were inferior to PBB, PBB+R, ZT and ZT+R plots. Retention of both-season crop residues could significantly improve SOC concentration in surface (0–5cm) soil. The PBB+R resulted in highest SOC pool at 0–30cm soil layer, which was significantly higher than that in CT. This system showed maximum carbon sequestration potential. Thus, this CA practice, which involves PBB+R is superior to other practice. This would save water through higher water-use efficiency, and lead to accumulation of more carbon in soil with higher sequestration potential, besides giving sustainable production through maize-wheat system over the years. This can be adopted across the IGP regions of India, where irrigated rice-wheat system is in practice, and in similar agro-ecologies of the tropics and sub-tropics under irrigated conditions.

Assessments of Natural Radioactivity Concentration and Radiological Hazard Indices in Surface Soils from the Gözlek Thermal SPA (Amasya-Turkey)

Assessments of Natural Radioactivity Concentration and Radiological Hazard Indices in Surface Soils from the Gözlek Thermal SPA (Amasya-Turkey)

Effect of Plastic Film Mulching on Methane Emission from a Vegetable Field

Using the static opaque chamber method and choosing a chili-radish cropping system, a field experiment, located in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University in Chongqing, was conducted in situ for one year. Mulching and non-mulching treatments were set in the field, and the seasonal variation of CH4 flux and CH4 concentrations in the soil profile and the seasonal changes in soil moisture and temperature were observed for different treatments to explore the effect of plastic film mulching on soil moisture and temperature. The results showed that plastic film mulching can significantly improve the surface soil temperature during the pepper growing season in spring and summer (P<0.01), but no significant difference was seen during the radish growing season in autumn and winter (P>0.05). The soil moisture of the plastic film mulching treatment was significantly higher than that of no mulching in the radish growing season (P<0.05), but no significant difference was observed for the pepper growing season (P>0.05). During the whole observation period and under the condition of plastic film mulching and conventional planting, the CH4 flux from soil had no significant seasonal variation under all treatments, and the mean CH4 fluxes were -7.64 μg·(m2·h)-1 and -9.00 μg·(m2·h)-1, respectively. The cumulative CH4 emissions for plastic film mulching and conventional planting were -0.54 kg·hm-2 and -0.64 kg·hm-2, respectively, in the whole observation period, and all the treatments showed a net absorption of CH4 for the whole observation period. The results showed that the plastic film mulching could weaken the ability of CH4 as a sink of the CH4 for the whole observation period. The CH4 concentrations in different soil profiles were in the order 10 cm>20 cm>30 cm, and the concentrations of CH4 change patterns in different soil layers were almost identical during the whole observation period. The CH4 concentrations at the depths of 20 cm and 30 cm under the plastic film mulching soil were significantly lower than those under no mulching soil (P<0.05), but no significant difference was observed for the depth of 10 cm (P>0.05). Correlation analysis showed that, under the plastic film mulching conditions, CH4 flux and the 5 cm geothermal showed significant positive correlation (P<0.05), but CH4 flux and soil moisture showed significant negative correlation (P<0.05). However, under the conventional cultivation conditions, there were no correlations between CH4 flux and the 5 cm geothermal or soil moisture. There was also significant positive correlation between CH4 concentration in the 10 cm and 20 cm depth soil layers with the CH4 concentration in surface soil (P<0.01), and the CH4 concentration in the 30 cm depth soil layer had significant positive correlation with the surface soil temperatures and the 5 cm geothermal. There was no significant correlation between soil CH4 concentration and soil water content.

Soil organic carbon stock in relation to aggregate size and stability under tree-based cropping systems in Typic Ustochrepts

The growing of tree crops along with the field crops is a common practice in foothills of lower Himalayas with the twin objective of checking soil erosion by water and covering the risk of crop failure due to frequently occurring droughts. A study was conducted to evaluate dry and water stable aggregates for their soil organic carbon (SOC) stocks under different tree-based cropping systems. The treatments consisted of three cropping systems viz. maize-wheat (sole crop), agroforestry and agrohorticulture (tree-based) in the similar soil texture and in 6 year old plantations. The soil samples were obtained from different layers (0–15, 15–30, 30–60, 60–90 and 90–120 cm) and analyzed for SOC. The undisturbed aggregate samples (as big clods) were collected from 0–15 and 15–30 cm soil layer for dry and wet aggregate stability. The data so obtained was analyzed by using CRD factorial deigns at LSD (P ≤ 0.05). The SOC concentration decreased with soil depth, the decrease was higher (89.6%) in soils under maize-wheat than in soils under agrohorticulture (81.3%) and agroforestry (77.8%). The mean SOC concentration decreased with the size of the dry stable aggregates (DSA) and water stable aggregates (WSA). In DSA, the mean SOC concentration was 58.06 and 24.2% higher in large and small macroaggregates than in microaggregates respectively; in WSA it was 295.6 and 226.08% higher in large and small macroaggregates than in microaggregates respectively in surface soil layer. The mean SOC concentration in surface soil was higher in DSA (0.79%) and WSA (0.63%) as compared to bulk soil (0.52%). The SOC concentration and stock being highest in soils under agroforestry resulted in higher SOC concentration in dry as well as WSA.