Overview
This source page is a mechanical bulk-ingest record for a PDF in the methylmercury infant-formula research pull. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.
Key numbers
The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:
- Ju, X. T., Kou, C. L., Zhang, F. S., & Christie, P. (2006). Nitrogen balance and groundwater nitrate
- Environmental Pollution 143 (2006) 117e125
- China Agricultural University, Beijing 100094, China
- Institute of Soils and Fertilizers, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China
- Agricultural and Environmental Science Department, Queen’s University Belfast, Belfast BT9 5PX, UK
- 1358, 1881 and 402 kg N ha1 on average, representing 2.5, 37.5 and 83.8 times the corresponding values in wheat (Triticum aestivum L.)e
- maize (Zea mays L.) rotations and 2.1, 10.4 and 68.2 times the values in apple (Malus pumila Mill.) orchards. The N surplus values were
- 349, 3327 and 746 kg N ha1, with residual soil nitrate-N after harvest amounting to 221e275, 1173 and 613 kg N ha1 in the top 90 cm of
- the soil profile and 213e242, 1032 and 976 kg N ha1 at 90e180 cm depth in wheatemaize, greenhouse vegetable and orchard systems, respec-
- tively. Nitrate leaching was evident in all three cropping systems and the groundwater in shallow wells (<15 m depth) was heavily contaminated
- were only about 40% of total N inputs.
- Ó 2005 Elsevier Ltd. All rights reserved.
-
- Introduction been poor development of rational fertilizer recommendations
- and fruit trees) in China over the last 20 years. From 1980 to A systematic investigation conducted in Shandong province
- 2002 the area under cereal crops stabilized at about 110 M ha in 1997/1998 found that the average N fertilizer rate was
- but the area under vegetables increased from 3.16 to 17.35 M 280 kg N ha1 in 957 winter wheat fields, 208 kg N ha1 in
- ha and under fruit trees from 1.78 to 9.10 M ha (China 896 summer maize fields, 1700 kg N ha1 per crop in 147 pro-
- Agricultural Yearbook, 1981e2003). However, there has tected vegetable fields (plastic film greenhouses), and
-
- Corresponding author. Tel.: þ86 10 62732499; fax: þ86 10 62731016. in intensive vegetable and fruit producing areas, and might
- 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
- 118 X.T. Ju et al. / Environmental Pollution 143 (2006) 117e125
- ter samples from 22% of the agricultural area exceeded the (Granstedt, 2000; Ju et al., 2004). Accumulated nitrate is
- (50 mg NO3 L1) for drinking water (Laegreid et al., 1999). or heavy rainfall (Ju et al., 2003), and thus irrigation agricul-
- nitrate pollution of groundwater (Eichler and Schulz, 1998). In et al., 2000; Stites and Kraft, 2000). The relationships between
- a US study conducted in Wisconsin, NO 3 -N concentrations soil nitrate accumulation and groundwater nitrate concentra-
- exceeding 10 mg N L1 (the threshold for drinking water set tions in different cropping systems are still not fully
- 10% of 800,000 wells, and 17e26% of wells in the agricul- Calculation of N balance is one potentially useful method
- tural production areas exceeded the limit (Postle, 1999). for predicting the risk of nitrate leaching into groundwater
- Nitrate contamination in groundwater is closely related to (Barry et al., 1993; Puckett et al., 1999). Many factors influ-
- and Follett, 1991; Rass et al., 1999). Using 15N tracer techni- maintain soil fertility while minimizing environmental pollu-
- ques, Townsend et al. (1996) found that high nitrate-N concen- tion (Schroder et al., 1996; Parris, 1998). A study by Schleef
- trations (12e60 mg N L1) in groundwater in the southwest of and Kleihanss (1994) indicated that 100 kg ha1 of annual N
- sugar beet fields. Thorburn et al. (2003) investigated ground- into ground- or surface-water on a regional scale. The climate
- of northeast Australia using 15N techniques and found that nental monsoon, with cold winters and hot summers. The
- 14e21% of the wells were contaminated by nitrate, and in annual cumulative mean temperature for days with mean
- about half of these the nitrate was derived from N fertilizer ap- temperatures over 10 C is 4000e5000 C and the annual
- plication. A survey of groundwater nitrate-N concentrations frost-free period is 175e220 days (Sun et al., 1994). Taking
- and Shanxi showed that about 45% of 600 groundwater sam- limiting factors for adequate crop yields (Zhu et al., 1994;
- ples exceeded the WHO and European limit for nitrate in drink- Sun et al., 1994). The annual precipitation is 500e700 mm,
- ing water of 11.3 mg NO 3 -N L (50 mg NO 3 L ), with the with 60e70% of the rainfall occurring during summer
- highest nitrate-N concentration reaching 113 mg L1 (Zhang (JuneeAugust). The amount and distribution pattern of rain-
- et al., 2004). The proportion of samples above the limit was fall vary widely among years as affected by the continental
Methods (brief)
- ter samples from 22% of the agricultural area exceeded the (Granstedt, 2000; Ju et al., 2004). Accumulated nitrate is
- et al., 2004). The proportion of samples above the limit was fall vary widely among years as affected by the continental
- average evaporation is 1882 mm and is typical of the warm-temperate subhu- to collect groundwater samples from different depths. Thirdly, the wells were
- mid continental monsoon climate. The precipitation in the year of study from located in the same fields where plant and soil samples were collected.
- October 2002 to September 2003 was 508 mm, and 304 mm in June, July and Groundwater samples were collected once a month from every well and the
- August, accounting for 60% of total rainfall during the year. The main soil depth of the groundwater table was also measured. The samples were placed
- and fruit trees, of which the wheatemaize rotation system accounts for irrigation water samples were collected and the amount of irrigation water
- low groundwater pumped from an adjacent greenhouse. Water samples were
- systems from a total of 14 townships throughout the county. Secondly, we ran- Rainwater samples were collected from three sites in Huimin County during
- domly selected two villages from a total of 63e103 villages in each selected each rainfall event over 1 year using rain gauges. The samples were stored fro-
- ples of these manures were collected when farmers were applying them in the
- field. Samples of about 1 kg were collected from 10 to 15 points within each
- thoroughly and a sub-sample of about 0.5 kg was obtained using the quartering
- and straw yields. Plant samples were also taken to analyze the N content of
- procedure. Part of this sub-sample was used to determine water content and the
- remainder was air-dried for nutrient analysis. Three to seven samples of each
- Mill.) and 11 of capsicum pepper (Capsicum annuum Linn.)) were selected 2.3. Sample analysis
- tions before the plastic film greenhouses were established 3e20 years previ- Each fresh soil sample was extracted with 0.01 mol L1 CaCl2 to deter-
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